Question

During nitrification process $\text{NO}_2^-$ is converted by $\text{NO}_3^-$ by}

• A. Nitrobacter
• B. Nitrogenes
• C. Thiobacillus
• D. Nitrosomonas

Hint:

Remember the alphabetical and chronological sequence of nitrification: Ammonia \(\rightarrow\) Nitrite (Nitrosomonas) followed by Nitrite \(\rightarrow\) Nitrate (Nitrobacter).

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
Nitrification is a crucial biological process in the nitrogen cycle where soil bacteria oxidize ammonia into nitrate, which is the form of nitrogen most readily absorbed by plants.
This biological oxidation occurs in two distinct, sequential steps carried out by different groups of specialized autotrophic bacteria.
Detailed Explanation:
The nitrification pathway consists of the following phases:
1. Ammonium to Nitrite: In the first step, ammonia (\(\text{NH}_4^+\)) is oxidized to nitrite (\(\text{NO}_2^-\)). This reaction is carried out by ammonia-oxidizing bacteria (AOB), primarily of the genus Nitrosomonas:
\[ 2\text{NH}_4^+ + 3\text{O}_2 \rightarrow 2\text{NO}_2^- + 4\text{H}^+ + 2\text{H}_2\text{O} \] 2. Nitrite to Nitrate: In the second step, the toxic intermediate nitrite (\(\text{NO}_2^-\)) is rapidly oxidized to nitrate (\(\text{NO}_3^-\)). This step is carried out by nitrite-oxidizing bacteria (NOB), primarily belonging to the genus Nitrobacter:
\[ 2\text{NO}_2^- + \text{O}_2 \rightarrow 2\text{NO}_3^- \] Because the prompt asks for the organism responsible for converting nitrite (\(\text{NO}_2^-\)) to nitrate (\(\text{NO}_3^-\)), Nitrobacter is the correct organism.

Step 2: Final Answer:
The conversion of \(\text{NO}_2^-\) to \(\text{NO}_3^-\) is mediated by Nitrobacter.