MCS - Introduction to Microbiology

1. Microbiology: the study of the biology of microscopic organism. 2. Name some examples of microscopic organism ?: viruses, bacteria, algae, fungi, slime moulds, and protozoa. 3. Difference between Eukaryotic and Prokaryotic cells ?: Prokaryotes have no nucleus while Eukoryotes do. 4. Features of a prokaryote cell ?: - small cells (< 5 µm) - unicellular - no membrane-bound organelles or nucleus - circular DNA - Small ribosomes 70s - no cytoskeleton - cells divide by binary fission - asexual reproduction 5. Features of a Eukaryotic cell ?: - larger cells (> 10 µm) - multicellular - has a nucleus and membrane-bound organelles - Linear DNA that bind to proteins to form chromatin - Large ribosomes 80s - has a cytoskeleton - cells divide by mitosis or meiosis - asexual and sexual reproduction 6. Gram positive bacteria description: - much thicker peptidoglycan layer (therefore able to retain initial crystal violet stain and appears purple under a microscope) -provides protection from environmental stresses - composed of 20 layers of peptidoglycan (90% of the cell wall) and teichoic acid 7. Teichoic acid: - either polymers of glycerol phosphate or ribitol phosphate - Some are covalently linked to the NAM residues of peptidogycan or to lipids in plasma membrane (lipoteichoic acid) - Up to 50% of the Gram positive wall may be teichoic acids - they are an essential part of the Gram positive cell wall structure because they anchor the wall to the cell - the ones that protude out of the cell provide an overall negative charge 8. How does providing an negative charge aid bacteria ?: They are able to evade phagocytosis 9. Gram negative bacteria description: - Thin peptidoglycan layer (10% of the cell wall) = Some of the peptidoglycan forms a single layered sheet around the cell and the rest, with minimal cross-linking, forms a gel-like substance which is called the periplasmic gel. 1 / 10 - outer lipopolysaccharide membrane - they are not susceptible to some antibiotics such as penicillin or lysosomes in tears - has a periplasm 10. Periplasm: - contains various proteins including enzymes with hydrolytic functions (e.g akaline phosphatase) - antibiotic-inactivating enzymes (e.g. ²lactamases) - various binding proteins with roles in chemotaxis and active transport of solutes into the cell. 11. Outer membrane of Gram negative bacteria function: - creation of the periplasm - provision of an outer surface with a strong negative charge - acts as a permeability barrier against host lysozyme, bile salts, digestive enzymes & many antibiotics 12. Gram -ve bacteria lipopolysaccharide layer: - called endotoxin - extremely toxic to humans and other animals - minute amounts of LPS can produce fever and shock 13. What does the lipopolysaccharide layer consist of ?: - Lipid A = phospholipid containing glucosamine (toxic component) rather than glycerol - Core polysaccharide = Contains some unusual carbohydrate residues e.g Salmonella contains keto deoxyoctonate, heptoses, glucose, galactose & N-acetylgucosamine (NAG) - O-antigen polysaccharide= major surface antigen of Gram -ves galactose, glucose, rhamnose & mannose (hexoses) & unusual dideoxy sugars e.g abequose, colitose, paratose or tyvelose 14. Lipid A: a phospholipid containing glucosamine (toxic component) rather than glycerol 15. Core polysaccharide: Contains some unusual carbohydrate residues e.g Salmonella contains keto deoxyoctonate, heptoses, glucose, galactose & N-acetylgucosamine (NAG) 16. O-antigen polysaccharide: major surface antigen of Gram -ves galactose, glucose, rhamnose & mannose (hexoses) & unusual dideoxy sugars e.g abequose, colitose, paratose or tyvelose 17. Function of Lipopolysaccharide in the outer membrane: - acts as barrier that blocks the passage of most organic molecules into the cell = therefore Gram negatives must make provision for the rapid entry of nutrients - Special proteins form pores through the outer membrane called porins = allow hydrophilic molecules of low MW to diffuse into the periplasm. 2 / 10 18. what occurs during the Lag phase for Bacteria?: Metabolic activity of the cells increases due to synthesis of enzymes, proteins, DNA or increase in the cell size. 19. what occurs during the log phase (exponential)?: Cell population doubles at regular intervals. 20. what occurs during the stationary phase?: No net increase or decrease in the cell number. 21. what occurs during the death phase?: Cell viability decreases exponentially. The death rate exceeds the cell division rate. 22. Generation time: Time taken for a bacterial cell or population to double. - vary between 12 mins - 24 hrs for bacteria - e.g., E.coli under laboratory conditions has generation time of 15-20 minutes. 23. How to calculate the mean generation time ?: - (t x log10 2) ÷ (log10 b - log10 a) t = (tb - ta) tb = time in minutes at the end of the selected growth phase ta = time in minutes at the start of the selected growth phase log10 b = log10 cell number at the end of the selected growth phase log10 a = log10 cell number at the start of the selected growth phase 24. Where is the genetic material of prokaryotes found?: The chromosomes are located inside an area in the cytoplasm called the nucleoid. 25. Describe the process of Binary fission for bacterial reproduction ?: - DNA of the bacterium replicates by dividing into two. - bacterial cell elongates and splits into two daughter cells - each daughter cell has identical DNA to the parent cell so it is a clone of the parent cell 26. Benefits of Binary fission: - only one parent is needed to reproduce - division is rapid ( E.coli divides every 20 mins) - daughter cells are clones of their parent cells - lots of daughter cells produced in limited time 27. Cons of binary fission: - they lack genetic recombination so the bacterial species can not survive changes in their environment so the whole population is wiped out. 28. semi-conservative replication: - separation of the two strands of nucleotides - template strand formed from both strands - free nucleotides are then able to bind to and create two identical daughter strands - each daughter strand has half of the DNA from the original strand and half newly-formed DNA. 3 / 10 29. How can bacteria be treated with Penicillin?: It prevents cell wall synthesis. It affects the formation of the cell wall during the growth and division of bacterial cells. 30. How can bacteria be treated with chloramphenicol?: It prevent protein synthesis. 31. How can bacteria be treated with polymyxins?: They disrupt the membrane of the gram negative bacteria. 32. How can bacteria be treated with fluoroquinolones?: It targets DNA synthesis. 33. Protective characteristics of virus structure ?: - Genome (nucleic acid core) = contains genetic information as RNA or DNA - Capsid = this is often targeted by the host's immune response. Its protein coat acts as protection during transmission - Outer envelope 34. How can Acyclovir be used to treat viruses?: - It is an antiviral medication - primary use = treats herpes simplex virus infections, chickenpox, and shingles 35. What else can Acyclovir be used to treat?: - prevention of cytomegalovirus infections following transplant - severe complications of Epstein-Barr virus infection. 36. What is AZT (zidovudine)?: - antiretroviral medication - used for viruses with RNA in their nucleic acid instead of DNA - used to prevent + treat HIV/AIDS - generally recommended for use in combination with other antiretrovirals. 37. bidirectional replication: replicating DNA in two directions at the same time. This is from the origin of replication in the circular DNA found in most bacteria. 38. Horizontal Gene transfer: - Direct transfer of genetic material (DNA) between different genomes. - The movement of genetic material between unicellular and/or multicellular organisms other than by the transmission of DNA from parent to offspring (vertical). 39. What is the primary mechanism for the spread of antibiotic resistance in bacteria?: Horizontal gene transfer as it plays an important role in the adaptation and evolution of organism. 40. What common techniques can be used to introduce a foreign gene into host cells ?: - Transfection - Transduction - Conjugation - Transformation 41. Transfection: The process of introducing foreign nucleic acids into cells by non-viral methods to produce genetically modified cells. 4 / 10 42. Transduction: The process whereby foreign DNA is introduced into another cell via a viral vector. 43. Conjugation: The process where one bacterium transfers genetic material to another through direct contact. 44. Transformation: The process of DNA uptake by the bacteria from the surrounding environment. 45. Describe the process of bacterial conjugation ?: - The bacteriophage first infects the donor cells and begins the lytic cycle - virus then develops its components using the host cell machinery - host cell DNA is hydrolysed into small fragments by viral enzymes - small pieces of bacteria DNA is now integrated into viral genome - virus then infects another bacteria and transfers the DNA into it. 46. What occurs during Bacterial conjugation ?: - One bacterium serves as the donor of the genetic material - The other serves as the recipient. - Donor bacterium carries a DNA sequence called the fertility factor, or F-factor. 47. Ways to make artificially competent bacteria ?: - Use of chemicals - Electroporation (use of electical pulses) 48. How to Identify Transformed Cells?: - some bacteria are grown on an agar medium with antibiotics - the bacteria containing the antibiotic resistance gene will grow in the presence of antibiotics - cells that survive and grow are transformed cells. The others are non-transformed. 49. Name an example of a transgenic microorganism ?: The bacterial strain that produces human Insulin (genetic engineering). - Made from Recombinant DNA of Bacteria 50. What percentage of bacteria are human pathogens ?: 1% 51. What percentage of bacteria are plant diseases ?: 4 % 52. What percentage of bacteria are non-pathogenic ?: 95 % 53. Examples of foods and drinks that are produced by Microbes ?: - cheese - pickles - sauerkraut - green olives - yogurt - soy sauce - vinegar - bread - beer - wine 5 / 10 - alcohol - mushrooms 54. Probiotics: - Mixture of live bacteria and/or yeast that lives in your body. - they are good bacteria that prevents pathogens from gaining access to our body. 55. How can probiotics be used to help during the flu season ?: Prevents the replication of viruses in the body = stimulates the secretion of antibodies. These antibodies: 1. protect against respiratory infections. 2. Maintain a healthy gut microbiome. 56. Probiotic strains that can be used for treatment of flu-like sickness ?: Lactobacillus rhamnosus, LGG and Bifidobacterium, BB-12. 57. Insect Pest Control Bacteria: - Bacillus thuringiensis - it is used to control insect population 58. What is Bioremediation ?: Decontamination of hazardous wastes - Microbes used to clean up pollutants and toxic wastes Bacteria used : Pseudomonas sp. , Bacillus sp. 59. Bacteria: Unicellular prokaryotes with peptidoglycan cell walls 60. Archaea: e.g., thermophiles, halophiles Unicellular prokaryotes with no peptidoglycan cell wall 61. Name some Eukaryote kingdoms ?: Protista, Fungi, Plantae, Animalia 62. What does the bacterial world consist of?: bacteria archaea protozoa fungi algae nematodes 63. What is the function of Bacteria cell membrane ?: selective permeability 64. What is the function of Bacteria cell wall ?: - it is rigid and provides support and protection from mechanical disruption + burst by osmotic pressure - maintains a high conc of solutes inside the cell - surrounds all bacterial cells except mycoplasmas - gives the cell its shape & rigidity 65. Benefits of a cell wall for bacteria ?: - Gram staining - provides ligands for adherence to host cell receptors - provides ligands for receptor sites for drugs or viruses - it provides immunological distinction between bacteria 66. Describe peptidoglycan: - consists of a linear glycan chain of two alternating sugar derivatives: NAG (N-acetylglucosamine) 6 / 10 NAM (N-acetylmuramic acid) - strong Beta 1-4 glycosidic bonds but do not give rigidity in all directions = due to this the glycan chains are cross linked with tetrapeptide amino acid side chains 67. peptidoglycan sac: This is when cross-links between other tetrapeptides connect the peptidoglycan sheets to form a 3-D, rigid matrix which forms a scaffold-like giant molecule. 68. What is the function of Bacteria Ribosomes ?: Protein synthesis 69. What is the function of Bacteria inclusion bodies ?: - storage of carbon, phosphorous, & other substances - not essential for cell survival - provide energy and nutrients (can act as a reserve) - reserves increase under favourable conditions and decrease when conditions are adverse - e.g., Volutin granules consist of high energy phosphate reserves 70. What is the function of Bacteria Nucleoid ?: Genetic material 71. Capsules & Slime Layers: resistance to phagocytosis, adherence to surfaces 72. Flagella: aids motility 73. Endospore: - survival under harsh conditions - examples include - bacillus and clostridium - show no signs of life (cryptobiotic or dormant) - small metabolically-inert cells - thick cell walls formed by some Gram positive bacteria in adverse conditions - spores appear oval or round within the vegetative cells - spores are resistant to high temps, irradiation, strong acids, disinfectants 74. What is the advantage of the Endospore ?: Resistant to: - High temperatures - Irradiation - Strong acids - Disinfectants 75. Pili (fimbriae): - hair-like projections - found on the surface of cells - composed of molecules of a protein called pilin - Fimbriae/common pili - cover cell surface + act as adhesions = allows bacteria to colonise surface and cells 76. Neisseria gonorrhoeae (pili Q's): - adheres strongly to human cervical or urethral epithelium using lots of pili. 77. Streptococcus pyogenes (pili Q's): - have pili all round the cell wall = protects it against phagotrophic engulfment 7 / 10 78. What does the cell envelope consist ?: Capsule, cell wall, plasma membrane 79. Cell membrane in bacteria: - the phospholipid bilayer contains hopanoids = to provide some rigidity - acts as a selective permeability barrier = regulates the movement of substances in and outside of the cell. - it regulates essential nutrient uptake by active transport mechanisms - Extracellular enzymes are secreted from the cell membrane = e.g., amylase is excreted and will break down important food sources and make them accessible to the bacteria. - Cell-wall components are synthesised in and exported from the cell membrane, and energy generating functions e.g., respiration (ATP-synthesizing ATPase) take place here. 80. Capsule for bacteria: - a hydrophilic gel - True capsule = material is defined in shape - Slime layer (biofilm) = amorphous in appearance - examples of capsules made from polypeptides: 1. Bacillus anthracis = capsule consisting of polyglutamic acid 2. Pseudomonas aeruginosa = capsule called mannuronic acid which is also referred to as alginate - Can protect bacteria: Staphylococcus aureus can avoid phagocytosis due to the present of a true capsule - Capsules assist in colonisation = by assisting the cell to attach to surfaces and allow bacteria to form biofilms. 81. Describe the Nucleoid in Prokaryotic cells ?: - Prokaryotic DNA = extensively folded & condensed into a nucleoid structure which does not have a nuclear membrane. - It is single (haploid) circular chromosome consisting of double-stranded DNA which encodes all the genes required for essential cell functions. - Extra-chromosomal genetic elements exist called plasmids. 82. Antibiotic action in bacteria: - Bacterial ribosomes are targeted by aminoglycoside antibiotics (e.g gentamicin, streptomycin). - These drugs bind irreversibly to the 30S subunit of the bacterial ribosomes, inhibit RNA translation and bacterial protein synthesis. 83. Flagellum hair parts:: A - monotrichous (one hair) B - Lophotrichous (tuft of hair) C - Amphitrichous (Hair on both sides) D - Peritrichous (around the cell) e.g., salmonella 84. Chemotaxis: Motile response to certain chemicals; Bacteria are attracted to useful substances (e.g. nutrients) or repelled from toxic substances 8 / 10 85. Phototaxis: motile response to light 86. Aerotaxis: motile response to oxygen 87. Magnetotaxis: motile response to magnetic fields which is useful behaviour for sourcing ferrous metals. 88. flagellin: This single protein forms the H-antigen of the bacterium which is often used for serological identification of bacterial strains e.g. Kauffman- White identification of Salmonella species. 89. Bacillus anthracis: can produce a polypeptide capsule consisting of polyglutamic acid 90. Pseudomonas aeruginosa: produce a polysaccharide capsule called mannuronic acid which is also referred to as alginate 91. How do Flagella move?: - propel the cell by rotating at the point of insertion in the cell envelope. - allow tactic behavior - ability to move in response to environmental stimuli 92. How to diagnose Mycobacterium tuberculosis ?: - mycobacteria fail to stain because of their unique cell wall structure and therefore an ACID FAST is used. 93. Describe the stages of Peptidoglycan Synthesis ?: 1. Autolysins (Bacterial enzymes) break the glycosidic bonds between the peptidoglycan monomers and break the peptide cross-bridges. 2. Peptidoglycan monomers are then synthesised in the cytosol and carried across the cytoplasmic membrane by bactoprenols 3. Transglycosidase enzymes insert and link new peptidoglycan monomers into the breaks in the growing peptidoglycan chains 4. Transpeptidase enzymes reform the peptide cross-links between the rows and layers of peptidoglycan to make the walls strong 94. Antibiotic action against the bacterial cell wall: - B-lactam antibiotics (penicillin) inhibit transpeptidation - Newly synthesised peptidoglycan cannot be cross linked - Lattice weakens resulting in cell lysis 95. What is the effect of Bacitracin on bacteria cell wall ?: blocks bactoprenols and this will cause bacterial cells to lyse. 96. Thermophilic bacteria: - live in thermal vents at the bottom of the deep ocean where light does not penetrate - thrive in hot environments - produce biomass for creatures that live in those vents 9 / 10 97. Chemoheterotrophic: - An organism that obtains its energy from the oxidation of organic compounds - e.g., bacteria, fungi - can be involved in processes such as, 1. waste water treatment 2. reclamation of contaminated water and land after oil pollution 98. How many microbes does a healthy human have ?: 1 x 10 ^14 microbes 99. Microflora of anatomical sites ?: - called normal flora or indigenous microbiota - have little or no effect on us - do not provide positive effects 100. Escherichia coli: - located in the human gut - thrives in warm anaerobic environments - consumes some ingested food - produces as a by-product of metabolism, excessive amounts of B vitamins and vitamin K ( excreted out of the cell) - essential for good human health 101. How does E.coli protect the body from infection ?: - adheres to cells of the intestinal lining - forms a barrier to the colonization of pathogenic microbes 102. Primary metabolites: - a compound directly involved in normal growth, development and reproduction. e.g., amino acids, vitamins, citric acid, acetic acid, ethanol 103. Secondary metabolites: - a compound that is not directly involved in normal growth, development, and reproduction. - e.g., antibiotics 104. Antibiotics: A substance produced by a micro-organism which at low concentrations kill or inhibit the growth of other micro-organisms. 105. The processes of food decomposition: putrefaction - meat decomposition souring - milk, fruit juices rotting - fruit and vegetables rancidity - butter spoilage mouldy - fungal growth on food slimy - bacterial surface growth 106. Pathogen: An organism capable of causing disease in host. 10 / 10