Question

Given below are two statements:
Statement I : Nitrification is a two-step process. In the first step, ammonia is oxidized to nitrite (NO_2^-) and in the second step, NO_2^- is oxidized to nitrate (NO_3^-)
Statement II : A single microbial genus can perform both steps of nitrification
In light of the above statements, choose the correct answer from the options given below:

• A. Both Statement I and Statement II are true
• B. Both Statement I and Statement II are false
• C. Statement I is correct but Statement II is false
• D. Statement II is correct but Statement I is false

Hint:

Classical nitrification requires two distinct genera: Nitrosomonas ($ ext{NH}_4^+ \to ext{NO}_2^-$) and Nitrobacter ($ ext{NO}_2^- \to ext{NO}_3^-$).

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
Nitrification is the biological aerobic oxidation of reduced nitrogen compounds to inorganic nitrate.

Step 2: Detailed Explanation:
1. Statement I is correct: Canonical nitrification is a two-stage process:

Step 1: Ammonia oxidation to nitrite ($2\text{NH}_4^+ + 3\text{O}_2 \to 2\text{NO}_2^- + 4\text{H}^+ + 2\text{H}_2\text{O}$).

Step 2: Nitrite oxidation to nitrate ($2\text{NO}_2^- + \text{O}_2 \to 2\text{NO}_3^-$).
2. Statement II is false: In standard classical soil nitrification, two distinct chemoautotrophic bacterial genera are required: ammonia oxidizers (Nitrosomonas, Nitrosococcus) and nitrite oxidizers (Nitrobacter, Nitrospira).

Step 3: Final Answer:
Hence, Statement I is correct but Statement II is false.