Which of the following fixes `CO_(2)` into carbohydrates

Options

A. Rhizobium
B. nitrobacter
C. Bacillus
D. Rhodospirillum

Answer

To determine which organism fixes CO₂ into carbohydrates, let's analyze the options provided:

1. **Understanding the Organisms**:
- **Rhizobium**: This is a nitrogen-fixing bacterium that forms symbiotic relationships with legumes. It primarily fixes nitrogen, not carbon dioxide.
- **Nitrobacter**: This bacterium is involved in the nitrification process, converting ammonia into nitrites and then nitrates. It does not fix carbon dioxide.
- **Bacillus**: This genus includes various bacteria, some of which are denitrifying. They also do not fix carbon dioxide.
- **Rhodospirillum**: This is an anaerobic, photosynthetic bacterium that can utilize carbon dioxide as a carbon source and convert it into carbohydrates through photosynthesis.

2. **Identifying the Correct Option**:
- Among the options, only **Rhodospirillum** is known for fixing carbon dioxide into carbohydrates. It is classified as a photoautotroph, meaning it uses light energy to convert carbon dioxide into organic compounds.

3. **Conclusion**:
- Therefore, the correct answer to the question "Which of the following fixes CO₂ into carbohydrates?" is **Rhodospirillum**.

### Step-by-Step Solution:
1. Identify the organisms listed in the options.
2. Analyze the role of each organism concerning carbon fixation.
3. Conclude which organism is capable of fixing CO₂ into carbohydrates.