Question

1. In the blank provided for each biochemical test write a chemical equation that describes each test, circle the end product that is detected by the reagents added to the test, and state the color of a positive result.

Voges-Proskauer (5-4) ____________________________________

Methyl red (5-4) ____________________________________

Phenol Red Glucose (5-3) ____________________________________

Catalase Production (5-5) ____________________________________

Nitrate Reduction (5-7) ____________________________________

2. Match each enzyme or reagent with the appropriate biochemical test media, substrate or product by placing the correct letter in the blank provided.

Catalase________ A. NO3

Nitrate reductase________ B. H2O2

Citrate permease________ C. Carbohydrate

2,3 butanediol ______ D. Simmons Citrate

Phenol Red_______ E. MRVP

Answer 1

Answer 1a) Voges-Proskauer test; It detects the fermentation of glucose if the glucose is converted to pyruvic acid and then into acetoin. this acetoin is detected by the given reaction.

Reaction; Acetoin + added alpha-naphthol + added KOH = Colored Acetoin

Positive result; Red color

1b) Methyl Red test; It is used to detect the mixed acid fermentation of glucose.

Reaction; i) Glucose---> pyruvic acid ---> mixed acids ii) Methyl red + mixed acids ----> color

Positive result; production of mixed acid makes the PH of the medium very low as PH 4.4. at this low PH, methyl red gives red color.

1c) Phenol red glucose test; It is used to identify whether the bacteria can utilize glucose for its energy production or not.

Reaction; i) Glucose ---> Acids ii) Acids + Phenol red ----> color

Positive result; if the acids are formed, then change the PH of the medium to the 6.8. at this PH, Phenol red turns yellow. therefore, yellow color indicated the glucose utilization by this test.

1d) Catalase test; this test is used to distinguish between gram-negative streptrococci and gram-positive staphylococci.

Positive result; production of bubbles indicate the utilization of catalase to break down Hydrogen peroxide into water and oxygen molecules.