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Biology 15 - General Microbiology > Lab Exam 3 Gram - > Flashcards

Lab Exam 3 Gram - Flashcards

1
Q

You should know a few of the potential genera used in the unknown experiment.

A
  1. Escherichia
  2. Pseudomonas
  3. Citrobacter
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2
Q

For each test, you should know what a positive test result looks like and what a negative test result looks like.

A
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3
Q

What color is the Simmons’ slant before it is inoculated?

A

Green

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4
Q

The Simmons’ slant contains bromothymol blue. In this case, the pH indicator will not turn yellow. What color is a Simmons’ slant that is positive for nutrient utilization?

A

Blue

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5
Q

What color is the tube before it is incubated? Simmons slant test.

A

Green

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6
Q

What is the carbon source in the Simmons’ slant?

A

Citrate

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7
Q

What is the nitrogen source in the Simmons’ slant?

A

Ammonia

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8
Q

How does nutrient utilization affect the pH of the Simmons’ slant?

A

Increases pH, making it more alkaline

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9
Q

Litmus Milk

Litmus milk broth contains two key ingredients, skim milk and litmus powder. What are the two functions of the litmus powder in the litmus milk broth?

A

1.) pH indicator
2.) Litmus can be reduced

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10
Q

Litmus Milk

What are the three reactions that can occur with the litmus powder?

A

1.) Purple = negative for fermentation (alkaline)
2.) Pink = positive for fermentation (acidic)
3.) White = reduction (can see white at bottom of tube)

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11
Q

Litmus Milk

Each of the litmus reactions produce a different color. Match each of the three litmus reactions to pink, purple, or white.

A

1.) Purple = negative for fermentation (alkaline)
2.) Pink = positive for fermentation (acidic)
3.) White = reduction (can see white at bottom of tube)

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12
Q

Litmus Milk

What are the two possible reactions that can occur with the milk protein in the litmus milk broth?

A

1.) pH indicator
2.) Litmus can be reduced

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13
Q

Litmus Milk

What is peptonization?

A

Enzymes breakdown proteins into peptides

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14
Q

Litmus Milk

How will coagulation affect the broth?

A

Broth solidifies

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15
Q

Litmus Milk

What causes the broth to coagulate?

A

Too much acid release into media

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16
Q

SIM stab

What does the abbreviation ‘SIM’ stand for?

A
  • Sulfide
  • Indole
  • Motility
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17
Q

SIM stab

Which of the three tests did we not record data for?

A

Motility

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18
Q

SIM stab

Which amino acid is degraded to produce ‘S’?

A

Cysteine

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19
Q

SIM stab

What is the enzyme that is responsible for ‘S’?

A

Cysteine desulfurase.

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20
Q

SIM stab

What are the three products that are produced as part of ‘S’?

A

Hydrogen sulfide (H2S), pyruvic acid, and ammonia

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21
Q

SIM stab

What are the three products that are produced as part of ‘S’?

A

Hydrogen sulfide (H2S), pyruvic acid, and ammonia.

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22
Q

SIM stab

Which specific product of the three is detected by ‘S’?

A

Hydrogen sulfide (H2S)

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23
Q

SIM stab

What color is a positive ‘S’ test?

A

Black precipitate

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24
Q

SIM stab

Which amino acid is degraded to produce ‘I’?

A

Tryptophan

25
Q

SIM stab

What is the enzyme that is responsible for ‘I’?

A

Tryptophanase

26
Q

SIM stab

What are the three products that are produced as part of ‘I’?

A

Indole, pyruvic acid, and ammonia

27
Q

SIM stab

Which specific product of the three is detected by ‘I’?

A

Indole

28
Q

SIM stab

What reagent is used to test for ‘I’?

A

Kovac’s reagent

29
Q

What color is a positive ‘I’ test?

A

Red ring at the top of tube

30
Q

MRVP

What does the abbreviation ‘MRVP’ stand for?

A

Methyl Red Voges-Proskauer

31
Q

MRVP

Which reagent tests for the production of mixed acids by fermentation?

A

Methyl red reagent

32
Q

MRVP

How does the color of the reagent that tests for mixed acid fermentation change with decreasing pH?

A

Turns red with decreasing pH

33
Q

MRVP

How many days does the 2,3-butanediol test using an MRVP tube incubate for?

A

5 days

34
Q

MRVP/2,3-butanediol

Why doesn’t 2,3-butanediol react with a pH indicator, like phenol red?

A

Because alcohol doesn’t change the pH, therefore the pH indicator doesn’t react.

35
Q

Vogues Proskaver

What is the exact procedure for performing the VP test in lab?

A
  1. Label empty test tube for our unknown
  2. Pipette 1 ml of MRVP into the unknown tube
  3. Add 18 drops of reagent A and 18 drops of reagent B to the unknown tube
  4. Shake tube every 10 minutes
  5. After 30 minutes, check color
36
Q

Vogues Proskaver

What is the purpose of shaking the small tube?

A

We shake to oxidize acetoin into diacetyl (if its’s present)

37
Q

Vogues Proskaver

Which final chemical product will be created in the VP test?

A

Diacetyl

38
Q

Vogues Proskaver

How long does the VP test sit before the color change is complete?

A

30 Minutes

39
Q

What color is a positive VP test? What color is a negative test result?

A
  • Positive: Red
  • Negative: Brown
40
Q

Brilliant Green Agar

What kills Gram + & some Gram – in the Brilliant Green Agar? (how is it selective?)

A

Brilliant green dye selects against gram + bacteria, and some gram - bacteria.

41
Q

Brilliant Green Agar

What sugars are found in the Brilliant Green?

Hint: Two of them

A
  1. Sucrose
  2. Lactose
42
Q

Brilliant Green Agar

What is the pH indicator for the Brilliant green agar?

A

Phenol red

43
Q

Brilliant Green Agar

What color is brilliant green agar that is positive for fermentation (Acidic)?

A

Lime green

44
Q

Brilliant Green Agar

What color is brilliant green agar for a nonfermenter (Basic)?

A

Bright pink

45
Q

Brilliant Green Agar

What color is brilliant green agar when the bacteria is dead (negative)?

A

Orangish-Brown since the plate remains the same color

46
Q

Catalase Test

What type of media was used for the catalase test?

A

Hydrogen peroxide (H2O2)

47
Q

Catalase Test

You should be able to write out the complete catalase reaction, including the names and molecular formulas of all substrates and products.

A

Catalase reaction: 2 H2O2 → 2 H2O + O2
* Substrate: Hydrogen Peroxide
* Product: Water and Oxygen

48
Q

Briefly describe the appearance of a positive catalase test.

A

Bubble formation

49
Q

Which product of catalase activity is responsible for the visible reaction?

A

Oxygen gas

50
Q

What is the protein cytochrome oxidase normally used for? Where specifically is cytochrome oxidase located?

A

Cytochrome oxidase is involved in the electron transport chain. It is located in the bacterial cell membrane.

51
Q

What is the exact reaction of cytochrome oxidase?

A

The reduction of cytochrome c using oxygen as the final electron acceptor

52
Q

What color is a positive cytochrome oxidase test?

A

Dark purple

53
Q

What type of media was used for the oxidase test?

A

TSA plate streaked with the unknown on one half and Pseudomonas aeruginosa on the other half.

54
Q

What is in the Hektoen agar that makes it selective?

A

Bile

55
Q

Hektoen Agar

What three carbohydrates does it contain?

A
  1. Lactose
  2. Sucrose
  3. Salicin
56
Q

Hektoen Agar

What are the pH indicators?

A
  1. Bromthymol Blue
  2. Andrades Acid
57
Q

Hektoen Agar

What is the fermentation color change (acidic)?

A

Turns Bright Orange

58
Q

Hektoen Agar

What is the non-fermenter color change (basic)?

A

Blue-Green

Biology 15 - General Microbiology (29 decks)

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