Bacteria photosynthesis is characterised by

Options

A. Evolution of `O_(2)`
B. Evolution of `H_(2)`
C. Evolution of `CO_(2)`
D. Non -evolution of `O_(2)`.

Answer

### Step-by-Step Solution:

1. **Understanding Bacterial Photosynthesis**:
- Bacterial photosynthesis primarily occurs in certain types of bacteria, including purple bacteria and green sulfur bacteria. Unlike plants and some algae, which perform oxygenic photosynthesis (producing oxygen), these bacteria perform anoxygenic photosynthesis.

2. **Identifying the Process**:
- In oxygenic photosynthesis, water (H2O) is used as an electron donor, leading to the release of oxygen (O2) as a byproduct. However, in anoxygenic photosynthesis, bacteria use substances like hydrogen sulfide (H2S) instead of water.

3. **Byproducts of Bacterial Photosynthesis**:
- The byproducts of anoxygenic photosynthesis are not oxygen but rather elemental sulfur (S) or other compounds, depending on the type of bacteria. Therefore, the key characteristic of bacterial photosynthesis is the non-evolution of oxygen.

4. **Evaluating the Options**:
- Given the options:
1. Evolution of O2 - Incorrect, as anoxygenic bacteria do not produce oxygen.
2. Evolution of H2 - Incorrect, as there is no production of hydrogen gas.
3. Evolution of CO2 - Incorrect, as CO2 is not a byproduct of this process.
4. Non-evolution of O2 - Correct, as these bacteria do not produce oxygen.

5. **Conclusion**:
- The correct answer to the question "Bacteria photosynthesis is characterized by" is the fourth option: **non-evolution of O2**.