Question

Nitrate broth lab

1. what role does nitrate play in respiration

2. what nitrate reduction result would you expect in an obligate anaerobe. Explain

3. Why does the presence of a red color after zinc addition indicate a negative result for nitrate reduction

4. A facultative anaerobe can reduce nitrate. Would you expect to see a positive result when the test is done under conditions where the bacteria is exposed to large amounts of oxygen? Explain

Answer 1

1: Nitrate plays a major role in nitrate respiration. It acts as the terminal hydrogen acceptor and thus gets reduced in the process. Denitrifying bacteria are capable of nitrate respiration.

2. In an obligate anaerobe, nitrate reduction would result in the formation of ammonia.

3. Zinc acts as a catalyst for nitrate reduction. If nitrate is present in nitrate broth after addition of sulphanilic acid in the first step of nitrate reduction test, addition of zinc will catalyse the conversion and lead to production of red colour.