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45 Cards in this Set
- Front
- Back
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3 types of cell membranes to protect bacteria
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gram +, gram -, acid fast
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Cell walls of gram positive bacteria are made heavily of ...
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murein (peptidoglycan), that absorbs the gram staining = purple
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LPS is characteristic of Gram (+ or -) bacteria?
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LPS is on gram - bacteria
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3 parts of LPS
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Lipid A, sugar core (heptose, ketodeoxyoctanoic acid), O antigen (sugar chain)
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Broadly speaking, which class of bacteria are more antibiotic resistant? Gram - or +
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Gram negative are less affected by most antibiotics, especially penicillin. most antibiotics work to inhibit murein synthesis (in gram +) anyways
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What makes up the cell wall of acid fast bacteria?
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waxes (long hydrocarbon chains), very impervious to acid so acid doesn't wash the strong dye out
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Vancomycin inhibits murein synthesis at what step?
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prevents growing chain of murein by inhibiting disaccharide linking
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How does bacitracin inhibit murein synthesis?
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prevents regeneration of lipid carrier = monomeric units of murein cannot cross membrane into periplasm for further synthesis
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Penicillin and cephalosporin inhibit what step of murein synthesis?
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transpeptidation; prevents peptide linkages
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Bacteria treated with penicillin die by lysis. Even though only murein synthesis has been blocked, why does lysis occur?
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with no murein, the cell walls are very weak. as growth continues in the bacterial cell, it will exert pressure on the weaker wall and lyse eventually
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Why do we not want to give a patient penicillin and a drug that inhibits cell growth concurrently?
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penicillin will inhibit murein synthesis, leading to a weak cell wall. this cell will only die if it continues to grow so it will eventually lyse due to the weal cell wall. but if we also inhibit growth, then it can survive just fine with a weak cell wall
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Penicillin resistant bacteria are deficient in autolysin. Explain why they might be resistant.
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autolysin should cause the cell to lyse and facilitate its lysis after penicillin treatment makes the wall very weak; deficits in autolysin make it harder to lyse the cell even if the wall is weak
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What are siderophores?
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chelating agents used by bacteria to take up as much free iron out of the blood as possible to use for its own growth
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Function of DNA gyrase
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wind DNA back up after replication; introduce supercoils
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Function of topoisomerase
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unwind DNA for replication
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FACT: rate of DNA polymerase movement is INdependent of the cell's growth rate
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cool beans
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Metronizadole mechanism
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inhibit DNA synthesis
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Why is metronizadole a safe drug for human use?
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must be PARTIALLY reduced to be active (to inhibit DNA synthesis); only bacteria can partially reduce it, humans fully reduce is (making it inactive again)
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Nalidixic acid mechanism
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inhibits DNA synthesis by inhibiting DNA gyrase. bactericidal
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Mechanism of fluoroquinolones
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inhibit DNA synthesis by inhibiting DNA gyrase or topoisomerase, can lead to dsDNA breaks
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RNA production rate is proportional to # of RNA polymerases. True or False.
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true
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Rifampin mechanism
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inhibits bacterial transcription at initiation; only binds to free RNA polymerases unbound to DNA
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Why is rifampin safe for humans? (used in TB and leprosy)
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mammalian free RNA polymerases don't bind rifampin
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Chloramphenicol and erythromycin (macrolides) inhibit which part of bacterial life?
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Protein synthesis, bind at tRNA site on large ribosomal subunit
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Why is chloramphenicol's action reversible?
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binds to tRNA site on large (50S) ribosomal subunit. when cycle is finished, the complex disassociates and can bind to a new mixture of subunits = chloramphenicol/erythromycin must be continued
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Mechanism of aminoglycosides (streptomycin, gentomycin, neomycin)
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inhibit protein synthesis; bind to small 30S ribosome subunit; inhibits elongation of peptide chains
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Accumulation of 70S ribosomes is characteristic of bacterial cell death after being treated with which class of antibiotics?
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aminoglcosides (streptomycin, gentomycin, neomycin)
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Aminoglycosides are (bactericidal or bacteriostatic)?
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bactericidal. irreversible death
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Chloramphenicol/erythromycin are (bactericidal or bacteriostatic)?
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bacteriostatic, because they are reversible if treatment is discontinued
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Clock-wise spinning of flagella is associated with travel (in straight line or tumble)?
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tumble; counter-clockwise = streamlined
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Sex pili exchange information via what process?
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conjugation
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Why is it difficult to vaccinate against gonococci? (related to pili)
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their pili can express many different antigens
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All pathogenic microbes are (photosynthetic/chemosynthetic or rely on preformed organic compounds)?
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rely on preformed organic compounds
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TB is a (strict aerobe or obligate anaerobe)?
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strict aerobe, thats why its in the lungs
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Botox and tetanus are (strict aerobe or obligate anaerobe)?
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obligate anaerobe, dont want oxygen at all
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FACT: Facultative anaerobes are the most medically relevant and hardest to treat since they can live most places.
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E. coli and other intestinal microbes are most common
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Fermentation uses what organic compounds as a final electron acceptor mostly?
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pyruvate
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What does it mean if a bacteria is nutritionally fastidious?
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has high, specific nutrient requirements
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What is the bacterial SOS response?
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when DNA damage is detected (from UV light), genes are expressed to repair them
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Strep makes their hemolysins mainly in the stationary phase. Why does this make sense?
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they aren't growing to they have more energy to make hemolysins and get more nutrients from host RBCs
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A bacteria is growing in culture. leucine is added to the culture and bacterial production of endogenous leucine stops and uses the exogenous source. This is an example of...
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Parsimony/efficiency
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Where does RNA polymerase bind on an operon?
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promoter
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A repressor would bind where on an operon?
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operator, just past the promoter
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What is an inducible enzyme vs. a constitutive enzyme?
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inducible = only made when needed. constitutive = always made
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In the presence of lactose, how are B-galactosidase genes transcribed.
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allolactose (inducer; indicates presence of lactose) binds to the repressor. this acts as an allosteric modifier and inactivates the repressor. the repressor now does not bind the operator and B-galactosidase is transcribed
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