Lecture 7: microbial metabolism Flashcards
What type of organisms will use electron sources for their food?
- lithotrophs use reduced inorganic substance
- organotrophs use electrons from organic compounds
Where do phototrophs obtain energy?
- light sources
Where do chemotrophs obtain energy?
- oxidation of chemical compounds
What are the two major types of microorganisms?
- photolithotrophs (photo autotrophs)
- chemoorganoheterotrophs (chemoheterotrophs)
How does microbial metabolism impact our lives as humans?
- metabolic waste is used as our energy
- their waste contributes to our disease
- their processes are targets for antibiotics
What are the three basic needs that organisms need?
- ATP for energy
- ability to reduce compounds to produce electrons
- metabolites for biosynthesis
What type of processes can chemoorganotrophic organisms use to “refuel”
- anaerobic respiration
- aerobic respiration
- fermentation
What are the different exogenous acceptors of the final electron in anaerobic respiration?
- nitrate
- sulfate
- carbon dioxide
- ferric iron
- selenium tetraoxide
How is ATP generated with fermentation?
- formed by substrate level phosporylation
- electron acceptor is normally endogenous (pyruvate)
What is a catabolic pathway?
- enzyme catalyzed reaction where the product of one reaction serves as the substrate for the next reaction
What are three important amphibolic pathways?
- embden meyerhof pathway
- pentose phosphate pathway
- tricarboxylic acid (TCA) cycle
What is used in aerobic respiration in order to catabloize an organic energy source?
- glycolysis
- TCA
- electron transport chain
What are three common ways to break glucose down to pyruvate?
- pentose phosphate pathway
- embden meyerhof pathway
- entner duodoroff pathway
Where does the embden meyerhof pathway most likely occur?
- cytoplasmic matrix
In what stage of aerobic respiration does the embden meyerhof pathway consist of?
stage 2
What are the two phases of the embden meyerhof pathway?
- 6 carbon and 3 carbon phase
The embden meyerhof pathway is also known as?
glycolysis
What organism uses the Entner-duodoroff pathway?
- gram negative bacteria
What is the cycle of glucose degradation with the entner-duodoroff pathway?
- glucose (2) glucose-6-p (3) 6-phosphogluconate (4) 2keto3deoxy6phosphogluconate KDPG (5) pyruvate and G3P
What is the reaction of the pentose phosphate pathway?
glucose-6-p + 12 NADP + 7 water
6 CO2 + 12 NADPH + 12 H
What is the major role of the TCA cycle?
produce carbon skeletons for use in other biosynthetic pathways (FA synthesis…)
What are the products generated with 1 acetyl CoA molecule?
- 2 CO2
- 3 NADH
- 1 FADH2
- 1 GTP
Where are bacterial and archaeal electron transport chains located, and how do they differ from eukaryotes?
- plasma membrane
- different e- carrier
- branched
- shorter
What does the chemiosmotic hypothesis say with regards to electron transport systems?
- the electron movement causes active transport of H ions, creating a proton gradient that can be used to generate ATP
What is the maximum theoretical yield of ATP production and what is reality?
theoretically 38
reality 30
What factors can affect the amount of ATP produced in an organism?
- growth/environment conditions
- nature/health of the ETC
What factors will contribute to a lower than expected ATP production?
- shorter ETC
- environment
- use PMF to energize other actions
- use of metabolites for other processes
Why does anaerobic respiration generally yield less ATP than aerobic?
the electronegativity of oxygen is much higher than any of the electron acceptors in anaerobic
How is ATP produced in fermentation?
substrate level phosphorylation
What is the endogenous electron acceptor in fermentation?
pyruvate
Streptococcus, lactobacillus and bacillus use pyruvate to form?
lactic acid
Saccharomyces use fermentation to convert pyruvate to?
ethanol and carbon dioxide
Propionibacterium use fermentation to convert pyruvate to_______?
propionic acid
acetic acid
carbon dioxide and hydrogen
Clostridium convert pyruvic acid to what in fermentation?
butyric acid, butanol, acetone, carbon dioxide.
Escherichia and salmonella convert pyruvate to what product of fermentation?
ethanol, lactic acid, succinic acid, acetic acid, carbon dioxide
Enterobacteria are able to convert pyruvate to what, via fermentation?
ethanol, lactic acid, formic acid, butanediol, acetoin
What are some monosaccharides that can be used for energy in pathways?
- galactose
- glucose
- mannose
- fructose
What are some di-/polysaccharides that require some amount of cleavage before they can be used in pathways?
- maltose
- sucrose
- lactose
- cellobiose
What is polyhydroxybutyrate?
a reserve of energy that is converted to acetyl-CoA which can enter the TCA cycle
After a protein is degraded and deaminated what can the remaining amino acids be converted back to?
- pyruvate
- acetyl CoA
- other TCA intermediates
What will the oxidase test for?
Determines the presence of cytochrome oxidase
If the test strip turns blue for the oxidase test, what does this mean?
cytochrome c oxidase is present in the microbe, and uses oxygen as the final hydrogen acceptor
If a oxidase test turns the strip blue does this indicate an anaerobic or aerobic microbe?
aerobic as oxygen is acting as the hydrogen acceptor
What is the catalase test used for?
detecting the presence of catalase, which catalyzes the degradation of H2O2 into whater and oxygen
What would a positive catalase test look like?
upon reagent addition, the sample would produce bubbles, indicating that catalase is present in the microbe
What is phenol red broth?
a pH indicator
- yellow = 6.8 or below
- pink = 7.4 above
- red = in between
In the phenol red broth test, what does a yellow color indicate?
Acid production via fermentation process
In phenol red broth test, what does a pink color indicate?
production of ammonia, as peptides are being deaminated
What is the methyl red and voges-proskauer test used to differentiate between?
gram negative rods of enterobacteriacea
What bacterial activities does the SIM Medium test for presence of?
- sulfur reduction
- indole production from tryptophan
- motility
What is sulfur reduction useful for differentiating?
differentiates between enteric organisms
What are the two methods of sulfur reduction?
- cysteine desulfurase (cysteine to pyruvate)
- thiosulfate reductase (sulfur reduction at end of anaerobic ETC
Both enzymes, cysteine desulfurase and thiosulfate reductase, produce what product?
hydrogen sulfide (H2S)
The SIM Medium starts as a yellow solution. What are the results if sulfur reduction is present?
- if present the solution will turn black as the hydrogen sulfide will react with iron to form ferric sulfide
- if no sulfur reduction occurs the ferric sulfide will not form and no blackening of the solution occurs
The SIM Medium can be used to detect the presence of indole, formed as a by-product of tryptophanase.
- if a red reagent layer appears, this indicates the presence of an indole and therefore the presence of tryptophanase
The SIM Medium can also detect motility. What indicate the organisms ability to be motile?
- motility will produce a pattern of fuzzy appearance in a semisolid solution
- no fuzzy appearance indicates no motility
SIM Medium works as a whole to differentiate between what two organisms?
salmonella and shigella
The decarboxylation test will determine if what enzyme is present?
decarboxylase presence or absence
A positive decarboxylation test will produce what results?
a more alkaline solution (>6.8pH) and will be purple
A negative decarboxylation test will produce what results?
an acidic solution (
What is the result of a decarboxylase reaction?
R-H and CO2 thereby reducing the amount of H ions
With the citrate test, what ways determine if citrate is used for carbon and energy?
blue color or green color with sample growth
When is citrate not utilized as a source of energy and carbon in the citrate test?
green color and no increase of the sample
The urea hydrolysis test is used to detect the presence of urease. What does the presence and absence of this enzyme look like?
- presence is a pink end product
- absence is a yellow product
What is the purpose of the gelatin hydrolysis test?
The purpose is to see if the microbe can use the protein gelatin as a source of carbon and energy for growth. Use of gelatin is accomplished by the enzyme gelatinase
What does a positive gelatin hydrolysis test look like and what does it mean?
- gelatin becomes more liquid in nature, and less solid.
- indicates presence of gelatinase which allows gelatin to be used for energy and carbon source
What is the purpose of the nitrate reduction test?
This test determines whether the microbe produces the enzymes nitrate reductase and nitrite reductase. If both are present then N2 gas is produced
If there is a bubble and the solution did not change colors. indicates what for the nitrate reduction test.
the organism is not a fermenter but is able to completely reduce nitrate to nitrogen gas
If there is no bubble present and the solution turns red after drops of reagents A and B, what is the result?
the organism is able to reduce nitrate to nitrite
If reagents A, B and zinc are added and the solution turns red, what does this indicate?
nitrate reduction is not possible
If reagents A, B and zinc are added and the solution remains yellow, what is the indication?
The nitrate is reduced to some other compound. test complete
What is able to cause Beta hemolysis on a blood agar?
- release of streptolysin O or sterptolysin S
- both of which are endotoxins
Group A streptococcus are able to produce beta hemolysis via what compound?
streptolysin O and S, which clears the surface and under the surface of the agar
