Question

Which of the following converts nitrites to nitrates?

• A. Clostridium
• B. Nitrobacter
• C. Nitrosomonas
• D. Nitrococcus

Hint:

Use a mnemonic to separate the two steps of nitrification: Bacteria with "nitroso-" in their name (like {Nitroso}monas) come first, converting ammonia to nitrite. Bacteria with "nitro-" (like {Nitro}bacter) come second, converting nitrite to nitrate.

Answer 1

The Correct Option is B

Step 1: Understanding the Concept:
The question requires identifying the bacterium responsible for the second step of nitrification in the nitrogen cycle.
Step 2: Detailed Explanation:
Nitrification occurs in two steps:
Ammonia Oxidation: Ammonia (\(NH_3\)) or ammonium (\(NH_4^+\)) is oxidized to nitrite (\(NO_2^-\)). This process is performed by ammonia-oxidizing bacteria such as {Nitrosomonas} and {Nitrococcus}.
Nitrite Oxidation: Nitrite (\(NO_2^-\)) is oxidized to nitrate (\(NO_3^-\)). This process is performed by nitrite-oxidizing bacteria. A common example is {Nitrobacter}.
Clostridium is involved in nitrogen fixation and fermentation, not nitrification.
Therefore, Nitrobacter converts nitrites to nitrates.
Step 3: Final Answer:
Nitrobacter converts nitrites to nitrates.