Which of the following statement is correct ?

Options

A. All bacteria are heterotrophic
B. Bacteria are either heterotrophic, chemoautotrophic
C. Bacteria can also be photoautotrophic
D. Bacteria are either chemoautotrophic or photoautotrophic

Answer

To solve the question regarding which statement about bacteria is correct, we need to analyze each statement based on our understanding of bacterial nutrition.

### Step-by-Step Solution:

1. **Understanding Bacterial Nutrition**:
- Bacteria can be classified based on their mode of nutrition into two main categories: **autotrophic** and **heterotrophic**.
- **Autotrophic bacteria** can synthesize their own food from inorganic substances. They are further divided into:
- **Photoautotrophic bacteria**: These use light to synthesize food (e.g., green sulfur bacteria, purple sulfur bacteria).
- **Chemoautotrophic bacteria**: These obtain energy from chemical compounds (e.g., nitrifying bacteria, ammonifying bacteria).
- **Heterotrophic bacteria** cannot synthesize their own food and must obtain it from organic sources.

2. **Analyzing the Statements**:
- **Statement 1**: "All bacteria are heterotropic."
- This is incorrect because there are autotrophic bacteria that can synthesize their own food.
- **Statement 2**: "Bacteria are either heterotropic or chemoautotropic."
- This is also incorrect because bacteria can be photoautotropic as well.
- **Statement 3**: "Bacteria can also be photoautotropic."
- This is correct as it acknowledges the existence of photoautotrophic bacteria.
- **Statement 4**: "Bacteria are either chemoautotropic or photoautotropic."
- This is incorrect because it excludes heterotrophic bacteria.

3. **Conclusion**:
- The only correct statement among the options provided is **Statement 3**: "Bacteria can also be photoautotropic."

### Final Answer:
The correct statement is: **Bacteria can also be photoautotropic.**

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