Which of the following is not related to `N_(2)` fixation?

Options

A. Rhizobium
B. Anabaena
C. Pseudomonas
D. Azotobacter

Answer

To determine which of the following options is not related to nitrogen (N₂) fixation, we will analyze each option provided.

### Step-by-Step Solution:

1. **Identify the Options**: The options given are Rhizobium, Anabaena, Pseudomonas, and Azotobacter.

2. **Analyze Rhizobium**:
- Rhizobium is a type of bacteria that forms a symbiotic relationship with leguminous plants.
- It is well-known for its ability to fix nitrogen from the atmosphere into a form that plants can use.
- **Conclusion**: Rhizobium is related to nitrogen fixation.

3. **Analyze Anabaena**:
- Anabaena is a genus of cyanobacteria that can also fix atmospheric nitrogen.
- It often exists in symbiotic relationships with certain plants and can convert N₂ into ammonia.
- **Conclusion**: Anabaena is related to nitrogen fixation.

4. **Analyze Pseudomonas**:
- Pseudomonas is a genus of bacteria that is primarily involved in the process of denitrification.
- Denitrification is the conversion of nitrates back into nitrogen gas (N₂), which is the opposite of nitrogen fixation.
- **Conclusion**: Pseudomonas is **not** related to nitrogen fixation.

5. **Analyze Azotobacter**:
- Azotobacter is a free-living nitrogen-fixing bacterium that can fix nitrogen from the atmosphere without needing a symbiotic relationship with plants.
- **Conclusion**: Azotobacter is related to nitrogen fixation.

### Final Answer:
The option that is not related to nitrogen fixation is **Pseudomonas**.

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