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106 Cards in this Set
- Front
- Back
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What are the three features that distinguish proks from euks?
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1. Single circular chromosome
2. No nuclear membrane or mitotic apparatus 3. Transcription is coupled to translation |
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What is the major thing that makes prokaryotic translation different from eukaryotic?
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The ribosome - 70S instead of 80S
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What good is the fact that prok ribosomes are different in shape and function from eukaryotic?
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They are a good target for antimicrobials.
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What is an optimal antimicrobial target in comparison to those that target ribosomes?
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Antimicrobials that target the cell wall
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What is the prokaryotic cytoplasm like compared to eukaryotic?
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Simple
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What makes up for the fact that prokaryotic cytoplasm lacks vesicles, organelles, etc?
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The cytoplasmic MEMBRANE is much more complex.
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What is the fundamental unit of taxonomy in the classification of organisms?
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Species
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What natural boundaries separate eukaryotic species?
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The ability to produce fertile offspring
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What separates prokaryotic species? Why?
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Phenotype (metabolism)
and Genotype (DNA) -Because prokaryotes replicate by binary fission and produce identical offspring |
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What are the Classical methods by which we have identified different prokaryotic species?
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-Morphology of clonal isolates
-Biochemistry of clonal isolates |
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What is the goal of identification of a prokaryotic species?
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Rapid diagnosis of pathogens
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What is the up and coming method of identifying prokaryotic species?
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Using molecular methods to determine DNA composition which is a reflection of bacterial relationships
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What are the 2 main types of molecular identification of bacteria?
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-Hybridization (to DNA or RNA)
-Amplification |
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Although high expectations haven't been met yet, what are 3 potential advantages of molecular ID over classical techniques?
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-Automation
-Speed -Greater accuracy |
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What are 3 types of molecular diagnostic DNA analysis?
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1. Hybridizations
2. RFLP analysis 3. Amplification of pathogen specific DNA |
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What are the two ways that hybridization can be done?
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-DNA to DNA
-DNA to RNA |
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When is RFLP analysis mostly useful?
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In determining whether nosocomial infections are community based and from multiple sources, or from one person.
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How will RFLP show if one person is responsible for a spreading nosocomial infection?
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The RFLPs will be identical
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What is the method for amplifying pathogen specific DNA for rapid ID?
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PCR
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What is in situ hybridization used as a diagnostic tool for?
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Viruses
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How is in situ hybridization done?
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By adding a labeled DNA probe to a tissue sample, heating to denature the DNA, cooling for hybridization, and adding substrate for the label.
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What is an example of a bacterial disease in which in situ hybridization is essential for diagnosis?
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Whipple's disease - caused by Tropheryma whipplei
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What is the best strength of bond for hybridization? What is intermediate? What is worst?
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Best: RNA-RNA
Intermed: DNA-RNA Worst: DNA-DNA |
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What happens as Glucose gets oxidized to pyruvate during metabolism?
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-NAD gets reduced to NADH2
-ATP gets produced |
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What happens to pyruvate in aerobic metabolism?
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It gets converted to H2O and CO2 in an Energy efficient manner.
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What happens to Pyruvate in anaerobic metabolism?
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Fermentation to lactate or different end products
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Though fermentation is less energy efficient, why are we glad bacteria do it?
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Their end products are unique to different microbes which is of diagnostic use for us.
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What 2 enterobacteriacae are gas producers? What 2 are NOT?
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Gas pos: E.coli, Salmonella
Gas neg: Shigella, S. typhi |
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What is the "Constitutive" energy pathway that is common to most bacteria?
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The embden meyerhoff glycolytic pathway
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What takes place in the EM pathway?
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Glucose --> 2 pyruvate, 2 ATP, and 2 NADH2
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What pathway exists as either a complement to, or an alternate to the EM pathway?
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The Pentose Phosphate pathway
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What type of fermentation is tested for by the VP reagent?
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Butanediol fermenation
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What pathways complement the EM pathway? How?
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-Fatty acid biosynthesis (produces NADPH2)
-Nucleic acid biosynthesis (produces Pentose) |
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What 3 species are VP pos?
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-Enterobacter
-Bacillus -Serratia |
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What pathways can exist in the ABSENCE of the EM pathway?
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-Entero-douderoff pathway (pseudomonas) or
-Phosphoketolase pathway (streps) |
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What is the stage of glucose metabolism that really lets us differentiate microbes?
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The 2nd stage - oxidation of NADH2 back to NAD+ to balance the oxidation state of the cell!
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What are the 4 phases of bacterial growth?
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1. Lag
2. Exponential 3. Stationary 4. Death |
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What are the 2 ways that prokaryotes oxidize NADH2?
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-Fermentation
-Respiration |
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What is the electron acceptor from NADH2 in fermentation?
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Pyruvate
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What is the electron acceptor from NADH2 in Respiration?
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O2 (if this is aerobic respiration)
OR NO3 (if this is anaerobic respiration) |
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What occurs in the lag phase?
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No cell division
Adaptations to increase metabolism |
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What determines whether a microbe will ferment or oxidize glucose?
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Its ability to metabolize oxygen
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What occurs in the exponential phase?
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Balanced growth in a logarithmic fashion
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What are Aerobes?
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Bugs that metabolize oxygen and only grow in oxygen
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What are microaerophiles?
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Bugs that metabolize oxygen but grow only in LOW oxygen
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How do we know that respiration is much more efficient than respiration?
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A LOT more potential energy remains in the chemical bonds of lactate than in CO2/H2O
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What are facultative anaerobes?
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Bugs that metabolize oxygen when it's present, or else ferment if it's not.
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What occurs in the stationary phase?
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Depletion of nutrients
Buildup of acid and toxic products |
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What are anaerobes?
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Bugs that do not metabolize oxygen so only grow in the absence of it.
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Why do bacteria use fermentation mechanisms then?
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It gives them a selective advantage in the environment.
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What occurs in the death phase?
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death
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What are aerotolerant microbes?
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Bugs that do not metabolize oxygen, but will grow in its absence or presence.
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What is an example of aerobic bugs?
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Pseudomonads
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What are 3 types of bacteria based on temperature requirements?
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-Psychrophiles
-Mesophiles -Thermophiles |
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What ferments Pyruvate to Ethanol?
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Yeast
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What is an example of Microaerophilic bugs?
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Leptospira
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What is a good example of aerotolerant bugs?
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Streptococci
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What does the OXIDASE test differentiate?
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Aerobes (ie, pseudomonads) from Facultative anaerobes (e coli)
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What ferments Pyruvate to Acrylate?
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Streptococcus
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What is the optimal range for Psychrophilic growth?
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10-20
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What is the basic principle of the oxidase test?
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-Strict aerobes use cyto C to metabolize oxygen; facultative aerobes use cyto D; cyto C reacts with compounds that turn a color so we see which is which
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What are the steps in aerobic respiration?
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1. NADH passes its electrons to flavo proteins
2. Flavo proteins pass electrons to Cytochrome C 3. Terminal electron acceptor accepts electrons (O2) |
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What is the optimal range for Mesophilic growth?
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20-40
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What gets produced by Clostridium species fermentation of pyruvate?
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A wide array of organic solvents.
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What are the steps in anaerobic respiration?
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1. NADH+ gives electrons to NO3-
2. NO3- (nitrate) is now NO2 (nitrite) 3. Nitrite converts to N2 |
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What is the optimal range for Thermophilic growth?
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50-60
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How is nitrate reduction useful?
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As a diagnostic test - not all bacteria reduce nitrates
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What type of Pyruvate fermentation do the Enterobacteriaceae perform?
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Mixed acid fermentation
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When is Fermentation done, and what is the purpose of doing it?
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-When oxygen is not metabolized
-Purpose is to preserve the overall redox balance |
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What are most human pathogens in terms of temp requirements?
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Mesophiles
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How do the enterobacteriaceae make pyruvate?
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By the normal glycolytic pathway
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What is the usual electron acceptor in fermentation?
Is this good or bad? |
Pyruvate
-It's not as efficient in energy production as respiration |
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What is the useful feature of fermentation?
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Each bacterial species performs a unique fermentation, which is extremely useful in diagnosis.
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Then what do the enterobacteriaceae do with pyruvate?
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Ferment it
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What is the pH range in which most pathogenic bacteria grow?
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7.2-7.6
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What are the 4 acids that enterobacteriaceae can reduce pyruvate down to?
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-Acetylaldehyde
-Acetate -Lactate -Formate |
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What is the final endproduct from Formate?
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Ethanol
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What bacteria can survive the acidic environment of the stomach?
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Helicobacter
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What do some enterobacteriaceae do under acidic conditions to reduce the acidity? Via what enzyme?
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Reduce formate down to CO2 and Hydrogen gas via Hydrogenase
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What are 4 products that enterobacteriaceae then reduce Pyruvate to, in order to oxidize NADH2 to regenerate NAD+?
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-Acetylaldehyde
-Lactate -Acetate -Formate |
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What do some bacteria do in too high of acidity?
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Use formate hydrolase to break formate down to CO2/H2 (gas producers)
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What do the enterobacteriaceae normally do with Formate?
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Reduce it to Ethanol in order to oxidize more NADH to NAD+
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What do the enterobacteriaceae do with Formate under acidic conditions to decrease the acidity?
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Reduce formate to CO2 and H2
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What sort of osmotic conditions do most bacteria tolerate?
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Only moderate salt concentrations
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What do we call microbes that can tolerate high salt?
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Halophiles
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What is the enzyme that reduces Formate to CO2 and H2?
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Hydrogenase
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What microbes are fairly salt tolerant? Which are salt sensitive?
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Tolerant = gram pos
Sensitive = gram neg |
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What 2 enterobacteriaceae are Gas producers by their Hydrogenase enzyme?
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-E. coli
-All Salmonella spp except S. typhi |
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What 2 enterobacteriaceae are NOT Gas producers by the fact that they lack hydrogenase?
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-Shigella
-Salmonella typhi |
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What is the salt concentration in Mannitol salt media and what does it allow us to differentiate?
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7.5% NaCl
-We can differentiate Staph aureus from E. coli |
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What is a special "Alternative life style" seen in some bugs?
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Sporulation
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What does the VP test detect?
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An enterobacteriacea's ability to ferment BUTANEDIOL
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What enterobacteriaceae are VP pos?
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The enterobacters
(Klebsiella, Enterobacter, Serratia) |
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What do spore formers do in the life cycle?
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Sporulate instead of going into the death phase when nutrients are depleted.
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What are the 3 important spore formers?
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-Bacillus
-Clostridia -Sporosarcina |
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What are the steps in sporulation?
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1. DNA synthesis
2. Assymetric cell division 3. DNA packaged into spore and coated w/ unique PG 4. Hydrolysis and release of the spore |
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What do spores resist?
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-Dehydration
-Temps -Staining |
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How long can spores survive dormant?
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hundreds of years
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When do spores germinate?
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In water and metabolites
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How can spores be inactivated?
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By autoclaving in 120 degrees for 20 minutes.
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What enterobacteriaceae are VP neg?
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E. coli
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What are the steps in converting Pyruvate down to Butanediol?
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Pyruvate -> acetolactate -> acetoin -> butanediol
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What does the VP reagent react with to produce the red color?
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Acetoin
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So do VP positive organisms ferment pyruvate to butanediol?
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No, actually the VP neg organisms do.
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What is a diagnostic use of the VP test?
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Determining whether enteric contaminated water is from sewage (VP neg, E.coli) or vegetation (VP pos, Enterobacter)
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Why do all the fermentors have different products that they convert Pyruvate down to?
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It gives them a selective advantage in the environment.
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