which of the following is not a symbiotic nitrogen fixing bacterium ?

Options

A. Clostridium
B. Rhoizobium leguminosarum
C. Frankia
D. Mycobacterium

Answer

To determine which of the following is not a symbiotic nitrogen-fixing bacterium, we need to understand the characteristics of nitrogen-fixing bacteria and their symbiotic relationships with plants.

### Step-by-Step Solution:

1. **Understanding Nitrogen-Fixing Bacteria**:
- Nitrogen-fixing bacteria are prokaryotic organisms that convert atmospheric nitrogen (N₂) into ammonia (NH₃), which can be utilized by plants. This process is essential for soil fertility.

2. **Identifying Symbiotic Relationships**:
- Symbiotic nitrogen-fixing bacteria live in close association with plants, particularly legumes. They form nodules on the roots of these plants, where they convert nitrogen into a form that the plants can absorb.

3. **Examples of Symbiotic Nitrogen-Fixing Bacteria**:
- Common examples include **Rhizobium**, which is found in the root nodules of legumes, and **Frankia**, which associates with non-leguminous plants. Both of these bacteria have a symbiotic relationship with their host plants.

4. **Identifying Non-Symbiotic Nitrogen-Fixing Bacteria**:
- **Clostridium** is a genus of bacteria that is known to fix nitrogen but does not form symbiotic relationships with plants. It is an anaerobic bacterium, meaning it thrives in environments without oxygen and is saprophytic, feeding on decaying organic matter.

5. **Conclusion**:
- Based on the definitions and examples discussed, the bacterium that is not a symbiotic nitrogen-fixing bacterium is **Clostridium**.

### Final Answer:
**Clostridium** is not a symbiotic nitrogen-fixing bacterium.

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