Some bacteria function as denitrifers, they

Options

A. Oxidise `NH_(3)` to Nitrate
B. Oxidise nitrate to Nitrite
C. Reduce `N_(2)` to `NH_(3)`
D. Reduce `NO_(3)` to `N_(2)`

Answer

**Step-by-Step Solution:**

1. **Understanding Denitrifiers**: Denitrifying bacteria are a specific group of bacteria that play a crucial role in the nitrogen cycle. They are responsible for converting nitrates (NO3-) present in the soil into nitrogen gas (N2), which is released into the atmosphere.

2. **Identifying the Process**: The process by which denitrifying bacteria convert nitrates to nitrogen gas is known as denitrification. This process is essential for maintaining the nitrogen balance in the ecosystem.

3. **Analyzing the Options**:
- **Option 1**: "Oxidize ammonia or NH3 to nitrate" - This is incorrect because denitrifiers do not oxidize ammonia; that process is typically carried out by nitrifying bacteria.
- **Option 2**: "Oxidize nitrate to nitrite" - This is also incorrect as denitrifiers do not oxidize nitrates; they reduce them.
- **Option 3**: "Reduce nitrogen to ammonia" - This is incorrect as well; this process is known as nitrogen fixation, which is performed by different types of bacteria.
- **Option 4**: "Reduce nitrate to nitrogen" - This is the correct function of denitrifying bacteria.

4. **Conclusion**: Based on the analysis of the options, the correct answer is that denitrifying bacteria reduce nitrate to nitrogen gas (N2).

**Final Answer**: Denitrifying bacteria reduce nitrate to nitrogen.

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