Question

Which of the following pair of bacteria is involved in two step conversion of $N{H}_3$ into nitrate?

• A. Azotobacter and Nitrosomonas
• B. Nitrosomonas and Nitrobacter
• C. Azotobacter and Achromobacter
• D. Pseudomonas and Nitrobacter

Answer 1

Answer: (B)

Nitrosomonas and Nitrobacter

Plants cannot directly consume atmospheric nitrogen as it is present in stable diatomic form. Plants absorb nitrogen from soil in the form of nitrates, nitrites and ammonium ions.

Nitrosomonas and Nitrobacter are soil nitrifying bacteria, which convert ammonium ions into nitrate ions in two stages. Nitrosomonas bacteria first convert ammonia into nitrites. Nitrobacter convert the nitrites into nitrates, which are readily absorbed by the plants.