Lecture 1: Major Categories Of Microbiology

LECTURE 1 5 Major Categories of Microbiology 1.​ Bacteriology: study of bacteria 2.​ Virology: study of viruses 3.​ Mycology: study of fungi and yeast 4.​ Parasitology: study of protozoa (1 celled organisms, ex. amoeba), metazoa (worms), and ectoparasites 5.​ Immunology: study of immunity Innate Immunity Adaptive Immunity The immunity you’re born with Created in response to exposure to a foreign substance - Rapid - Non-specific response to foreign molecules - Response fixed (non adaptive) - Delayed response - Highly specific response to antigen - No immunological memory - Response adaptive (chances over time) - Immunological memory (body develops memory cells that remember infections agents) Ex. Skin, mucous, phagocytes Ex measles vaccine Prokaryotes vs Eukaryotes Prokaryotes means pre nucleus Eukaryotes means true nucleus 1. DNA not in enclosed envelope 2. DNA not associated with histones 3. Lack membrane-enclosed organelles (e.g., Golgi apparatus) 4. Cell walls almost always contain peptidoglycan 5. Divide by binary fission 6. All proteins start with the amino acid formylmethionine 7. Large (10=100 micrometers) 1. DNA in cell nucleus, bounded by a nuclear membrane 2. DNA in nucleus found in multiple chromosomes 3. DNA associated with histones (chromosomal proteins) 4. Number of membrane enclosed organelles (e.g., Golgi apparatus, mitochondria, etc.) 5. Cell walls, if present, are very simple 6. Usually divide by mitosis 7. All proteins start with the amino acid methionine 8. Small General Introduction A.​ Size of Microorganisms Extremely Small Small Medium Large Prions—infectious protein molecules (not microorganisms) that have been misfolded and do not function properly (e.g., Mad Cow Disease) Microbes (i.e., virus, certain special bacteria such as mycoplasma and chlamydia) “Microbes” (i.e., amoeba, algae, bacteria, large viruses) “Microbes” (lice, worms) . 30–100 nanometers (.01–.1 micron) 1–100 microns >1000 microns (1 mm) Most of the disease-producing (pathogenic) bacteria encountered in infectious diseases are in this category (e.g., Streptococcus, Staphylococcus, Salmonella, etc.) Visible with an electron microscope Visible with a light microscope Visible with naked eye B.​ Bacterial Naming Most commonly, organisms are classified into families based on the relatedness of their ribosomal RNA or rRNA (a stable sequence appropriate to use for classifying organisms). Bacteria are named by: Genus, species, and subspecies (in special cases) C.​ Bacterial Shape (Morphology. Genus tells us bacterial shape and how they are grouped) Differentiation of Bacterial Organisms Differentiation of organisms is important for the classification of bacteria into functional groups. ●​ Structures associated with prokaryotes determine the characteristics of bacteria with respect to: ○​ staining reactions such as the Gram stain ○​ mechanisms of pathogenesis (how bacteria exert deleterious effects on the host) ○​ choice of antimicrobial drugs. ●​ The most important practical distinction to know about bacteria is the staining characteristic—the Gram stain. Staining help us tell bacteria apart if they are the same shape: 1.​ Gram stain: divides most bacteria into 2 groups based on cell wall structure (amount of peptidoglycan (structural mesh) in the bacterial cell wall a.​ Gram + : retain purple stain (ex. Streptococcus pneumoniae) b.​ Gram - : lose purple stain (ex. Escherichia coli) ​ ​ **Note: Knowing which can help steer antibiotic treatment b/c gram stain is still used as one of the major diagnostic test to identify disease-causing bacteria** ​ 2.​ Acid Fast Stain: used for mycobacterium (we can’t use gram stain for this bacteria b/c they have a different type of cell wall that doesn’t allow stain to get in) -​ -