Which one of the following is a denitrifying bacterium ?

Options

A. Nitrobacter
B. Nitrosomonas
C. Pseudomonas
D. Escherichia coli

Answer

To determine which of the given options is a denitrifying bacterium, we can follow these steps:

### Step-by-Step Solution:

1. **Understand Denitrifying Bacteria**: Denitrifying bacteria are microorganisms that convert nitrates (NO3-) in the soil into nitrogen gas (N2), which is then released into the atmosphere. This process is known as denitrification.

2. **List the Given Options**: The options provided are:
- Nitrobacter
- Nitrosomonas
- Pseudomonas
- E. coli

3. **Identify the Function of Each Bacterium**:
- **Nitrobacter**: This bacterium is involved in the nitrification process, converting nitrites (NO2-) to nitrates (NO3-).
- **Nitrosomonas**: This bacterium also plays a role in nitrification, converting ammonia (NH3) to nitrites (NO2-).
- **Pseudomonas**: This genus includes some species that are known to be denitrifying bacteria, capable of converting nitrates to nitrogen gas.
- **E. coli**: This is a common bacterium found in the intestines of humans and animals and is not known for denitrification.

4. **Select the Correct Answer**: Based on the functions of the bacteria, **Pseudomonas** is identified as a denitrifying bacterium. Therefore, the correct answer is **Pseudomonas**.

### Final Answer:
The denitrifying bacterium among the options is **Pseudomonas**.

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