Denitrification is carried by bacteria

Options

A. Pseudomonas and Thiobacillus
B. Nitrosomonas and Nitrococcus
C. Nitrosomonas and Nitrobacter (
D. Pseudomonas and Nihococcus (

Explanation

**Step-by-Step Solution:**

1. **Understanding Denitrification**: Denitrification is a biological process in which nitrates (NO3-) are converted into nitrogen gas (N2) or, to a lesser extent, nitrous oxide (N2O), which is then released into the atmosphere. This process is crucial for the nitrogen cycle as it helps to remove excess nitrates from the soil and water.

2. **Identifying Denitrifying Bacteria**: Denitrification is primarily carried out by specific types of bacteria known as denitrifying bacteria. The key bacteria involved in this process include Pseudomonas and Thiobacillus.

3. **Analyzing the Options**:
- **Option A: Pseudomonas and Thiobacillus**: This option includes both Pseudomonas, which is known for its role in denitrification, and Thiobacillus, which also participates in this process. Therefore, this option is correct.
- **Option B: Nitrosomonas and Nitrobacter**: These bacteria are involved in nitrification, where Nitrosomonas converts ammonia to nitrites and Nitrobacter converts nitrites to nitrates. They do not participate in denitrification, making this option incorrect.
- **Option C: Nitrosomonas and Nitrobacter**: This option is the same as option B, reiterating the role of these bacteria in nitrification, not denitrification. Thus, it is incorrect.
- **Option D: Pseudomonas and Nitrococcus**: While Pseudomonas is a denitrifying bacterium, Nitrococcus is involved in nitrification, converting ammonia to nitrites. Therefore, this option is also incorrect.

4. **Conclusion**: After analyzing all the options, the correct answer is **Option A: Pseudomonas and Thiobacillus**, as both are known denitrifying bacteria.

**Final Answer**: Denitrification is carried out by bacteria Pseudomonas and Thiobacillus (Option A).

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