`2NO_2^(-) +O_2rarr2NO_3^(-)` This step of nitrification is done by ……….bacteria

Options

A. Pseudomonas
B. Thiodacillus
C. Nirobacter
D. Nitrococcus

Answer

To solve the question regarding the nitrification step represented by the reaction \(2NO_2^{-} + O_2 \rightarrow 2NO_3^{-}\), we need to identify the bacteria responsible for this specific step of nitrification.

### Step-by-Step Solution:

1. **Understanding Nitrification**:
- Nitrification is a two-step process where ammonia is first oxidized to nitrite (\(NO_2^{-}\)) and then nitrite is further oxidized to nitrate (\(NO_3^{-}\)).

2. **Identifying the Reaction**:
- The given reaction \(2NO_2^{-} + O_2 \rightarrow 2NO_3^{-}\) indicates that nitrite ions are being oxidized to form nitrate ions.

3. **Bacteria Involved in Nitrification**:
- The first step of nitrification involves the conversion of ammonia to nitrite, which is carried out by bacteria such as Nitrosomonas and Nitrococcus.
- The second step, which is the conversion of nitrite to nitrate, is specifically carried out by the bacteria known as Nitrobacter.

4. **Conclusion**:
- Since the question asks for the bacteria responsible for the oxidation of nitrite to nitrate (the step represented in the reaction), the correct answer is **Nitrobacter**.

### Final Answer:
The step of nitrification represented by the reaction \(2NO_2^{-} + O_2 \rightarrow 2NO_3^{-}\) is done by **Nitrobacter**.