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Microbiology 101 > Lab Final Exam Part I (Ex 8) > Flashcards

Lab Final Exam Part I (Ex 8) Flashcards

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1
Q

Many of the detectable differences between bacteria are ______ in nature, and reflect different _____ paths taken by each bacterium.

A

Biochemical; Evolutionary

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2
Q

Aerobic respiration results in the formation of _______ which are converted to toxic _______ as part of the electron transport chain.

A

Hydrogen ions (H+); hydrogen peroxides (H2O2)

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3
Q

What enzyme breaks down peroxides into non-toxic H2O and O2?

A

Catalase

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4
Q

This enzyme is needed in order for a cell to exist in the presence of oxygen.

A

Catalase

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5
Q

Most bacteria are catalase ______ with the exception of bacteria that cannot carry out aerobic respiration (for example, _____ _____ (type of bacteria)).

A

Positive; Obligate anaerobes

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6
Q

In a catalase test, what will a positive result show?

A

Bubble formation after placing a drop of hydrogen peroxide on the colony on a slide.

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7
Q

This enzyme is involved in the reduction of oxygen at the end of the electron transport chain.

A

Cytochrome oxidase

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8
Q

Due to the relationship with the electron transport chain, organisms will rarely be oxidase ____ and catalase ____.

A

Positive; Negative

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9
Q

In an oxidase text, what will a positive result show?

A

A purple color change in the edging after adding Kovac’s reagent.

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10
Q

Carbohydrates (sugars and starches) can be broken down by ___, which results in _______.

A

Fermentation; Acid production

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11
Q

This is used in the media for carbohydrate utilization testing, to support the growth of the bacteria if the carbohydrate cannot be utilized.

A

Peptone

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12
Q

This is used in carbohydrate utilization testing, to test the bacteria.

A

Carbohydrate

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13
Q

This is used in carbohydrate utilization testing, and it a pH indicator that changes color

A

Phenol Red

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14
Q

What is the color change that occurs during a carbohydrate fermentation test, and what does the color change indicate?

A

Red to yellow; Indicates acid production

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15
Q

This is used in carbohydrate utilization testing, and is an inverted tube used to collect gas that is formed.

A

Durham Tube

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16
Q

The end products in fermentation are ___.

A

Acids

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17
Q

These tests look for either acetoin or mixed acid production

A

MR-VP (Methyl Red–Voges-Proskauer)

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18
Q

This reagent is used to identify bacteria that produce stable acid end products by means of mixed acid fermentation of glucose

A

Methyl Red

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19
Q

In the MR test, after incubation, a pH indicator is inserted. In ____ environments, it will turn red. In ___ environments, it will be yellow.

A

Acidic; Neutral

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20
Q

A positive test result in the Methyl Red test would present as ____.

A

Red color change indicating mixed acid production

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21
Q

This test determines the ability of the organism to produce acetoin as an end product of fermentation.

A

Voges-Proskauer

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22
Q

A positive test result in the Voges-Proskauer test would show as ____, indicating ____ production.

A

Red color change; Acetoin

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23
Q

A negative test result in the Voges-Proskauer test would show as ___.

A

The reagent will turn the media a darker yellow.

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24
Q

Many bacteria species have enzymes that can break down ___ ___ into small molecules that can be used for energy.

A

Large polysaccharides

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25
Q

In our case, a hydrolytic enzyme called ___ and the addition of a water molecule will break the ___ down into useable glucose.

A

Amylase; Polysaccharide

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26
Q

In the Starch Hydrolysis test, which is testing for the enzyme amylase, a positive result will appear as _____.

A

A clear halo around the colonies after the addition of Gram’s iodine.

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27
Q

In the Starch Hydrolysis test, which is testing for the enzyme amylase, a negative result will appear as _____.

A

The entire medium is dark blue/brown

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28
Q

What is the reagent used in the starch hydrolysis test?

A

Gram’s iodine

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29
Q

What does the media contain in the nitrate reduction test?

A

Peptone, beef extract, and potassium nitrate

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30
Q

What is the reagent used in the nitrate reduction test?

A

Paba

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31
Q

How will a positive nitrate reduction test appear?

A

Yellow, pink, or red color after adding the Paba.

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32
Q

How will a negative nitrate reduction test appear?

A

No color change after adding the Paba.

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33
Q

How long should the sample sit after the addition of the reagent, before reading the results, in the nitrate reduction test?

A

Appx 5 minutes, no more than 20 minutes

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34
Q

H2S Production test looks for the production of what?

A

Hydrogen sulfide

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35
Q

What is the meda used in the H2S production test

A

Iron Peptone Agar (PIA)

36
Q

Some organisms have a ______that liberates _____ _____ from sulfur containing organic compounds (H2S production test)

A

Enzyme; Hydrogen Sulfide

37
Q

What does a positive result H2S production test look like?

A

Growth with black precipitate in the media

38
Q

What does a negative result H2S production test look like?

A

Grown with no black precipitate in the media

39
Q

What causes the positive H2S test result to appear as it does?

A

When H2S is liberated by the enzyme, the sulfur of the H2S combines with the iron in the medium to form an iron sulfide (black precipitate).

40
Q

What is the name of the medium used in the citrate utilization test?

A

Simmons citrate agar`

41
Q

What does the Simmons citrate agar test for? (2 answers)

A

It tests for the ability of organisms to utilize citrate as a sole carbon source; It tests for the presence of alkaline (basic) products as a result of citrate utilization

42
Q

The enzymes ___ or ___ transport citrate into the cell to make it available for energy catabolizing processes.

A

citrase; citrate-permease

43
Q

What does a positive citrate utilization test look like?

A

Color changes from green to blue

44
Q

What does a negative citrate utilization test look like?

A

No color change (stays green)

45
Q

What does a positive citrate utilization test mean?

A

Citrate was utilized as the sole carbon source

46
Q

What does a negative citrate utilization test mean?

A

Citrate was not utilized

47
Q

What kind of media is used for motility tests?

A

Motility agar deeps

48
Q

What color does the dye in the motility agar test show growth?

A

Pink

49
Q

What does a positive motility test look like?

A

Growth with fanning out from the stab line

50
Q

What does a negative motility test look like?

A

No fanning out from the stab line

51
Q

True/False: A positive motility test may look cloudy

A

True. A positive motility test may appear cloudy

52
Q

What is the urea hydrolysis looking for?

A

The enzyme urease

53
Q

What is the name of the medium used in the urea hydrolysis test?

A

Christensen’s Urea Broth

54
Q

What is the pH indicator in the urea hydrolysis test?

A

Phenol red

55
Q

What does a positive urea hydrolysis test look like?

A

Bright pink slant

56
Q

What does a negative urea hydrolysis test look like?

A

Light orange to yellow

57
Q

What does a positive urea hydrolysis test mean?

A

Urease is present, urea was hydrolyzed

58
Q

What does a negative urea hydrolysis test mean?

A

There is no urease present, urea was not hydrolyzed

59
Q

What does the phenylalanine deamination test look for?

A

The presence of phenylalanine deaminase

60
Q

In the phenylalanine deamination test, it utilizes the amino acid ___ that is converted to ___.

A

phenylalanine; phenylpyruvic acid

61
Q

What is the reagent in the phenylalanine deaminase test?

A

FeCl3

62
Q

What does a positive phenylalanine test look like?

A

Dark green color

63
Q

What does a negative phenylalanine test look like?

A

No color change

64
Q

What does a positive phenylalanine test mean?

A

Phenylalanine deaminase is present (phenylalanine was metabolized to phenylpyruvic acid)

65
Q

What does a negative phenylalanine test mean?

A

Phenylalanine deaminase is NOT present (phenylalanine was not metabolized)

66
Q

What does a positive bile esculin test look like?

A

Growth of bacteria with a color change of the media to black

67
Q

What does a negative bile esculin test look like?

A

Grown of bacteria without color change, or no growth of bacteria

68
Q

What does a positive bile esculin test mean?

A

Bacteria able to hydrolyze esculin and survive in the bile salts

69
Q

What does a negative bile esculin test mean?

A

Bacteria are unable to hydrolyze esculin, or unable to grow in the presence of bile.

70
Q

What does MSA stand for?

A

Mannitol salt agar

71
Q

What does mannitol salt agar select for?

A

Gram positive organisms that can survive the high salt content

72
Q

What does the mannitol salt agar differentiate?

A

Species that ferment mannitol into acid

73
Q

What does a positive MSA test look like?

A

Growth of bacteria, with a color change of the media to yellow

74
Q

What does a negative MSA test look like?

A

Growth of bacteria without color change, or no growth of bacteria.

75
Q

What does a negative MSA test mean?

A

Bacteria are unable to tolerate high salt, or unable to ferment mannitol

76
Q

What does EMB stand for?

A

Eosin Methyline Blue Agar

77
Q

What is EMB used for?

A

Identification and isolation of gram-negative rods

78
Q

What does EMB select for?

A

Inhibits growth of Gram-positive organisms

79
Q

What does EMB differentiate?

A

lactose fermenting and non-lactose fermenting organisms

80
Q

What does a positive EMB look like?

A

Growth of bacteria with a color change of the colonies that have dark centers (magenta or purple) or a metallic green sheen

81
Q

What does a negative EMB look like?

A

Growth of bacteria without color change (same as media color), or no growth of bacteria

82
Q

On an EMB test, how do lactose fermenters appear?

A

Dark centers with clear borders

83
Q

On an EMB test, how do non-lactose fermenters appear?

A

Colorless colonies (take on media color)

84
Q

What is MacConkey agar used for?

A

Identifies lactose fermenting, Gram-negative enteric organisms

85
Q

What does MacConkey Agar select for?

A

Inhibits growth of Gram-positive organisms

86
Q

What does a positive MAC test look like?

A

Growth of bacteria with a color change of the media to bright pink

87
Q

What does a negative MAC test look like?

A

Growth of bacteria with no color change, or no growth of bacteria.

Microbiology 101 (10 decks)

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