Which one is a denitrifying bacteria?

Options

A. Nitrosomonas
B. Nitrococcus
C. Nitrobacter
D. Thiobacillus

Answer

**Step-by-Step Solution:**

1. **Understanding Denitrification:**
- Denitrification is the process where nitrate ions (NO3-) in the soil are reduced to nitrogen gas (N2), which is then released into the atmosphere. This process is crucial for the nitrogen cycle as it helps in maintaining the balance of nitrogen in the environment.

2. **Identifying Nitrifying Bacteria:**
- Before identifying denitrifying bacteria, it is essential to understand nitrifying bacteria. Nitrification is the conversion of ammonia (NH3) into nitrite (NO2-) and then into nitrate (NO3-). The bacteria responsible for this process include:
- **Nitrosomonas**: Converts ammonia to nitrite.
- **Nitrococcus**: Converts nitrite to nitrate.
- **Nitrobacter**: Also converts nitrite to nitrate.
- These bacteria are not denitrifying bacteria; they are involved in the nitrification process.

3. **Identifying Denitrifying Bacteria:**
- Denitrifying bacteria are responsible for the conversion of nitrate back to nitrogen gas. Examples of denitrifying bacteria include:
- **Thiobacillus**
- **Pseudomonas**
- Among the options given in the question (Nitrosomonas, Nitrococcus, Nitrobacter, Thiobacillus), **Thiobacillus** is identified as a denitrifying bacterium.

4. **Conclusion:**
- The correct answer to the question "Which one is a denitrifying bacteria?" is **Thiobacillus**.