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Bacterial biochemistry

Terms in this set (135)

What is the goal of metabolism?
produce ATP
Respiration involves what 3 cycles?
1. glycolysis
2. krebs cycle
3. oxidative phosphorylation (ETC)
in respiration, a reduction of ______ produces the ATP
enzymes
Is more ATP made in respiration or fermentation?
respiration ~ 38 ATP
If oxygen is the final electron acceptor for respiration, then it is ____
aerobic
if anything other than oxygen is the final electron acceptor for respiration, then it is _____
anaerobic
respiration is always an (organic/inorganic) acceptor
inorganic
3 products of fermentation
gas, alcohol, acid
What is the most common product of fermentation?
gas (CO2)
Gas is visible by an inverted _____ tube within broths
Durham
Why is alcohol production during fermentation difficult to ascertain?
it is colorless and has little effect on pH
Acid production (raises/lowers) pH
lowers
Bacteria can (increase/decrease) pH
increase
When bacteria increases pH, the breakdown of proteins releases ______, which is then released into ____
ammonia; water
Phenol red broth is what type of medium?
differential and undefined
What type of tube is during for a phenol red broth test?
durham tube
What are the 2 carbon sources for a phenol red broth test?
carbohydrate (sugar) and peptone (partially digested protein)
What is the pH indicator for the phenol red broth test?
phenol red
In the phenol red broth test, a pH of < 6.8 is what color?
yellow
in a phenol red broth test, a pH of > 7.4 is what color?
pink
in a phenol red broth test, a pH in between 6.8 and 7.4 is what color?
red
Which biochemical test aids in distinguishing Enterobacteriaceae members?
decarboxylase assay
What type of medium is decarboxylase assay?
undefined medium
What are the 4 ingredients in a decarboxylase assay?
1. peptone
2. glucose
3. brocresol purple
4. pyridoxal phosphate (decarboxylase coenzyme)
In a decarboxylase assay, if the bromcresol purple has a pH > 6.8, what color is it?
purple
In a decarboxylase assay, if the bromcresol purple has a pH < 5.2, what color is it?
yellow
Low pH induced ______ gene expression in the presence of respective amino acids
decarboxylase
A change in pH followed by a consequent change in pH due to biochemical processes occurring as a result of the first change in pH
Reversion
Does reversion occur in a decarboxylase assay?
yes
Decarboxylation of amino acids produced _____ products that turn the medium purple
alkaline
What two amino acids turn the medium purple during decarboxylation?
1. putrescine
2. cadaverine
_____ _____ added to seal the medium from external oxygen promotes fermentation
immersion oil
Which biochemical test has a medium shallow agar slant with a deep butt?
triple sugar iron agar
triple sugar iron agar provides both ______ and ____ growth environments
aerobic and anerobic
What are the 2 steps in the inoculation method for TSI agar?
1. fishtail on slant
2. stab in butt
Which biochemical tests differentiates enteric bacteria on bases of glucose/lactose/sucrose fermentation and sulfur reduction?
TSI agar
What type of medium is TSI agar?
differential
What are the 4 ingredients in a TSI agar?
1. carbohydrates
2. animal proteins
3. sodium thiosulfate
4. ferrous sulfate
What are two animal proteins found in a TSI agar?
carbon; nitrogen
What are two sources of sulfur for accepting electrons (sulfur reduction) in a TSI agar?
sodium thiosulfate and ferrous sulfate
Ferrous sulfate is an indicator of ____ production
H2S
iron reacts with H2S to produce ____ _____
ferrous sulfide
ferrous sulfide is a _____ precipitate
black
What is the pH indicator of a TSI agar?
phenol red
In a TSI agar, if the organism is glucose-only fermenter, then the acid produces (higher/lower) pH
lower
In a TSI agar, if the organism is a glucose-only fermenter, then glucose fermentation (increases/decreases) hydrogen concentration
increases
In a TSI agar, if the organism is a glucose-only fermenter, then the entire medium turns _____
yellow
In a TSI agar, after 12 hours, glucose in the aerobic region runs out and starts to break down the _____ ____
amino acids
In a TSI agar, what happens when amino acids are broken down? (3)
1. NH3 is produced
2. pH increases
3. reversion
In a TSI agar, why is NH3 produced?
due to peptone catabolism under aerobic conditions
In a TSI agar, if the organism is a glucose-only fermenter, the final product is a ____ slant and a ____ butt
red; yellow
In a TSI agar, if an organism is a glucose and lactose and/or sucrose fermenter, then the more _____ carbon is available for utilization
organic
In a TSI agar, if an organism is a glucose and lactose and/or sucrose fermenter, then more fermentation is produced, which means more ____ is produced
acid
In a TSI agar, if an organism is a glucose and lactose and/or sucrose fermenter, after 24 hours, the entire medium remains ____
yellow
In a TSI agar, if an organism is a glucose and lactose and/or sucrose fermenter, then the gas produced by fermentation may cause: (2)
1. fissures in the medium
2. lifting of agar off the bottom of the tube
in a TSI agar, _____ may be produced by the reduction of thiosulfate or by the breaking down of cysteine in the peptone
H2S
in a TSI agar, ferrous sulfate + H2S forms a ____ precipitate
black
in a TSI agar, in order for a black precipitate to exist, _____ conditions must exist first
acidic
in a TSI agar, blackening of a medium is an indicator of: (2)
1. sulfur reduction
2. fermentation
in a TSI agar, black precipitate obscures the color of the ____
butt
in a TSI agar: a red slant =
only glucose fermentation
in a TSI agar: a yellow slant =
glucose and lactose/sucrose fermentation
In a TSI agar, if the organism is a non-fermenter, it may utilize (2)
peptones and AA
In a TSI agar, if the organism is a non-fermenter, it may make the medium more ____
alkaline
In a TSI agar, if the organism is a non-fermenter, then raising the pH turns the medium _____
red
In a TSI agar, if the organism is a non-fermenter, then it can use the peptone aerobically and acerbically, so both slant and butt will be ____
red
In a TSI agar, if the organism is a non-fermenter, the obligate aerobe will have a ____ slant
red
Which biochemical test is a nutrient utilization test?
Simmons citrate assay
What type of medium is Simmons citrate assay?
differential; defined medium
Which biochemical test differentiates based on an organisms' ability to grow without a specific nutrient (carbon or nitrogen)?
Simmons citrate assay
in Simmons citrate assay, what is the only source of carbon?
citrate
in Simmons citrate assay, what is the only source of nitrogen?
ammonium phosphate
What is the pH indicator for in Simmons citrate assay?
bromothymol blue
in Simmons citrate assay, if bromothymol blue pH is 6.9, what color is it?
green
in Simmons citrate assay, if bromothymol blue pH is 7.6, what color is it
blue
in Simmons citrate assay, if a bacterium possesses citrate-permeate, it can utilize _____ and convert it to _____
citrate; pyruvate
in Simmons citrate assay, ______ is normally used in the beginning of the Krebs/tricarboxylic acid cycle
citrate
in Simmons citrate assay, sodium citrate yields (3):
pyruvic acid, oxalacetic acid and CO2
in Simmons citrate assay, if organisms grow and use citrate and ammonium phosphate, then it will produce (2)
ammonium and ammonium hydroxide
in Simmons citrate assay, during alkaline conditions, pH (increases/decreases) and the medium turns ___
increases; blue
in Simmons citrate assay, a positive result is what color?
blue
in Simmons citrate assay, a negative result is what color?
green with or without growth
Bile esculin is what type of medium?
undefined; selective and differential
What are the 5 ingredients in bile esculin?
1. beef extract
2. digest of gelatin
3. esculin
4. oxgall (bile)
5. ferric citrate
What ingredient of bile esculin is a glycoside composed of glucose and esculetin?
esculin
What 2 ingredients of bile esculin are sources of nutrients and energy?
beef extract and gelatin
Which ingredient of bile esculin is a selective agent?
bile
in bile esculin, the bile separates the _____ ____ group and _____ from other streptococci
streptococcus bovis and enterococci
Which ingredient of bile esculin is the source of oxidized iron?
ferric citrate
What are the two purposes of a bile esculin test?
1. hydrolyze esculin under acidic conditions
2. tolerate bile
In a bile esculin test, among streptococci, typically only members of enterococci and streptococcus bovis can tolerate ___ and hydrolyze _____
bile; esculin
in a bile esculin test, ____ reacts with Fe3+ from ferric citrate
esculetin
Bile esculin forms a _____ precipitate
brown
in a bile esculin test, if the medium is darkened, it is a (+/-) test?
+
in a bile esculin test, if the medium has no darkening, then it is a (+/-) test?
-
What type of medium is a SIM medium?
differential
S in SIM medium stands for?
sulfur reduction
In a SIM medium, the goal is to reduce sulfur to ____
H2S
What is the sulfur source in a SIM medium?
sodium thiosulfae
What two pathways are associated with sulfur reduction in a SIM medium?
1. cysteine desulfurase
2. thiosulfate reductase
In a SIM medium, the cysteine desulfurase pathway changes ____ to _____
cysteine to pyruvate
in a SIM medium, thiosulfate reductase reduced sulfur at the end of the _____ _____ _____
anaerobic respiratory ETC
Both pathways in a SIM medium produce ____ gas
H2S
in a SIM medium, H2S + Fe (II) (ferrous ammonium sulfate)=
Fe (II) S (ferric sulfide)
In a SIM medium, if ferric sulfide blackens the medium, then the result is (positive/negative)?
+
In a SIM medium, if ferric sulfide does not blacken the medium, then no sulfur reduction occurs, causing a (+/-) result?
-
What does the I in SIM medium mean?
indole production from tryptophan
In the SIM medium, Tryptophan is found in (2)
casein and animal protein
In the SIM medium, Tryptophan yeilds what 3 enzymes?
pyruvate, ammonia, and indole
In the SIM medium, the addition of ____ reagent reacts with indole
Kovacs'
In the SIM medium, if Kovac's reagent is present, then it turns _____ and has a (+/-) result
red; positive
In the SIM medium, if Kovac's reagent is not present, then there is no color change and a (+/-) result
-
What does M stand for in SIM medium?
motility
In the SIM medium, the media is inoculated by ____, NOT a loop
STAB
In the SIM medium, motile organisms can move about a _____ medium
semisolid
In the SIM medium, motile organisms can be detected by "_____" growth extending outward in all directions from central stab line
radiating
In the SIM medium, how are you supposed to move the STAB around when inoculating?
straight down and up again
polysaccharide made of alpha-D glucose subunits
starch
starch is too large to pass through a _____ cell membrane
bacterial
starch must be broken down into _____ subunits
glucose
in a starch agar, bacteria produce what 2 enzymes:
alpha-amylase and oligo-1,6-glucosidase
in a starch agar, enzymes break down ____ linkages between sugar subunits
glycosidic
What is the primary carbon source for starch hydrolysis?
soluble starch
during starch hydrolysis, if organisms produce amylases, then starch is ____ in the area surrounding the growth
hydrolyzed
during starch hydrolysis, if organisms produce amylases, they are usually _____ in the medium
invisible
during starch hydrolysis, if organisms produce amylases, you must add ____ to dettect presence/absence of starch
iodine
in a starch agar, iodine + starch = what color?
blue or dark brown color
hydrolysis in a starch agar is presented where?
a clear zone surrounding growth
if a starch agar is +, there (is/is not) a zone of clearing around the growth
is
if a starch agar is -, there (is/is not) clearing and the media absorbs _____
is not; iodine
protein derived from collagen
gelatin
Which biochemical tests contains nutrient gelatin that is a solidifying agent and a substrate for enzymatic activity?
gelatin agar
in a gelatin agar, what is the enzyme that hydrolyzes gelatin?
gelatinase
Gelatinase-positive organisms ____ the medium and are very (fast/slow)
liquefy; slow
Gelatinase-negative organisms do not ____ the medium
liquefy
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