Lab 20-23

Question 1

Indole Test

Answer 1

Tests for use of tryptophan as a carbon/nitrogen/energy source.

Question 2

Methyl Red/Voges Proskauer

Answer 2

Tests for acid production as an end product of glucose fermentation.

Question 3

Citrate test

Answer 3

Sodium citrate for carbon/energy source. Bromothymol blue will turn from green to blue if citrate is used.

Question 4

Indole Results

Answer 4

E. Coli : indole produced
Enterobacter cloacae : no
Klebsiella penumoniae : no

Question 5

Methyl Red results

Answer 5

E. Coli : acid
Enterobacter cloacae : no
Klebsiella penumoniae : acid

Question 6

VP Results

Answer 6

E. coli : No
Enterobacter cloacae : non acid produced (acetyl methyl carbon)
Klebsiella penumoniae : no

Question 7

Citrate results

Answer 7

E. coli : no
Enterobacter cloacae : citrate used
Klebsiella penumoniae : citrate used

Question 8

Test for H2S production

Answer 8

Tell between gram negative rods that do not ferment lactose

Question 9

Peptone Iron Agar - PIA

Answer 9

Contain peptones for bacteria to use

Contains Iron for H2S indicator

Question 10

IMViC Tests

Answer 10

Indole Production, methyl red test, Voges-Proskauer, citrate utilization

Question 11

Sulfur Indole Motility (SIM)

Answer 11

Same ingredients as PIA, peptones and iron, plus tryptophan. Determines H2S production and motility.

Question 12

Shigella Flexnerii PIA/SIM

Answer 12

H2S : no
Indole : no
Motile : no

Question 13

Proteus vulgaris PIA/SIM

Answer 13

H2S : yes
Indole : yes
Motility : yes

Question 14

Salmonella typhimurium PIA/SIM

Answer 14

H2S : yes
Indole : no
Motility : yes

Question 15

Fermentation RXN

Answer 15

2 stages, glycolysis - 2ATP, fermentation- oxidizes NADH to be reused in another glycolysis

Question 16

Fermentation Test Media

Answer 16

Specific sugar, phenol red (ph)

Question 17

Carb fermentation results

Answer 17

No : red media/no bubble
Yes : yellow/no bubble
Yes/gas : yellow/bubble

Question 18

Litmus Dye

Answer 18

pH indicator, can oxidation/reduction rxns

Question 19

Role of milk/Lactose (acid production)

Answer 19

Litmus causes media to turn pink/red, if litmus milk reduced, tube is white at bottom with red color or ring at top.

Question 20

Role of milk/lactose (curd formation)

Answer 20

Acid produced coagulates casein to form a curd, over time produce whey (liquid on top)

Question 21

Role of lactose/milk (gas production)

Answer 21

Usually bubbles in curd, can produce lots of gas, causing curd to explode and forming “stormy fermentation”

Question 22

Casein Coagulation: Hard Curd

Answer 22

Solid curd with lactose ferment/acid production. Acid causes curd to harden. Acidity increase causes whey to form on top if curd.

Question 23

Casein Coagulation : Rennet Type Curd

Answer 23

Semi-soft curds in tube If bacteria can make Renin. Renin causes casein to form insoluble soft clot, usually formed at neutral pH

Question 24

Casein Proteolysis : Peptonization

Answer 24

Gradual clearing of milk makes media transparent/clear.

Question 25

Casein Proteolysis : Alkaline Reaction.

Answer 25

Casein breakdown yields lots of ammonia causing pH to become alkaline. Litmus dye causes media to turn purple/blue.

Question 26

Litmus Milk Results : E. coli

Answer 26

Ac/AcG(not likely)

Question 27

Litmus Milk Results : P. vulgaris

Answer 27

AlkP

Question 28

Litmus Milk Results : B. cereus

Answer 28

AlkP

Question 29

Litmus Milk Results : L. acidophilus

Answer 29

AcR

Question 30

Litmus Milk Results : C. xerosis

Answer 30

No Change

Question 31

What enzymes are needed for lactose fermentation?

Answer 31

Beta Galactosidase

Question 32

What enzymes are needed for Casein Hydrolysis.

Answer 32

Renin.

Question 33

Hard curd vs soft curd.

Answer 33

Hard : Lactose fermentation/acid production

Soft : Rennet type curd produced by Renin secretion at neutral pH.