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Microbiology > Lab Exam > Flashcards

Lab Exam Flashcards

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Biology 101 flashcards
1
Q

What do molecular methods of microbial identification rely on

A

distinctive features microbial nucleic acids for identification

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2
Q

What does serological methods of microbial identification rely on

A

recognition of microbial features by antibody proteins; based on the use of blood serum

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3
Q

What can antibody-based methods of microbe recognize

A

individual features on microbial cells called antigens

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4
Q

What does mass spectroscopy methods identify microbes based on

A

most abundant proteins in the cells

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5
Q

What are tests that help identify chemoheterotrophic bacteria

A

gram stain
motility
oxygen relationship
glucose fermentation
catalase
oxidase

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6
Q

What does the glucose fermentation test detect

A

whether the microbe can grow in the medium and if it can ferment glucose

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7
Q

What does a tube of carbohydrate fermentation broth contain that is the target component of the medium

A

specific sugar as a potentially fermentable carbon and energy source

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8
Q

What does brom-cresol purple do in glucose fermentaiton broth

A

changes to a yellow color as a result of the considerable acid production from fermentative breakdown of the sugar

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9
Q

What percent of gas is considered a positive result

A

10

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10
Q

What does the nitrate reduction test detect

A

whether the microbe can grow on the medium supplied using anaerobic respiration with nitrate as the final electron acceptor

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11
Q

What is the target component in the medium for nitrate reduction test

A

potassium nitrate

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12
Q

With the use of a durham tube in the medium reduction of nitrate to _______ or _____________ can be detected

A

nitrite; nitrogen gas

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13
Q

What do you look for to observe reduction of nitrate to nitrogen gas

A

large bubble in durham tube

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14
Q

What is the complete reduction of nitrate to n gas

A

denitrification

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15
Q

To test for reduction of nitrate to nitrite what do you need to add to the test tube and mix? what do you look for upon mixing

A

nitrite reagents (sulfanilamid and N-ethylenediamine); pink or red color

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16
Q

If you see no red in the test of reduction from nitrate to nitrite what do you do

A

add a few more drops of each reagent, mix well, and observe again

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17
Q

How do we check for unreduced nitrate

A

adding a small amount of granulated zinc to any tube not showing a positive reaction for nitrite or gas

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18
Q

If nitrate is present what will it look like

A

be reduced by the zinc to nitrite which will react with the reagents already added forming a pink or red color so it is negative for the reaction

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19
Q

Motility test detects

A

microbes that are motile with flagella can usually swim through a semi-solid medium containing a small amount of agar

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20
Q

How much agar is in the motility test

A

0.4

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21
Q

What is the target in the medium for motility

A

agar

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22
Q

What does the catalase test for

A

enzyme catalase present

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23
Q

what does catalase do

A

breakdown of toxic hydrogen peroxide

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24
Q

What type of respiring microbes would possess catalase

A

stric aerobes or facultative anaerobes

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25
Q

What is the hydrogen peroxide breakdown

A

2H2O2 –> 2H2O + O2

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26
Q

Prior to catalase how are the grown

A

on a slant or plate of an al purpose medium

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27
Q

What percent of hydrogen peroxide is added for the catalase test

A

3-5%

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28
Q

What type of reaction is the oxidase test

A

colorimetric reaction

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29
Q

What is oxidase testing for

A

cytochrome C oxidase enzyme in the respiratory electron transport chain

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30
Q

what color will the plastic strips turn when the oxidase test is positive

A

purple

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31
Q

T/F you must look for an immediate response to the oxidase test

A

T

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32
Q

The enterobacteriaceae is a family of gram ______ __________

A

negative proteobacteria

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33
Q

All enteric are…

gram stain
shape

A

gram negative rods

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34
Q

When are enteric bacteria mistaken for cocci

A

in older cultures as cells shorten up to a coccobaccilus shape

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35
Q

All enteric are…

_______heterotroph
respiration

A

chemoorganoheterotrophic
true facultative anaerobes

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36
Q

Are enterics able to ferment glucose

A

yes

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37
Q

All enteric are…

catalase
oxidase

A

positive
negative

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38
Q

T/F most enteric are motile

A

T

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39
Q

The KIA test is used only for gram _____ bacteria mainly enterics and pseudomonas

A

negative

40
Q

What is the purpose of KIA test

A

test fermentation of a major sugar (lactose) and a minor sugar (glucose) as well as production of hydrogen sulfide

41
Q

What is the purpose of the methyl red test

A

the purpose of this test is to identify the end products from glucose fermentation

42
Q

what does the voges proskauer test indicate

A

the neutral products formed by the butanediol

43
Q

generally enterics are positive for the MR or the VP test but not

A

both

44
Q

What is the color for MR test that is postive and what does it mean

A

red; mixed acid fermentation; pH has dropped and then remained below 4.4

45
Q

What is the color for a negative MR test and what does it mean

A

yellow; indicative of butanediol fermentation; pH has dropped and then risen to 6.2 or above

46
Q

What is the purpose of the simmons citrate test

A

test for the use of citrate as a carbon and energy source

47
Q

What is the target component in the medium simmons citrate test

A

sodium citrate

48
Q

If citrate has been used….

A

an alkaline reaction results and turns bright blue

49
Q

What medium is known to give false positive when there is too-heavy innoculation

A

simmons citrate agar

50
Q

what does emb agar inhibit

A

growth of gram positive bacteria due to eosin and methylene blue dyes

51
Q

What gram bacteria is typically used on EMB

A

negative

52
Q

Can EMB be used to identify lactose fermenting bacteria

A

yes

53
Q

Is EMB both differential and selective

A

yes

54
Q

What will a coli type look like on EMB

A

colonies appear dark, and have bright green metallic sheen if observed by reflected light

55
Q

Why does a sheen result

A

rapid fermentation of lactose, causing a low pH to precipitate methylene bue

56
Q

What will a aerogenes type look like on EMB

A

colonies appear less dark; normally light colored with mucoid rim surrounds a dark center

57
Q

What do non lactose fermenting microbes look like on EMB

A

light

58
Q

What is the purpose of the phenylaline test

A

test for the deamination of the AA phenylalanine

59
Q

if phenylalanine deamination has taken place, the reagent will react with the phenyl pyruvic acid formed and turn what color

A

dark green

60
Q

What does MIO test

A

motility
ability to produce indole
ability to decarboxylate ornithine

61
Q

how do bacteria produce indole, pyruvic acid, and ammonia

A

produce the enzyme tryptophan’s and degrade tryptophan

62
Q

What is in kovac’s reagent

A

p-dimethylaminobenzoladhyde, butanol, and hydrochloric acid

63
Q

What color is produced in MIO when there is a reaction with indole

A

red color

64
Q

indole is detected in MIO by its reaction

A

with the chemicals in kovac’s reagent

65
Q

How to test for ornithine decarboxylation in MIO

A

observe the lower 3/4 (anaerobic region) of the medium for change in color of the pH indicator; growth must be present in this part of the tube

66
Q

What color will be present in ornithine decarboxylation of MIO when there is a positive reaction

A

gray, blue, purple

67
Q

decarboxylation of lysine, ornithine, and histidine will result in production of

A

cadaverine, putrescine, and histamine

68
Q

What is a negative reaction for lysine decarboxylase broth

A

yellow color

69
Q

What is a positive reaction for lysine decarboxylase and what it means

A

gray, blue, purple–alkaline product that neutralizes the acid produced from glucose fermentation

70
Q

will a strict aerobe such as pseudomonas grow in decarboxylase control test

A

no it will remain purple

71
Q

What does the lactose fermentation test detect

A

whether the microbe can grow in the medium; and if so, if it can ferment lactose

72
Q

What is the target component in lactose fermentation broth

A

lactose

73
Q

What color change occurs if the lactose fermentation broth is positive

A

purple to yellow

74
Q

What do multitest systems provide savings in terms of

A

time and reagents used

75
Q

What number of multi test identification is used for enteric bacteria

A

20E

76
Q

If the methyl red results are yellow what does it mean

A

negative reaction and has butanediol fermentation

77
Q

If the methyl red results are orange what does it mean

A

equivocal reaction

78
Q

How long must MR test incubate

A

about 2 days

79
Q

How long must KIA be incubated

A

24 hours only

80
Q

What type of medium is EMB

A

differentail and selective

81
Q

What is the selevtive part of EMB

A

eosin and methylene blue dyes

82
Q

What is the differentail part of EMB

A

lactose

83
Q

How long must you incubate EMB

A

only 24 hours

84
Q

What type of lactose bacteria will look fisheye on EMB

A

aerogenes type

85
Q

How do you innoculate the phenylalanine test

A

streak across top of the penylalanine agar slant only

86
Q

What does a dark green color appearing on the slant of a phenylalalinine test mean

A

phenylalanine deamination has occurred the reagent will react with the phenylpyruvic acid formed

87
Q

How do you inoculate the MIO agar

A

stab the medium about 3/4 the depth of the tube

88
Q

What reagent must be added to the test tube to determine if phenylalnine deamination ahs occured

A

FeCl3

89
Q

If the bottom 3/4 (anaerobic region) is yellow in the MIO what does it mean

A

glucose fermentation occured

90
Q

To determine indole production in MIO what must be added

A

kovacs reagent

91
Q

Where is it best to detect formation of highly alkaline diamine

A

anaerobic growth region of the medium

92
Q

What type of microbe will not grow in the decarboxylase control test

A

pseudomonas–a strict aerobe

93
Q

What does pseudomonas look like in the decarboxylase broth

A

purple

94
Q

Define obligate aerobic

A

requires oxygen

95
Q

Define microaerophile

A

requires low levels of oxygen

96
Q

Define facultative respirer

A

can grow with or without oxygen

97
Q

Define obligate anaerobic respirer

A

oxygen free

Microbiology (29 decks)

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