Which of the following can use molecule nitrogen as nutrient

Options

A. (a) Methanomonas
B. (b) Mucor
C. (c) Rhizobium
D. (d) Spirogyra

Answer

To determine which organism can use molecular nitrogen as a nutrient, we will analyze each option provided in the question step by step.

### Step-by-Step Solution:

1. **Examine Option A: Methanomonas**
- Methanomonas is a type of bacteria that utilizes methane as its primary source of energy and nutrients through a process known as methanotrophy.
- **Conclusion**: Methanomonas does not use molecular nitrogen as a nutrient.
- **Result**: This option is incorrect.

2. **Examine Option B: Mucor**
- Mucor is a genus of fungi that acts as a saprotroph, meaning it feeds on dead and decaying organic matter, primarily plant material.
- **Conclusion**: Mucor does not utilize molecular nitrogen as a nutrient.
- **Result**: This option is also incorrect.

3. **Examine Option C: Rhizobium**
- Rhizobium is a type of nitrogen-fixing bacteria that forms a symbiotic relationship with leguminous plants. These bacteria are capable of converting molecular nitrogen (N₂) from the atmosphere into a form that plants can use, such as ammonia.
- **Conclusion**: Rhizobium can use molecular nitrogen as a nutrient and is essential for the nitrogen cycle.
- **Result**: This option is correct.

4. **Examine Option D: Spirogyra**
- Spirogyra is a genus of green algae that performs photosynthesis to produce its own food using sunlight, carbon dioxide, and water.
- **Conclusion**: Spirogyra does not utilize molecular nitrogen as a nutrient.
- **Result**: This option is incorrect.

### Final Answer:
The organism that can use molecular nitrogen as a nutrient is **C: Rhizobium**.

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