Which of these microorganisms does NOT play a role in increasing the fertility of soil?

Options

A. Lactobacillus
B. Nitrobacter
C. Rhizobium
D. Nostoc

Answer

To determine which microorganism does NOT play a role in increasing the fertility of soil, we will analyze each of the given options: Lactobacillus, Nitrobacter, Rhizobium, and Nostoc.

### Step-by-Step Solution:

1. **Identify the Microorganisms**:
- The microorganisms listed are Lactobacillus, Nitrobacter, Rhizobium, and Nostoc.

2. **Analyze Lactobacillus**:
- Lactobacillus is a type of bacteria that is primarily known for its role in fermentation, particularly in converting milk into curd. It does not contribute to soil fertility.

3. **Analyze Nitrobacter**:
- Nitrobacter is a bacteria involved in the process of nitrification. It converts ammonia into nitrites and then into nitrates, which are essential nutrients for plants. This process increases the nitrogen content in the soil, thus enhancing soil fertility.

4. **Analyze Rhizobium**:
- Rhizobium is a symbiotic nitrogen-fixing bacteria that forms a relationship with leguminous plants. It converts atmospheric nitrogen into ammonia, making it available for plants. This process significantly contributes to soil fertility.

5. **Analyze Nostoc**:
- Nostoc is a type of blue-green algae (cyanobacteria) that can also fix atmospheric nitrogen. It has specialized cells called heterocysts that help in this process. By fixing nitrogen, Nostoc increases the nitrogen content in the soil, contributing to its fertility.

6. **Conclusion**:
- After analyzing all four microorganisms, we find that Lactobacillus does NOT play a role in increasing soil fertility, while Nitrobacter, Rhizobium, and Nostoc do.

### Final Answer:
**Lactobacillus does NOT play a role in increasing the fertility of soil.**

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