The bacteria which converts nitrate in to molecular nitrogen is called

Options

A. Nitrifying bacteria
B. Methanobacteria
C. Diazotrophic bacteria
D. Denitrifying bacteria

Answer

To answer the question, "The bacteria which converts nitrate into molecular nitrogen is called," we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Question**: The question is asking for a specific type of bacteria that converts nitrate (NO3-) into molecular nitrogen (N2). This process is known as denitrification.

2. **Identify the Options**: The options provided are:
- A) Nitrifying bacteria
- B) Methanobacteria
- C) Diazotropic bacteria
- D) Denitrifying bacteria

3. **Analyze Each Option**:
- **A) Nitrifying bacteria**: These bacteria convert atmospheric nitrogen into nitrates or ammonia. They do not convert nitrate into nitrogen gas. Examples include Nitrobacter.
- **B) Methanobacteria**: These are involved in energy production under anaerobic conditions and are not related to nitrate conversion. They produce methane from formate.
- **C) Diazotropic bacteria**: These bacteria convert atmospheric nitrogen into ammonia, not nitrate into nitrogen gas. An example is Francia.
- **D) Denitrifying bacteria**: These bacteria are specifically involved in the process of denitrification, where they convert nitrates or nitrites into molecular nitrogen (N2), thus returning nitrogen to the atmosphere. Examples include Pseudomonas and Thiobacillus.

4. **Select the Correct Answer**: Based on the analysis, the correct answer is **D) Denitrifying bacteria**.

### Final Answer:
The bacteria which converts nitrate into molecular nitrogen is called **denitrifying bacteria**.

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