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Microbiology
Unit 4
| Question | Answer |
|---|---|
| Basic defenses of the digestive system | Saliva, stomach acid, Paneth cells, Payer's patch, M cell, mucous & rapid movement. |
| Saliva | Best. Full of bacteria. Millions/mL. |
| Stomach acid | Kills most microbes. HCl and rapid flux. |
| Paneth Cells | Phagocytic. Produce lysozyme & antibacterial proteins called defensins. |
| M Cells on Payer's patch | A lymphoid organ that has M Cells that take up antigens & transfer them to lymphocytes & antigen-presenting cells in the Peyer's patch (dedritic & B-cells). Antibodies are formed (mostly IgA for mucosal immunity). |
| Large intestine | In the large intestine, large #s of anaerobes aid in digestion & make vitamins K and B12. |
| Mucous | Is good even though it seems gross. |
| Rapid movement | Prevents infection. |
| Steps for the most common mode of bacterial reproduction: Binary Fission | 1 Cell elongates & DNA is replicated. 2 Cell wall & plasma membrane begin to constrict. 3 Cross-wall forms, completely separating the 2 DNA copies. 4 Cells separate. |
| What is the role of FtsZ in bacterial reproduction? | Homologous to tubulin. Participates in cell division. Forms a ring around the cell midpoint & contracts. Visulized by using a FtsZ-GFP fusion protein. |
| N=2^nNo | n=number of generations. No=initial number of cells. N=final number of cells. Bacterial growth curves are exponential. |
| Bacterial Growth Curve | doubling time=generation time=the time it takes the bacteria to divide once. |
| How fast can E. coli double? | Twenty minutes. Not all bacteria are this fast. |
| What does a typical bacterial growth curve look like? | Log of number of bacteria. A hump. Lag, Log, Stationary, Death. |
| Lag phase | Growth is limited as cells adjust to the conditions. It is a period of intense metabolic activity. |
| Log phase | Exponential growth. Maximum growth. |
| Stationary phase | Growth is limited because nutrients are depleted and toxins accumulate (pH drops). |
| Death phase | Death rate faster than growth rate. Huge drop in pH & toxin buildup. |
| Microscopic Direct counts | Advantages: counts cells directly, gives accurate number. Disadvantages: Cant tell if cells are alive or dead, Use stain to distinguish living cells. |
| Viable plate counts (dilution series) | Advantages: Can tell live vs. dead. Can differentiate species somewhat. Do tests on colonies: PCR. Disadvantages: Hardest to do, time intensive, must dilute & then wait for growth. |
| Turbidity (the spectrophometer) | Advantages: Gives rapid measurement. Disadvantages: Can't tell is cells are dead or alive. Solution must be at 10^7-10^10 cells/mL. |
| Macronutrients needed by all bacteria | Four molecules of life: Nucleotides, Amino Acids, Sugars (ribose), Fatty Acids. Nutrients are required to make lipids, AAs, & nucleic acids which comprise membranes, proteins, ribosomes, RNA & DNA. Need C, O, N, H, P in high concentration. |
| Difference between solid & liquid media | Liquid: Study growth rates & conditions. Study large numbers of cells. Solid: Isolation into pure culture. Study large number of samples. Study growth conditions. |
| Amphibolic Pathways-catabolism & anabolism | All components of the cell are made from precursors made in the central pathways of glycolysis, TCA, pentose phosphate pathway. |
| Colony | A population of cells arising from a single cell or spore or from a group of attached cells. |
| Pure Culture | Contains only one species or strain. |
| Defined Media | You know what is in there. Exact chemical composition is known. |
| Complex Media | Extracts and digests of yeasts, meat, or plants (aka nutrient broth or nutrient agar). |
| Selective Media | Suppresses unwanted microbes and encourages desired microbes. |
| Differential Media | Makes it easy to distinguish colonies of different microbes. |
| Thermophile | Heat loving. Properties: A larger proportion of charged amino acids on surfaces of proteins-this allows additional ionic bonds to hold it together. Protein chaperones help them fold. DNA has protective proteins, high Mg, & reverse gyrase that supercoils. |
| Psychrophile | Capable of growth and reproduction in cold temperatures, ranging from −15°C to +10°C. Lowest T microbes. Freezer T. |
| Mesophile | an organism that grows best in Moderate temperature loving, neither too hot nor too cold, typically between 20 and 45 °C. Room T. |
| Acidophile | Acid loving. |
| Alkaliphile | Base loving. |
| Halophile | Like hypertonic environments, or an increase in salt or sugar. Lik high osmotic pressure. |
| Obligate anaerobe | Can't grow in the presence of oxygen. |
| Facultative anaerobe | An organism that can grow in either the presence or absence of oxygen. It does not require O2 to grow, but grows at a faster rate in its presence. It uses O2 when available. |
| Obligate aerobe | Requires oxygen to grow. |
| Microaerophile | Require a very specific amount of oxygen for growth. Less than in air. |
| aerotolerant anerobe | Grow equally well in the presence or absence of oxygen. |
| Oxygen: the good and the bad. | Required for many bacteria, but also toxic. Last e- acceptor. Toxic oxygen radicals are removed by SOD's, catalase, & peroxidase. |
| What does cellular catalase do and what is a catalase test? | Removes toxic oxygen radicals. The test is one of the main 3 tests used by microbiologists to identify species of bacteria. Catalase positive or negative. Bubbles=positive. Shows if microbe requires O2 to grow. |
| Variability among bacteria in their requirements for growth | Used to characterize them. Mannitol salt agar, blood agar, etc. All culture media have electron source, energy source, carbon source if not autotrophic, and nitrogen source if not N2 fixer. |
| Commercial Sterilization | Killing C. botulinum endospores. Sterilization is removing all microbial life. |
| D-value | Time to kill 90% of cells. Microbes die at a logarithmic rate. 2 D-values=time to kill 99% of cells. Antimicrobial agents decreases D-value. kills cells faster. |
| Decimal Reduction Time (DRT) | Minutes to kill 90% of a population at a given temperature. Depends on # of microbes, environment (organic matter, temp, biofilms), time of exposure, and microbial characteristics. |
| How does radiation prevent microbial growth? | Ionizing (x-ray, gamma rays, e-beams): ionizes water to release OH. Damages DNA, proteins, lipids. Nonionizing (UV, 260 nm): Damages DNA. Microwaves: Kill by heat, not especially antimicrobial. |
| How does oxygen prevent microbial growth? | Toxic O2 species made by cellular respiration-some e-s leak away from main path & interact w/ O2 to make superoxide anion. Ionizing radiation. Synthesized by phagocytic cells like neutrophils & macrophages to kill microbes. |
| How does temperature prevent microbial growth? | Growth rate increases w/ temperature until temp is too high & proteins denature. |
| Refrigerator | May allow some slow growth of spoilage bacteria, very few pathogens. |
| Freezer | No significant growth. |
| Pasteurization | 63C for 30min. Don't kill all cells. Pasteurized food spoils eventually. Leaves food tasting normal. |
| Autoclaving | Moist heat denatures proteins. Steam under pressure. Temperature & Pressure. |
| Under what conditions would filtration be used as a method of sterilization rather than autoclaving? | HEPA removes microbes >0.3um. Membrane filtration removes microbes >0.22um. The best method to sterilize heat-labile solutions. |
| Commonly used antiseptics and disinfectants | Bleach, Iodine, Soap/surfactants, Ethanol, Detergents, Aldehydes, Quartinary ammoinion compounds (lysol/trislocan), & heavy metals. Kill microbes & eukaryotic cells. Cant use inside pts. |
| Bleach (chlorine) | Common & effective against protein, DNA, & lipids. Oxidizing agent. Kills even endospores and mycobacteria! |
| Iodine (Betadyne) | Common & effective against protein, DNA, & lipids. Alter protein synthesis and membranes. |
| Soap/surfactants | Disinfectant. Degerming. The power of hand washing: the single most important factor in reducing transmission of skin microorganisms. |
| Ethanol | Common and effective target against protein, DNA & lipids. Denature proteins, dissolve lipids. Require water. |
| Detergents | Common and effective target against protein, DNA & lipids. Acid-anionic detergents react with plasma membrane. Sanitizing. Disrupt plasma membranes. |
| Aldehydes | Disinfectants. Good for medical equipment. Safe. Acts rapidly. Attacks all microorganisms. Not effected by organic material. Mode of action: Inactivate proteins by cross-linking with functional groups. |
| Quarternary ammonium compounds | Cationic detergents. Bactericidal, denature proteins, disrupt plasma membrane. Lysol, trislocan. In many household cleaners & toothpaste. Disrupt membrane. Highly toxic to fish, moderately toxic to birds & only slightly toxic to humans. |
| Heavy metals | Disinfectant. Ag, Hg, & Cu. Silver nitrate may be used to prevent gonorrheal ophthalmia neonatorum. Silver sulfadiazine used as a topical cream on burns. Copper sulfate is an algicide. Denatures proteins. |
| Ionizing UV radiation, bleach, ethanol & iodine are all commonly used modes of killing microbes because they damage__1___, whereas detergents (like biguanide) usually just damage ____2____. | 1. Protein, Lipids, & DNA 2. Plasma membranes |
| Why is gluteraldehyde considered the most effective disinfectant for hospital use? | Safety in transport. Safe for equipment. Rapid acting. Attacks all microorganisms. Not effected by organic material. |
| How do microbial characteristics determine the effectiveness of microbial control strategies? | Most-least resistant: Prions, endospres, mycobacteria, cysts, vegetative protozoa, gram-, fungi, viruses w/o envelopes, gram+, viruses w/ lipid envelopes. |
| What microbes are generally the most resistant to chemical biocides? | Prions=misfolded protein. |
| How do endospores & biofilms protect against biocides? | E: Lots of layers. Spore coat. B: Barrier is extremely resistant to chemicals, etc. Allows them to concentrate nutrients. |
| Why are prions so hard to get rid of? | Your own misfolded proteins. |
| What is taxonomy and how is it useful? | The science of classifying organisms. Provides universal names for organisms and a reference for identifying them. |
| How does the definition of species for higher eukaryotes differ from the definition of microbial species? | Eukaryotic species are defined by mating/breeding. Microorganisms don't mate. The current system for microbes includes the 2 domains of life made by sequencing DNA. |
| What type of mutations act as a molecular clock? | Neutral mutations because they stick around and don't take over a population like beneficial mutations or get lost like detrimental mutations. |
| Phylogenetic Tree | A flow chart that looks at similarities. Relates differences between sequences of 16S rRNA to time since species divergence. Assumes fewest possible changes (maximum parsimony). Test trees via probability. |
| Why is the 16S RNA used as the primary DNA sequence for making phylogenetic trees? | Present in all life. It is a component of both 30S and 40S rRNA. |
| What factors complicate our ability to make phylogenetic trees? | Horizontal gene transfer, mitochondrian & chloroplasts, endosymbiotic theory, lack of a root, & differences in mutation rate. |
| Horizontal gene transfer | Makes trees complex. Tree can be trusted with some transfer early on. |
| Mitochondrion & Chloroplasts | These look like bacteria. Where should we put them on the map? They jump branches. |
| Endosymbiotic theory | Eukaryotes originated as an early cell that incorporated bacteria & archaea as organelles. |
| Lack of a root | We know nothing about the last common ancestor. |
| Differences in mutation rate | Generation time differs. Ability to tolerate, correct mutation differs. Can be difficult to calibrate to time in years. |
| What are the 3 domains of life? | Archaea, Bacteria, & Eukarya. |
| Archaea | Prokaryotic. Cell wall. Met. No common arm of tRNA. |
| Bacteria | Prokaryotic. Peptidoglycan cell wall. FMet. Sensitive to antibiotics. rRNA loop. Common arm of tRNA. |
| Eukarya | Eukaryotic. Carbohydrate cell wall. Met. Common arm of tRNA. |
| Geological evidences of early life | Fossils of filamentous cyanobacteria. Essential elements C, H, N, O, etc. available on early earth. Temperature between boiling & freezing points of water. Source of energy: reduced minerals & sunlight. No molecular oxygen at first. |
| Geological evidences continued. | Microfossils match modern species. Stromatolites. Isotope ratios: carbon dating. CO2 & iron enriched where a living organism was=Biosignatures. Oxidation state. |
| Four theories for the origin of life | Prebiotic soup, Metabolist, first information (RNA), and Origin Elsewhere (Panspermia). |
| Prebiotic Soup Model | Small organic molecules arise abiotically. Created by lightning-adenine & simple AAs. Replicated in laboratory. Found on other planets. Lipids spontaneously organize into micelles. |
| Metabolist Model | FeS catalyzes fixation of carbon. Self-sustaining reaction. Inorganic compounds making organic material. |
| First information molecule (RNA) | RNA is precursor to DNA. Used as genome by some viruses. Has catalytic activity: Splices introns, regulates gene expression, synthesizes proteins. |
| Origin elsewhere (Panspermia) | The existence of diverse life so quickly means that evolution most likely occurred quicker, or occurred somewhere else & arrived on a meteorite or something. Most widely accepted model. |
| Dichotomous keys | Series of simple tests to determine the identity of an unknown microbe. Yes or no answer. |
| ELISA | Enzyme-Linked Immunosorbent Assay. Known antibodies & unknown type of bacterium. Antibodies link to enzyme that gives a signal when it is activated & makes product from substrate. Color change. |
| Western Blot | Detects protein. Used often to confirm HIV & Lyme disease. Antibodies in pts serum bind to specific microbial proteins. Cell is lysed & inside proteins are accessible. Antibody lights up on gel when it finds what it binds. Fast ~1 day. |
| Genetic Analysis & PCR | DNA base composition: G + C moles%. If >10% dif, then not related. DNA fingerprinting: Electrophoresis of restriction enzyme digests. rRNA sequencing. PCR. |
| Nucleic acid hybridization | Take isolated DNA & known lab control DNA. Heat to separate. Combine single strands. Cool to allow renaturation of ds DNA. Does it match? |
| FISH | Fluorescent in situ hybridization. Allows identity w/o culturing. DNA or RNA probes. Use on MRSA. Acts as a fluorescent tag for use on crude sample. Lights up when it finds what specifically it's fishing for. |
| DNA probes | DNA fragment cloned. Marked w/ florescent dye & separated into ss, forming DNA probes. Unknown bacterial cells lysed. DNA separated. Probes added & hybridize w/ DNA from sample that matches. Excess probe washed off. Florescence indicates match found. |
| Phage typing | Phages are highly specialized and only infect certain species or strains w/i species. Spot different phage on agar plate to see what bacteria you have. |
| Basic defenses of the female urinary & reproductive systems | Urine, valves, mechanical flushing, vaginal lactobacilli. |
| Urine | Acidic. |
| Valves | Prevent backflow to kidneys. |
| Mechanical flushing | Flushes a lot. No time for microbes to stick. |
| Vaginal lactobacilli | Produce H2O2, grow on glycogen secretions & secrete lactic acid. |
| Why is E. coli the most common cause of cystitis, especially in females? | It lives in our intestine & is pooped out close to urethra. Stimulates exfoliation of bladder lining by Hemolysin toxin. Pili stick to & invade cells. Grows in cells. Type 3 secretion system. Lays dormant for weeks. |
Created by:
punkaloo
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