Which of the following bacteris is present in the rumen of cattle?

Options

A. Azotobacter
B. Rhizobium
C. Methanobacterium
D. Azospirillum

Explanation

To determine which bacteria is present in the rumen of cattle, we will analyze each of the given options step by step.

### Step-by-Step Solution:

1. **Identify the Options**: The options provided are:
- A) Azotobacter
- B) Rhizobium
- C) Methanobacterium
- D) Azospirillum

2. **Analyze Azotobacter**:
- Azotobacter is a free-living nitrogen-fixing bacterium.
- It is primarily found in the soil and plays a role in nitrogen fixation for plants.
- **Conclusion**: Azotobacter is not present in the rumen of cattle.

3. **Analyze Rhizobium**:
- Rhizobium is also a nitrogen-fixing bacterium.
- However, it is not free-living; it forms a symbiotic relationship with the root nodules of leguminous plants.
- **Conclusion**: Rhizobium is not found in the rumen of cattle.

4. **Analyze Methanobacterium**:
- Methanobacterium is a member of the archaebacteria, known as methanogens.
- These bacteria produce methane as a metabolic product, especially under hypoxic conditions.
- Methanobacterium is indeed present in the rumen of cattle, where it helps in the breakdown of cellulosic materials from their feed.
- **Conclusion**: Methanobacterium is present in the rumen of cattle.

5. **Analyze Azospirillum**:
- Azospirillum is another free-living nitrogen-fixing bacterium.
- Similar to Azotobacter, it is not associated with the rumen of cattle.
- **Conclusion**: Azospirillum is not present in the rumen of cattle.

6. **Final Conclusion**:
- Based on the analysis, the only bacterium that is present in the rumen of cattle is **C) Methanobacterium**.

### Final Answer:
**C) Methanobacterium**