Question

please answer the following questions.

1. the indole test detects an organisms ability to:

a) ferment lactose
b) hydrolyze urea
c) break down tryptophan into indole
d) utilize citrate as a carbon source

1. the reagent used in the indole test is:

a) methyl red
b) barritts reagents a and b
c) kovacs reagent
d) bromothymol blue

1. a positive methyl red test indicates:

a) the organism produces stable acid end products from glucose fermentation
b) the organism produces neutral end products
c) the medium becomes alkaline due to ammonia production
d) the organism cannot ferment glucose

1. the voges-proskauer test detects the presence of:

a) indole
b) hydrogen sulfide
c) acetoin (a neutral fermentation end product)
d) ammonia

Explanation:

1. The Indole test is based on the ability of some bacteria to produce the enzyme tryptophanase, which breaks down the amino acid tryptophan into indole, pyruvic acid, and ammonia.
2. Kovac's reagent is used in the Indole test. It consists of p - dimethylaminobenzaldehyde in amyl alcohol. Indole reacts with Kovac's reagent to form a red - colored complex.
3. The Methyl Red (MR) test is used to determine if an organism produces stable acid end - products from glucose fermentation. A positive MR test shows that the organism can maintain a low pH (acidic conditions) in the medium due to the production of stable acids.
4. The Voges - Proskauer (VP) test detects the presence of acetoin. Bacteria that ferment glucose to produce acetoin (a neutral fermentation end - product) will give a positive VP test. Barritt's reagents A and B are used in the VP test. Reagent A is α - naphthol and reagent B is potassium hydroxide with creatine.

Answer:

1. c) Break down tryptophan into indole
2. c) Kovac’s reagent
3. a) The organism produces stable acid end products from glucose fermentation
4. c) Acetoin (a neutral fermentation end product)