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Quiz 3 Flashcards

1
Q

What is the purpose of the decarboxylase test?

A

to determine whether bacteria can decarboxylate lysine or ornithine

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2
Q

What is lysine and ornithine and what are we removing in a decarboxylase test?

A
  • they are an amino group
  • removing a carboxyl group
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3
Q

Why is glucose included in the media recipe for the decarboxylase test?

A
  • for fermentation (bacteria use glucose 1st (at a low concentration) to lower the pH
  • when glucose is fermented, acids are produced and acids need to be present for decarboxylase to be active
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4
Q

What is the pH indicator for the decarboxylase test and what are the different colors produced at the different pH?

A

bromocresol purple
- yellow = acidic
- orange = neutral
- purple = alkaline

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5
Q

What is the required coenzyme for the decarboxylase test?

A

pyridoxyl - decarboxylase will not be active unless pyridoxyl is present

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6
Q

What are the amino acid substrates in the decarboxylase test?

A

L-lysine or L-ornithine

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7
Q

What is the endoenzyme of the decarboxylase test?

A

decarboxylase
- specifically, lysine decarboxylase or ornithine decarboxylase

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8
Q

What are the three requirements for the enzyme to be active in the decarboxylase test?

A

1) low pH
2) pyridoxyl is a required coenzyme
3) anaerobic

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9
Q

What are the products of the decarboxylase test and what are their associated substrates?

A

cadaverine or putrescine depending on the substrate and carbon dioxide
- lysine if cadaverine is product
- ornithine if putrescine is product

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10
Q

What does a positive decarboxylase test look like and what are their associated substrates?

A

purple
- it is alkaline
- bacteria decarboxylated amino acid and produced diamine which raised the pH

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11
Q

What does a negative decarboxylase test look like and what does the indicative color tell you?

A

yellow
- it is acidic
- bacteria metabolized sugar and produced acids which lowered the pH

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12
Q

What is the purpose of the phenylalanine deaminase test?

A

Determine whether bacteria can deaminate phenylalanine

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13
Q

What is the name of the media in the phenylalanine deaminase test?

A

Phenylalanine slant

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14
Q

What is the amino acid substrate of the phenylalanine test?

A

phenylalanine

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15
Q

What is the endoenzyme used in the phenylalanine test?

A

phenylalanine deaminase

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16
Q

What are the products of the phenylalanine deaminase test?

A

ammonia and phenyl pyruvic acid

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17
Q

Why can’t we use a pH indicator in the phenylalanine deaminase test and what do we use instead?

A

Ammonia will raise the pH while phenyl pyruvic acid lowers pH
- we use ferric chloride as a reagent instead
- this detects the phenyl pyruvic acid

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18
Q

What does a negative and positive test look like in the phenylalanine deaminase test?

A

negative = stays yellow (no phenyl pyruvic acid produced)

positive = turns green (phenyl pyruvic acid present)

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19
Q

What is the difference between deamination and decarboxylation?

A

deaminated = aerobic

decarboxylated = anaerobic

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20
Q

What is the purpose of the casein hydrolysis?

A

to determine whether bacteria can hydrolyze casein

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21
Q

What is the substrate in the casein hydrolysis test?

A

non-fat milk (casein)

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22
Q

Why is an intact protein, instead of peptones, not usually included in the microbiology media?

A

an intact protein is fairly large compared to that of peptones that are small and already partially digested
- intact proteins have trouble getting into cell

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23
Q

What is the exoenzyme of the casein hydrolysis?

A

Casease

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24
Q

What are the products of the casein hydrolysis test?

A

amino acids + polypeptides

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25
What does a positive casein hydrolysis test look like?
milk becomes clear - there will be a clearing around the growth
26
What does a negative casein hydrolysis test look like?
no clearing
27
What is the purpose of the urease test?
to determine whether bacteria can hydrolyze urea
28
What is the substrate of the urease test and where can it be found?
urea - found in urine and stomach juice
29
What is the enzyme of the urease test?
Exoenzyme - urease
30
What are the products of the urease test?
ammonia (alkaline) - raises the pH carbon dioxide - released as gas
31
What is the pH indicator in the urease test?
phenol red
32
What does a positive and negative test of the urease test look like?
positive = pink (alkaline) because ammonia was produced negative = yellow (acidic) or orange because ammonia was not produced
33
What is an example of a medically important urease positive bacteria?
Proteus mirabilis - cause of diaper rash Proteus vulgaris - found in feces
34
Helicobacter pylori is another example of a urease positive bacteria. Why is it able to live in the stomach?
Due to urease activity, urease is able to hydrolyze the urea in stomach and produce ammonia which neutralizes stomach acid which gives bacteria advantage and allows it to live in stomach - Causes ulcers in stomach lining
35
What is the purpose of the gelatin hydrolysis test?
To determine whether bacteria can hydrolyze gelatin
36
What is the substrate of the gelatin hydrolysis test?
Gelatin- a large, bulky protein substrate (solid)
37
What is enzyme of the gelatin hydrolysis test?
exoenzyme - gelatinase
38
What are the products of the gelatin hydrolysis test?
Polypeptides and amino acids
39
What is a positive test for the gelatin hydrolysis test?
A blue indication on the strip - Blue means that the gelatin was hydrolyzed and there is no gelatin on the strip
40
What is a medically important gelatinase (+) bacteria?
Clostridium perfringens - causes gangrene Or Pseudomonas aeruginosa - common cause of death in burn victims
41
What is the inoculation procedure in the TSI test?
Stab inoculate the bottom with a needle then zig zag streak the slant using a loop
42
What is the purpose of the TSI?
To differentiate bacteria on the basis of the glucose fermentation, lactose fermentation, sucrose fermentation, and sulfur reduction
43
What is the amino acid substrate from peptones in the TSI test?
Cysteine
44
What is the substrate that was put in the media in the TSI test?
Sodium thiosulfate
45
What are the two endoenzymes used in the TSI test?
- Cysteine desulfurase - Thiosulfate reductase Both require low pH from fermentation of sugar
46
What is the product of the TSI test?
Hydrogen sulfide (H2S)
47
What is the reagent used in the TSI test?
Ferrous ammonium sulfate
48
What does a positive test of sulfur reduction in the TSI test?
Black will indicate + for sulfur reduction (H2S was produced) - No black would be a negative
49
What are the substrates of the metabolism of sugar aspect of the TSI test?
Glucose (low concentration) and Sucrose and/or lactose
50
What is the enzyme used for the metabolism of sugar of the TSI test?
Various endoenzymes
51
What is the product of the metabolism of sugar of the TSI test?
Acids, alcohol, + or - gas
52
What is the pH indicator for the metabolism of sugar of the TSI test?
Phenol red
53
What does a yellow yellow tube mean in the TSI test?
The bacteria can metabolize glucose and either sucrose and/or lactose
54
What does a yellow butt and a pink slant mean?
The bacteria is a glucose only fermenter then uses the protein as a food source
55
What does pink all throughout mean?
Bacteria was only able to use peptones non-aerobically
56
What does an orange butt and pink slant mean?
Bacteria is only able to use peptones aerobically
57
What was the purpose of the anaerobic jar?
To determine the oxygen requirements of an organism
58
What is the O2 indicator of the anaerobic jar test?
Resazurin - strip indicator Pink = oxidized (aerobic) Clear = reduced (anaerobic)
59
What does oxidation and reduction mean?
OIL RIG Oxidation: loss of electrons Reduction: gain of electrons
60
What is an obligate aerobe?
Grows only in the presence of oxygen
61
What is a microaerophile?
Grows with a low concentration of oxygen
62
What is an obligate anaerobe?
Grows only in the absence of oxygen
63
What is a facultative anaerobe?
Grows with or without oxygen but grows better with oxygen
64
What is an aerotolerant anaerobe?
Grows with or without oxygen but does not use oxygen as the final electron acceptor They tolerate oxygen but do not use it
65
What is catalase positive?
-Uses oxygen to grow -Catalase is used to oxidize hydrogen peroxide to form water and oxygen
66
What is an example of an obligate aerobe and obligate anaerobe?
67
What is the purpose of the thioglycollate medium?
To determine the oxygen requirements of an organism
68
What is the purpose of the sodium thioglycollate and L-cystine in the thio broth?
- To reduce oxygen into water (make anaerobic) - L-cystine is a dimer of cysteine amino acid
69
What is resazurin?
It is an oxygen indicator Pink = oxidized, oxygen is present Colorless = reduced, oxygen is absent
70
What is the purpose of the oxidase test?
To test bacteria for the oxidase enzyme - Testing if oxygen can act as the final electron acceptor during aerobic respiration
71
What is the substrate in the oxidase test?
Oxygen
72
What is the enzyme in the oxidase test?
Cytochrome C oxidase
73
What is the product in the oxidase test?
Water
74
What is the reagent in the oxidase test?
Oxidase reagent
75
What does a positive and negative look like on the oxidase test?
Positive = pink/red within 20 seconds Negative = no pink/red OR pink/red after 20 seconds
76
What is the purpose of the catalase test?
To test bacteria for the catalase enzyme
77
What is catalase?
Produced by organisms that use oxygen as the final electron acceptor in the electron transport chain Used to neutralize hydrogen peroxide
78
What is the substrate in the catalase test?
Hydrogen peroxide
79
What is the enzyme in the catalase test?
Catalase
80
What is the product of the catalase test?
Water and oxygen gas
81
What does a positive and negative look like in the catalase test?
Positive = Bubbles when hydrogen peroxide is added (oxygen is produced) Negative = no bubbles when hydrogen peroxide is added (no oxygen is produced)

Micro Biology (9 decks)

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