Name a photoautotrophic bacterium.

Explanation

**Step-by-Step Solution:**

1. **Understanding Photoautotrophic Bacteria**:
- The term "photoautotrophic" can be broken down into two parts: "photo" meaning light and "autotrophic" meaning self-nourishing. This indicates that these bacteria can produce their own food using light energy.

2. **Function of Photoautotrophic Bacteria**:
- Photoautotrophic bacteria are capable of converting sunlight into chemical energy. They utilize sunlight to synthesize their own food through a process similar to photosynthesis.

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