Thiobacillus bacteria are invloled in

Options

A. Nitrogen fixation
B. Nitrification
C. Denitrification
D. Ammonification

Explanation

**Step-by-Step Solution:**

1. **Understanding Thiobacillus Bacteria**:
- Thiobacillus is a genus of bacteria that plays a significant role in the nitrogen cycle.

2. **Identifying the Process**:
- The question specifically asks about the involvement of Thiobacillus bacteria. The key process associated with Thiobacillus is denitrification.

3. **Explaining Denitrification**:
- Denitrification is the process where nitrates (NO3-) in the soil are converted into nitrogen gas (N2) or, to a lesser extent, nitrous oxide (N2O). This process is crucial for returning nitrogen to the atmosphere.

4. **Role of Thiobacillus in Denitrification**:
- Thiobacillus bacteria, along with Pseudomonas denitrificans, are responsible for carrying out the denitrification process. They reduce nitrates to gaseous nitrogen, thus completing the nitrogen cycle.

5. **Conclusion**:
- Therefore, Thiobacillus bacteria are involved in the process of denitrification, which is essential for maintaining the nitrogen balance in the ecosystem.

---