Nitrosomonas, Nitrococcus and Nitrobacter are

Options

A. Photoautotroph
B. Chemoheterotrophs
C. Chemoautotroph
D. Decomposers

Answer

### Step-by-Step Solution:

1. **Identify the Bacteria**: The question mentions three specific bacteria: Nitrosomonas, Nitrococcus, and Nitrobacter.

2. **Understand Their Role**: These bacteria are involved in the process of nitrification, which is crucial for the nitrogen cycle in ecosystems.

3. **Define Nitrification**: Nitrification is the biological process where ammonia (NH3) is converted into nitrate (NO3-) through a series of steps. This process is essential for soil fertility and plant nutrition.

4. **Identify the Function of Each Bacteria**:
- **Nitrosomonas**: This bacterium converts ammonia into nitrite (NO2-).
- **Nitrococcus**: This bacterium also plays a role in converting ammonia to nitrite, similar to Nitrosomonas.
- **Nitrobacter**: This bacterium converts nitrite into nitrate.

5. **Classify the Bacteria**: Based on their metabolic processes, these bacteria are classified as:
- **Chemoautotrophs**: They obtain energy by oxidizing inorganic substances (like ammonia) and use this energy to fix carbon dioxide into organic compounds.

6. **Eliminate Incorrect Options**:
- **Photoautotrophs**: These are organisms that use light energy to synthesize their own food, which does not apply to these bacteria.
- **Chemoheterotrophs**: These organisms obtain energy by consuming organic compounds, which is not the case for Nitrosomonas, Nitrococcus, and Nitrobacter.
- **Decomposers**: While these bacteria contribute to nutrient cycling, they are specifically involved in nitrification rather than decomposing organic matter.

7. **Conclusion**: The correct classification for Nitrosomonas, Nitrococcus, and Nitrobacter is that they are **chemoautotrophs**.

### Final Answer:
Nitrosomonas, Nitrococcus, and Nitrobacter are **chemoautotrophs**.

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