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Microbiology Lab > March 1st PL Quiz > Flashcards

March 1st PL Quiz Flashcards

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1
Q

what is phenol red broth

A

a differential test medium prepared as a base to which a carbohydrate is added

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2
Q

what is included in the base medium

A

peptone and phenol red

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3
Q

what does phenol red do

A

it is a pH indicator

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4
Q

when is phenol red yellow

A

when the pH is below 6.8

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5
Q

when is phenol red pink

A

when the pH is above 7.4

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6
Q

what is added to each tube as an indicator of gas production

A

an inverted durham tube

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7
Q

what is indicated by a bubble in the tube where the broth was displaced

A

gas production from fermentation

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8
Q

what is PR broth used for

A

to differentiate members of Enterobacteriaceae and to distinguish them from other gram negative rods
also differentiates between gram positive fermenters

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9
Q

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

A

carbohydrate fermentation

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10
Q

what does the fermentation of glucose begin with

A

the production of pyruvate

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11
Q

what do MR and VP stand for

A

Methyl red and Voges-Proskauer broth

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12
Q

what are MR and VP

A

combination medium

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13
Q

what do MR and VP contain

A

peptone, glucose and phosphate buffer

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14
Q

what is the MR test designed to do

A

detect organisms capable of performing a mixed acid fermentation ad produce stable end products

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15
Q

what is unique about the acids produced by organisms capable of performing a mixed acid fermentation

A

they tend to be stable whereas acids produced by other organisms tend to be unstable

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16
Q

what is mixed acid fermentation verified by

A

the addition of methyl red indicator dye following incubation

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17
Q

at what pH is methyl red actually red

A

at pH 4.4

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18
Q

what was the VP test designed for

A

organisms that are able to ferment glucose but quickly convert their acid products to acetoin and butanediol

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19
Q

how does adding the VP reagents determine the result

A

they oxidize the acetoin to diacetyl which reacts with guanidine nuclei and produces a red color

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20
Q

what color is a positive VP result

A

red

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21
Q

what was the citrate utilization test designed for

A

to differentiate members of the Enterobacteriaceae

22
Q

what are all facultative anaerobes

A

Eneterobacteriaceae

23
Q

this means they have the ability to ferment carbohydrates, aerobically respire, and have a citric acid cycle

A

facultative anaerobes

24
Q

what does the citrate utilization test tell us

A

about the ability of organisms to use citrate as their sole carbon source and perform citrate fermentation

25
Q

what does it mean to be a defined medium

A

the amount and source of all ingredients are carefully controlled

26
Q

what is an example of a defined medium

A

simmons citrate agar

27
Q

what will happen t bacteria that do not possess citrate permease

A

they will not grow on this medium(ammonium)

28
Q

citrate positive bacteria hydrolyze citrate into oxaloacetate and acetate using what

A

citrate lyase

29
Q

what is oxaloacetate converted to

A

pyruvate

30
Q

what can some bacterial fermentation pathways make

A

ATP and reducing power

31
Q

why do citrate positive organisms occasionally grow on the simmons citrate slant without producing a change in color

A

due to incomplete incubation

32
Q

what are citrate slants typically inoculated with

A

lightly with inoculating needle

33
Q

this is used to determine the ability of an organism to use citrate as its sole source of carbon

A

citrate utilization test

34
Q

how do you know if citrate is utilized(positive)

A

it will turn blue

35
Q

what is the SIM medium used for

A

determination of three bacterial activities:

sulfur reaction, indole production from tryptophan, and motility

36
Q

both systems produce what

A

hydrogen sulfide gas

37
Q

what is an indication of a sulfur reaction and a positive test

A

any blackening of the medium

38
Q

what is indole production in the medium made possible by

A

the presence of tryptophan

39
Q

what can be detected by the addition of kovac’s reagent

A

tryptophan hydrolysis in the SIM medium

40
Q

what indicates a positive reaction and the presence of tryptophanase

A

the formation of red color in the reagent layer

41
Q

what is determination of motility in SIM medium made possible by

A

the reduced agar concentration and the method of inoculation

42
Q

what does hazziness/fuzziness usually indicate

A

motility

43
Q

what does TSIA stand for

A

triple sugar iron agar

44
Q

TSIA is a rich medium designed to differentiate bacteria on the basis of what

A

glucose fermentation, lactose fermentation, sucrose fermentation, and sulfur reduction

45
Q

what is the pH indicator

A

Phenol red

46
Q

what is the hydrogen sulfide indicator

A

iron in the ferrous sulfate

47
Q

when TSIA is inoculated with a glucose only fermenter what happens

A

acid products lower the pH ad turn the entire medium yellow within a few hours

48
Q

what is reversion

A

the process that occurs in the slant when organisms break down available amino acids which raises the pH

49
Q

what does a TSIA with a red slant and yellow butt indicate

A

the organism ferments glucose but not lactose or sucrose.

50
Q

what color do organisms turn that are able to ferment glucose and sucrose/lactose

A

yellow throughout

Microbiology Lab (25 decks)

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