March 1st PL Quiz Flashcards
what is phenol red broth
a differential test medium prepared as a base to which a carbohydrate is added
what is included in the base medium
peptone and phenol red
what does phenol red do
it is a pH indicator
when is phenol red yellow
when the pH is below 6.8
when is phenol red pink
when the pH is above 7.4
what is added to each tube as an indicator of gas production
an inverted durham tube
what is indicated by a bubble in the tube where the broth was displaced
gas production from fermentation
what is PR broth used for
to differentiate members of Enterobacteriaceae and to distinguish them from other gram negative rods
also differentiates between gram positive fermenters
the metabolic process by which an organic molecule acts as an electron donor and one or more of its organic products acts as the final electron acceptor
carbohydrate fermentation
what does the fermentation of glucose begin with
the production of pyruvate
what do MR and VP stand for
Methyl red and Voges-Proskauer broth
what are MR and VP
combination medium
what do MR and VP contain
peptone, glucose and phosphate buffer
what is the MR test designed to do
detect organisms capable of performing a mixed acid fermentation ad produce stable end products
what is unique about the acids produced by organisms capable of performing a mixed acid fermentation
they tend to be stable whereas acids produced by other organisms tend to be unstable
what is mixed acid fermentation verified by
the addition of methyl red indicator dye following incubation
at what pH is methyl red actually red
at pH 4.4
what was the VP test designed for
organisms that are able to ferment glucose but quickly convert their acid products to acetoin and butanediol
how does adding the VP reagents determine the result
they oxidize the acetoin to diacetyl which reacts with guanidine nuclei and produces a red color
what color is a positive VP result
red
what was the citrate utilization test designed for
to differentiate members of the Enterobacteriaceae
what are all facultative anaerobes
Eneterobacteriaceae
this means they have the ability to ferment carbohydrates, aerobically respire, and have a citric acid cycle
facultative anaerobes
what does the citrate utilization test tell us
about the ability of organisms to use citrate as their sole carbon source and perform citrate fermentation
what does it mean to be a defined medium
the amount and source of all ingredients are carefully controlled
what is an example of a defined medium
simmons citrate agar
what will happen t bacteria that do not possess citrate permease
they will not grow on this medium(ammonium)
citrate positive bacteria hydrolyze citrate into oxaloacetate and acetate using what
citrate lyase
what is oxaloacetate converted to
pyruvate
what can some bacterial fermentation pathways make
ATP and reducing power
why do citrate positive organisms occasionally grow on the simmons citrate slant without producing a change in color
due to incomplete incubation
what are citrate slants typically inoculated with
lightly with inoculating needle
this is used to determine the ability of an organism to use citrate as its sole source of carbon
citrate utilization test
how do you know if citrate is utilized(positive)
it will turn blue
what is the SIM medium used for
determination of three bacterial activities:
sulfur reaction, indole production from tryptophan, and motility
both systems produce what
hydrogen sulfide gas
what is an indication of a sulfur reaction and a positive test
any blackening of the medium
what is indole production in the medium made possible by
the presence of tryptophan
what can be detected by the addition of kovac’s reagent
tryptophan hydrolysis in the SIM medium
what indicates a positive reaction and the presence of tryptophanase
the formation of red color in the reagent layer
what is determination of motility in SIM medium made possible by
the reduced agar concentration and the method of inoculation
what does hazziness/fuzziness usually indicate
motility
what does TSIA stand for
triple sugar iron agar
TSIA is a rich medium designed to differentiate bacteria on the basis of what
glucose fermentation, lactose fermentation, sucrose fermentation, and sulfur reduction
what is the pH indicator
Phenol red
what is the hydrogen sulfide indicator
iron in the ferrous sulfate
when TSIA is inoculated with a glucose only fermenter what happens
acid products lower the pH ad turn the entire medium yellow within a few hours
what is reversion
the process that occurs in the slant when organisms break down available amino acids which raises the pH
what does a TSIA with a red slant and yellow butt indicate
the organism ferments glucose but not lactose or sucrose.
what color do organisms turn that are able to ferment glucose and sucrose/lactose
yellow throughout
