…………. bacteria are those which use chemical energy for reduction of `CO_2`.

Explanation

**Step-by-Step Solution:**

1. **Understanding the Question:**
- The question asks for the type of bacteria that utilize chemical energy to reduce carbon dioxide (CO2) into organic material.

2. **Identifying the Process:**
- In plants, CO2 is reduced to form organic compounds (like sugars) through photosynthesis, which uses light energy. However, the question specifies bacteria that do not rely on light energy.

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