Which one is a denitrifying bacteria?

Options

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

Answer

### Step-by-Step Solution:

1. **Understanding Denitrifying Bacteria**: Denitrifying bacteria are microorganisms that play a crucial role in the nitrogen cycle by converting nitrates (NO3-) in the soil into nitrogen gas (N2), which is then released into the atmosphere. This process is known as denitrification.

2. **Identifying the Process**: Denitrification is essential for maintaining the nitrogen balance in the ecosystem. It helps in reducing the excess nitrates in the soil, which can lead to problems such as water pollution.

3. **Examples of Denitrifying Bacteria**: Some well-known denitrifying bacteria include:
- **Pseudomonas denitrificans**
- **Thiobacillus denitrificans**

4. **Distinguishing Between Bacteria Types**: It is important to differentiate denitrifying bacteria from nitrifying bacteria. Nitrifying bacteria, such as:
- **Nitrosomonas**
- **Nitrobacter**
- **Nitrospira**
These bacteria are involved in the conversion of ammonia (NH3) to nitrates (NO3-), which is the opposite process of denitrification.

5. **Choosing the Correct Answer**: Given the options provided in the question, the correct denitrifying bacteria from the examples is **Thiobacillus denitrificans**.

### Final Answer:
**Thiobacillus denitrificans** is a denitrifying bacteria.

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