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106 Cards in this Set

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