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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
In our case, a hydrolytic enzyme called ___ and the addition of a water molecule will break the ___ down into useable glucose.
Amylase; Polysaccharide
26
In the Starch Hydrolysis test, which is testing for the enzyme amylase, a positive result will appear as _____.
A clear halo around the colonies after the addition of Gram's iodine.
27
In the Starch Hydrolysis test, which is testing for the enzyme amylase, a negative result will appear as _____.
The entire medium is dark blue/brown
28
What is the reagent used in the starch hydrolysis test?
Gram's iodine
29
What does the media contain in the nitrate reduction test?
Peptone, beef extract, and potassium nitrate
30
What is the reagent used in the nitrate reduction test?
Paba
31
How will a positive nitrate reduction test appear?
Yellow, pink, or red color after adding the Paba.
32
How will a negative nitrate reduction test appear?
No color change after adding the Paba.
33
How long should the sample sit after the addition of the reagent, before reading the results, in the nitrate reduction test?
Appx 5 minutes, no more than 20 minutes
34
H2S Production test looks for the production of what?
Hydrogen sulfide
35
What is the meda used in the H2S production test
Iron Peptone Agar (PIA)
36
Some organisms have a ______that liberates _____ _____ from sulfur containing organic compounds (H2S production test)
Enzyme; Hydrogen Sulfide
37
What does a positive result H2S production test look like?
Growth with black precipitate in the media
38
What does a negative result H2S production test look like?
Grown with no black precipitate in the media
39
What causes the positive H2S test result to appear as it does?
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
What is the name of the medium used in the citrate utilization test?
Simmons citrate agar`
41
What does the Simmons citrate agar test for? (2 answers)
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
The enzymes ___ or ___ transport citrate into the cell to make it available for energy catabolizing processes.
citrase; citrate-permease
43
What does a positive citrate utilization test look like?
Color changes from green to blue
44
What does a negative citrate utilization test look like?
No color change (stays green)
45
What does a positive citrate utilization test mean?
Citrate was utilized as the sole carbon source
46
What does a negative citrate utilization test mean?
Citrate was not utilized
47
What kind of media is used for motility tests?
Motility agar deeps
48
What color does the dye in the motility agar test show growth?
Pink
49
What does a positive motility test look like?
Growth with fanning out from the stab line
50
What does a negative motility test look like?
No fanning out from the stab line
51
True/False: A positive motility test may look cloudy
True. A positive motility test may appear cloudy
52
What is the urea hydrolysis looking for?
The enzyme urease
53
What is the name of the medium used in the urea hydrolysis test?
Christensen's Urea Broth
54
What is the pH indicator in the urea hydrolysis test?
Phenol red
55
What does a positive urea hydrolysis test look like?
Bright pink slant
56
What does a negative urea hydrolysis test look like?
Light orange to yellow
57
What does a positive urea hydrolysis test mean?
Urease is present, urea was hydrolyzed
58
What does a negative urea hydrolysis test mean?
There is no urease present, urea was not hydrolyzed
59
What does the phenylalanine deamination test look for?
The presence of phenylalanine deaminase
60
In the phenylalanine deamination test, it utilizes the amino acid ___ that is converted to ___.
phenylalanine; phenylpyruvic acid
61
What is the reagent in the phenylalanine deaminase test?
FeCl3
62
What does a positive phenylalanine test look like?
Dark green color
63
What does a negative phenylalanine test look like?
No color change
64
What does a positive phenylalanine test mean?
Phenylalanine deaminase is present (phenylalanine was metabolized to phenylpyruvic acid)
65
What does a negative phenylalanine test mean?
Phenylalanine deaminase is NOT present (phenylalanine was not metabolized)
66
What does a positive bile esculin test look like?
Growth of bacteria with a color change of the media to black
67
What does a negative bile esculin test look like?
Grown of bacteria without color change, or no growth of bacteria
68
What does a positive bile esculin test mean?
Bacteria able to hydrolyze esculin and survive in the bile salts
69
What does a negative bile esculin test mean?
Bacteria are unable to hydrolyze esculin, or unable to grow in the presence of bile.
70
What does MSA stand for?
Mannitol salt agar
71
What does mannitol salt agar select for?
Gram positive organisms that can survive the high salt content
72
What does the mannitol salt agar differentiate?
Species that ferment mannitol into acid
73
What does a positive MSA test look like?
Growth of bacteria, with a color change of the media to yellow
74
What does a negative MSA test look like?
Growth of bacteria without color change, or no growth of bacteria.
75
What does a negative MSA test mean?
Bacteria are unable to tolerate high salt, or unable to ferment mannitol
76
What does EMB stand for?
Eosin Methyline Blue Agar
77
What is EMB used for?
Identification and isolation of gram-negative rods
78
What does EMB select for?
Inhibits growth of Gram-positive organisms
79
What does EMB differentiate?
lactose fermenting and non-lactose fermenting organisms
80
What does a positive EMB look like?
Growth of bacteria with a color change of the colonies that have dark centers (magenta or purple) or a metallic green sheen
81
What does a negative EMB look like?
Growth of bacteria without color change (same as media color), or no growth of bacteria
82
On an EMB test, how do lactose fermenters appear?
Dark centers with clear borders
83
On an EMB test, how do non-lactose fermenters appear?
Colorless colonies (take on media color)
84
What is MacConkey agar used for?
Identifies lactose fermenting, Gram-negative enteric organisms
85
What does MacConkey Agar select for?
Inhibits growth of Gram-positive organisms
86
What does a positive MAC test look like?
Growth of bacteria with a color change of the media to bright pink
87
What does a negative MAC test look like?
Growth of bacteria with no color change, or no growth of bacteria.

Microbiology 101 (10 decks)

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