The bacterium capable of anaerobic `N_2` fixations known as

Options

A. Azotobacter
B. Clostridium
C. Bacillus
D. Rhizobium

Answer

To answer the question, "The bacterium capable of anaerobic N2 fixation known as," follow these steps:

### Step-by-Step Solution:

1. **Understand Nitrogen Fixation**:
- Nitrogen fixation is the process of converting atmospheric nitrogen (N2) into nitrogenous compounds (like ammonia) that can be utilized by living organisms. This process is crucial for the nitrogen cycle and is primarily carried out by certain bacteria.

2. **Identify Types of Nitrogen-Fixing Bacteria**:
- There are two main types of nitrogen-fixing bacteria:
- **Symbiotic Bacteria**: These bacteria live in association with plants (e.g., Rhizobium with legumes).
- **Free-Living Bacteria**: These bacteria do not require a host plant and can fix nitrogen independently.

3. **Differentiate Between Aerobic and Anaerobic Bacteria**:
- **Aerobic Bacteria**: These require oxygen to fix nitrogen (e.g., Azotobacter and Rhizobium).
- **Anaerobic Bacteria**: These can fix nitrogen in the absence of oxygen (e.g., Clostridium).

4. **Evaluate the Options Provided**:
- The options given are:
- Azeotopectin
- Clostridium
- Bacillus
- Rhizobium

5. **Identify the Correct Answer**:
- Among the options, **Clostridium** is known for its ability to fix nitrogen anaerobically. The other options either do not fix nitrogen or are aerobic nitrogen fixers.

6. **Conclusion**:
- Therefore, the bacterium capable of anaerobic N2 fixation is **Clostridium**.

### Final Answer:
The correct answer is **Clostridium**.

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