Lab #16

Question 1

Starch Hydrolysis

Answer 1

• If starch is hydrolyzed by amylase (produced by the bacteria), then no starch will be present around the bacteria.
• Reagent- Iodine will detect starch in the medium by producing a blue-black precipitate.
• Positive for starch hydrolysis - clear zone around the bacteria.

Question 2

Catalases

Answer 2

*Catalase(enzyme) breaks down hydrogen peroxide (substrate) into water and oxygen - oxygen bubbles = effervescence is a positive result for catalase production.

Question 3

Phenylalanine

Answer 3

by removing the amine group to produce phenylpyruvic acid and ammonia. Reagent - Ferric Chloride combines with phenylpyruvic acid to produce a green color.(Positive for Phenylalnine Deaminase)

Question 4

SIM

Answer 4

hydrogen sulfide - Amino acids that are metabolized, Thiosulfates, sulfates, and
sulfites are reduced by the bacteria produce hydrogen sulfide. Presence is a black precipitate in medium.

Question 5

Indole

Answer 5

Tryptophanase is the enzyme that hydrolyzes Tryptophan.
Indole is a product of Tryptophan hydrolysis.
*Reagent- Kovac’s reagent - Dark pink color is a positive for Indole

Question 6

Motility

Answer 6

medium is semi-solid and allows the bacteria to move throughout themedium if it is motile. Motile bacteria will make the entire medium look cloudy or opaque.

Question 7

Ureases

Answer 7

urease(enzyme) breaks down urea(substrate) producing ammonia.- phenol red - Positive for urease production is a hot pink (fuchsia)

Question 8

Citrate

Answer 8

Citrate – Simmon’s Citrate – Tests for the ability of the bacteria to utilize the citrate in the media as the sole source of carbon. Bacteria that do this then use the ammonium hydroxide and ammonium phosphate as a sole source of nitrogen. When they break down the ammonium phosphate and ammonium hydroxide, they release ammonia. This raises the pH to produce a basic environment. Bromthymol blue in the medium is
the indicator which will turn Prussian Blue (or as I call it “KU Blue”) when it is basic and yellow when it is acidic. So a positive result for Citrate Utilization is a Prussian
Blue (KU Blue) color. A Negative result for Citrate Utilization is no change in the color
(remains a “Forrest green” or blue-green color)