Chung Microbiology Lab Quiz 1 and 2

0.0(0)
studied byStudied by 1 person
learnLearn
examPractice Test
spaced repetitionSpaced Repetition
heart puzzleMatch
flashcardsFlashcards
Card Sorting

1/93

encourage image

There's no tags or description

Looks like no tags are added yet.

Study Analytics
Name
Mastery
Learn
Test
Matching
Spaced

No study sessions yet.

94 Terms

1
New cards

the ph indicator in carbohydrate broth

phenol red

2
New cards

In the carbohydrate broths, deamination of amino acids supplied by peptone results in an alkaline reaction from the ___ that is produced and turns the medium ___ (color).

ammonia, pink/red

3
New cards

Acid production from fermentation of the carbohydrate in the carbohydrate broths lowers the pH below the neutral range of the indicator and turns the medium ___

yellow

4
New cards

Gas production from the fermentation of a sugar in the carbohydrate broths, is indicated by a bubble, or pocket, in the inverted tube in the broth, also known as a ___ tube.

durham

5
New cards

When inoculating microorganisms onto a mannitol salt agar plate, the selective component of the medium is ___.

salt

6
New cards

When inoculating microorganisms onto a mannitol salt agar plate, the differential components of the medium are the pH indicator ___ and the sugar ___.

phenol red, mannitol

7
New cards

EMB agar is a complex ___ and ___ medium.

differential, selective

8
New cards

The two functions of eosin Y and methylene blue in EMB agar are to inhibit the growth of ___ bacteria and to serve as indicators of vigorous ___ fermentation.

gram positive, lactose

9
New cards

MacConkey agar is a commonly used selective and differental medium. ___ and ___ inhibit the growth of Gram (+) bacteria.

bile salts, crystal violet

10
New cards

The differential agents found in the MacConkey agar plate include the sugar ___ and the pH indicator ___.

lactose, neutral red

11
New cards

Vigorous lactose fermenters growing on the EMB plate produce ___ colonies while non-lactose fermenters produce ___ colonies.

black, colorless

12
New cards

Vigorous lactose fermenters growing on the MacConkey agar plate produce ___ colonies while non-lactose fermenters produce ___ colonies.

red, colorless

13
New cards

the enzyme catalase breaks down ___ into ___ and ___

hydrogen peroxide, oxygen, water

14
New cards

When hydrogen peroxide is added to a catalase-positive culture, oxygen gas ___ form immediately.

bubbles

15
New cards

Nitrate reduction is an example of ___, reduction of (transfer of electrons to) an inorganic molecule other than oxygen.

anaerobic respiration

16
New cards

Nitrate broth is an undefined medium of beef extract, peptone, and ___

potassium nitrate

17
New cards

Many Gram-negative bacteria (including most Enterobacteriaceae) contain the enzyme ___ and perform a single-step reduction of nitrate to nitrite.

nitrate reductase

18
New cards

Before a broth can be tested for single-step nitrate reduction activity (nitrate reduction to nitrite), it must be examined for evidence of ___. This is simply a visual inspection for the presence of gas in the ___tube.

denitrification, durham

19
New cards

denitrification reaction:

___ > ___ > ___ > ___ > ___

NO3 > NO2 > NO > N2O > N2

20
New cards

If there is no visual evidence of denitrification upon visual inspection, nitrate reagent A ___ and nitrate reagent B ___ are added to the medium to test for nitrate reduction to nitrite.

sulfanilic acid, naphthylamine

21
New cards

Most of the time, we do not use CHO broths to differentiate among organisms, but ___ is an important sugar in differentiating among Gram (-) bacteria, specifically Gram (-) bacteria short rods.

lactose

22
New cards

Bacteria ferment sugars to produce ___ and/or gas. If bacteria do not ferment the sugar in a phenol red carbohydrate broth, it will then use the protein in the media, produce ___ and increase the pH of the solution.

acid, ammonia

23
New cards

Members of the Enterobacteriaceae all ferment ___ but not all of them ferment lactose. They tend to produce catalase and nitrate reductase, classifying them as ___ (oxygen preference).

glucose, facultative anaerobe

24
New cards

___ and ___ do not ferment any sugars because both bacteria are ___ (oxygen preference).

micrococcus, pseudomonas, obligate aerobes

25
New cards

When oxygen is excited to a higher state, reactive oxygen species are produced, such as ___, ___, and ___.

hydroxyl radical, peroxide anion, superoxides

26
New cards

___ and ___ convert peroxide to water and/or oxygen gas.

catalase, peroxidase

27
New cards

All of the bacteria sampled in lab tested positive for the catalase test except for ___

strep lactis

28
New cards

To an inoculated nitrate broth growing for over 48 hours, if the broth does not turn red after you add nitrate solutions A and B, the microbe either does not have the enzyme ___ or does have the enzyme and is a ___.

nitrate reductase, denitrifier

29
New cards

To confirm a negative nitrate reductase test, we add ___ powder, which is a ___, that will force nitrate to nitrite.

zinc, chemical catalyst

30
New cards

Most of the bacteria sampled in class are single-step nitrate reducers. Only two bacteria, ___ and ___ do not reduce nitrate, and only ___ is a denitrifier.

micrococcus, streptococcus, pseudomonas

31
New cards

Selective agents in MacConkey's Agar?

Bile Salts, crystal violet

32
New cards

What does MacConkey Agar inhibit growth of

Gram positive bacteria

33
New cards

What are the differential components in MacConkey's agar?

neutral red, lactose

34
New cards

What does EMB stand for?

Eosin Methylene Blue

35
New cards

Functions of E/MB in EMB agar?

dyes inhibit growth of gram positive bacteria and indicators of fermentation of lactose

36
New cards

pH indicator in carb broths?

Phenol red

37
New cards

Differential components in MSA plate

Phenol red, mannitol

38
New cards

Selective agent of MSA plate?

Salt. Encourages growth of halophiles

39
New cards

Nitrate reduction reaction and enzyme?

Nitrate (NO3) converted to NO2 by nitrate reductase

40
New cards

Catalase reaction and enzyme?

H2O2 converted to H2O + O2 by catalase

41
New cards

What is the key step of gram staining?

Alcohol (decolorizer)

42
New cards

The SIM medium is used for determination of three bacterial activities: (answers in S, I, M order please)

Sulfur reduction, indole production, motility

43
New cards

Sulfur reduction to H2S can be accomplished by bacteria in two different ways, depending on the enzymes present: thiosulfate reductase and

cysteine desulfurase

44
New cards

Bacteria possessing the enzyme _______ can hydrolyze tryptophan to ____________ and __________ (these 2 answers in alphabetical order), with the waste product ammonia.

Tryptophanase, indole, pyruvic acid

45
New cards

Urea can be hydrolyzed to _______ and _______ (these 2 answers in alphabetical order) by bacteria possessing the enzyme __________ .

Ammonia, carbon dioxide, urease

46
New cards

The pH indicator in the urea broth is ________ , which turns the media hot pink when the pH rises due to the increased levels of __________.

Phenol red, ammonia

47
New cards

Organisms that produce the enzyme _________ can be identified by their ability to deaminate the amino acid ___________ .

Phenylalanine deaminase, phenylalanine

48
New cards

Starch is a complex polysaccharide compound composed of _________ and ________ (answers in alphabetical order). There are three enzymes involved in starch digestion: an alpha-1,6-glucosidase and an alpha and beta-___________ .

Amylose, amylopectin, amylase

49
New cards

Gelatin is a protein derived from collagen and can be hydrolyzed by the enzyme _________ . Because the enzymes that hydrolyze both starch and gelatin are secreted extracellularly, they are referred to as __________ .

Gelatinase, exoenzymes

50
New cards

The purpose of the IMViC battery of tests is to differentiate among Gram-________ short rod ___________ __________.

Negative, lactose, fermenters

51
New cards

What is Gram's Crystal Violet in a gram stain?

Primary stain

52
New cards

What is Gram's Iodine in a gram stain?

Mordant

53
New cards

What is Safranin in a gram stain?

Counterstain

54
New cards

What is a SIM stab composed of?

0.75% agar, iron salts (protein)

55
New cards

Sulfur reduction reaction

Cytesine ——→ (Cytesine desulfurase) pyruvic acid + NH3 + H2S

56
New cards

Indole production reaction

Tryptophan + water ——> (Tryptophanase) indole +Pyruvic acid

57
New cards

Reagent for indole production

Kovac’s

58
New cards

Positive test for indole production?

A red layer forms on top of the media as Kovac’s reagent binds to indole meaning the enzyme tryptophanase is present

59
New cards

How is motility tested for?

Tested in the SIM stab where cloudiness surrounding the stab in the media indicates motile bacteria

60
New cards

Urease hydrolysis reaction

Urea + water ——> (urease) ammonia + CO2

61
New cards

What is the pH indicator in a urea hydrolysis test?

Phenol red

62
New cards

What is a positive and negative urea hydrolysis test and why do they occur?

Positive test = media turns pink, negative media orange/yellow. Occurs as pH increases with the production of ammonia if the bacteria has the enzyme urease

63
New cards

Phenylalanine deaminase reaction

Phenylalanine —→ (Phenylalanine deaminase) Phenylpyruvic acid + NH3 +H2S

64
New cards

Reagent in phenylalanine deaminase reaction

Ferric chloride

65
New cards

What does a positive test look like for phenyalanine deaminase and why does it occur?

If phenylpyruvic acid is present in the media as a result of the phenylalanine deaminase enzyme, ferric chloride will bind to it and form a dark green color. Negative tests remain yellow

66
New cards

What is starch agar composed of?

substrate starch, protein, 1.5% agar

67
New cards

What is starch made of?

Amylose, amylopectin

68
New cards

What is the enzyme that breaks down starch?

Amylase

69
New cards

Why is a protein source required in a starch hydrolysis and gelatin hydrolysis test?

So bacteria can grow regardless of their ability to hydrolyze starch or gelatin

70
New cards

What is the reagent used in a starch hydrolysis test?

Gram’s iodine

71
New cards

What does a negative and positive test look like for a starch hydrolysis test.

Gram’s iodine will bind to remaining starch forming a dark complex indicating that the bacteria can not hydrolyze starch. A clearing around a bacteria indicates that starch is not present and the bacteria possesses the enzyme amylase.

72
New cards

What is gelatin agar made of?

Gelatin, 1.5% agar, protein source

73
New cards

What is the enzyme we are looking for in a gelatin hydrolysis test?

Gelatinase

74
New cards

What is/are the reagent(s) used in a gelatin hydrolysis test?

Mercuric chloride in hydrochloric acid

75
New cards

What does a positive and negative gelatin hydrolysis test look like

Mercuric chloride in hydrochloric acid forms a white precipitate around bacteria with gelatin present. Bacteria with the enzyme gelatinase will have hydrolyzed the gelatin leaving a clearing around the bacteria.

76
New cards

What are the IMVC tests used for?

Differentiate between members of enterobacteriaceae, specifically short rod, gram negative, lactose fermenters

77
New cards

What do MRVP broths contain in their media?

Buffered peptone, glucose

78
New cards

What do MRVP broths test for?

Glucose fermentation

79
New cards

What 2 pathways do bacteria use to ferment glucose in an MRVP test?

Mixed acid fermentation, 2-3, butanediol fermentation

80
New cards

Which pathway does the MR test test for?

Mixed acid fermentation

81
New cards

What is the reagent used in an MR test?

Methyl red

82
New cards

What does a positive and negative test look like in an MR test?

Red = positive for mixed acids, pH <4. yellow = negative for mixed acids, pH >6

83
New cards

What pathway does the VP test test for?

2,3 -butanediol fermentation.

84
New cards

What is the VP test testing for in the media?

Acetoin. Come before 2,3 -butanediol

85
New cards

What are the reagents used in a VP test?

Alpha naphthol and KOH (potassium hydroxide)

86
New cards

What does a positive VP test look like?

Red = positive for acetoin

87
New cards

What does the citrate test test for?

The ability of microbes to use citrate as the sole source of carbon

88
New cards

What is a positive and negative citrate test?

Blue media = positive, green media = negative

89
New cards

What is the pH indicator in a citrate test?

Bromothymol blue

90
New cards

What are the pH’s of a positive and negative citrate test?

Positive = pH >7, negative = pH <7

91
New cards

Parfocal

Object remains in focus as one changes from one objective lens to another, requiring only minor adjustments with the fine adjustment knob to bring the object back into focus

92
New cards

Resolution

The ability of a microscope objective to clearly distinguish two adjacent points lying close together in a magnified specimen

93
New cards

Chromophore

Color bearing ion of a dye

94
New cards

What is the reaction that forms a black precipitate following the cysteine reaction

H2S + FeSO4 —-> FeS + H2SO4, black precipitate is FeS