Bacteria involved in two -step conversion of ammonia into nitrate are

Options

A. Azotobacter and Nitrosomonas
B. Pseudomonas and Nitrobacter
C. Azotobacter and Achromobacter
D. None

Answer

To answer the question about the bacteria involved in the two-step conversion of ammonia into nitrate, we can break down the process of nitrification and identify the specific bacteria responsible for each step.

### Step-by-Step Solution:

1. **Understanding Nitrification**:
- Nitrification is the biological process that converts ammonia (NH₃) into nitrate (NO₃⁻) through two main steps.

2. **Step 1 - Conversion of Ammonia to Nitrite**:
- The first step involves the conversion of ammonia (NH₃) into nitrite (NO₂⁻). This step is primarily carried out by nitrifying bacteria known as **Nitrosomonas** and **Nitrococcus**.

3. **Step 2 - Conversion of Nitrite to Nitrate**:
- The second step involves the conversion of nitrite (NO₂⁻) into nitrate (NO₃⁻). This step is performed by another nitrifying bacterium called **Nitrobacter**.

4. **Identifying the Bacteria**:
- Therefore, the complete process of nitrification involves:
- **Nitrosomonas/Nitrococcus**: Converts ammonia to nitrite.
- **Nitrobacter**: Converts nitrite to nitrate.

5. **Evaluating the Options**:
- Based on the options provided in the question:
- **Option 1**: Azotobacter and Nitrosomonas - Incorrect (Azotobacter is not a nitrifying bacterium).
- **Option 2**: Pseudomonas and Nitrobacter - Incorrect (Pseudomonas is a denitrifying bacterium).
- **Option 3**: Azotobacter - Incorrect (Again, not a nitrifying bacterium).
- **Option 4**: None is correct - This is the correct answer because the specific nitrifying bacteria (Nitrosomonas and Nitrobacter) were not listed together in any of the options.

### Conclusion:
The bacteria involved in the two-step conversion of ammonia into nitrate are **Nitrosomonas** (or **Nitrococcus**) for the first step and **Nitrobacter** for the second step. Since none of the provided options correctly pair these bacteria, the answer is **None is correct**.

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