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BIOL 270 > LAB EXAM #2 > Flashcards

LAB EXAM #2 Flashcards

1
Q

Indole is an end product of casein hydrolysis?

A

False

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2
Q

Yellow color indicates a positive reaction for Citrate utilization.

A

False- blue

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3
Q

The gas bubble in the Durham tube is hydrogen sulfide released by carbohydrate fermentation.

A

False

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4
Q

A strict Anaerobe will grow_______ in Thioglycollate agar.

A

At the bottom

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5
Q

If you did a Gram stain on a culture that came out looking gram negative even though you knew it should be gram positive, which of the following could have caused the misleading results?

A
  • You forgot to add ethanol

- You used too much alcohol during decolorization

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6
Q

For the Oxidative–Fermentative Test, what does it mean when both tubes are Yellow?

A

Fermentative- Acidic pH

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7
Q

SIM Agar is 3 tests in one tube. What are the tests ?

A

Sulfur reduction
Indole
Motility

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8
Q

Why do we need to check the fermentation broths twice, at 24 and 48 hours?

A

Some organisms are fast fermenters and will go after the peptone in the broth after they have fermented the carbohydrates

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9
Q

How does DNase enzyme help bacteria?

A

Hydrolyzes DNA into small fragments

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10
Q

A strict Aerobe will grow_______ in Thioglycollate agar.

A

On the surface

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11
Q

For the Oxidative–Fermentative Test, what does it mean the tube with no oil is yellow and the tube with oil is green?

A

Oxidative

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12
Q

For the Oxidative–Fermentative Test, what does it mean when both tubes are green?

A

Neither fermenter or an oxidizer

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13
Q

S. aureus:
B. cereus:
E. coli:

A

Gram + cocci
Gram + rod
Gram - rod

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14
Q

In the motility exp, if your organism reduces the 2, 3, 5- triphenyltetrazolium chloride it is:

A

Motile, red, and will move away from stab line

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15
Q

If your organism did not reduce the 2,3,5-triphenyltetrazolium chloride and is motile:

A

Media will be red and hazy/cloudy

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16
Q

If your organism reduced the 2,3,5-triphenyltetrazolium chloride and is non-motile you should see:

A

A red color in the stab line only

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17
Q

If your organism is gram + and a non-spore forming rod you will need to do:

A

An acid fast stain

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18
Q

What is the oxygen indicator in the sodium thioglycollate medium?

Controls?

A

Resazurin

  • red/pink when O2 is present
  • colorless in the absence of O2
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19
Q

Why don’t we shake the sodium thioglycollate tube?

A

It will disperse the O2 in the tube

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20
Q

2 experiments using TSA plate?

A
  • Pattern of growth

- Catalase

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21
Q

Hemolysis:

A

Lysis of RBC

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22
Q

3 types of hemolysis:

A
  1. Alpha: partial breakdown of RBC-> green color
  2. Beta: complete breakdown of RBC-> clearing
  3. Gamma: No lysis of RBC-> no change
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23
Q

Purpose of catalase test:

A

To produce the enzyme catalase that degrades hydrogen peroxide to O2 and water

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24
Q

Controls of catalase test:

A

Positive: Gas bubbles
Negative: No bubbles

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25
Q

Controls for methyl red test?

A

Positive: red/pink color after adding methyl red
Negative: orange/yellow color after adding methyl red

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26
Q

Controls for voges-proskauer test?

A

Positive: brick red color after the addition of VP A + VP B
Negative: copper color after the addition of VP A + VP B

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27
Q

Used with Barritt’s Reagents A + B:

A

VP test

28
Q

Purpose of MR test:

A

Detects mixed acid end products of glucose metabolism

29
Q

Purpose of VP test:

A

To carry out fermentation of glucose to acetoin and 2, 3 -Butanediol

30
Q

Controls of fermentation test?

Why?

A

Positive: Acid/gas and yellow in color due to carbohydrate fermentation and acid production
Negative/basic: no color change or pink color change due to deanimation and the production of ammonia

31
Q

Purpose of oxidative-fermentative test:

A

To oxidize or ferment a specific carbohydrate

32
Q

Why is oil overlaid in 1 of the tubes in the O/F test?

A

To create an anaerobic environment

33
Q

Purpose of Simmon’s citrate test?

A

To utilize citrate as a sole carbon source

34
Q

Control of Simmon’s citrate test?

A

Positive: Green to blue
Negative: Yellow or green

35
Q

Purpose of nitrate test:

A

To reduce nitrate to nitrite or nitrogen gas

36
Q

The reduction of nitrate to nitrite is done by the enzyme:

A

Nitrate reductase

37
Q

Controls for nitrate test:

A

Positive: Dark red OR no color change after adding zinc (reagent C)
Negative: no color change or dark red color after adding zinc (reagent C)

38
Q

Purpose of starch test?

A

To hydrolyze starch by the production of amylase

39
Q

Control for starch test:

A

Positive: Clearing or halo around margins of growth after adding iodine

40
Q

Purpose of skim milk test?

A

To hydrolyze casein from milk with the enzyme casease

41
Q

Control for skim milk test?

A

Positive: Clearing or halo around margins of growth

42
Q

Purpose of spirit blue (lipase) test?

A

To cleave fatty acids from glycerol using the enzyme lipase

43
Q

Controls of spirit blue (lipase) test?

A

Positive: Dark blue precipitate (hydrolyzes oil and lowers pH)
Negative: Lightening of plate

44
Q

Purpose of urea test:

A

To hydrolyze urea into CO2 and ammonia using the enzyme urease

45
Q

Control of urea test?

A

Positive: Pink color

46
Q

pH indicator of the fermentation test and urea test?

A

Phenol red

47
Q

pH indicator of spirit blue (lipase) test?

A

Tributyrin oil and spirit blue dye

48
Q

pH indicator of Simmon’s citrate test and O/F test?

A

Bromthymol blue

49
Q

Purpose of phenylalanine test?

A

To deanimate phenylalanine into phenylpyruvic acid and ammonia using the enzyme phenylalanine deaminase

50
Q

Control of phenylalanine test?

A

Positive: Green after addition of ferric chloride
Negative: Yellow after addition of ferric chloride

51
Q

Purpose of DNase test?

A

To hydrolyze DNA into small fragments using the enzyme DNase

52
Q

Control of DNase test?

A

Positive: Clearing around the margins of growth

53
Q

Indicator of DNase test?

A

Methyl green

54
Q

Purpose of decarboxylase test?

A

To produce decarboxylase enzyme that will remove a carboxyl group from the amino acid

55
Q

pH indicator of decarboxylase test?

A

Bromcresol purple

56
Q

Controls for decarboxylase test?

A

Positive: Alkaline/purple
Negative: Acidic/yellow

57
Q

3 amino acids used in decarboxylase test?

A

Arginine, ornithine, lysine

58
Q

Why is oil placed over each tube in the decarboxylase test?

A

To remove external O2 and promote fermentation

59
Q

Purpose of gelatin test:

A

To hydrolyze gelatin using the enzyme gelatinase

60
Q

Control for gelatin test:

A

Positive: Liquid media
Negative: Solid media

61
Q

1 drawback of gelatin test?

A

Gelatin is liquid at temp higher than 28 C so we have to refrigerate tube for 15 minutes to see if it’s truly a liquid or solid

62
Q

Purpose of indole/SIM test?

A

To produce the enzyme tryptophanase to hydrolyze tryptophan to produce -> ammonia, indole, and pyruvate

63
Q

Control of indole/SIM test?

A

Positive: Red layer on top of media

64
Q

Detection of indole in the indole/SIM test is due to:

A

Kovac’s reagant

65
Q

Purpose of sulfur reduction test?

A

To reduce sulfur to hydrogen sulfide

66
Q

Control for sulfur reduction/SIM test?

A

Positive: Black precipitate

67
Q

Purpose of durham tube in fermentation test?

A

To trap any CO2 as a result of fermentation

BIOL 270 (26 decks)

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