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Microbio Lab Test 2 > Metabolic Activities > Flashcards

Metabolic Activities Flashcards

1
Q

Starch digestion

A
  • Tests for amylase
  • Amylase turns starch into sugars
  • Iodine turns stach black, but not sugar
  • Reagent: Iodine
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2
Q

Starch digestion positive

A

Clearing around streak

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3
Q

Starch digestion negative

A

Entire plate is black - no clearing

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4
Q

Milk Agar Plate

A
  • Casein digestion
  • Tests for caseinase
  • Caseinase converts casein into amino acids
  • No reagent
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5
Q

Milk Agar Positive

A

Clearing around streak

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6
Q

Milk Agar Negative

A

No clearing around streak

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7
Q

TSA Plate

A
  • Catalase

- Oxidase Production

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8
Q

Catalase

A
  • TSA Plate
  • Tests for presence of catalase
  • Reagent: H2O2
  • Catalase converts H202 to water and oxygen gas
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9
Q

Catalase Positive

A

Bubbles after adding peroxide

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10
Q

Catalase Negative

A

No bubbles after adding peroxide

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11
Q

Oxidase Production

A
  • TSA Plate
  • Tests for presence of cytochrome oxidase
  • Cytochrome oxidase is last enzyme in ETS
  • Reagent: on swab
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12
Q

Oxidase Production Positive

A

Dark Purple (pink = weak positive) on swab

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13
Q

Oxidase Production Negative

A

No color change on swab

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14
Q

SIM Media

A
  • H2S Production

- Indole Production

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15
Q

H2S Production

A
  • SIM Media
  • Tests for cysteine desulfurase
  • Cysteine desulfurase converts cysteine into pyruvate by removing H2S
  • Reagent: iron in medium
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16
Q

H2S Production Positive

A

Black precipitate

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17
Q

H2S Production Negative

A

No black precipitate

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18
Q

Indole Production

A
  • SIM Media
  • Tests for tryptophanase
  • Tryptophanase converts tryptophan into indole
  • Reagent: Kovac’s reagent
19
Q

Indole Production Positive

A

Red layer on tope of broth

20
Q

Indole Production Negative

A

No color change

21
Q

Citrate Utilization

A
  • Tests for ability to use citrate as a carbon source
  • No other carbon source (sugar) available in medium
  • Reagent: ammonium ions and brom thymol blue in medium (pH indicator)
22
Q

Citrate Utilization Positive

A

Bacteria will grow

Usually turns deep blue color

23
Q

Citrate Utilization Negative

A

Bacteria do not grow
No color change
(However bacteria may grow without changing color)

24
Q

Urea Broth

A
  • Tests for urease
  • Urease converts urea into ammonia
  • Reagent: Phenol red in medium
25
Q

Urea Broth Positive

A

Cerise or hot pink

26
Q

Urea Broth Negative

A

Any color besides cerise or hot pink

27
Q

Nitrate Broth

A
  • Tests for nitrate reductase
  • Nitrate reductase converts nitrate into nitrite
  • Reagent: Nitrate 1 (Sulfanilic acid) and Nitrate 2 (dimethyl-a-napthalamine)
  • Secondary reagent Zinc (to confirm negative)
28
Q

Nitrate Broth Positive

A

-Red color after adding reagents
OR
-No color change, then add zinc > still no color change

29
Q

Nitrate Broth Negative

A

No color change, then red after adding zinc

30
Q

Nitrate Broth Explanation

A

Sometimes instead of converting Nitrate to Nitrite nitrate reductase converts it to “something else,” so there is no color change to red (no nitrite present). However nitrate reductase is still present.

To confirm a negative, add zinc to tube. Zn reacts with nitrate to produce a red color. If NR was present, there will be no color change after adding zinc because the nitrate was converted to “something else”

31
Q

MRVP Broth

A
  • Methyl Red

- Voges-Proskauer

32
Q

Methyl Red

A
  • Tests for dextrose fermentation

- Reagent: methyl red

33
Q

Methyl Red Positive

A

Red color

34
Q

Methyl Red Negative

A

No red color

35
Q

Voges-Proskauer

A
  • Tests for Butanediol fermentation

- Reagent: Barritt’s Solution A (a-naphtol) and B (KOH)

36
Q

Voges-Proskauer Positive

A

Pink to red color

37
Q

Voges-Proskauer Negative

A

No pink or red

38
Q

Fermentation Tests

A
  • Tests for specific enzymes that can ferment each sugar
  • Dextrose
  • Sucrose
  • Mannitol
  • Lactose
  • Reagent: Phenol Red
  • Durham Tube to collect gas
39
Q

Durham Tube

A

Upside down tube in test tube

Collects gas created during rxn

40
Q

Fermentation Test Possible Results

A

+ acid + gas
+ acid - gas
- acid - gas

41
Q

Fermentation Test Positive

A

Acid: Yellow
Gas: Bubble in Durham tube

42
Q

Fermentation Test Negative

A

Acid: Red (does not turn yellow)
Gas: No bubble in Durham tube

43
Q

IMVC Tests

A

Indole Production
Methyl Red
Voges-Proskauer
Citrate Utilization
-Used to differentiate between E. coli and E. aerogenes (very morphologically similar)
-E. coli is positive for I and M, negative for V and C
-E aerogenes is opposite

Microbio Lab Test 2 (5 decks)

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