Question

Given below are two statements
Statement I: Nitrification is the biological oxidation of ammonia to nitrates, in two steps.
Statement II: Members of genus Nitrobacter are involved in the oxidation of nitrites to nitrates.
In light of the above statements, choose the most appropriate answer from the options given below

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

Hint:

Remember: Nitros- (Nitrosomonas) starts the process (Ammonia to Nitrite), while Nitrob- (Nitrobacter) finishes the process (Nitrite to Nitrate).
This process requires well-aerated soil as it is strictly aerobic.

Answer 1

The Correct Option is A

Step 1: Understanding the Question:
The question explores the process of nitrification, a critical part of the nitrogen cycle in soil where ammonia is converted into more plant-accessible forms like nitrate through microbial action.
Detailed Explanation:

• Process of Nitrification: Nitrification is a two-step aerobic process performed by chemoautotrophic bacteria.

• Step 1 (Ammonia to Nitrite): In the first step, ammonia ($NH_3$ or $NH_4^+$) is oxidized to nitrite ($NO_2^-$). This is primarily carried out by bacteria of the genus Nitrosomonas and Nitrosococcus.

• Step 2 (Nitrite to Nitrate): In the second step, the produced nitrite is further oxidized to nitrate ($NO_3^-$). This step is mainly facilitated by members of the genus {Nitrobacter, Nitrococcus, and Nitrospira.

• Evaluation: Statement I is correct as it accurately defines nitrification as a two-step biological oxidation process ending in nitrate. Statement II is also correct as it specifies the correct genus responsible for the second step of the process.
Final Answer:
Since both statements regarding the steps and the organisms involved in nitrification are factually accurate, the correct choice is option (A).