Microbiology Glossary

Glossary A site In a ribosome, a binding site that accommodates tRNA delivering an amino acid. Abscess An isolate site of infection, such as a pimple, boil, or pustule. Abyssal zone In marine habitats, the zone of water beneath the benthic zone, virtually devoid of life except around hydrothermal vents. Acellular Noncellular. Acetyl-CoA Combination of two-carbon acetate and coenzyme A. Acid Compound that dissociates into one or more hydrogen ions and one or more anions. Acid-fast bacilli (AFB) (acid­fast rod, AFR) Bacilli that retain stain during decolorization by acid-­ alcohol, particularly species of Mycobacterium. Acid-fast rod (AFR) Bacilli that retain stain during decolorization by acid-alcohol, particularly species of Mycobacterium. Acid-fast stain In microscopy, a differential stain used to penetrate waxy cell walls. Acidic dye In microscopy, an anionic chromophore used to stain alkaline structures. Works most effectively in acidic environments. Acidophile Microorganism requiring acidic pH. Acne Skin disorder characterized by presence of whiteheads, blackheads, and, in severe cases, cysts; typically caused by infection with Propionibacterium acnes. Acquired immunodeficiency syndrome (AIDS) The presence of several opportunistic or rare infections along with infection by human immunodeficiency virus (HIV) or a severe decrease in the number of CD4 + cells (200/mL) along with a positive test showing the presence of HIV. Acquired (secondary) immunodeficiency diseases Any of a group of immunodeficiency diseases that develop in older children, adults, and the elderly as a direct consequence of some other recognized cause, such as infectious disease. Actinomycetes High G+C Gram-positive bacteria that form branching filaments and produce spores, thus resembling fungi. Actinomycosis Disease caused by Actinomyces; characterized by formation of multiple, interconnected abscesses in skin or mucous membrane. Activation energy The amount of energy needed to trigger a chemical reaction. Active site Functional site of an enzyme, the shape of which is complementary to the shape of the substrate. Active transport The movement of a substance against its electrochemical gradient via carrier proteins and requiring cell energy from ATP. Acute anaphylaxis Condition in which the release of inflammatory mediators overwhelms the body’s coping mechanisms. Acute disease Any disease that develops rapidly but lasts only a short time, whether it resolves in convalescence or death. Acute inflammation Type of inflammation that develops quickly, is short lived, and is usually beneficial. Adaptive immunity Resistance against pathogens that acts more effectively upon subsequent infections with the same pathogen. Adenine Ring-shaped nitrogenous base found in nucleotides of DNA and RNA. Adenosine triphosphate (ATP) The primary short-term, recyclable energy molecule fueling cellular reactions. Adherence Process by which phagocytes attach to microorganisms through the binding of complementary chemicals on the cytoplasmic membranes. Adhesins Molecules that attach pathogens to their target cells. Adhesion The attachment of microorganisms to host cells. Adhesion factors A variety of structures or attachment proteins by which microorganisms attach to host cells. Adjuvant Chemical added to a vaccine to increase its ability to stimulate active immunity. Aerobe An organism that uses oxygen as a final electron acceptor. Aerobic respiration Type of cellular respiration requiring oxygen atoms as final electron acceptors. Aerosol A cloud of water droplets that travels more than 1 meter in airborne transmission and less than 1 meter in droplet transmission. Aerotolerant anaerobe Microorganism that prefers anaerobic conditions but can tolerate exposure to low levels of oxygen. Aflatoxin Carcinogenic mycotoxin produced by Aspergillus. African trypanosomiasis (African sleeping sickness) Potentially fatal disease caused by a bite from a tsetse fly carrying Trypanosoma brucei and characterized by formation of a lesion at the site of the bite, followed by parasitemia and central nervous system invasion. Agar Gel-like polysaccharide isolated from red algae and used as thickening agent. Agglutination Aggregation (clumping) caused when antibodies bind to two antigens, perhaps hindering the activity of pathogenic microorganisms and increasing the chance that they will be phagocytized. Agglutination test In serology, a procedure in which antiserum is mixed with a sample that potentially contains its target antigen. Agranulocyte Type of leukocyte having a uniform cytoplasm lacking large granules. Agroterrorism The use of microbes to terrorize humans by destroying the livestock and crops that constitute their food supply. Airborne transmission Spread of pathogens to the respiratory mucous membranes of a new host via the air or in droplets carried more than 1 meter. Alcohol Intermediate-level disinfectant that denatures proteins and disrupts cell membranes. Aldehyde Compound containing terminal groups; used as a high-level disinfectant because it cross-links organic functional groups in proteins and nucleic acids. Algae Eukaryotic unicellular or multicellular photosynthetic organisms with simple reproductive structures. Alginic acid Cell wall polysaccharide of brown algae. Alkalinophile Microorganism requiring alkaline pH environments. Allergen An antigen that stimulates an allergic response. Allergic contact dermatitis Type of delayed hypersensitivity reaction in which chemically modified skin proteins trigger a cell-mediated immune response. Allergy An immediate hypersensitivity response against an antigen. Allograft Type of graft in which tissues are transplanted from a donor to a genetically dissimilar recipient of the same species. Allylamines Class of antifungal drugs that disrupt cytoplasmic membranes. Alpha interferons (IFN@A) Interferons secreted by virally infected monocytes, macrophages, and some lymphocytes within hours after infection. Alphaproteobacteria Class of aerobic Gram-negative bacteria in the phylum Proteobacteria capable of growing at very low nutrient levels. Alternation of generations In algae, method of sexual reproduction in which diploid bodies alternate with haploid bodies. Alveolar macrophage Fixed macrophage of the lungs. Alveolates Protozoa with small membrane-bound cavities called alveoli beneath their cell surfaces. Amebiasis A mild to severe dysentery that, if invasive, can cause the formation of lesions in the liver, lungs, brain, and other organs; caused by infection with Entamoeba histolytica. Amensalism Symbiotic relationship in which one member harms another without receiving any benefit or harm itself. American trypanosomiasis (Chagas’ disease) Potentially fatal disease caused by a bite from a kissing bug carrying Trypanosoma cruzi and characterized by the formation of swelling at the site of the bite, followed by fever, swollen lymph nodes, myocarditis, organ enlargement, and eventually congestive heart failure. Ames test Method for screening mutagens that is commonly used to identify potential carcinogens. Amination Reaction involving the addition of an amine group to a metabolite to make an amino acid. Amino acid A monomer of polypeptides. Aminoglycoside Antimicrobial agent that inhibits protein synthesis by changing the shape of the 30S ribosomal subunit. Ammonification Process by which microorganisms disassemble proteins in soil wastes into amino acids, which are then converted to ammonia. Amoebas (amoebae) Protozoa that move and feed by pseudopods. Amphibolic reaction A reversible metabolic reaction; that is, a reaction that can be catabolic or anabolic. G-1 Z04_BAUM7206_05_SE_GLOS.indd 1 11/30/16 8:14 PM Glossary Anabolism All of the synthesis reactions in an organism taken together. Anaerobe An organism that cannot tolerate oxygen. Anaerobic respiration Type of cellular respiration not requiring oxygen atoms as final electron acceptors. Analog Chemicals that have similar molecular shapes. Analytical epidemiology Detailed investigation of a disease, including analysis of data to determine the probable cause, mode of transmission, and possible means of prevention. Anammox Anaerobic ammonium oxidation, which is one aspect of the nitrogen cycle. Anaphase Third stage of mitosis, during which sister chromatids separate and move to opposite poles of the spindle to form chromosomes. Also used for the comparable stage of meiosis. Anaphylactic shock Condition in which the release of inflammatory mediators overwhelms the body’s coping mechanisms, causing suffocation, edema, smooth muscle contraction, and often death. Anaplasmosis (human granulocytic anaplasmosis, HGA) Tick-borne disease caused by a rickettsia, Anaplasma phagocytophilum, manifesting with flulike signs and symptoms. Formerly called human granulocytic ehrlichiosis. Anion A negatively charged ion. Anisakiasis Gastrointestinal disease caused by fish nematode parasite Anisakis, which may also manifest as an allergic reaction to the worm. Anthrax Gastrointestinal, cutaneous, or pulmonary disease that is can be fatal without aggressive treatment; caused by ingestion, inoculation, or inhalation of spores of Bacillus anthracis. Antibiotic Antimicrobial agent that is produced naturally by an organism. Antibody (immunoglobulin) Proteinaceous antigen-binding molecule secreted by plasma cells. Antibody-dependent cellular cytotoxicity (ADCC) Process whereby natural killer lymphocytes (NK cells) lyse cells covered with antibodies. Antibody immune response (humoral immune response) The immune response centered around B lymphocytes and immunoglobulins. Anticodon Portion of tRNA molecule that is complementary to a codon on mRNA. Antigen Molecule that triggers a specific immune response. Antigen-binding site Site formed by the variable regions of a heavy and light chain of an antibody. Antigen-presenting cell (APC) Dendritic cells, macrophages, and B cells, which process antigens and activate cells of the immune system. Antigenic determinant (epitope) The three-­ dimensional shape of a region of an antigen that is recognized by the immune system. Antigenic drift Phenomenon that occurs every two to three years when a single strain of influenzavirus mutates within a local population. Antigenic shift Major antigenic change that occurs on average every 10 years and results from the reassortment of genomes from different influenzavirus strains within host cells. Antihistamines Drugs that specifically neutralize histamine. Antimicrobial (antimicrobial drug) Any compound used to treat infectious disease; may also function as intermediate-level disinfectant. Z04_BAUM7206_05_SE_GLOS.indd 2 Antimicrobial-associated diarrhea (C. diff. ­associated diarrhea) Severe diarrhea caused by opportunistic growth of Clostridium difficile following ­inhibition of other bacteria by antimicrobial drugs. Antimicrobial drug (antimicrobial) Chemotherapeutic agent used to treat microbial infection. Antimicrobial enzyme Enzyme that acts against microbes. Antimicrobial peptide (defensin) Chain of about 20 to 50 amino acids that acts against microorganisms. Antiretroviral therapy (ART) A cocktail of antiviral drugs including nucleotide analogs, integrase inhibitors, protease inhibitors, and reverse transcriptase inhibitors. Antisense nucleic acid RNA or single-stranded DNA with a nucleotide sequence complementary to a molecule of mRNA; used to control translation of polypeptide. Antisense RNA RNA with a nucleotide sequence complementary to a molecule of mRNA; used to control translation of polypeptide. Antisepsis The inhibition or killing of microorganisms on skin or tissue by the use of a chemical antiseptic. Antiseptic Chemical used to inhibit or kill microorganisms on skin or tissue. Antiserum In serology, blood fluid containing antibodies that bind to the antigens that triggered their production. Antitoxin Antibodies formed by the host that bind to and protect against toxins. Antivenin (antivenom) Antitoxin used to treat snake bites. Antiviral proteins (AVPs) Proteins triggered by alpha and beta interferons that prevent viral replication. Apicomplexans In protozoan taxonomy, group of pathogenic alveolate protozoa characterized by the complex of special intracellular organelles located at the apices of the infective stages of these microbes. Apoenzyme The protein portion of protein enzymes that is inactive unless bound to one or more cofactors. Apoptosis Programmed cell suicide. Applied microbiology Branch of microbiology studying the commercial use of microorganisms in industry and foods. Arachnid Group of arthropods distinguished by the presence of eight legs, such as spiders, ticks, and mites. Arboviral encephalitis Inflammation of the brain and/or meninges caused by viruses transmitted by bloodsucking arthropods. Arboviruses Viruses that are transmitted by arthropods; they include members of several viral families. Archaea (archaeon, sing.) In Woese’s taxonomy, domain that includes all prokaryotic cells having archaeal rRNA sequences. Archaezoa Protozoa that lack mitochondria, Golgi bodies, chloroplasts, and peroxisomes. Arenaviruses Group of segmented, negative ssRNA viruses that cause zoonotic diseases. ART (antiretroviral therapy) A cocktail of antiviral drugs including nucleotide analogs, integrase inhibitors, protease inhibitors, and reverse transcriptase inhibitors. G-2 Arthropod Animal with a segmented body, hard exoskeleton, and jointed legs, including arachnids and insects. Arthropod vector Animals with segmented bodies, external skeletons, and jointed legs that carry pathogens; vectors include ticks, mites, fleas, flies, and true bugs. Artificial wetlands Use of successive ponds, marshes, and meadowlands to remove wastes from sewage as the water moves through the wetlands. Artificially acquired active immunity Type of immunity that occurs when the body receives antigens by injection, as with vaccinations, and mounts a specific immune response. Artificially acquired passive immunotherapy Treatment in which patient receives via injection preformed antibodies in antitoxins or antisera, which can destroy fast-acting and potentially fatal antigens, such as rattlesnake venom. Ascariasis Symptomatic but not typically fatal disease caused by infection with the nematode Ascaris lumbricoides. Ascomycota Division of fungi characterized by the formation of haploid ascospores within sacs called asci. Ascospore Haploid germinating structure of ascomycetes. Ascus Sac in which haploid ascospores are formed and from which they are released in fungi of the division Ascomycota. Aseptate Lacking cross walls. Aseptic Characteristic of an environment or procedure that is free of contamination by pathogens. Aspergillosis Term for several localized and invasive diseases caused by infection with Aspergillus species. Assembly In virology, fourth stage of the lytic replication cycle, in which new virions are assembled in the host cell. Asthma Hypersensitivity reaction affecting the lungs and characterized by bronchial constriction and excessive mucus production. Astroviruses Group of small, round enteric viruses that cause diarrhea, typically in children. Asymptomatic (subclinical) Characteristic of disease that may go unnoticed because of absence of symptoms, even though clinical tests may reveal signs of disease. Atom The smallest chemical unit of matter. Atomic force microscope (AFM) Type of probe microscope that uses a pointed probe to traverse the surface of a specimen. A laser beam detects vertical movements of the probe, which a computer translates to reveal the atomic topography of the specimen. Atomic mass (atomic weight) The sum of the masses of the protons, neutrons, and electrons in an atom. Atomic number The number of protons in the nucleus of an atom. ATP synthase (ATPase) Enzyme that phosphorylates ATP in oxidative phosphorylation and photophosphorylation. Attachment In virology, first stage of the lytic replication cycle, in which the virion attaches to the host cell. Attenuated vaccine Inoculum in which pathogens are weakened so that, theoretically, they no longer cause disease; residual virulence can be a problem. 11/30/16 8:14 PM G-3 Glossary Attenuation The process of reducing vaccine virulence. Autoantigens Antigens on the surface of normal body cells. Autoclave Device that uses steam heat under pressure to sterilize chemicals and objects that can tolerate moist heat. Autograft Type of graft in which tissues are moved to a different location within the same patient. Autoimmune disease Any of a group of diseases that result when an individual begins to make autoantibodies or cytotoxic T cells against normal body components. Autoimmune hemolytic anemia Disease resulting when an individual produces antibodies against his or her own red blood cells. Avirulent Harmless. Axenic Having only one organism present. Axial filament In cell morphology, structure composed of rotating endoflagella that allows a spirochete to “corkscrew” through its medium. Azoles Class of antifungal drugs that disrupt cytoplasmic membranes. B cell B lymphocyte. B cell receptor (BCR) Antibody integral to the cytoplasmic membrane and expressed by B lymphocytes. B lymphocyte (B cell) Lymphocyte that arises and matures in the red bone marrow in adults and is found primarily in the spleen, lymph nodes, red bone marrow, and Peyer’s patches of the intestines and that secretes antibodies. Bacillus Rod-shaped prokaryotic cell. Bacitracin Antimicrobial that blocks NAG and NAM secretion from the cytoplasm, prompting cell lysis. Bacteremia The presence of bacteria in the blood; often caused by infection with Staphylococcus aureus or Streptococcus pneumoniae. Bacteria Prokaryotic microorganisms typically having cell walls composed of peptidoglycan. In Woese’s taxonomy, domain that includes all prokaryotic cells having bacterial rRNA sequences. Bacterial gastroenteritis Inflammation of the mucous membrane of the stomach and intestines, caused by a bacterial pathogen. Bacterial intoxication (toxification) Food poisoning caused by bacterial toxin. Bacteriophage (phage) Virus that infects and usually destroys bacterial cells. Bacteriorhodopsin Purple protein synthesized by Halobacterium that absorbs light energy to synthesize ATP. Bacteroid Diverse group of Gram-negative microbes that have similar rRNA nucleotide sequences, such as Bacteroides. Balantidiasis A mild gastrointestinal illness caused by Balantidium coli. Barophile Microorganism requiring the extreme hydrostatic pressure found at great depth below the surface of water. Base Molecule that binds with hydrogen ions when dissolved in water. Base pair (bp) A complementary arrangement of nucleotides in a strand of DNA or RNA. For example, in both DNA and RNA, guanine and cytosine pair. Z04_BAUM7206_05_SE_GLOS.indd 3 Base-excision repair Mechanism by which enzymes excise a section of a DNA strand containing an error, and then DNA polymerase fills in the gap. Basic dye In microscopy, a cationic chromophore used to stain acidic structures. Works most effectively in alkaline environments. Basidiocarp Fruiting body of basidiomycetes; includes mushrooms, puffballs, stinkhorns, jelly fungi, bird’s nest fungi, and bracket fungi. Basidiomycota Division of fungi characterized by production of basidiospores and basidiocarps. Basophil Type of granulocyte that stains blue with the basic dye methylene blue. Bejel Childhood disease caused by the spirochete Treponema pallidum endemicum; characterized by rubbery oral lesions. Benign tumor Mass of neoplastic cells that remains in one place and is not generally harmful. Benthic zone Bottom zone of freshwater or marine water, devoid of light and with scarce nutrients. Beta interferons (IFN@B) Interferons secreted by virally infected fibroblasts within hours after infection. Beta-lactam Antimicrobial whose functional portion is composed of beta-lactam rings, which inhibit peptidoglycan formation by irreversibly binding to the enzymes that cross-link NAM subunits. Beta (B)@lactamase Bacterial enzyme that breaks the beta-lactam rings of penicillin and similar molecules, rendering them inactive. Beta-oxidation A catabolic process in which enzymes split pairs of hydrogenated carbon atoms from a fatty acid and join them to coenzyme A to form acetyl-CoA. Betaproteobacteria Class of diverse Gram-negative bacteria in the phylum Proteobacteria capable of growing at very low nutrient levels. Binary fission The most common method of asexual reproduction of prokaryotes, in which the parental cell disappears with the formation of progeny. Binomial nomenclature The classification method used in the Linnaean system of taxonomy, which assigns each species both a genus name and a specific epithet. Biochemical oxygen demand (BOD) A measure of the amount of oxygen aerobic bacteria require to metabolize organic wastes in water. Biochemistry Branch of chemistry that studies the chemical reactions of living things. Biodiversity The number of species living in a given ecosystem. Biofilm A slimy community of microbes growing on a surface. Biogeochemical cycling The movement of elements and nutrients from unusable forms to usable forms because of the activities of microorganisms. Biological vector Biting arthropod or other animal that transmits pathogens and serves as host for the multiplication of the pathogen during some stage of the pathogen’s life cycle. Biomass The quantity of all organisms in a given ecosystem. Biomining The use of microbes to convert metals to soluble forms that can be more easily extracted. Bioremediation The use of microorganisms to metabolize toxins in the environment to reclaim soils and waterways. Bioreporter Type of biosensor composed of microbes with innate signaling capabilities. Biosensor Device that combines bacteria or microbial products such as enzymes with electronic measuring devices to detect other bacteria, bacterial products, or chemical compounds in the environment. Biosphere The region of Earth inhabited by living organisms. Biotechnology Branch of microbiology in which microbes are manipulated to manufacture useful products. Bioterrorism The use of microbes or their toxins to terrorize human populations. Blastomycosis Pulmonary disease found in the southeastern United States, caused by infection with Blastomyces dermatitidis. Blood group antigens The surface molecules of red blood cells. Bodily fluid transmission Spread of pathogenic microorganisms via blood, urine, saliva, or other bodily fluids. Botulism Potentially fatal intoxication with botulism toxin; three types include foodborne botulism, infant botulism, and wound botulism. Bradykinin Peptide chain of nine amino acids that is a potent mediator of inflammation. Broad-spectrum drug Antimicrobial that works against many different kinds of pathogens. Bronchitis Inflammation of the bronchi. Broth A liquid, nutrient-rich medium used for cultivating microorganisms. Broth dilution test Test for determining the minimum inhibitory concentration in which a standardized amount of bacteria is added to serial dilutions of antimicrobial agents in tubes or wells containing broth. Brucellosis Disease caused by Brucella; usually asymptomatic or mild, though it can result in sterility or abortion in animals. Bruton-type agammaglobulinemia An inherited disease in which affected babies cannot make immunoglobulins and experience recurrent bacterial infections. Bt toxin (Bt) Insecticidal poison produced by Bacillus thuringiensis bacteria. Bubo Swollen inflamed lymph node. Bubonic plague Severe systemic disease, fatal if untreated in 50% of patients, and characterized by fever, tissue necrosis, and the presence of buboes; caused by infection with Yersinia pestis. Budding In prokaryotes and yeasts, reproductive process in which an outgrowth of the parent cell receives a copy of the genetic material, enlarges, and detaches. In virology, extrusion of enveloped virions through the host’s cell membrane. Buffer A substance, such as a protein, that prevents drastic changes in pH. Bulbar poliomyelitis Infection of the brain stem and medulla resulting in paralysis of muscles in the limbs or respiratory system; caused by infection with poliovirus. Bunyaviruses Group of zoonotic pathogens that have a segmented genome of three –ssRNA molecules and are transmitted to humans via arthropods. Burkitt’s lymphoma Infectious cancer of the jaw caused by infection with Epstein-Barr virus. 11/30/16 8:14 PM Glossary Caliciviruses Group of small, round enteric viruses that cause diarrhea, nausea, and vomiting. Calor Heat. Calvin-Benson cycle Stage of photosynthesis in which atmospheric carbon dioxide is fixed and reduced to produce glucose. Cancer Disease characterized by the presence of one or more malignant tumors. Candidiasis Term for several opportunistic diseases caused by infection with Candida species. Candin Antifungal drug that inhibits cell wall synthesis. Capnophile Microorganism that grows best with high levels of carbon dioxide in addition to low levels of oxygen. Capsid A protein coat surrounding the nucleic acid core of a virion. Capsomere A proteinaceous subunit of a capsid. Capsule Glycocalyx composed of repeating units of organic chemicals firmly attached to the cell surface. Capsule stain (negative stain) In microscopy, a staining technique used primarily to reveal bacterial capsules and involving application of an acidic dye that leaves the specimen colorless and the background stained. Carbohydrate Organic macromolecule consisting of atoms of carbon, hydrogen, and oxygen. Carbon cycle Biogeochemical cycle in which carbon is cycled in the form of organic molecules. Carbon fixation The attachment of atmospheric carbon dioxide to ribulose 1,5-bisphosphate (RuBP). Carbuncle The coalescence of several furuncles extending deep into underlying tissues; caused by infection with Staphylococcus aureus. Carcinogen Chemical capable of causing cancer. Caries (cavities) Tooth decay; caused by viridans streptococci and other bacteria. Carotenoid Plant pigment that acts as an antioxidant. Carrageenan Gel-like polysaccharide isolated from red algae and used as thickening agent. Carrier In human pathology, continuous asymptomatic human source of infection. Catabolism All of the decomposition reactions in an organism taken together. Catarrhal phase In pertussis, initial phase lasting 1 to 2 weeks and characterized by signs and symptoms resembling those of a common cold. Cation A positively charged ion. Cat scratch disease Common and occasionally serious infection in children; characterized by fever and malaise plus localized swelling; caused by infection with Bartonella henselae. CD4 Distinguishing cytoplasmic membrane protein of helper T cells, which is the initial binding site of HIV. CD4 + cell (helper T cell, Th cell) In cell-mediated immune response, a type of cell characterized by CD4 cell-surface glycoprotein; regulates the activity of B cells and cytotoxic T cells. CD8 Distinguishing cytoplasmic membrane protein of cytotoxic T cells. CD8 + cell (cytotoxic T cell, Tc cell) In cell-­mediated immune response, type of cell characterized by CD8 cell-surface glycoprotein; secretes perforins and granzymes that destroy infected or abnormal body cells. Z04_BAUM7206_05_SE_GLOS.indd 4 CD95 pathway In cell-mediated cytotoxicity, pathway involving CD95 protein that triggers apoptosis of infected cells. C. diff. (Clostridium difficile) ­diarrhea (anti­ microbial­associated diarrhea) Watery stools resulting from elimination of normal intestinal microbiota by antimicrobial drug therapy, which allows ­Clostridium difficile endospores to germinate. Cell culture Cells isolated from an organism and grown on the surface of a medium or in broth. Viruses can be grown in a cell culture. Cell wall In most cells, structural boundary composed of polysaccharide or protein chains that provides shape and support against osmotic pressure. Cell-mediated hypersensitivity reaction (type IV hypersensitivity, delayed hypersensitivity) T cell–­ mediated inflammatory reaction that takes 24 to 72 hours to reach maximal intensity. Cell-mediated immune response Immune response used by T cells to fight intracellular pathogens and abnormal body cells. Cellular respiration Metabolic process that involves the complete oxidation of substrate molecules and production of ATP via a series of redox reactions. Cellular slime mold Individual haploid myxamoeba that phagocytizes bacteria, yeasts, dung, and decaying vegetation. Central dogma In genetics, fundamental description of protein synthesis that states that genetic information is transferred from DNA to RNA to polypeptides, which function alone or in conjunction as proteins. Centrioles Nonmembranous organelles in animal cells that appear to function in the formation of flagella and cilia and in cell division. Centrosome Region of a cell containing centrioles. Cesspool Home equivalent of primary wastewater treatment in which wastes enter a series of porous concrete rings buried underground and are digested by microbes. Cestodes (tapeworms) Group of helminths that are long, flat, and segmented and lack digestive systems. Chagas’ disease (American trypanosomiasis) Potentially fatal disease caused by a bite from a kissing bug carrying Trypanosoma cruzi and characterized by the formation of swellings at the site of the bite, followed by fever, swollen lymph nodes, myocarditis, organ enlargement, and eventually congestive heart failure. Chancre Painless red lesion that appears at the site of infection with Treponema pallidum, the agent of syphilis. Chancroid Soft, painful, venereal ulcer at site of infection by Haemophilus ducreyi. Chemical bond An interaction between atoms in which electrons are either shared or transferred in such a way as to fill their valence shells. Chemical fixation In microscopy, a technique that uses methyl alcohol or formalin to attach a smear to a slide. Chemical reaction The making or breaking of a chemical bond. Chemiosmosis Use of ion gradients to generate ATP. Chemoautotroph Microorganism that uses carbon dioxide as a carbon source and catabolizes organic molecules for energy. G-4 Chemoheterotroph Microorganism that uses organic compounds for both energy and carbon. Chemokine An immune system cytokine that signals leukocytes to rush to the site of inflammation or infection and activate other leukocytes. Chemostat A continuous culture device controlled by adding fresh medium at the same rate old medium is removed. Chemotactic factors Chemicals, such as peptides derived from complement and cytokines, that attract cells. Chemotaxis Cell movement that occurs in response to chemical stimulus. Chemotherapeutic agent Chemical used to treat disease. Chemotherapy A branch of medical microbiology in which chemicals are studied for their potential to destroy pathogenic microorganisms. Chickenpox (varicella) Highly infectious disease characterized by fever, malaise, and skin lesions, caused by infection with varicella-zoster virus. Chitin Strong, flexible nitrogenous polysaccharide found in fungal cell walls and in the exoskeletons of insects and other arthropods. Chlamydia Any of the small Gram-negative pathogenic cocci that grow and reproduce within the cells of mammals, birds, and a few invertebrates and that spread as elementary bodies. Chloramphenicol Antimicrobial drug that blocks the enzymatic site of the 50S ribosomal subunit, inhibiting polypeptide synthesis. Chlorophyll Pigment molecule that captures light energy for use in photosynthesis. Chlorophyta Green-pigmented division of algae that have chlorophylls a and b, store sugar and starch as food reserves, and have rRNA sequences similar to plants. Considered the progenitors of plants. Chloroplast Light-harvesting organelle found in photosynthetic eukaryotes. Cholera Disease contracted through the ingestion of food and water contaminated with Vibrio cholerae and characterized by vomiting and watery diarrhea. Cholera toxin Exotoxin produced by Vibrio chol­ erae that causes the movement of water out of the intestinal epithelium. Chromatin Threadlike mass of DNA and associated histone proteins that becomes visible during mitosis as chromosomes. Chromatin fiber An association of nucleosomes and proteins found within the chromosomes of eukaryotic cells. Chromoblastomycosis Cutaneous and subcutaneous disease characterized by lesions that can spread internally; caused by traumatic introduction of ascomycete fungi into the skin. Chromosome A molecule of DNA associated with protein. In prokaryotes, typically circular and localized in a region of the cytosol called the nucleoid. In eukaryotes, chromosomes are threadlike and are most visible during mitosis and meiosis. Chronic disease Any disease that develops slowly, usually with less severe symptoms, and is continual or recurrent. Chronic granulomatous disease Primary immunodeficiency disease in which children have recurrent infections characterized by the development of large masses of inflammatory cells in lymph nodes, lungs, bones, and skin. 11/30/16 8:14 PM G-5 Glossary Chronic inflammation Type of inflammation that develops slowly, lasts a long time, and can cause damage (even death) to tissues, resulting in disease. Chrysophyta Division of algae including the golden algae, yellow-green algae, and diatoms. Cilia Short, hairlike, rhythmically motile projections of some eukaryotic cells. Ciliate In protozoan taxonomy, group of alveolate protozoa characterized by the presence of cilia in their trophozoite stages. Class Taxonomical grouping of similar orders of organisms. Class switching The process in which a plasma cell changes the type of antibody Fc region (stem) that it synthesizes and secretes. Clinical laboratory scientist An expert in health care–related microbiological laboratory procedures who has at least a bachelor degree. Clinical specimen Sample of human material, such as feces or blood, that is examined or tested for the presence of microorganisms. Coinfection Simultaneous infection with more than one pathogen. Clonal deletion Process by which cells with receptors that respond to autoantigens are selectively killed via apoptosis. Clonal expansion In immunology, the reproduction of activated lymphocytes. Clonal selection In antibody immunity, recognition and activation only of B lymphocytes with BCRs complementary to a specific antigenic determinant. Coccidioidomycosis Pulmonary disease found in the southwestern United States, caused by infection with Coccidioides immitis. Coccobacillus A prokaryotic cell intermediate in shape between a sphere and a rod, such as an elongated coccus. Coccus Spherical prokaryotic cell. Codon Triplet of mRNA nucleotides that codes for specific amino acids. For example, AAA is a codon for lysine. Coenocyte Multinucleate cell resulting from repeated mitosis but postponed or absent cytokinesis. Coenzyme Organic cofactor. Cofactor Inorganic ions or organic molecules that are essential for enzyme action. Coinfection Simultaneous infection with more than one pathogen. Cold enrichment Incubation of a specimen in a refrigerator to enhance the growth of cold-tolerant species. Cold sore Common name for oral lesion of a herpesvirus. Coliforms Enteric Gram-negative bacteria that ferment lactose to gas and are found in the intestinal tracts of animals and humans. Colony Visible population of microorganisms living in one place; an aggregation of cells arising from a single parent cell. Colony-forming unit (CFU) A single cell or group of related cells that produce a colony. Colorado tick fever Zoonosis caused by Coltivi­ rus that is typically characterized by mild fever and chills. Combination vaccine Inoculum composed of antigens from several pathogens that are administered simultaneously. Z04_BAUM7206_05_SE_GLOS.indd 5 Commensalism Symbiotic relationship in which one member benefits without significantly affecting the other. Communicable disease Any infectious disease that comes either directly or indirectly from another host. Competence Ability of a cell to take up DNA from the environment. Competitive inhibition (in immunity) Activities of members of the microbiome of the body that make it less likely that a pathogen can produce disease. Competitive inhibitor (metabolism) Inhibitory substance that blocks enzyme activity by blocking active sites. Complement fixation test A complex assay used to determine the presence of specific antibodies in serum. Complement system (complement) Set of blood plasma proteins that act as chemotactic attractants, trigger inflammation and fever, and ultimately effect the destruction of foreign cells. Complementary DNA (cDNA) DNA synthesized from an mRNA template using reverse transcriptase. Complex medium Culturing medium that contains nutrients released by the partial digestion of yeast, beef, soy, or other proteins; thus, the exact chemical composition is unknown. Complex transposon Transposon containing genes not connected with transposition. Compound A molecule containing atoms of more than one element. Compound microscope Microscope using a series of lenses for magnification. Concentration gradient The difference in concentration of a chemical on the two sides of a membrane. Also called a chemical gradient. Condenser lens In a compound microscope, a lens that directs light through the specimen as well as one or more mirrors that deflect the light’s path. Condylomata acuminata Large, cauliflowerlike genital warts caused by infection with a papillomavirus. Confocal microscope Type of light microscope that uses ultraviolet lasers to illuminate fluorescent chemicals in a single plane of the specimen. Congenital syphilis Disease characterized by mental retardation, organ malformation, and, in some cases, death of the fetus of a woman infected with Treponema pallidum, the agent of syphilis. Conjugation In genetics: method of horizontal gene transfer in which a bacterium containing a fertility plasmid forms a conjugation pilus that attaches and transfers plasmid genes to a recipient; in reproduction of ciliates: coupling of mating cells. Conjugation pilus Proteinaceous, rodlike structure extending from the surface of a cell; mediates conjugation. Conjunctivitis (pinkeye) Inflammation of the lining of an eyelid. Consumption Tuberculosis; refers to wasting away of a body affected with TB at several sites. Contact immunity Immunity conferred to an unvaccinated individual following contact with an individual vaccinated with an attenuated vaccine. Contagious disease A communicable disease that is easily transmitted from a reservoir or patient. Contamination The presence of microorganisms in or on the body or other site. Continuous cell culture Type of cell culture created from tumor cells. Contrast The difference in visual intensity between two objects, or between an object and its background. Convalescence In the infectious disease process, final stage during which the patient recovers from the illness, and tissues and systems are repaired and return to normal. Convalescent phase In pertussis, final phase lasting three to four weeks, during which the ciliated lining of the trachea grows back and frequency of coughing spells diminishes, but secondary bacterial infections may ensue. Cord factor A cell wall component of pathogenic Mycobacterium tuberculosis that produces strands of daughter cells, inhibits migration of neutrophils, and is toxic to body cells. Coronaviruses Group of enveloped ssRNA viruses that cause colds as well as severe acute respiratory syndrome. Coronavirus respiratory syndrome Severe respiratory disease caused by coronaviruses SARS virus and MERS virus. Corticosteroids Another name for immunosuppressive agents that suppress the action of T cells. Counterstain In a Gram stain, red stain that provides contrasting color to the primary stain, causing Gram-negative cells to appear pink. Covalent bond The sharing of a pair of electrons by two atoms. Coxsackieviruses Group of enteroviruses that cause a variety of diseases in humans, ranging from mild fever and colds to myocarditis and heart failure. Crenation Shriveling of a cell caused by osmosis in a hypertonic environment. Cristae Folds within the inner membrane of a mitochondrion that increase its surface area. Cross resistance Phenomenon in which resistance to one antimicrobial drug confers resistance to similar drugs. Crossing over Process in which portions of homologous chromosomes are recombined during the formation of gametes. Croup Inflammation and swelling of the larynx, trachea, and bronchi and a “seal bark” cough, often caused by infection with a parainfluenza or rarely by other respiratory viruses. Cryptococcosis Disease caused by the dimorphic fungus Cryptococcus; typically manifests as meningitis. Cryptosporidiosis (Cryptosporidium enteritis) A gastrointestinal disease caused by infection with Cryptosporidium parvum; in humans, characterized by diarrhea, fluid loss, and weight loss; may be fatal in HIV-positive patients. Culture Act of cultivating microorganisms or the microorganisms that are cultivated. Cutaneous anthrax Disease of the skin caused by inoculation with spores of Bacillus anthracis. Cuticle Outer protective “skin” of a nematode. Cyanobacteria Gram-negative photosystem bacteria that vary greatly in shape, size, and method of reproduction. Cyclic photophosphorylation Return of electrons to the original reaction center of a photosystem after passing down an electron transport chain. 11/30/16 8:14 PM Glossary Cycloserine Semisynthetic antimicrobial used to treat infections with Gram-positive bacteria. Cyclosporine Immunosuppressive drug that inhibits action of activated T cells. Cyst In protozoan morphology, the hardy resting stage characterized by a thick capsule and a low metabolic rate. Cysticercus Immature tapeworm, usually in muscle of intermediate host. Cytokines Proteins secreted by many types of cells that regulate adaptive immune responses. Cytokinesis Division of a cell’s cytoplasm. Cytoplasm General term used to describe the semiliquid, gelatinous material inside a cell. Cytoplasmic membrane Membrane surrounding all cells, and composed of a fluid mosaic of phospholipids and proteins. Cytosine Ring-shaped nitrogenous base found in nucleotides of DNA and RNA. Cytoskeleton Internal network of fibers contributing to the basic shape of eukaryotic and rod-shaped prokaryotic cells. Cytosol The liquid portion of the cytoplasm. Cytotoxic drugs Group of drugs that inhibit cells. Cytotoxic T cell (Tc cell, CD8 + cell) In cell-­ mediated immune response, type of cell characterized by CD8 cell-surface glycoprotein; secretes perforins and granzymes that destroy infected or abnormal body cells. Dark-field microscope Microscope used for studying pale or small specimens; deflects light rays so that they miss the objective lens. Dark repair (nucleotide excision repair) Mechanism by which enzymes cut a section of a single strand of damaged DNA from a molecule, creating a gap that is repaired by DNA polymerase and DNA ligase. Deamination Process in which amine groups are split from amino acids. Death phase Phase in a growth curve in which the organisms are dying more quickly than they are being replaced by new organisms. Decimal reduction time (D) The time required to destroy 90% of the microbes in a sample. Decline In the infectious disease process, period in which the body gradually returns to normal as the patient’s immune response and any medical treatments vanquish the pathogens. Decolorizing agent In a stain, a solution that washes the primary stain away. Decomposition reaction A chemical reaction in which the bonds of larger molecules are broken to form smaller atoms, ions, and molecules. Deep-freezing Long-term storage of cultures at temperatures ranging from - 50° C to - 95° C. Deeply branching bacteria Prokaryotic autotrophs with rRNA sequences and growth characteristics thought to be similar to those of earliest bacteria. Defensins (antimicrobial peptides) Small peptide chains that act against a broad range of pathogens. Defined medium (synthetic medium) Culturing medium of which the exact chemical composition is known. Definitive host In the life cycle of parasites, host in which mature and sometimes sexual forms of the parasite are present and usually reproducing. Z04_BAUM7206_05_SE_GLOS.indd 6 Degerming The removal of microbes from a surface by scrubbing. Dehydration synthesis Type of synthesis reaction in which two smaller molecules are joined together by a covalent bond, and a water molecule is formed. Delayed hypersensitivity reaction (type IV hypersensitivity, cell­mediated hypersensitivity) T cell-­ mediated inflammatory reaction that takes 24 to 72 hours to reach maximal intensity. Deletion Type of mutation in which a nucleotide base pair is deleted. Deltaproteobacteria Group of Proteobacteria that includes Desulfovibrio, Bdellovibrio, and myxobacteria. Denaturation Process by which a protein’s three-dimensional structure is altered, eliminating function. Dendritic cells Cells of the epidermis and mucous membranes that devour pathogens. Dengue fever Self-limiting but extremely painful disease caused by a flavivirus transmitted by Aedes mosquitoes. Dengue hemorrhagic fever (DHF) Potentially fatal disease involving a hyperimmune response to reinfection with dengue virus and causing ruptured blood vessels, internal bleeding, and shock. Denitrification The conversion of nitrate into nitrogen gas by anaerobic respiration. Deoxyribonucleic acid (DNA) Nucleic acid consisting of nucleotides made up of phosphate, a deoxyribose pentose sugar, and an arrangement of the bases adenine, guanine, cytosine, and thymine. Dermatophyte Fungus that normally lives on skin, nails, or hair. Dermatophytoses Any of a variety of superficial skin, nail, and hair infections caused by dermatophytes. Dermis The layer of the skin deep to the epidermis and containing hair follicles, glands, and nerve endings. Descriptive epidemiology The careful recording of data concerning a disease. Desiccation Inhibition of microbial growth by drying. Detergent Positively charged organic surfactant. Deuteromycetes Informal grouping of fungi having no known sexual stage. Diapedesis (emigration) Process whereby leukocytes leave intact blood vessels by squeezing between lining cells. Diatom Type of alga in the division Chrysophyta; has cell walls made of silica arranged in nesting halves called frustules. Dichotomous key Method of identifying organisms in which information is arranged in paired statements, only one of which applies to any particular organism. Differential interference contrast microscope Type of phase microscope that uses prisms to split light beams, giving images a three-dimensional appearance. Differential medium Culturing medium formulated such that either the presence of visible changes in the medium or differences in the appearances of colonies help microbiologists differentiate among kinds of bacteria growing on the medium. Differential stain In microscopy, a stain using more than one dye so that different structures can G-6 be distinguished. The Gram stain is the most commonly used. Differential white blood cell count Lab technique that indicates the relative numbers of leukocytes. Diffusion The net movement of a chemical down its concentration gradient. Diffusion susceptibility test (Kirby­Bauer test) Simple, inexpensive test widely used to reveal which drug is most effective against a particular pathogen. Procedure involves inoculating a Petri plate uniformly with a standardized amount of the pathogen in question and arranging on the plate disks soaked in the drugs to be tested. DiGeorge syndrome Failure of the thymus to develop, and thus, absence of T cells. Dimorphic Having two forms; for example, dimorphic fungi have both yeastlike and moldlike bodies. Dinoflagellate In protozoan taxonomy, group of unicellular, flagellated, alveolate protozoa characterized by photosynthetic pigments. Dioecious Male and female sex organs are in separate individuals. Diphtheria Mild to potentially fatal respiratory disease caused by diphtheria toxin following infection with Corynebacterium diphtheriae. Diphtheroids Generally nonpathogenic pleomorphic bacilli named for the similarity of their appearance to Corynebacterium diphtheriae. Diplococcus A pair of cocci. Diploid A nucleus with two copies of each chromosome. Diploid cell culture Type of cell culture created from embryonic animal, plant, or human cells that have been isolated and provided appropriate growth conditions. Dipstick immunochromatographic assay Rapid modification of ELISA test in which an antigen solution flows through a porous strip, encountering labeled antibody; used for pregnancy testing and for rapid identification of infectious agents. Direct antibody test Immune test allowing direct observation of the presence of antigen. Direct contact transmission Spread of pathogens from one host to another involving body contact between the hosts. Direct fluorescent antibody test Immune test allowing direct observation of the presence of antigen in a tissue sample flooded with labeled antibody. Disaccharide Carbohydrate consisting of two monosaccharide molecules joined together. Disease Any adverse internal condition severe enough to interfere with normal body functioning. Disease process Definite sequence of events following contamination and infection. Disinfectant Physical or chemical agent used to inhibit or destroy microorganisms on inanimate objects. Disinfection The use of physical or chemical agents to inhibit or destroy microorganisms on inanimate objects. In water treatment, ozone, UV light, or chlorination kill most microorganisms. Disseminated intravascular coagulation (DIC) The formation of blood clots within blood vessels throughout the body; triggered by lipid A. DNA fingerprinting (genetic fingerprinting) Technique that identifies unique sequences of DNA to 11/30/16 8:14 PM G-7 Glossary determine paternity; connect blood, semen, or skin cells to suspects in criminal investigations; or identify pathogens. DNA microarray Numerous distinct ssDNA molecules bound to a substrate and used to probe for complementary sequences. Dolor Pain. Domain Any of three basic types of cell groupings distinguished by Carl Woese, containing the Linnaean taxon of kingdoms. Donor cell In horizontal gene transfer, a cell that contributes part of its genome to a recipient. Droplet transmission Spread of pathogens from one host to another via aerosols, which exit the body during exhaling, coughing, and sneezing and travel less than 1 meter. Dysentery Disease characterized by severe diarrhea, often with stools containing blood and mucus. Dyspnea Difficulty in breathing. Dysuria Painful urination. E site In translation, site at which tRNA exits from the ribosome. Eastern equine encephalitis (EEE) Potentially fatal infection of the brain caused by a togavirus. Ebola hemorrhagic fever Often fatal disease beginning with flu-like symptoms and progressing to severe internal hemorrhaging. Caused by Ebolavirus. Echinocandin Antifungal drug that inhibits cell wall synthesis. Echoviruses (enteric cytopathic human orphan viruses) Group of enteroviruses that cause viral meningitis and colds. Ecosystem All of the organisms living in a particular habitat and the relationships between the two. Efflux pump Transmembrane pump that removes antimicrobial drugs from a cell or from the periplasm. Ehrlichiosis (human monocytic ehrlichiosis, HME) Tick-borne disease caused by a rickettsia, Ehrli­ chia chaffeensis, manifesting with flulike signs and symptoms. Also previously used to refer to human granulocytic ehrlichiosis, now called anaplasmosis. Electrical gradient Voltage across a membrane created by the electrical charges of the chemicals on either side. Electrochemical gradient The chemical and electrical gradients across a cell membrane. Electrolyte Any hydrated cation or anion; can conduct electricity through a solution. Electron A negatively charged subatomic particle. Electron transport chain Series of redox reactions that pass electrons from one membrane-bound carrier to another and then to a final electron acceptor. Electronegativity The attraction of an atom for electrons. Elek test Immunodiffusion assay used to detect the presence of diphtheria toxin in a fluid sample. Element Matter that is composed of a single type of atom. Elephantiasis Enlargement and hardening of tissues, especially in the lower extremities, where lymph has accumulated following infection with Wuchereria bancrofti. Empyema In patients with staphylococcal pneumonia, the presence of pus in the alveoli of the lungs. Z04_BAUM7206_05_SE_GLOS.indd 7 Encephalitis Inflammation of the brain. Encystment In the life cycle of protozoa, stage in which cysts form in host tissues. Endemic In epidemiology, a disease that occurs at a relatively stable frequency within a given area or population. Endemic typhus (murine typhus) Disease transmitted by fleas and characterized by high fever, headache, chills, muscle pain, and nausea; caused by infection with Rickettsia typhi. Endocarditis Potentially fatal inflammation of the endocardium; typically caused by infection with Staphylococcus aureus or Streptococcus pneumoniae. Endocytosis Active transport process, used by some eukaryotic cells, in which pseudopods surround a substance and move it into the cell. Endoflagellum A special flagellum of spirochetes that spirals tightly around a cell rather than protruding from it. Endogenous antigen Antigen produced by microbes that multiply inside the cells of the body. Endogenous healthcare-associated infection An infection arising within a patient from opportunistic pathogens. Endoplasmic reticulum (ER) Netlike arrangement of hollow tubules continuous with the outer membrane of the nuclear envelope and functioning as a transport system. Endosome A sac formed during endocytosis containing the endocytized substance. Endospore Environmentally resistant structure produced by the transformation of a vegetative cell of the Gram-positive genera Bacillus or Clostridium. Endosymbiotic theory Proposal that eukaryotes were formed from the phagocytosis of small prokaryotes by larger prokaryotes, forming organelles. Endothermic reaction Any chemical reaction that requires energy. Endotoxins Lipopolysaccharides released from the outer membrane of the cell wall of dead and dying Gram-negative bacteria whose lipid portion (lipid A), is toxic Enrichment culture Technique used to enhance the growth of less abundant microorganisms by using a selective medium. Enterobacteriaceae (enteric bacteria) Family of ­oxidase-negative Gram-negative bacteria, which can be pathogenic. Enteroviruses Group of picornaviruses that are transmitted via the fecal-oral route but cause disease in any of a variety of target organs. Entner-Doudoroff pathway Series of reactions that catabolize glucose to pyruvic acid using different enzymes from those used in either glycolysis or the pentose phosphate pathway. Entry In virology, second stage of the lytic replication cycle, in which the virion or its genome enters the host cell. Envelope In virology, membrane surrounding the viral capsid. Environmental microbiology Branch of microbiology studying the role of microorganisms in soils, water, and other habitats. Environmental specimen Sample of material taken from such sources as ponds, soil, or air and tested for the presence of microorganisms. Enzyme An organic catalyst. Enzyme immunoassay (EIA), enzyme-linked immunosorbent assay (ELISA) A family of simple immune tests that use enzymatic products as a label and that can be readily automated and read by machine. Eosinophil Type of granulocyte that stains red to orange with the acidic dye eosin. Eosinophilia An abnormal blood condition in which the number of eosinophils is greater than normal. Epidemic In epidemiology, a disease that occurs at a greater than normal frequency for a given area or population. Epidemiology Study of the occurrence, distribution, and spread of disease in humans. Epidermis The outermost layer of the skin. Epididymitis Inflammation of the epididymis. Epitope (antigenic determinant) The three-­ dimensional shape of a region of an antigen that is recognized by the immune system. Epsilonproteobacteria Group of Gram-negative rods, vibrios, and spiraled bacteria in the phylum Proteobacteria. Erysipelas Impetigo spreading to lymph nodes, accompanied by pain and inflammation and caused by infection with group A Streptococcus. Erythema infectiosum (fifth disease) Harmless red rash occurring in children and caused by infection with B19 virus. Erythrocyte Red blood cell. Erythrocytic cycle In the life cycle of Plasmodium, stage during which merozoites infect and cause lysis of erythrocytes. Eschar Black, swollen, crusty, painless skin ulcer of anthrax. Etest Test for determining minimum inhibitory concentration; a plastic strip containing a gradient of the antimicrobial agent being tested is placed on a plate inoculated with the pathogen of interest. Ethambutol Antimicrobial drug that disrupts formation of arabinogalactan-mycolic acid by mycobacteria. Etiology The study of the causation of disease. Euglenids Protozoa that store food as paramylon, lack cell walls, and have eyespots used in positive phototaxis. Eukarya In Woese’s taxonomy, domain that includes all eukaryotic cells. Eukaryote Any organism made up of cells containing a nucleus composed of genetic material surrounded by a distinct membrane. Classification includes animals, plants, algae, fungi, and protozoa. Eutrophication The overgrowth of microorganisms in aquatic systems. Evolution Changes in the genetic makeup of a population leading to the production of new varieties. Exchange reaction Type of chemical reaction in which atoms are moved from one molecule to another by means of the breaking and forming of covalent bonds. Excystment In the life cycle of protozoa, stage following ingestion by the host, in which cysts become trophozoites. Exfoliative toxins Toxins of certain strains of Staphylococcus aureus that break down desmosomes in the skin, causing the outer layers of skin to slough off. Exocytosis Active transport process, used by some eukaryotic cells, in which vesicles fuse with the 11/30/16 8:14 PM Glossary cytoplasmic membrane and export their substances from the cell. Exoerythrocytic phase (liver phase) In the life cycle of Plasmodium (cause of malaria), stage during which sporozoites, injected into the blood by an Anopheles mosquito, infect the liver. Exogenous antigen Antigen produced by microorganisms that multiply outside the cells of the body. Exogenous healthcare-associated infection An infection caused by pathogens acquired from the health care environment. Exon Coding sequence of mRNA. Exons are connected to produce a functional mRNA molecule. Exothermic reaction Any chemical reaction that releases energy. Exotoxin Toxin secreted by a pathogenic microorganism into its environment. Experimental epidemiology The testing of hypotheses resulting from analytical epidemiology concerning the cause of a disease. Exponential (logarithmic) growth Increase in size of a microbial population in which the number of cells doubles in a fixed interval of time. Extensively drug-resistant (XDR) tuberculosis Tuberculosis caused by extensively drug-­resistant Mycobacterium. Extremophile Microbe that requires extreme conditions of temperature, pH, and/or salinity to survive. F (fertility) plasmid (F factor) Small, circular, extrachromosomal molecule of DNA coding for conjugation pili. Bacterial cells that contain an F plasmid are called F + cells and serve as donors during conjugation. FC region The stem region of an antibody. Facilitated diffusion Movement of substances across a cell membrane via protein channels. Facultative anaerobe Microorganism that can live with or without oxygen. Family Taxonomical grouping of similar genera of organisms. Fats Compounds composed of three fatty acid molecules linked to a molecule of glycerol. Fecal-oral infection Spread of pathogenic microorganisms in feces to the mouth, such as results from drinking sewage-contaminated water. Fecal transplant Injection of feces into a patient, typically via an enema tube; used to restore normal microbiota of the colon especially in recurrent cases with Clostridium difficile infection. Feedback inhibition (negative feedback) Method of controlling the action of enzymes in which the end product of a series of reactions inhibits an enzyme in an earlier part of the pathway. Fermentation In metabolism, the partial oxidation of sugar to release energy using an endogenous organic molecule rather than an electron transport chain as the final electron acceptor. In food microbiology, any desirable change to food or beverage induced by microbes. Fever Body temperature above 37°C. Fever blisters (cold sores) Painful, itchy lesions on the lips; characteristic of infection with human her­ pesvirus 1. Filariasis Infection of the lymphatic system caused by a filarial nematode. Z04_BAUM7206_05_SE_GLOS.indd 8 Filtration The passage of air or liquid through a material that traps and removes microbes. In water treatment, a process in which microbial biofilms on sand particles trap and remove other microbes. Fimbriae Sticky, proteinaceous extensions of some bacterial cells that function to adhere cells to one another and to environmental surfaces. Firmicutes Phylum of bacteria that includes clostridia, mycoplasmas, and low G+C Gram-­ positive bacilli and cocci. Flagellates Group of protozoa that possess at least one long flagellum, generally used for movement. Flagellum A long, whiplike structure protruding from a cell. Flavin adenine dinucleotide (FAD) Important vitamin-derived electron carrier molecule. Flea Vertically flattened, bloodsucking, wingless insect; vector of some pathogens. Flocculation Process in water treatment in which alum (aluminum ammonium sulfate) added to the water forms sediments with particles and microorganisms. Fluid mosaic model Model describing the arrangement and motion of the proteins within the cytoplasmic membrane. Fluorescence microscope Type of light microscope that uses an ultraviolet light source to fluoresce objects. Fluoroquinolone A type of quinolone antimicrobial that inhibits gyrase, the enzyme that corrects supercoiling by replicating bacterial DNA. Fly Insect with transparent wings that are not hidden or covered, including mosquitoes; vectors for many pathogens. Folliculitis Infection of a hair follicle by Staphy­ lococcus aureus. Fomites (fomes, sing.) Objects inadvertently used to transfer pathogens to new hosts, such as a glass or towel. Food infection Type of food poisoning in which living organisms are consumed. Food intoxication Type of food poisoning resulting from consumption of microbial toxin. Food microbiology The use of microorganisms in food production and the prevention of foodborne illnesses. Food vesicle Sac formed during endocytosis of a solid; also called an endosome or phagosome. Foodborne transmission Spread of pathogenic microorganisms in or on foods that are poorly processed, undercooked, or improperly refrigerated. Foraminifera Type of armored marine amoeba. Formed elements Cells and cell fragments suspended in blood plasma. Frameshift mutation Type of mutation in which nucleotide triplets subsequent to an insertion or deletion are displaced, creating new sequences of codons that result in vastly altered polypeptide sequences. Functional group An arrangement of atoms common to all members of a class of organic molecules, such as the amine group found in all amino acids. Fungi Eukaryotic organisms that have cell walls and obtain food from other organisms. Furuncle A large, painful, nodular extension of folliculitis into surrounding tissue; may be caused by infection with Staphylococcus aureus. G-8 Gametocyte In sexual reproduction of protozoa, cell that can fuse with another gametocyte to form a diploid zygote. Gamma interferons (IFN@G) Interferon produced by T lymphocytes and NK lymphocytes; activates macrophages and neutrophils days after an infection. Gammaproteobacteria Largest and most diverse class of Proteobacteria, including purple sulfur bacteria, methane oxidizers, pseudomonads, and others. Gas gangrene Death of muscle and connective tissues accompanied by gaseous waste, caused by Clostridium perfringens. Gaseous agent High-level disinfecting gas used to sterilize heat-sensitive equipment and large objects. Gastroenteritis Inflammation of the mucous membrane of the stomach and intestines. Gastrointestinal anthrax Disease that can be fatal without aggressive treatment; caused by ingestion of spores of Bacillus anthracis. GC content The percentage of a cell’s DNA bases that are guanine and cytosine. Gel electrophoresis Technique used in recombinant DNA technology to separate molecules by size, shape, and electrical charge. Gene A specific sequence of nucleotides that codes for a polypeptide or an RNA molecule. Gene library Collection of bacterial or phage clones, each of which carries a fragment of an organism’s genome. Gene therapy The use of recombinant DNA technology to insert a missing gene or repair a defective gene in human cells. Genera Plural of genus. Generation time Time required for a cell to grow and divide. Genetic engineering The manipulation of genes via recombinant DNA technology for practical applications. Genetic fingerprinting (DNA fingerprinting) Technique that identifies unique sequences of DNA to determine paternity; connect blood, semen, or skin cells to suspects in criminal investigations; or identify pathogens. Genetic mapping Application of recombinant DNA technology in which genes are located on a nucleic acid molecule. Genetic recombination The exchange of segments, typically genes, between two DNA molecules. Genetic screening Procedure by which laboratory tests are used to screen patient and fetal DNA for mutant genes. Genetics The study of inheritance and heritable traits as expressed in an organism’s genetic material. Genital herpes Painful, itchy lesions in or around the genitalia or anus caused by herpesviruses 1 or 2. Genome The sum of all the genetic material in a cell or virus. Genomics The sequencing, analysis, and comparison of genomes. Genotype Actual set of genes in an organism’s genome. Genus Taxonomical grouping of similar species of organisms. Germ theory of disease Hypothesis formulated by Pasteur in 1857 that microorganisms are responsible for disease. 11/30/16 8:14 PM G-9 Glossary German measles (rubella) Disease caused by infection with Rubivirus resulting in characteristic rash lasting about 3 days; mild in children but potentially teratogenic to fetuses of infected women. Giardiasis A mild to severe gastrointestinal illness caused by ingestion of cysts of Giardia intestinalis. Gingivitis Inflammation of the gums. Glomerulonephritis Deposition of immune complexes in the walls of the glomeruli—networks of minute blood vessels in the kidneys—that may result in kidney failure; typically caused by infection with group A Streptococcus. Glucocorticoids (corticosteroids) Immunosuppressive agents, including prednisone and methylprednisolone, that suppress the response of T cells. Glycocalyx (glycocalyces, pl.) Sticky external sheath of prokaryotic and eukaryotic cells. Glycolysis (Embden­Meyerhof­Parnas pathway) First step in the catabolism of glucose via respiration and fermentation. Goblet cells Mucus-secreting cells in the epithelium of mucous membranes. Golgi body In eukaryotic cells, a series of flattened, hollow sacs surrounded by phospholipid bilayers and functioning to package large molecules for export in secretory vesicles. Gonorrhea A sexually transmitted disease caused by infection with Neisseria gonorrhoeae. gp41 Antigenic HIV glycoprotein that promotes fusion of the viral envelope with a target cell. gp120 Antigenic glycoprotein that is the primary attachment molecule of HIV. Graft Tissue or organ transplanted to a new site. Graft rejection Rejection of donated tissue or organs by a transplant recipient. Graft-versus-host disease Disease resulting when donated bone marrow cells mount an immune response against the recipient’s cells. Gram-negative cell Generally, a prokaryotic cell having a wall composed of a thin layer of wall material, an external membrane, and a periplasmic space between; appears pink after the Gram-staining procedures. Gram-positive cell Prokaryotic cell having a thick wall; in bacteria, composed of a thick layer of peptidoglycan containing teichoic acids; Gram-positive cells retain the crystal violet dye used in the Gram-staining procedure, appearing purple. Gram stain Technique for staining microbial samples by applying a series of dyes that leave some microbes purple and others pink. Developed by Christian Gram in 1884. Granulocyte Type of leukocyte having large granules in the cytoplasm. Granzyme Protein molecule in the cytoplasm of cytotoxic T cells that causes an infected cell to undergo apoptosis. Graves’ disease Production of autoantibodies that stimulate excessive production of thyroid hormone and growth of the thyroid gland. Gross mutation Major change in the nucleotide sequence of DNA resulting from inversions, duplications, transpositions, or large insertions or deletions of nucleotides. Group A Streptococcus (S. pyogenes) A Gram-­ positive coccus that produces protein M and a hyaluronic acid capsule, both of which contribute to the pathogenicity of the species. Z04_BAUM7206_05_SE_GLOS.indd 9 Group B Streptococcus (S. agalactiae) A Gram-­ positive coccus that normally resides in the lower GI, genital, and urinary tracts but can cause disease in newborns. Group translocation Active process, occurring in some prokaryotes, by which a substance being actively transported across a cell membrane is chemically changed during transport. Growth An increase in size; in bacteriology, an increase in population. Growth curve Graph that plots the number in a population over time. Growth factor Organic chemical, such as a vitamin, required in very small amounts for metabolism. In immunology, an immune system cytokine that stimulates stem cells to divide, ensuring that the body is supplied with sufficient leukocytes of all types. Guanine Ring-shaped nitrogenous base found in nucleotides of DNA and RNA. Gumma Lesion that occurs in bones, in nervous tissue, or on skin in patients with tertiary syphilis. Gyrase Bacterial enzyme that relieves DNA supercoils that form when a bacterium replicates circular DNA. HAART (highly active antiretroviral therapy) A cocktail of antiviral drugs including nucleoside analogs, integrase inhibitors, protease inhibitors, and reverse transcriptase inhibitors. Habitat The physical localities in which organisms are found. Halogen One of the four very reactive, nonmetallic chemical elements: iodine, chlorine, bromine, and fluorine. Used in disinfectants and antiseptics. Halophile Microorganism requiring a saline environment (greater than 9% NaCl). Hamus Proteinaceous, filamentous, helical extension of some archaeal cells that functions to attach the cells to one another and environmental surfaces. Hansen’s disease (leprosy) Disease caused by infection with Mycobacterium leprae that produces either a nonprogressive tuberculoid form or a progressive lepromatous form that destroys tissues, including facial features, digits, and other structures. Hantavirus pulmonary syndrome (HPS) Rapid, severe, and often fatal pneumonia caused by infection with Hantavirus. Hantaviruses Group of bunyaviruses that are transmitted to humans via inhalation of virions in dried deer-mouse excreta and that cause Hantavirus pulmonary syndrome. Haploid A nucleus with a single copy of each chromosome. Haustoria Modified hyphae that penetrate the tissue of the host to withdraw nutrients. Hay fever Allergic reaction localized to the upper respiratory tract and characterized by nasal discharge, sneezing, itchy throat and eyes, and excessive tear production. Healthcare-associated disease (nosocomial dis­ ease) A disease acquired in a health care facility. Healthcare-associated infection (HAI) (nosocomial infection) An infection acquired in a health care facility. Heat fixation In microscopy, a technique that uses the heat from a flame to attach a smear to a slide. Heavy-metal ions The ions of relatively high density metals, such as arsenic and mercury, that are toxic at low concentrations. They can be used as antimicrobial agents, though they are seldom used to treat patients, because they are toxic to humans. Helminths Multicellular eukaryotic worms, some of which are parasitic. Helper T cell (Th cell, CD4+ cell) In cell-mediated immune response, a type of cell characterized by CD4 cell-surface glycoprotein; regulates the activity of B cells and cytotoxic T cells. Hemagglutinin (HA) Component of glycoprotein spikes in the lipid envelope of influenzaviruses that help them attach to pulmonary epithelial cells. Hemolytic disease of the newborn Disease that results when antibodies made by an Rh-negative woman cross the placenta and destroy the red blood cells of an Rh-positive fetus. Hemorrhagic fever Viral syndrome characterized by fever, bleeding in the skin and mucous membranes, low blood pressure, and shock. HEPA (high-efficiency particulate air) filter Filters built into biological safety cabinets; they prevent exposure to microbes by maintaining a barrier of moving filtered air across the cabinet’s openings. Hepatitis Inflammation of the liver. Hepatitis A Inflammation of the liver resulting from infection with hepatitis A virus. Hepatitis B Inflammatory condition of the liver caused by infection with hepatitis B virus and characterized by jaundice. Hepatitis C Chronic inflammation of the liver that can cause permanent liver damage or hepatic cancer; caused by infection with hepatitis C virus. Hepatitis D Inflammation of liver that can cause severe liver damage or hepatic cancer; caused by infection with hepatitis D virus. Hepatitis E (enteric hepatitis) Inflammation of the liver, which is fatal in 20% of infected pregnant women; caused by hepatitis E virus. Herd immunity Protection against illness provided to a population when a pathogen cannot spread because the majority of the group are resistant to the pathogen. Herpangina Lesions of the mouth and pharynx caused by coxsackie A virus; resemble those of herpesvirus. Herpes Painful, itchy skin lesions caused by herpesviruses. Herpes zoster (shingles) Extremely painful skin rash caused by reactivation of latent varicella-zoster virus. Heterocyst Thick-walled nonphotosynthetic cell of cyanobacteria; reduces nitrogen. Hfr (high frequency of recombination) cell Cell containing an F plasmid that is integrated into the prokaryotic chromosome. Hfr cells form pili and transfer cellular genes more frequently than normal F cells. Highly active antiretroviral therapy (HAART) A cocktail of antiviral drugs including nucleotide analogs, integrase inhibitors, protease inhibitors, and reverse transcriptase inhibitors. Histamine Inflammatory chemical released from damaged cells that causes vasodilation of capillaries. Histone Globular protein found in eukaryotic and archaeal chromosomes. 11/30/16 8:14 PM Glossary Histoplasmosis Pulmonary, cutaneous, ocular, or systemic disease found in the Ohio River valley and caused by infection with Histoplasma capsulatum. Holoenzyme The combination of an apoenzyme and its cofactors. Horizontal (lateral) gene transfer Process in which a donor cell contributes part of its genome to a recipient cell, which may be a different species or genus from the donor. Host In symbiosis, member of a parasitic relationship that supports the parasite. Human herpesviruses Group of viruses of humans that cause skin lesions, which are often creeping; diseases include herpes, chickenpox, mononucleosis, and roseola. Human immunodeficiency viruses Retroviruses that destroy the immune system. Human T-lymphotropic viruses Group of oncogenic retroviruses associated with cancer of lymphocytes. Humoral immune response (antibody immune response) The immune response centered around B lymphocytes and immunoglobulins. Hybridomas Tumor cells created by fusing antibody-secreting plasma cells with cancerous plasma cells called myelomas. Hydatid Fluid-filled. Hydatid disease Potentially fatal disease caused by infection with the canine tapeworm Echinococcus granulosus and characterized by the presence of fluid-filled cysts in the liver or other tissues. Hydrogen bond The electrical attraction between a partially charged hydrogen atom and a full or partial negative charge on a different region of the same molecule or another molecule. Hydrogen bonds confer unique properties to water molecules. Hydrolysis A decomposition reaction in which a covalent bond is broken and the ionic components of water are added to the products. Hydrophilic Attracted to water. Hydrophobia Literally, a fear of water; symptom caused by painful swallowing characteristic of rabies infection. Hydrophobic Insoluble in water. Hydrothermal vent Vent in marine abyssal zone that spews superheated, nutrient-rich water. Hydroxyl radical Most reactive of the toxic forms of oxygen. Hypersensitivity Any immune response against a foreign antigen that is exaggerated beyond the norm. Hypersensitivity pneumonitis A form of pneumonia. Hyperthermophile Microorganism requiring temperatures above 80°C. Hypertonic Characteristic of a solution having a higher concentration of solutes than another. Hyphae Long, branched, tubular filaments in the bodies of molds. Hypotonic Characteristic of a solution having a lower concentration of solutes than another. Iatrogenic infections A subset of healthcare-associated (nosocomial) infections that are the direct result of a medical procedure or treatment, such as surgery. Illness In the infectious disease process, the most severe stage, in which signs and symptoms are most evident. Z04_BAUM7206_05_SE_GLOS.indd 10 Immune complexes Antigen-antibody complexes. Immunization Administration of an antigenic inoculum to stimulate an adaptive immune response and immunological memory. Immunoblot (western blot) Variation of an ELISA test that can detect the presence of proteins, such as antibodies against multiple antigens. Immunochromatographic assay Immune test in which antigen molecules form visible immune complexes with antibodies labeled with a colored substance. Immunodiffusion An immune test in which antibodies and antigens diffuse from separate wells in agar to form a line of precipitate. Immunofiltration assay Rapid modification of ELISA test using membrane filters rather than plates. Immunoglobulin (Ig) (antibody) Proteinaceous antigen-binding molecule secreted by plasma cells. Immunoglobulin A (IgA) The antibody class most commonly associated with various body secretions, including tears and milk. IgA pairs with a secretory component to form secretory IgA. Immunoglobulin D (IgD) A membrane-bound antibody molecule found in some animals as a B cell receptor. Immunoglobulin E (IgE) Signal antibody molecule that triggers the inflammatory response, particularly in allergic reactions and infections by parasitic worms. Immunoglobulin G (IgG) The predominant antibody class found in the bloodstream and the primary defender against invading bacteria. Immunoglobulin M (IgM) The second most common antibody class and the predominant antibody produced first during a primary humoral immune response. Immunological synapse Interface between cells of the immune system that involves cell-to-cell signaling. Immunology Study of the body’s specific defenses against pathogens. Immunophilins Immunosuppressive drugs, such as cyclosporine, that inhibit T cell function. Immunotherapy Administration of antibodies (passive immunization) or dilute antigen so as to provide immunological protection against antigens. Impetigo Presence of red, pus-filled vesicles on the face and limbs of children; caused by infection with Staphylococcus aureus or Streptococcus pyogenes. Inactivated polio vaccine (IPV) Inoculum developed by Jonas Salk in 1955 for vaccination against poliovirus. Inactivated vaccine Inoculum containing either whole agents or subunits and often adjuvants. Incidence In epidemiology, the number of new cases of a disease in a given area or population during a given period of time. Inclusion Deposited substance such as a lipid, gas vesicle, or magnetite stored within the cytosol of a cell. Inclusion bodies In the life cycle of chlamydias, eukaryotic phagosomes full of chlamydial reticulate bodies. Incubation period Stage in infectious disease process between infection and occurrence of the first symptoms or signs of disease. In a laboratory culture, the period between adding a sample to a plate and the development of colonies. G-10 Index case In epidemiology, the first instance of the disease in a given area or population. Indicator organisms Fecal microbe found in the environment that reveals potential contamination by feces. Indirect contact transmission Spread of pathogens from one host to another via inanimate objects called fomites. Indirect fluorescent antibody test Immune test allowing observation through a fluorescence microscope of the presence of antigen in a tissue sample flooded with labeled antibody. Indirect selection (negative selection) Process by which auxotrophic mutants are isolated and cultured. Induced-fit model Description of way in which an enzyme changes its shape slightly after binding to its substrate so as to bind it more tightly. Inducible operon Type of operon that is not normally transcribed and must be activated by inducers. Induction In virology, excision of a prophage from the host chromosome, at which point the prophage reenters the lytic phase. Industrial microbiology Branch of microbiology in which microbes are manipulated to manufacture useful products. Infection Successful invasion of the body by a pathogenic microorganism. Infection control Branch of microbiology studying the prevention and control of infectious disease. Infectious mononucleosis (mono) Disease characterized by sore throat, fever, fatigue, and enlargement of the spleen and liver; caused by infection with Epstein-Barr virus. Influenza (flu) Infectious disease caused by two species of orthomyxoviruses and characterized by fever, malaise, headache, and myalgia; certain strains can be fatal. Innate immunity Resistance to pathogens conferred by barriers, chemicals, cells, and processes that remain unchanged upon subsequent infections with the same pathogens. Inoculum Sample of microorganisms. Inorganic chemical Molecule lacking carbon. Insect Arthropod with three distinct body divisions: head, thorax, abdomen; vectors for some helminthic, protozoan, bacterial, and viral pathogens. Insertion Type of mutation in which a base pair is inserted into a genetic sequence. Insertion sequence (IS) A simple transposon consisting of no more than two inverted repeats and a gene that encodes the enzyme transposase. Integrase Enzyme carried by the virions of HIV that allows integration into a human chromosome. Interferons (IFNs) Protein molecules that inhibit the spread of viral infections. Interleukins (ILs) Immune system cytokines that signal among leukocytes. Intermediate host In the life cycle of parasites, host in which immature forms of the parasite are present and undergoing various stages of maturation. Intoxication (bacterial) Food poisoning caused by bacterial toxin. Intron Noncoding sequence of mRNA that is removed to make functional mRNA. In-use test Method of evaluating the effectiveness of a disinfectant or antiseptic that tests efficacy under specific, real-life conditions. 11/30/16 8:14 PM G-11 Glossary Inverted repeat (IR) Palindromic sequence found at each end of a transposon. Ion An atom or group of atoms that has either a full negative charge or a full positive charge. Ionic bond A type of bond formed from the attraction of opposite electrical charges. Electrons are not shared. Ionizing radiation Form of radiation with wavelengths shorter than 1 nm that are energetic enough to create ions by ejecting electrons from atoms. Ischemia Local anemia due to interruption of blood supply by mechanical blockage. Isograft Type of graft in which tissues are moved between genetically identical individuals (identical twins). Isoniazid (INH) Antimicrobial drug that disrupts formation of arabinogalactan-mycolic acid by mycobacteria. Isotonic Characteristic of a solution having the same concentration of solutes and water as another. Isotopes Atoms of a given element that differ only in the number of neutrons they contain. Jaundice Yellowing of skin and eyes due to accumulation of bilirubin in the blood. Kelsey-Sykes capacity test Standard assessment approved by the European Union to determine the ability of a given chemical to inhibit microbial growth. Keratitis Inflammation of the cornea. Kinetoplastid Euglenozoan protozoan with a single large mitochondrion that contains an apical region of mitochondrial DNA called a kinetoplast. Kingdom Taxonomical grouping of similar phyla of organisms. Kinins Powerful inflammatory chemicals released by mast cells. Kissing bug Blood-eating insect of family Reduviidae that seemingly prefers oral blood vessels. Koch’s postulates A series of steps, elucidated by Robert Koch, that must be taken to prove the cause of any infectious disease. Koplik’s spots Mouth lesions characteristic of measles. Korarchaeota Phylum of archaea; known only from environmental RNA samples. Krebs cycle Series of eight enzymatically catalyzed reactions that transfer stored energy from acetyl-CoA to coenzymes NAD + and FAD. Lag phase Phase in a growth curve in which the organisms are adjusting to their environment. Lagging strand Daughter strand of DNA synthesized in short segments that are later joined. Synthesis of the lagging strand always moves away from the replication fork and lags behind synthesis of the leading strand. Laryngitis Inflammation of the larynx. Latency In virology, process by which an animal virus, sometimes not incorporated into the chromosomes of the cell, remains inactive in the cell, possibly for years. Latent disease Any disease in which a pathogen remains inactive for a long period of time before becoming active. Z04_BAUM7206_05_SE_GLOS.indd 11 Latent syphilis Clinically inactive phase of syphilis. Latent virus (provirus) An animal virus that remains inactive in a host cell. Lateral (horizontal) gene transfer Process in which a donor cell contributes part of its genome to a recipient cell, which may be a different species or genus from the donor. Leading strand Daughter strand of DNA synthesized continuously toward the replication fork as a single long chain of nucleotides. Legionnaires’ disease (legionellosis) Severe pneumonia caused by infection with a Legionella species, usually L. pneumophila. Leishmaniasis Any of three clinical syndromes caused by a bite from a sand fly carrying Leishmania and ranging from painless skin ulcers to disfiguring lesions to visceral leishmaniasis, which is systemic and fatal in 95% of untreated cases. Lepromin test Assay utilizing antigens of Myco­ bacterium leprae used in diagnosis of leprosy. Leprosy (Hansen’s disease) Disease caused by infection with Mycobacterium leprae that produces either a nonprogressive tuberculoid form or a progressive lepromatous form that destroys tissues, including facial features, digits, and other structures. Leptospirosis Zoonotic disease contracted by humans upon exposure to infected animals; characterized by pain, headache, and liver and kidney disease; caused by infection with Leptospira interrogans. Leukocyte White blood cell. Leukopenia Decrease in the number of white blood cells in the blood. Leukotrienes Inflammatory chemicals released from damaged cells that increase vascular permeability. Lichen Organism composed of a fungus living in partnership with photosynthetic microbes, either green algae or cyanobacteria. Light-dependent reaction Reaction of photosynthesis requiring light. Light-independent reaction Reaction of photosynthesis not requiring light and synthesizing glucose from carbon dioxide and water. Light repair Mechanism by which prokaryotic DNA photolyase breaks the bonds between adjoining pyrimidine nucleotides, restoring the original DNA sequence. Limnetic zone Sunlit, upper layer of freshwater or marine water away from the shore. Lincosamides Antimicrobial drugs that bind to the 50S subunit of bacterial ribosomes, preventing ribosomal movement. Lipid Any of a diverse group of organic macromolecules not composed of monomers and insoluble in water. Lipid A The lipid component of lipopolysaccharide, which is released from dead Gram-negative bacterial cells and can trigger shock and other symptoms in human hosts. Lipoglycopeptide Antimicrobial drugs consisting of side chains of carbohydrates (glycans) and of lipids attached to relatively short chains of amino acids (peptide). Lipopolysaccharide (LPS) (endotoxin) Toxic molecule composed of lipid A, which is the toxic portion, and polysaccharide found in the external membrane of Gram-negative cell walls. Listeriosis Disease caused by Listeria monocyto­ genes and usually manifesting as meningitis and bacteremia. Lithotroph Microorganism that acquires electrons from inorganic sources. Littoral zone Shoreline zone of freshwater or marine water. Liver phase (exoerythrocytic phase) In the life cycle of Plasmodium (cause of malaria), stage during which sporozoites, injected into the blood by an Anopheles mosquito, infect the liver. Log phase Phase in a growth curve in which the population is most actively growing. Logarithmic (exponential) growth Increase in size of a microbial population in which the number of cells doubles in a fixed interval of time. Louse (lice, pl.) Sucking or biting parasitic insects that vector some bacterial pathogens. Louse-borne relapsing fever Disease caused by Borrelia recurrentis transmitted between humans by the body louse Pediculus humanus. Lumbar puncture (spinal tap) Collection of cerebrospinal fluid from the lower vertebral column for diagnostic purposes. Lyme disease Disease carried by ticks infected with Borrelia burgdorferi and characterized by a “bull’s-eye” rash, neurologic and cardiac dysfunction, and severe arthritis. Lymph Fluid found in lymphatic vessels that is similar in composition to blood serum and intercellular fluid. Lymph nodes Organs that monitor the composition of lymph. Lymphangitis Condition in which inflamed lymphatic vessels become visible as red streaks under the skin. Lymphatic system Body system composed of lymphatic vessels and lymphoid tissues and organs. Lymphatic vessels Tubes that conduct lymph. Lymphocyte Type of small agranulocyte that originates in the red bone marrow and has nuclei that nearly fill the cell. Lymphocytic choriomeningitis (LCM) Zoonosis caused by an arenavirus; characterized by flulike symptoms and rarely by meningitis. Lymphogranuloma venereum Sexually transmitted disease caused by infection with Chlamydia tra­ chomatis and leading in some cases to proctitis or, in women, pelvic inflammatory disease. Lyophilization Removal of water from a frozen culture or other substance by means of vacuum pressure. Used for the long-term preservation of cells and foods. Lysogenic conversion Change in phenotype due to insertion of a lysogenic bacteriophage into a bacterial chromosome. Lysogenic phage Bacteriophage that does not immediately kill its host cell. Lysogenic replication cycle (lysogeny) Process of viral replication in which a bacteriophage enters a bacterial cell, inserts into the DNA of the host, and remains inactive. The phage is then replicated every time the host cell replicates its chromosome. Later, the phage may leave the chromosome. Lysogeny Lysosome Vesicle in animal cells that contains digestive enzymes. 11/30/16 8:14 PM Glossary Lysozyme Antibacterial protein secreted in sweat. Lytic replication cycle Process of viral replication consisting of five stages ending with lysis of and release of new virions from the host cell. Macrolide Antimicrobial agent that inhibits protein synthesis by inhibiting the ribosomal 50S subunits. Macrophage Mature form of monocyte, which is a phagocyte of bacteria, fungi, spores, and dust, as well as dead cells. Macule Any flat, reddened skin lesion; characteristic of early infection with a poxvirus. Magnification The apparent increase in size of an object viewed via microscopy. Major histocompatibility complex (MHC) A cluster of genes, located on each copy of chromosome 6 in humans, that codes for membrane-bound glycoproteins called major histocompatibility antigens. Malaise Feeling of general discomfort. Malaria A mild to potentially fatal disease caused by a bite from an Anopheles mosquito carrying any of four species of Plasmodium; characterized by fever, chills, hemorrhage, and potential destruction of brain tissue. Malignant tumor Mass of neoplastic cells that can invade neighboring tissues and may metastasize to cause tumors in distant organs or tissues. Marburg hemorrhagic fever Often fatal disease beginning with flu-like symptoms and progressing to severe internal hemorrhaging. Caused by Marburgvirus. Margination Process by which leukocytes stick to the walls of blood vessels at the site of infection. Mast cells Specialized cells located in connective tissue that release histamine when they are exposed to complement. Matter Anything that takes up space and has mass. MDR TB (multi-drug-resistant TB) Tuberculosis caused by Mycobacterium resistant to at least isoniazid and rifampin. Measles (rubeola) Contagious disease characterized by fever, sore throat, headache, dry cough, conjunctivitis, and lesions called Koplik’s spots; caused by infection with Morbillivirus. Mechanical vector Housefly, cockroach, or other animal that passively carries pathogens to new hosts on its feet or other body parts and is not infected by the pathogens it carries. Medical technologist An expert in health care-­ related microbiological laboratory procedures. Medium A collection of nutrients used for cultivating microorganisms. Meiosis Nuclear division of diploid eukaryotic cells resulting in four haploid nuclei. Membrane attack complexes (MACs) The end products of the complement cascade, which form circular holes in a pathogen’s membrane. Membrane filters Thin circles of nitrocellulose or plastic containing specific pore sizes, some small enough to trap viruses. Membrane filtration Direct method of estimating population size in which a large sample is poured through a filter small enough to trap cells. Membrane raft In a eukaryotic membrane, a distinct assemblage of lipids and proteins that remains together as a functional group. Z04_BAUM7206_05_SE_GLOS.indd 12 Memory B cell B lymphocyte that migrates to lymphoid tissues to await a subsequent encounter with antigen previously encountered. Memory response The rapid and enhanced immune response to a subsequent encounter with a familiar antigen. Memory T cell Type of T cell that persists in lymphoid tissues for months or years awaiting subsequent contact with an antigenic determinant matching its TCR, at which point it produces cytotoxic T cells. Meningitis Inflammation of the meninges, which can be caused by bacteria, viruses, fungi, or protozoa. Meningoencephalitis Inflammation of the brain and of its meninges. Mesophile Microorganism requiring temperatures ranging from 20°C to about 40°C. Messenger RNA (mRNA) Form of ribonucleic acid that carries genetic information from DNA to a ribosome. Metabolism The sum of all chemical reactions, both anabolic and catabolic, within an organism. Metachromatic granules Inclusions of Corynebac­ teria that store phosphate and stain differently from the rest of the cytoplasm. Metagenomic sequencing Sequencing all DNA from an environmental site to discover all microbes present. Metaphase Second stage of mitosis, during which chromosomes line up and attach to microtubules of the spindle. Also used for the comparable stage of meiosis. Metastasis The spreading of malignant cancer cells to nonadjacent organs and tissues, where they produce new tumors. Methane oxidizer Any Gram-negative bacterium that utilizes methane both as a carbon and as an energy source. Methanogen Obligate anaerobe that produces methane gas. Methicillin-resistant Staphylococcus aureus (MRSA) Strain of S. aureus that is resistant to many common antimicrobial drugs and has emerged as a major nosocomial problem. Methylation Process in which a cell adds a methyl group to one or two bases that are part of specific nucleotide sequences. Microaerophile Microorganism that requires low levels of oxygen. Microbe An organism or virus too small to be seen without a microscope. Microbial antagonism (microbial competition) Normal condition in which established microbiota use up available nutrients and space, reducing the ability of arriving pathogens to colonize. Microbial death Permanent loss of reproductive capacity of a microorganism. Microbial death rate A measurement of the efficacy of an antimicrobial agent. Microbial ecology The study of the interactions of microorganisms among themselves and their environment. Microbiome All the microbes in a particular environment. Microbiota The group of microbes that normally inhabit the body, usually without causing disease. Microglia Fixed macrophages of the nervous system. G-12 Micrograph A photograph of a microscopic image. Microorganism An organism too small to be seen without a microscope. MicroRNA (miRNA) Short (about 21-nucleotide) RNA molecule that binds to complementary segment of messenger RNA (mRNA), preventing translation. Microscopy The use of light or electrons to magnify objects. Microsporidia Unicellular, intracellular, parasitic fungi previously classified as protozoa. Middle East respiratory syndrome (MERS) Manifestation of infection by a coronavirus called MERS virus. Minimum bactericidal concentration (MBC) test An extension of the MIC test in which samples taken from clear MIC tubes are transferred to plates containing a drug-free growth medium and monitored for bacterial replication. Minimum inhibitory concentration (MIC) The smallest amount of a drug that will inhibit a pathogen. Mismatch repair Mechanism by which enzymes scan newly synthesized, nonmethylated DNA for mismatched bases, remove them, and replace them. Missense mutation A substitution in a nucleotide sequence resulting in a codon that specifies a different amino acid: What is transcribed makes sense but not the right sense. Mite Minute arachnid, which vectors Orientia, the agent of scrub typhus. Mitochondria Spherical to elongated structures found in most eukaryotic cells that produce most of the ATP in the cell. Mitosis Nuclear division of a eukaryotic cell resulting in two nuclei with the same ploidy as the original. Mold A typically multicellular fungus that grows as long filaments called hyphae and reproduces by means of spores. Molecular biology Branch of biology combining aspects of biochemistry, cell biology, and genetics to explain cell function at the molecular level, particularly via the use of genome sequencing. Molecular mimicry Process in which microorganisms with epitopes similar to self-antigens trigger autoimmune tissue damage. Molecule Two or more atoms held together by chemical bonds. Molluscum contagiosum Skin disease caused by Molluscipoxvirus; characterized by smooth, waxy papules. Monoclonal antibodies Identical antibodies secreted by a cell line originating from a single plasma cell. Monocyte Type of agranulocyte that has slightly lobed nuclei. Monoecious One individual contains both male and female organs. Monomer A subunit of a macromolecule, such as a protein. Monosaccharide (simple sugar) A monomer of carbohydrate, such as a molecule of glucose. Morbidity Any change from a state of health. Mordant In microscopy, a substance that binds to a dye and makes it less soluble. Mosquito Type of fly with bloodsucking females; vector for many pathogens. 11/30/16 8:14 PM G-13 Glossary Most probable number (MPN) method Statistical estimation of the size of a microbial population based upon the dilution of a sample required to eliminate microbial growth. Multi-drug-resistant (MDR) tuberculosis Tuberculosis caused by Mycobacterium resistant to at least isoniazid and rifampin. Multiple drug-resistant pathogens Disease-­ causing microbes insensitive to three or more different types of antimicrobial agents; colloquially called superbugs. Multiple sclerosis (MS) Autoimmune disease in which cytotoxic T cells attack and destroy the myelin sheath that insulates neurons. Mumps Disease caused by infection with the mumps virus and characterized by fever, parotitis, pain in swallowing, and, in some cases, meningitis or deafness. Mupirocin Antimicrobial drug that selectively binds to isoleucyl-tRNA synthetase, preventing this tRNA from functioning. Mutagen Physical or chemical agent that introduces a mutation. Mutant A cell with an unrepaired genetic mutation, or any of its descendants. Mutation In genetics, a permanent change in the nucleotide base sequence of a genome. Mutualism Symbiotic relationship in which both members benefit from their interaction. Myalgia Muscle pain. Mycelium Tangled mass of hyphae. Mycetismus Mushroom poisoning. Mycetoma Destructive, tumorlike infection of the skin, fascia, and/or bones of the hands or feet caused by mycelial fungi of several genera in the division Ascomycota. Mycolic acid Long carbon-chain waxy lipid found in the walls of cells in the genus Mycobacterium that makes them resistant to desiccation and staining with water-based dyes. Mycology The scientific study of fungi. Mycoplasmas Class of low G + C bacteria that lack cytochromes, enzymes of the Krebs cycle, and cell walls and are pleomorphic. Mycosis Fungal disease. Mycotoxicosis Poisoning caused by eating food contaminated with fungal toxins. Mycotoxins Secondary metabolites produced by fungi and toxic to humans. Myxobacteria Gram-negative, aerobic, soil-­ dwelling bacteria with a unique life cycle including a stage of differentiation into fruiting bodies containing resistant myxospores. Nanoarchaeum Small archaeon genus that possibly represents a fourth phylum of archaea; known only from environmental RNA samples. Narrow-spectrum drug Antimicrobial that works against only a few kinds of pathogens. Natural killer (NK) lymphocyte (NK cell) Type of defensive leukocyte of innate immunity that secretes toxins onto the surfaces of virally infected cells and neoplasms. Naturally acquired active immunity Type of immunity that occurs when the body responds to exposure to antigens by mounting specific immune responses. Z04_BAUM7206_05_SE_GLOS.indd 13 Naturally acquired passive immunity Type of immunity that occurs when a fetus, newborn, or child receives antibodies across the placenta or within breast milk. Necrosis Death of a tissue or organ. Necrotizing fasciitis Potentially fatal condition marked by toxemia, organ failure, and destruction of muscle and fat tissue following infection with group A Streptococcus. Negative feedback (feedback inhibition) Method of controlling the action of enzymes in which the end-product of a series of reactions inhibits an enzyme in an earlier part of the pathway. Negative selection (indirect selection) Process by which auxotrophic mutants are isolated and cultured. Negative stain (capsule stain) In microscopy, a staining technique used primarily to reveal bacterial capsules and involving application of an acidic dye that leaves the specimen colorless and the background stained. Negative-sense single-stranded RNA (negative single-stranded RNA, −ssRNA) Viral single-stranded RNA that is not recognized by ribosomes. Negri bodies Aggregates of virions in the brains of rabies patients. Nematodes Group of round, unsegmented helminths with pointed ends that have a complete digestive tract. Neoplasia Uncontrolled cell division in a multicellular animal. Nephelometry Automated method that measures the cloudiness of a solution by quantifying the amount of light it scatters. Neuraminidase (NA) Component of glycoprotein spikes in the lipid envelope of influenzaviruses that provides access to cell surfaces by hydrolyzing mucus in the lungs. Neutralization Antibody function in which the action of a toxin or attachment of a pathogen is blocked. Neutralization test Immune test that measures the ability of antibodies to neutralize the biological activity of pathogens and toxins. Neutron An uncharged subatomic particle. Neutrophil Type of granulocyte that stains lilac with a mixture of acidic and basic dyes. Neutrophile Microorganism requiring neutral pH. Next-generation sequencing (NGS) Automated techniques for determining large numbers of nucleotide sequences simultaneously. NGS largely replaces first-generation, Sanger sequencing methods. Nicotinamide adenine dinucleotide (NAD + ) Important vitamin-derived electron carrier molecule. Nicotinamide adenine dinucleotide phosphate (NADP + ) Important vitamin-derived electron carrier molecule. Nitrification The process by which bacteria convert reduced nitrogen compounds such as ammonia into nitrate, which is more available to plants. Nitrifying bacteria Chemoautotrophic bacteria that derive electrons from the oxidation of nitrogenous compounds. Nitrogen cycle Biogeochemical cycle involving nitrogen fixation, ammonification, nitrification, denitrification, and anammox reactions. Nitrogen fixation The conversion of atmospheric nitrogen to ammonia. NOD protein In innate immunity, intracellular receptor for microbial component. Noncommunicable disease An infectious disease that arises from outside of hosts or from normal microbiota. Noncompetitive inhibitor Inhibitory substance that blocks enzyme activity by binding to an allosteric site on the enzyme other than the active site. Noncyclic photophosphorylation The production of ATP by noncyclic electron flow. Nonionizing radiation Electromagnetic radiation with a wavelength greater than 1 nm. Nonliving reservoir of infection Soil, water, food, or inanimate object that is a continuous source of infection. Nonpolar covalent bond Type of chemical bond in which there is equal sharing of electrons between atoms with similar electronegativities. Nonsense mutation A substitution in a nucleotide sequence that causes an amino acid codon to be replaced by a stop codon. Normal microbiota Microorganisms that colonize the surfaces of the human body without normally causing disease. They may be resident or transient. Noroviruses Group of caliciviruses that cause diarrhea. Nosocomial disease (healthcare­associated disease) A disease acquired in a health care facility. Nosocomial infection (healthcare­associated infec­ tion) An infection acquired in a health care facility. Nuclear envelope Double membrane composed of phospholipid bilayers surrounding a cell nucleus. Nuclear pores Spaces in the nuclear envelope that function to control the transport of substances through it. Nucleoid Region of the prokaryotic cytosol containing the cell’s chromosome(s). Nucleolus Specialized region in a cell nucleus where RNA is synthesized. Nucleoplasm The semiliquid matrix of a cell nucleus. Nucleoside Component of a nucleotide consisting of a nitrogenous base and a five-carbon sugar. Nucleoside analog Chemical with a structure similar to a natural nucleoside. Nucleosome Bead of DNA bound to histone in a eukaryotic chromosome. Nucleotide Monomer of a nucleic acid, which is composed of a nucleoside and a phosphate. Nucleotide analog Compound structurally similar to a normal nucleotide that can be incorporated into DNA; may result in mismatched base pairing. Nucleotide excision repair (dark repair) Mechanism by which enzymes cut a section of a single strand of damaged DNA from a molecule, creating a gap that is repaired by DNA polymerase and ligase. Nucleus Spherical to ovoid membranous organelle containing a eukaryotic cell’s primary genetic material. Numerical aperture Measure of the ability of a lens to gather light. Nutrient Any chemical, such as carbon, hydrogen, and so on, required for growth of microbial populations. 11/30/16 8:14 PM Glossary Objective lens In microscopy, the lens immediately above the object being magnified. Obligate aerobe Microorganism that requires oxygen as the final electron acceptor of the electron transport chain. Obligate anaerobe Microorganism that cannot tolerate oxygen and uses a final electron acceptor other than oxygen. Obligate halophile Microorganism requiring high osmotic pressure. Occult septicemia The condition of an unidentified bacterial pathogen being present in the blood and causing signs of illness. Ocular herpes (ophthalmic herpes) Disorder characterized by conjunctivitis, a gritty feeling in the eye, and pain and characteristic of latent human herpes­ virus 1. Ocular lens In microscopy, the lens closest to the eyes. May be single (monocular) or paired (binocular). Operator Regulatory element in an operon where repressor protein binds to stop transcription. Operon A series of genes, a promoter, and often an operator sequence controlled by one regulatory gene. The operon model explains gene regulation in prokaryotes. Opportunistic pathogens Microorganisms that cause disease when the immune system is suppressed, when microbial antagonism is reduced, or when introduced into an abnormal area of the body. Opsonin Antimicrobial protein that enhances phagocytosis. Opsonization The coating of pathogens by proteins called opsonins, making them more vulnerable to phagocytes. Optimum growth temperature Temperature at which a microorganism’s metabolic activities produce the highest growth rate. Oral herpes Painful, itchy skin lesions around the mouth and lips, caused by herpesvirus 1 or 2. Oral polio vaccine (OPV) Inoculum developed by Albert Sabin in 1961 for vaccination against poliovirus. Orchitis Inflammation of a testis. Order Taxonomical grouping of similar families of organisms. Organelle Cellular structure that acts as a tiny organ to carry out one or more cell functions. Organic compounds Molecules that contain both carbon and hydrogen atoms. Organotroph Microorganism that acquires electrons from organic sources. Ornithosis (psittacosis, parrot fever) A respiratory disease of birds that can be transmitted to humans and is caused by infection with Chlamydophila psittaci. Orphan virus A virus that has not been specifically linked to any particular disease. Osmosis The diffusion of water molecules across a semipermeable membrane. Osmotic pressure The pressure exerted across a selectively permeable membrane by the solutes in a solution on one side of the membrane. The osmotic pressure exerted by high-salt or high-sugar solutions can be used to inhibit microbial growth in certain foods. Osteomyelitis Inflammation of the bone marrow and surrounding bone; often caused by infection with Staphylococcus. Z04_BAUM7206_05_SE_GLOS.indd 14 Otitis media Inflammation of the middle ear, often caused by Streptococcus pneumoniae. Oxazolidinone Antibacterial drug that inhibits initiation of polypeptide synthesis in Gram-­positive bacteria. Oxidase test Chemical test for presence of cytochrome oxidase in a cell. Oxidation lagoons Successive wastewaster treatment areas (lagoons) used by farmers and ranchers to treat animal wastes and from which water is released into natural water systems. Oxidation-reduction reaction (redox reaction) Any metabolic reaction involving the transfer of electrons from an electron donor to an electron acceptor. Reactions in which electrons are accepted are called reduction reactions, whereas reactions in which electrons are donated are oxidation reactions. Oxidative phosphorylation The use of energy from redox reactions to attach inorganic phosphate to ADP. Oxidizing agent Antimicrobial agent that releases oxygen radicals. P site In a ribosome, a binding site that holds a tRNA and the growing polypeptide. Palisade In cell morphology, a folded arrangement of bacilli. Pandemic In epidemiology, the occurrence of an epidemic on more than one continent simultaneously. Papilloma (wart) Benign growth of the epithelium of the skin or mucous membranes. Papule Any raised, reddened skin lesion that progresses from a macule; characteristic of infection with a poxvirus. Parabasalid Group of single-celled, animal-like microorganisms that contain a Golgi-like parabasal body. Paracoccidioidomycosis Pulmonary disease found from southern Mexico to South America caused by infection with Paracoccidioides brasiliensis. Parainfluenzaviruses Group of enveloped, negative ssRNA viruses that cause respiratory disease, particularly in children. Parasite A microbe that derives benefit from its host while harming it or even killing it. Parasitism Symbiotic relationship in which one organism derives benefit while harming or even killing its host. Parasitology The study of parasites. Parenteral route A means by which pathogenic microorganisms can be deposited directly into deep tissues of the body, as in puncture wounds and hypodermic injections. Paroxysmal phase In pertussis, second phase lasting two to four weeks and characterized by exhausting coughing spells. Parrot fever (psittacosis, ornithosis) A respiratory disease of birds that can be transmitted to humans and is caused by infection with Chlamydophila psittaci. Parvoviruses Group of extremely small, pathogenic ssDNA viruses. Passive immunotherapy (passive immunization) Delivery of preformed antibodies against pathogens to patients. Pasteurellaceae Family of gammaproteobacteria, two genera of which—Pasteurella and Haemophilus— are pathogenic. G-14 Pasteurization The use of heat to kill pathogens and reduce the number of spoilage microorganisms in food and beverages. Pathogen A microorganism capable of causing disease. Pathogen-associated molecular patterns (PAMPs) Molecules that are shared by a variety of microbes, are absent in humans, and trigger immune responses. Pathogenicity A microorganism’s ability to cause disease. Pelvic inflammatory disease (PID) Infection of the uterus and uterine tubes; may be caused by infection with any of several bacteria. Pentose phosphate pathway Enzymatic formation of phosphorylated pentose sugars from glucose 6-phosphate. Peptic ulcer Erosion of the mucous membrane of the stomach or duodenum, usually caused by infection with Helicobacter pylori. Peptide bond A covalent bond between amino acids in proteins. Peptidoglycan Large, interconnected polysaccharide composed of chains of two alternating sugars and crossbridges of amino acids. Main component of bacterial cell walls. Perforin Protein molecule in the cytoplasm of cytotoxic T cells that forms channels (perforations) in an infected cell’s membrane. Periodontal disease Inflammation and infection of the tissues surrounding and supporting the teeth. Periplasmic space In Gram-negative cells, the space between the cell membrane and the outer membrane containing peptidoglycan and periplasm. Peritrichous Term used to describe a cell having flagella covering the cell surface. Peroxide anion Toxic form of oxygen which is detoxified by catalase or peroxidase. Peroxisome Vesicle found in all eukaryotic cells that degrades poisonous metabolic wastes. Pertussis (whooping cough) Pediatric disease characterized by development of copious mucus, loss of tracheal cilia, and deep “whooping” cough; caused by infection with Bordetella pertussis. Petechiae Subcutaneous hemorrhages. Petri plate Dish filled with solid medium used in culturing microorganisms. pH scale A logarithmic scale used for measuring the concentration of hydrogen ions in a solution. Phaeohyphomycosis Cutaneous and subcutaneous disease characterized by lesions that can spread internally; caused by traumatic introduction of ascomycetes into the skin. Phaeophyta Brown-pigmented division of algae having cell walls composed of cellulose and alginic acid, a thickening agent. Phage (bacteriophage) Virus that infects and usually destroys bacterial cells. Phage typing Method of classifying microorganisms in which unknown bacteria are identified by observing plaques. Phagocytes Cells, often leukocytes, that are capable of phagocytosis. Phagocytosis Type of endocytosis in which solids are moved into the cell. Phagolysosome Digestive vesicle formed by the fusing of a lysosome with a phagosome. 11/30/16 8:14 PM G-15 Glossary Phagosome A sac formed by a phagocyte’s pseudopods; an intracellular food vesicle. Pharyngitis (strep throat) Inflammation of the throat, often caused by infection with group A Streptococcus. Phase microscope Type of microscope used to examine living microorganisms or fragile specimens. Phase-contrast microscope Type of phase microscope that produces sharply defined images in which fine structures can be seen in living cells. Phenol coefficient Method of evaluating the effectiveness of a disinfectant or antiseptic that compares the agent’s efficacy to that of phenol. Phenolic Compound derived from phenol molecules that have been chemically modified to denature proteins and disrupt cell membranes in a wide variety of pathogens. Phenotype The physical features and functional traits of an organism expressed by genes in the genotype. Phospholipid Phosphate-containing lipid made up of molecules with two fatty acid chains. Phospholipid bilayer Two-layered structure of a cell’s membranes. Phosphorus cycle Biogeochemical cycle in which phosphorus is cycled between oxidation states. Photoautotroph Microorganism that requires light energy and uses carbon dioxide as a carbon source. Photoheterotroph Microorganism that requires light energy and gains nutrients via catabolism of organic compounds. Photophosphorylation The use of energy from light to attach inorganic phosphate to ADP. Photosynthesis Process in which light energy is captured by chlorophylls and transferred to ATP and metabolites. Photosystem Network of light-absorbing chlorophyll molecules and other pigments held within a protein matrix on thylakoids. Phototaxis Cell movement that occurs in response to light stimulus. Phycoerythrin Red accessory pigment of photosynthesis in red algae. Phycology Study of algae. Phylum Taxonomical grouping of similar classes of organisms. Picornaviruses Family of viruses that contain positive single-stranded RNA with naked polyhedral capsids; many are human pathogens. Piedra Firm, irregular nodules on hair shafts caused by aggregates of fungal hyphae and spores. Pilus (conjugation pilus) A tubule involved in bacterial conjugation. Pinocytosis Type of endocytosis in which liquids are moved into the cell. Pinta Childhood disease caused by the spirochete Treponema carateum; characterized by hard, pusfilled lesions. Pinworm Common name of Enterobius vermicu­ laris, whose adult female has a tail like a straight pin. Pityriasis versicolor Condition characterized by depigmented or hyperpigmented patches of scaly skin resulting from infection with Malassezia furfur. Plague Disease caused by Yersinia pestis, often manifesting with enlarged lymph nodes (bubonic plague) or with severe pulmonary distress (pneumonic plague). Z04_BAUM7206_05_SE_GLOS.indd 15 Plaque In phage typing, the clear region within the bacterial lawn where growth is inhibited by bacteriophages. Plaque assay Technique for estimating phage numbers in which each plaque corresponds to a single phage in the original bacterium/virus mixture. Plasma The liquid portion of blood. Plasma cells B cells that are actively fighting against exogenous antigens and secreting antibodies. Plasmid A small, circular molecule of DNA that replicates independently of the chromosome. Each carries genes for its own replication and often for one or more nonessential functions such as resistance to antimicrobial drugs. Plasmodial slime mold (acellular slime mold) Streaming, coenocytic, colorful filaments of cytoplasm that phagocytize organic debris and bacteria. Platelet Cell fragments involved in blood clotting. Platelet activating factor (PAF) Cytokine that is a potent trigger for blood coagulation. Pleomorphic In cell morphology, term used to describe a variably shaped prokaryotic cell. Pneumococcal pneumonia Inflammation of the lungs caused by Streptococcus pneumoniae—the pneumococcus. Pneumococcus Common name of Streptococcus pneumoniae. Pneumocystis pneumonia (PJP) Debilitating fungal pneumonia that is a leading cause of death in AIDS patients and is caused by opportunistic infection with Pneumocystis jirovecii. Pneumonia Inflammation of the lungs; typically caused by infection with Streptococcus pneumoniae. Pneumonic plague Fever and severe respiratory distress caused by infection of the lungs with Yersinia pestis; fatal if untreated in nearly 100% of cases. Point mutation A genetic mutation affecting only one or a few base pairs in a genome. Point mutations include substitutions, insertions, and deletions. Polar In cell morphology, pertaining to either end of a cell, such as polar flagella. Polar covalent bond Type of bond in which there is unequal sharing of electrons between atoms with opposite electrical charges. Poliomyelitis (polio) Infection of varied degrees of severity from asymptomatic to crippling and caused by infection with poliovirus. Polluted Containing microorganisms or chemicals in excess of acceptable values. Polyenes Group of antimicrobial drugs such as amphotericin B that disrupt the cytoplasmic membrane of targeted cells by becoming incorporated into the membrane and damaging its integrity. Polymer Repeating chains of covalently linked monomers found in macromolecules. Polymerase chain reaction (PCR) Technique of recombinant DNA technology that allows researchers to produce a large number of identical DNA molecules in vitro. Polyomavirus A cancer-causing virus. Polysaccharide Carbohydrate polymer composed of several to thousands of covalently linked monosaccharides. Polyunsaturated fatty acid A long-chain organic acid with several double bonds between adjacent carbon atoms. Portal of entry Entrance site of pathogenic microorganisms, including the skin, mucous membranes, and placenta. Portal of exit Exit site of pathogenic microorganisms, including the nose, mouth, and urethra. Positive selection Process by which mutants are selected by eliminating wild-type phenotypes. Positive-sense single-stranded RNA (positivestrand RNA, +ssRNA) Viral single-stranded RNA that can act directly as mRNA. Postpolio syndrome Crippling deterioration of muscle function, likely due to aging-related aggravation of nerve damage by poliovirus. Potable Fit to drink. Pour-plate Method of culturing microorganisms in which colony-forming units are separated from one another using a series of dilutions. Pox (pocks; pustule) Any raised, pus-filled skin lesion; characteristic of infection with a poxvirus. Precursor metabolite Any of 12 molecules typically generated by a catabolic pathway and essential to the synthesis of organic macromolecules in cells. Prevalence In epidemiology, the total number of cases of a disease in a given area or population during a given period of time. Primary amebic meningoencephalopathy Often fatal inflammation of the brain characterized by headache, vomiting, fever, and destruction of neurological tissue; caused by infection with Naegleria or Acanthamoeba. Primary atypical pneumonia So-called walking pneumonia, characterized by mild respiratory symptoms that last for several weeks; caused by infection with Mycoplasma pneumoniae. Primary immunodeficiency diseases Any of a group of diseases detectable near birth and resulting from a genetic or developmental defect. Primary response The slow and limited immune response to a first encounter with an unfamiliar antigen. Primary stain In staining, the initial dye, which colors all cells. Primary syphilis Initial phase of the sexuallytransmitted disease caused by Treponema pallidum characterized by a small, painless, red, hard lesion called a chancre. Prion Proteinaceous infectious particle that lacks nucleic acids and replicates by converting similar normal proteins into new prions. Probe Nucleic acid molecule with a specific nucleotide sequence that has been labeled with a radioactive or fluorescent chemical so that its location can be detected. Probiotic Live microorganisms administered to improve health and prevent disease. Prodromal period In the infectious disease process, the short stage of generalized, mild symptoms that precedes illness. Products The atoms, ions, or molecules that remain after a chemical reaction is complete. Profundal zone Zone of freshwater or marine water beneath the limnetic zone and above the benthic zone. Proglottids Body segments of a tapeworm, produced continuously as long as the worm remains attached to its host. Progressive multifocal leukoencephalopathy (PML) Progressive, fatal disease in which JC virus 11/30/16 8:14 PM Glossary (a polyomavirus) kills cells of the central nervous system. Prokaryote Any unicellular microorganism that lacks a nucleus. Classification includes bacteria and archaea. Promoter Region of DNA where transcription begins. Prophage An inactive bacteriophage, which is inserted into a host’s chromosome. Prophase First stage of mitosis, during which DNA condenses into chromatids and the spindle apparatus forms. Also used for the comparable stage of meiosis. Prostaglandins Inflammatory chemicals released from damaged cells that increase vascular permeability. Protease Enzyme secreted by microorganisms that digests proteins into amino acids outside a microbe’s cell wall; in inflammatory reactions, chemicals released by mast cells that activate the complement system; in virology, an internal viral enzyme that makes HIV virulent. Protein A complex macromolecule consisting of carbon, hydrogen, oxygen, nitrogen, and sulfur that is important to many cell functions. Proteobacteria Phylum of prokaryotes that includes five classes (designated alpha, beta, gamma, delta, and epsilon) of Gram-negative bacteria sharing common 16S rRNA nucleotide sequences. Proton A positively charged subatomic particle, which is also the nucleus of a hydrogen atom. Proton gradient Electrochemical gradient of hydrogen ions across a membrane. Protozoa Single-celled eukaryotes that lack a cell wall and are similar to animals in their nutritional needs and structure. Provirus (latent virus) Inactive virus in an animal cell. Pseudohyphae Long cellular extension of the yeast Candida that look like the filamentous hyphae of molds. Pseudomembranous colitis Inflammation of the colon, which is covered by a membrane consisting of connective tissue and dead and dying cells; condition is last state of Clostridium difficile–associated diarrhea (C. diff.–associated diarrhea). Pseudomonad Any Gram-negative, aerobic, rod-shaped bacterium in the class Gamma proteobacteria that catabolizes carbohydrates by the EntnerDoudoroff and pentose phosphate pathways. Pseudopods Movable extensions of the cytoplasm and membrane of some eukaryotic cells. Psittacosis (ornithosis, parrot fever) A respiratory disease of birds that can be transmitted to humans and is caused by infection with Chlamydophila psittaci. Psychrophile Microorganism requiring cold temperatures (below 20°C). Psychrotolerant Ability of organisms to live in cold temperatures, though they do not grow best at these temperatures. Pulmonary anthrax Disease of the respiratory system that is usually fatal without aggressive treatment; caused by inhalation of spores of Bacil­ lus anthracis. Pure culture (axenic culture) Culture containing cells of only one species. Z04_BAUM7206_05_SE_GLOS.indd 16 Purple sulfur bacteria Group of gammaproteobacteria, which are obligate anaerobes and oxidize hydrogen sulfide to sulfur. Pustule (pox) Any raised, pus-filled skin lesion; characteristic of infection with a poxvirus. Pyoderma Any confined, pus-producing lesion on the exposed skin of the face, arms, or legs; often caused by infection with group A Streptococcus. Pyrimidine dimer Mutation in which adjacent pyrimidine bases covalently bond to one another; caused by nonionizing radiation in the form of ultraviolet light. Pyrogen Chemical that triggers the hypothalamic “thermostat” to reset at a higher temperature, inducing fever. Q fever Fever caused by the bacterium Coxiella burnetii; cause was questionable (thus “Q”) for many years. Quaternary ammonium compound (quat) Detergent antimicrobial that is harmless to humans. Quinolone An antimicrobial that inhibits gyrase, the enzyme that corrects supercoiling of replicating bacterial DNA. Quorum sensing Process by which bacteria measure their density in an environment by utilizing signal and receptor molecules. Rabies Neuromuscular disease characterized by hydrophobia, seizures, hallucinations, and paralysis; fatal if untreated. Caused by infection with the rabies virus. Radial immunodiffusion Type of immunodiffusion test in which an antigen solution is allowed to diffuse into agar containing specific concentrations of antibodies, causing a ring of precipitate to form. Radiation The release of high-speed subatomic particles or waves of electromagnetic energy from atoms. Radiolaria Amoebas with threadlike pseudopods and silica shells. Reactants The atoms, ions, or molecules that exist at the beginning of a chemical reaction. Reaction center chlorophyll In a photosystem, a chlorophyll molecule in which electrons excited by light energy are passed to an acceptor molecule that is the initial carrier of an electron transport chain. Real-time PCR Technique of recombinant DNA technology that allows researchers to determine how many copies of DNA are being made as a polymerase chain reaction (PCR) proceeds. Recipient cell In horizontal gene transfer, a cell that receives part of the genome of a donor cell. Recombinant Cell or DNA molecule resulting from genetic recombination between donated and recipient nucleotide sequences. Recombinant DNA technology Type of biotechnology in which scientists change the genotypes and phenotypes of organisms. Recombinant vaccine Vaccine produced using recombinant genetic technology. Red measles (rubeola, measles) Contagious disease characterized by fever, sore throat, headache, dry cough, conjunctivitis, and lesions called Koplik’s spots; caused by infection with Morbillivirus. Red tide Abundance of red-pigmented dinoflagellates in marine water. G-16 Redox reaction (oxidation­reduction reaction) Any metabolic reaction involving the transfer of electrons from an electron donor to an electron acceptor. Reactions in which electrons are accepted are called reduction reactions, whereas reactions in which electrons are donated are oxidation reactions. Reducing medium Special culturing medium containing compounds that combine with free oxygen and remove it from the medium. Regulatory RNA Form of ribonucleic acid used to control gene expression. Regulatory T cell (Tr cell, suppressor T cell) Thymusmatured lymphocyte that serves to repress adaptive immune responses and prevent autoimmune diseases. Release In virology, final stage of the lytic replication cycle, in which the new virions are released from the host cell, which lyses. Reoviruses Group of naked, segmented, dsRNA viruses that cause respiratory and gastrointestinal disease. Repressible operon Type of operon that is continually transcribed until deactivated by repressors. Reproduction An increase in number. Reservoir of infection Living or nonliving continuous source of infectious disease. Resolution The ability to distinguish between objects that are close together. Respiratory syncytial virus (RSV) infection Disease caused by a virus in genus Pneumovirus that causes fusion of cells in the lungs and difficulty in breathing. Responsiveness An ability to respond to environmental stimuli. Restriction enzyme Enzyme that cuts DNA at specific nucleotide sequences and is used to produce recombinant DNA molecules. Reticulate bodies Noninfectious stage in the life cycle of chlamydias. Retrovirus Any + ssRNA virus that uses the enzyme reverse transcriptase carried within its capsid to transcribe DNA from its RNA. Reverse transcriptase Complex enzyme that allows retroviruses to make dsDNA from RNA templates; used in recombinant DNA technology to make cDNA. Revolving nosepiece Portion of a compound microscope on which several objective lenses are mounted. Rh antigens Cytoplasmic membrane proteins common to the red blood cells of 85% of humans as well as rhesus monkeys. Rheumatic fever A complication of untreated group A streptococcal pharyngitis in which inflammation leads to damage of the heart valves and muscle. Rheumatoid arthritis (RA) A crippling, systemic autoimmune disease resulting from a type III hypersensitivity reaction in which antibody complexes are deposited in the joints, causing inflammation. Rhinosinusitis Inflammation of lining of nose and sinuses. Rhinoviruses Group of picornaviruses that cause upper respiratory tract infection and the “common cold.” Rhodophyta Red algae, generally containing the pigment phycoerythrin, the storage molecule floridean starch, and cell walls of agar or carrageenan. 11/30/16 8:14 PM G-17 Glossary Ribonucleic acid (RNA) Nucleic acid consisting of nucleotides made up of phosphate, a ribose pentose sugar, and an arrangement of the bases ­adenine, guanine, cytosine, and uracil. Ribosomal RNA (rRNA) Form of ribonucleic acid that, together with polypeptides, makes up the structure of ribosomes. Ribosome Nonmembranous organelle found in prokaryotes and eukaryotes that is composed of protein and ribosomal RNA and functions to make polypeptides. Riboswitch RNA molecule that changes shape in response to shifts in environmental conditions, which results in genetic regulation. Ribozyme RNA molecule functioning as an enzyme. Rickettsias Group of extremely small, Gram-­ negative, obligate intracellular parasites that appear almost wall-less. RNA polymerase Enzyme that synthesizes RNA by linking RNA nucleotides that are complementary to genetic sequences in DNA. RNA primer RNA molecule used by DNA polymerase or reverse transcriptase as a starting point for DNA synthesis. Rocky Mountain spotted fever (RMSF) Serious illness caused by infection with Rickettsia rickett­ sii transmitted by ticks and characterized by rash, malaise, petechiae, encephalitis, and death in 5% of cases. Roseola Endemic illness of children characterized by an abrupt fever, sore throat, enlarged lymph nodes, and faint pink rash; caused by infection with human herpesvirus 6. Rotaviruses Group of reoviruses that cause a potentially fatal infantile gastroenteritis. Rough endoplasmic reticulum (RER) Type of endoplasmic reticulum that has ribosomes adhering to its outer surface; these produce proteins for transport throughout the cell. R plasmid Extrachromosomal piece of DNA containing genes for resistance to antimicrobial drugs. Rubella (German measles) Disease caused by infection with Rubivirus resulting in characteristic rash lasting about three days; mild in children but potentially teratogenic to fetuses of infected women. Rubeola (measles, red measles) Contagious disease characterized by fever, sore throat, headache, dry cough, conjunctivitis, and lesions called Koplik’s spots; caused by infection with Morbillivirus. Rubor Redness. Salmonellosis A serious diarrheal disease resulting from consumption of food contaminated with the enteric bacterium Salmonella. Salt A crystalline compound formed by ionic bonding of metallic with nonmetallic elements. Sanitization The process of disinfecting surfaces and utensils used by the public. Saprobe Fungus that absorbs nutrients from dead organisms. Sarcina A cuboidal packet of cocci. Satellite virus A virus, such as hepatitis D virus, that requires glycoproteins coded by another virus to complete its replication cycle. Saturated fatty acid A long-chain, organic acid in which all but the terminal carbon atoms are covalently linked to two hydrogen atoms. Z04_BAUM7206_05_SE_GLOS.indd 17 Scabies Skin disease caused by a burrowing mite. Scalded skin syndrome Reddening and blistering of the skin caused by infection with Staphylococcus aureus. Scanning electron microscope (SEM) Type of electron microscope that uses magnetic fields within a vacuum tube to scan a beam of electrons across a specimen’s metal-coated surface. Scanning tunneling microscope (STM) Type of probe microscope in which a metallic probe passes slightly above the surface of the specimen, revealing surface details at the atomic level. Scarlet fever Diffuse rash and sloughing of skin caused by infection with group A Streptococcus. Schaeffer-Fulton endospore stain In microscopy, staining technique that uses heat to drive a malachite green primary stain into an endospore. Schistosomiasis A potentially fatal disease caused by infection with a blood fluke in the genus Schisto­ soma; may cause tissue damage in the liver, lungs, brain, or other organs. Schizogony Special type of asexual reproduction in which the protozoan Plasmodium undergoes multiple mitoses to form a multinucleate schizont. Schizont Multinucleate body that undergoes cytokinesis to release several cells. Scientific method Process by which scientists attempt to prove or disprove hypotheses through observations of the outcomes of carefully controlled experiments. Scolex Small attachment organ that possesses suckers and/or hooks used to attach a tapeworm to host tissues. Sebum Oily substance secreted by the sebaceous glands of the skin that lowers pH. Secondary immune response Enhanced immune response following a second contact with an antigen. Secondary syphilis Second phase of the sexuallytransmitted disease caused by Treponema pallidum characterized by sore throat, headache, mild fever, malaise, diseased lymph nodes, and a widespread rash. Secretory IgA The combination of IgA and a secretory component, found in tears, mucous membrane secretions, and breast milk, where it agglutinates and neutralizes antigens. Secretory vesicle In eukaryotic cells, vesicles containing secretions packaged by the Golgi body that fuse to the cytoplasmic membrane and then release their contents outside the cell via exocytosis. Sedimentation Settling of particulate matter; the first step in treating water for drinking. Segmented genome Genetic material consisting of more than one molecule of nucleic acid, used particularly for viruses. Selective medium Culturing medium containing substances that either favor the growth of particular microorganisms or inhibit the growth of unwanted ones. Selective toxicity Principle by which an effective antimicrobial agent must be more toxic to a pathogen than to the pathogen’s host. Selectively permeable In cell physiology, characteristic of a membrane that allows some substances to cross while preventing the crossing of others. Semisynthetic antimicrobial Antimicrobial that has been chemically altered. Septate Characterized by the presence of cross walls. Septic shock Extremely low blood pressure resulting from dilation of blood vessels triggered by bacteria or bacterial toxins. Septic tank The home equivalent of primary wastewater treatment, consisting of a sealed concrete holding tank in which solids settle to the bottom and the effluent flows into a leach field that acts as a filter. Septicemia (sepsis) The condition of pathogens being present in the blood and causing signs of illness. Serial dilution A stepwise dilution of a liquid culture in which the dilution factor at each step is constant. Serology The study and use of immunological tests to diagnose and treat disease or identify antibodies or antigens. Serum Blood plasma with clotting factors removed. Serum sickness Type III hypersensitivity resulting from antibodies directed against antisera. Severe acute respiratory syndrome (SARS) Manifestation of infection by a coronavirus called SARS virus. Severe combined immunodeficiency disease (SCID) Primary immunodeficiency disease in children that affects both T cells and B cells and causes recurrent infections. Sexually transmitted disease (STD) Disease resulting from a sexually transmitted infection. Sexually transmitted infection (STI) Invasion of a pathogen into the body resulting from sexual activity. Shiga toxin Exotoxin secreted by Shigella dysente­ riae that stops protein synthesis in host cells. Shigellosis A severe form of dysentery caused by any of four species of Shigella. Shine-Dalgarno sequence The sequence of nucleotides in a molecule of mRNA where the smaller ribosomal subunit initiates translation. The sequence is named for its discoverers. Shingles (herpes zoster) Extremely painful skin rash caused by reactivation of latent varicella-­zoster virus. Shock Severe disturbance of blood circulation resulting in insufficient delivery of oxygen to vital organs. Siderophore An iron-binding molecule released by some bacteria and fungi. Signs In pathology, objective manifestations of a disease that can be observed or measured by others. Silent mutation Mutation produced by base-pair substitution that does not change the amino acid sequence, because of the redundancy of the genetic code. Simple microscope Microscope containing a single magnifying lens. Simple stain In microscopy, a stain composed of a single dye such as crystal violet. Singlet oxygen Toxic form of oxygen, neutralized by pigments called carotenoids. Sinusitis Inflammation of the nasal sinuses; typically caused by Streptococcus pneumoniae. Slant tube (slant) Test tube containing agar media that solidified while the tube was resting at an angle. Slime layer Loose, water-soluble glycocalyx. 11/30/16 8:14 PM Glossary Slime mold Eukaryotic microbe resembling a filamentous fungus but lacking a cell wall and phagocytizing rather than absorbing nutrients. Sludge After primary treatment of wastewater, the heavy material remaining at the bottom of settling tanks. Small interfering RNA (siRNA) RNA molecule complementary to a portion of a molecule of mRNA, tRNA, or a gene, rendering the target ineffective. Smallpox Infectious disease eradicated in nature by 1980 and characterized by high fever, malaise, delirium, pustules, and death in about 20% of untreated cases. Smear In microscopy, the thin film of organisms on the slide. Smooth endoplasmic reticulum (SER) Type of endoplasmic reticulum that lacks ribosomes and plays a role in lipid synthesis and transport. Snapping division A variation of binary fission in Gram-positive prokaryotes in which the parent cell’s outer wall tears apart with a snapping movement to create the daughter cells. SOS response Mechanism by which prokaryotic cells with extensive DNA damage use a variety of processes to induce DNA polymerase to copy the damaged DNA. Southern blot Technique used in recombinant DNA technology that allows researchers to stabilize specific DNA sequences from an electrophoresis gel and then localize them using DNA dyes or probes. Species Taxonomic category of organisms that can successfully interbreed. Species resistance Property that protects a type of organism from infection by pathogens of other, very different organisms. Specific epithet In taxonomy, latter portion of the descriptive name of a species. Specific immunity The ability of a vertebrate to recognize and defend against distinct species or strains of invaders. Spectrum of action The number of different kinds of pathogens a drug acts against. Spinal tap (lumbar puncture) Collection of cerebrospinal fluid from the lower vertebral column for diagnostic purposes. Spiral In cell morphology, a spiral-shaped prokaryotic cell. Spirillus A stiff spiral-shaped prokaryotic cell. Spirochetes Group of helical, Gram-negative bacteria with axial filaments that cause the organism to corkscrew, enabling it to burrow into a host’s tissues. Spliceosome Protein-RNA complex that removes introns from eukaryotic RNA. Spoilage Any unwanted change to a food. Spontaneous generation The theory that living organisms can arise from nonliving matter. Sporadic In epidemiology, a disease that occurs in only a few scattered cases within a given area or population during a given period of time. Spore Reproductive cell of actinomycetes and fungi. Sporogonic phase In the life cycle of Plasmodium, stage during which sporozoites are produced in the mosquito’s digestive tract and migrate into the mosquito’s salivary glands. Sporotrichosis Subcutaneous infection usually limited to the arms and legs; lesions form around the site of infection with Sporothrix schenckii. Z04_BAUM7206_05_SE_GLOS.indd 18 Spotted fever rickettsiosis Serious illness caused by infection with a rickettsial bacterium transmitted by ticks and characterized by rash, malaise, petechiae, and encephalitis, and death in 5% of cases. Spp. Abbreviation used to indicate several species of a genus. Staining Coloring microscopy specimens with stains called dyes. Staphylococcal scalded skin syndrome (SSSS) Disease caused by exfoliative toxin of Staphylococcus aureus in which epidermis peels off. Staphylococcal toxic shock syndrome Potentially fatal syndrome characterized by fever, vomiting, red rash, low blood pressure, and loss of sheets of skin, usually caused by systemic infection with strains of Staphylococcus that produce toxic shock syndrome toxins. Staphylococcus A cluster of cocci. Starter culture Group of known microorganisms that carry out specific and reproducible fermentation reactions. Stationary phase Phase in a growth curve in which new organisms are being produced at the same rate at which older organisms are dying. Stem cells Generative cells capable of dividing to form daughter cells of a variety of types. Sterile Free of microbial contamination. Sterilization The eradication of all organisms, including bacterial endospores and viruses, although not prions, in or on an object. Steroid Lipids consisting of four fused carbon rings attached to various side chains and functional groups. Streak-plate Method of culturing microorganisms in which a sterile inoculating loop is used to spread an inoculum across the surface of a solid medium in Petri dishes. Streptococcal pharyngitis (strep throat) Inflammation of the throat, often caused by group A Streptococcus. Streptococcal toxic shock syndrome (TSS) Shock produced by toxins of Streptococcus with manifestations similar to toxic shock syndrome of Staphylococcus. Streptococcus A chain of cocci. Streptogramins Antimicrobial drugs that bind to the 50S ribosomal subunit and prevent ribosome movement along messenger RNA. Structural analog Chemical that competes with a structurally similar molecule. Sty Inflamed bacterial infection of the base of an eyelid. Subacute disease Any disease that has a duration and severity that lies somewhere between acute and chronic. Subacute sclerosing panencephalitis (SSPE) Slow, progressive disease of the central nervous system that results in memory loss, muscle spasms, and death several years after infection with a defective measles virus. Subclinical (asymptomatic) Characteristic of disease that may go unnoticed because of absence of symptoms, even though clinical tests may reveal signs of disease. Substitution Type of mutation in which a nucleotide base pair is replaced. Substrate The molecule upon which an enzyme acts. G-18 Substrate-level phosphorylation The transfer of phosphate to ADP from another phosphorylated organic compound. Subunit vaccine Type of vaccine developed using recombinant DNA technology that exposes the recipient’s immune system to a pathogen’s antigens but not the pathogen itself. Sulfonamide Antimetabolic drug that is a structural analog of para-aminobenzoic acid (PABA). Sulfur cycle Biogeochemical cycle in which sulfur is cycled between oxidation states. Superficial mycoses Fungal infections of the surface of the skin. Superinfection Condition in which a patient infected with hepatitis B virus is subsequently infected with hepatitis D virus. Superoxide radical Toxic form of oxygen that is detoxified by superoxide dismutase. Surfactant Chemical that acts to reduce the surface tension of solvents such as water by decreasing the attraction among solvent molecules. Symbiont A member of a symbiotic relationship. Symbiosis A continuum of close associations between two or more organisms that ranges from mutually beneficial to associations in which one member damages the other member. Symptoms Subjective characteristics of a disease that can be felt by the patient alone. Synapse In immunology, the interface between cells of the immune system that involves cell-to-cell signaling. Syncytium Giant, multinucleated cytoplasmic mass formed by fusion of a virally infected cell to its neighbors. Syndrome A group of symptoms, signs, and diseases that collectively characterizes a particular abnormal condition. Synergism Interplay between drugs that results in efficacy that exceeds the efficacy of either drug alone. Synthesis In virology, the production of new viral proteins and nucleic acids using the metabolic machinery of the host cell; third stage of lytic replication cycle. Synthesis reaction A chemical reaction involving the formation of larger, more complex molecules. Synthetic drug Antimicrobial that has been completely synthesized in a laboratory. Synthetic medium (defined medium) Culturing medium of which the exact chemical composition is known. Syphilis Sexually transmitted disease caused by infection with Treponema pallidum. Untreated, it can have four phases: primary syphilis, which manifests as a chancre; secondary syphilis, which typically manifests as a widespread rash; latent syphilis, which is clinically inactive; and tertiary syphilis, which involves severe hyperimmune complications. Systemic diseases Diseases caused by microbes spread via the blood and lymph that affect other body systems. Systemic lupus erythematosus (lupus) A systemic autoimmune disease in which the individual produces autoantibodies against numerous antigens, including nucleic acids. T cell T lymphocyte. Tc cell (cytotoxic T cell, CD8 + cell) In cell-mediated immune response, type of cell characterized by 11/30/16 8:14 PM G-19 Glossary CD8 cell-surface glycoprotein; secretes perforins and granzymes that destroy infected or abnormal body cells. Th cell (helper T cell, CD4+ cell) In cell-mediated immune response, a type of cell characterized by CD4 cell-surface glycoprotein; regulates the activity of B cells and cytotoxic T cells. Tr cell (regulatory T cell, suppressor T cell) Thymusmatured lymphocyte that serves to repress adaptive immune responses and prevent autoimmune diseases. T cell receptor (TCR) Antigen receptor generated in the cytoplasmic membrane of T lymphocytes. T lymphocyte (T cell) Lymphocyte that matures in the thymus and acts primarily against endogenous antigens in cell-mediated immune responses. T-dependent antibody immunity Adaptive immune response resulting in immunoglobulin production that requires the action of a specific helper T cell (Th2). T-dependent antigens Molecules that stimulate an immune response only with the involvement of a helper T cell. T-independent antibody immunity Adaptive immune response resulting in immunoglobulin production following cross-linking of BCRs on numerous B cells and lacking involvement of helper T cells. T-independent antigens Large molecules with repeating subunits that trigger an antibody immune response without the activation of T cells. Tapeworms (cestodes) Group of long, flat, and segmented helminths. Taxa Nonoverlapping groups of organisms sorted on the basis of mutual similarities. Taxis Cell movement that occurs as a positive or negative response to light or chemicals. Taxonomic system A system for naming and grouping similar organisms together. Taxonomy The science of classifying and naming organisms. Telophase Final stage of mitosis, during which nuclear envelopes form around the daughter nuclei. Also used for the comparable stage of meiosis. Temperate phage (lysogenic phage) Bacteriophage that does not immediately kill its host cell. Templating The process by which prions guide normal proteins with the same amino acid sequence as the prion to misfold into more prions. Teratogenic Characterized by an ability to cause birth defects. Terminator Region of DNA where transcription ends. Tertiary syphilis Final phase of the sexuallytransmitted disease caused by Treponema pallidum occurring years after the secondary phase and characterized by severe hyperimmune complications resulting indementia, blindness, paralysis, heart failure, or rubbery, swollen lesions called gummas. Tetanospasmin Neurotoxin of Clostridium tetani that blocks the release of inhibitory neurotransmitters in the central nervous system. Tetanus Potentially fatal infection with Clostrid­ ium tetani, which produces tetanospasmin, a potent neurotoxin. Tetracycline Antimicrobial agent that inhibits protein synthesis by blocking the tRNA docking site. Tetrad In genetics: two chromosomes, which are each made up of two DNA molecules, physically Z04_BAUM7206_05_SE_GLOS.indd 19 associated together during prophase I and metaphase I of meiosis; in cellular arrangements, four cocci remaining attached following cell division. Therapeutic index (TI) Ratio of the largest dose of a drug that is not toxic to the drug’s smallest effective dose. Therapeutic window Range of drug concentrations that are effective without being toxic to a patient. Thermal death point The lowest temperature that kills all cells in a broth in 10 minutes. Thermal death time The time it takes to completely sterilize a particular volume of liquid at a set temperature. Thermophile Microorganism requiring temperatures above 45°C. Thrombocytopenia Decrease in the number of platelets in the blood. Thylakoid In photosynthetic cells, portion of cellular membrane containing light-absorbing photosystems. Thymine Ring-shaped nitrogenous base found in nucleotides of DNA. Tick Bloodsucking arachnid, which vectors a number of bacterial and viral pathogens. Tick-borne relapsing fever Disease caused by Borrelia spp. transmitted between humans by soft ticks. Tincture Solution of antimicrobial chemical in alcohol. Titer In serology, a measure of the level of antibody in blood serum, determined by titration and expressed as a ratio reflecting the dilution. Titration Serial dilution of blood serum to test for agglutination activity. Toll-like receptors (TLRs) Integral membrane proteins that bind to specific microbial chemicals. Total magnification A multiple of the magnification achieved by the objective and ocular lenses of a compound microscope. Toxemia Presence in the blood of poisons called toxins. Toxic shock syndrome (nonstreptococcal; TSS) Potentially fatal condition characterized by fever, vomiting, red rash, low blood pressure, and loss of sheets of skin, caused by systemic infection with strains of Staphylococcus. Toxin Chemical that either harms tissues or triggers host immune responses that cause damage. Toxoid vaccine Inoculum using modified toxins to stimulate antibody-mediated immunity. Toxoplasmosis A disease affecting animals and caused by infection with Toxoplasma gondii. In humans, characterized by mild, febrile symptoms but may be fatal in AIDS patients; transplacental transmission may result in miscarriage, stillbirth, or severe birth defects. Trace element Element required in very small amounts for microbial metabolism. Trachoma Serious eye disease caused by Chla­ mydia trachomatis. Transamination Reaction involving transfer of an amine group from one amino acid to another. Transcription Process in which the genetic code from DNA is copied as RNA nucleotide sequences. Transducing phage Virus that transfers bacterial DNA from one bacterium to another. Transduction Method of horizontal gene transfer in which DNA is transferred from one cell to another via a replicating virus. Transfer RNA (tRNA) Form of ribonucleic acid that carries amino acids to the ribosome. Transformation Method of horizontal gene transfer in which a recipient cell takes up DNA from the environment. Transgenic organism Plant or animal that has been genetically altered by the inclusion of genes from other organisms. Translation Process in which the sequence of genetic information carried by mRNA is used by ribosomes to construct polypeptides with specific amino acid sequences. Transmission electron microscope (TEM) Type of electron microscope that generates a beam of electrons that passes through the specimen and produces an image on a fluorescent screen. Transport medium A special type of medium used to move clinical specimens from one location to another while preserving the relative abundance of organisms and preventing contamination of the specimen or environment. Transposition Mutation in which a genetic segment is transferred to a new position through the action of a DNA segment called a transposon. Transposon Segment of DNA found in most prokaryotes, eukaryotes, and viruses that codes for the enzyme transposase and can move from one location in a DNA molecule to another location in the same or a different molecule. Trematodes (flukes) Group of helminths that are flat, leaf-shaped, have incomplete digestive systems, and have oral and ventral suckers. Trench fever A disease common among World War I soldiers; caused by the bacterium Bartonella quintana. Trichomoniasis Inflammation of the genitalia caused by Trichomonas vaginalis. Trophozoite The motile feeding stage of a protozoa. Tubercle Hard pulmonary nodule resulting from infection with mycobacteria. Tuberculin response Type of delayed hypersensitivity reaction in which the skin of an individual exposed to tuberculosis or tuberculosis vaccine reacts to a subcutaneous injection of tuberculin. Tuberculin skin test Test for a delayed hypersensitivity reaction to a subcutaneous injection of tuberculin. Tuberculosis (TB) A respiratory disease caused by infection with Mycobacterium tuberculosis; its disseminated form can result in wasting away of the body and death. Tularemia Zoonotic disease causing fever, chills, malaise, and fatigue, and caused by infection with Francisella tularensis. Tumor In the pathology of cancer, a mass of neoplastic cells. In inflammation, a symptom of swelling (edema). Tumor necrosis factor (TNF) An immune system cytokine secreted by macrophages and T cells to kill tumor cells and to regulate immune responses and inflammation. Turbidimetry Automated method that measures the cloudiness of a solution by passing light through it. Type 1 diabetes mellitus Immunological attack on the islets of Langerhans cells in the pancreas resulting in the inability to produce the hormone insulin. 11/30/16 8:14 PM Glossary Type III secretion systems Complex proteinaceous structure that inserts into target cells, forming a channel for the secretion of bacterial toxin or enzymes. Typhoid fever Fever, headache, and malaise produced by infection with Salmonella enterica serotypes Typhi and Paratyphi; severe infections may cause peritonitis. Typhus (epidemic typhus, murine typhus, scrub typhus) A group of diseases caused by rickettsias transmitted by arthropod vectors. Uncoating In animal viruses, the removal of a viral capsid within a host cell. Unsaturated fatty acid A long-chain, organic acid with at least one double bond between adjacent carbon atoms, and thus at least one carbon atom bound to only a single hydrogen atom. Uracil Ring-shaped nitrogenous base found in nucleotides of RNA. Urinary tract infection (UTI) Invasion and multiplication of microorganisms, usually bacteria, in the kidneys, ureters, bladder, or urethra. Urticaria Hives. Use-dilution test Method of evaluating the effectiveness of a disinfectant or antiseptic against specific microbes in which the most effective agent is the one that entirely prevents microbial growth at the highest dilution. Vaccination Active immunization; specifically against smallpox. Vaccine The inoculum used in active immunization. Vacuole General term for membranous sac that stores or carries a substance in a cell. Vaginosis Noninflammatory infection of the vagina. Valence The combining capacity of an atom. Vancomycin Antimicrobial drug that disrupts formation of Gram-positive bacterial cell walls by interfering with alanine-alanine crossbridges linking N-acetylglucosamine subunits. Vancomycin-resistant Staphylococcus aureus (VRSA) Strain of S. aureus that is resistant to vancomycin and usually resistant to many common antimicrobial drugs as well. Variant Creutzfeldt-Jakob disease (vCJD) Dementia caused by a prion that destroys brain tissue such that the brain appears spongelike—full of holes. Varicella (chickenpox) Highly infectious disease characterized by fever, malaise, and skin lesions, and caused by infection with varicella-zoster virus. Varicella-zoster virus (VZV) Virus that causes chickenpox (varicella) and shingles (herpes zoster). Variola Common name for the smallpox virus. Variola major Variant of smallpox virus, which causes severe disease with a mortality rate of 20% or higher. Variola minor Variant of smallpox virus, which causes less severe disease and mortality rate of less than 1%. Vector In genetics and recombinant DNA technology, nucleic acid molecule such as a viral genome, transposon, or plasmid that is used to deliver a gene into a cell. In epidemiology, an animal (typically an arthropod) that transmits disease from one host to another. Z04_BAUM7206_05_SE_GLOS.indd 20 Vegetations Bulky masses of platelets and clotting proteins that surround and bury the bacteria involved in endocarditis. Vehicle transmission Spread of pathogens via air, drinking water, and food, as well as bodily fluids being handled outside the body. Venezuelan equine encephalitis (VEE) Potentially fatal infection of the brain caused by a togavirus. Vesicle General term for membranous sac that stores or carries a substance in a cell; in human pathology, any raised skin lesion filled with clear fluid. Viable plate count Estimation of the size of a microbial population based upon the number of colonies formed when diluted samples are plated onto agar media. Vibrio A slightly curved rod-shaped prokaryotic cell. Viral gastroenteritis Inflammation of the mucous membrane of the stomach and intestines, caused by a viral pathogen. Viral hemagglutination inhibition test Immune test commonly used to detect antibodies against influenza, measles, and other viruses that naturally agglutinate red blood cells. Viral neutralization Test of serum for the presence of antibodies against a particular virus in which test serum is mixed with the virus, and then the mixture is added to a cell culture. Survival of the cells indicates antibodies in the serum neutralized the viruses. Viremia Viral infection of the blood. Viridans streptococci Group of alpha-hemolytic streptococci, which produce a green pigment when grown on blood media and normally inhabit the mouth and throat, as well as the GI, genital, and urinary tracts. Virion A virus outside of a cell, consisting of a proteinaceous capsid surrounding a nucleic acid core. Viroid Extremely small, circular piece of RNA that is infectious and pathogenic in plants. Virulence A measure of pathogenicity. Virulence factors Enzymes, toxins, and other factors that affect the relative ability of a pathogen to infect and cause disease. Virus Tiny infectious acellular agent with nucleic acid surrounded by proteinaceous capsomeres that form a covering called a capsid. Viviparity Process by which live offspring are produced in the body of a mother. Wandering macrophage Type of macrophage that leaves the blood via diapedesis to travel to distant sites of infection. Warts (papillomas) Benign epithelial growths caused by papillomaviruses. Wastewater (sewage) Any water that leaves homes or businesses after being used for washing or flushed from toilets. Water mold Eukaryotic microbe resembling a filamentous fungus but having tubular cristae in their mitochondria, cell walls of cellulose, two flagella, and true diploid bodies. Waterborne transmission Spread of pathogenic microorganisms via water. Wavelength The distance between two corresponding points of a wave. G-20 Wax Alcohol-containing lipid made up of molecules with one fatty acid chain. West Nile encephalitis Potentially fatal infection of the brain caused by an arbovirus in the family Flaviviridae. Western blot test (immunoblot) Variation of an ELISA test that can detect the presence of antibodies against multiple antigens; used to verify the presence of antibodies against HIV in the serum of individuals who have tested positive by ELISA. Western equine encephalitis (WEE) Potentially fatal infection of the brain caused by a togavirus. Whitlow Inflamed blister that may result from infection with human herpesvirus 1 or human herpes­ virus 2 via a cut or break in the skin. Whooping cough (pertussis) Pediatric disease characterized by the development of copious mucus, loss of tracheal cilia, and deep “whooping” cough; caused by infection with Bordetella pertussis. Wild-type cell A cell normally found in nature (in the wild); a nonmutant. Wound Trauma to body’s tissue. XDR-TB Tuberculosis caused by extensively drug-resistant Mycobacterium. Xenodiagnosis Method of diagnosing Chagas’ disease in which an uninfected Triatoma vector is allowed to feed on a patient. Subsequent presence of trypanosomes in the bug’s gut indicates the patient is infected. Xenograft Type of graft in which tissues are transplanted between individuals of different species. Xenotransplant Technique involving recombinant DNA technology in which human genes are inserted into animals to produce cells, tissues, or organs that are then introduced into the human body. Yaws Large, destructive, pain-free lesions of the skin, bones, and lymph nodes caused by Treponema pallidum pertenue. Yeast A unicellular, typically oval or round fungus that usually reproduces asexually by budding. Yellow fever Often fatal hemorrhagic disease contracted through a mosquito bite carrying a flavivirus. Zetaproteobacteria Class of usually autotrophic, Gram-negative bacteria in the phylum Proteobacteria discovered through metagenomic sequencing. Zone of inhibition In a diffusion susceptibility test, a clear area surrounding the drug-soaked disk where the microbe does not grow. Zoonoses Diseases that are naturally spread from their usual animal host to humans. Zygomycoses Opportunistic fungal infections caused by various genera of fungi classified in the division Zygomycota. Zygomycota Division of fungi including coenocytic molds called zygomycetes. Most are saprobes. Zygosporangium Thick, black, rough-walled sexual structure of zygomycetes that can withstand desiccation and other harsh environmental conditions. Zygospores Haploid spores formed from the surviving nuclei within zygosporangia. Zygote In sexual reproduction, diploid cell formed by the union of gametes. 11/30/16 8:14 PM