Bacteria that convert nitrates into free nitrogen are

Options

A. Ammonifying
B. Nitrifying
C. Denitrifying
D. Nitrogen fixing bacteria.

Answer

To answer the question "Bacteria that convert nitrates into free nitrogen are:", we can follow these steps:

### Step 1: Understand the Types of Bacteria
We need to identify the different types of bacteria mentioned in the question and their functions related to nitrogen.

### Step 2: Analyze the Options
1. **Ammonifying Bacteria**: These bacteria convert atmospheric nitrogen into ammonia. They are also known as nitrogen-fixing bacteria. An example is Rhizobium.

2. **Nitrifying Bacteria**: These bacteria convert ammonia into nitrites and then into nitrates. An example is Nitrosomonas.

3. **Denitrifying Bacteria**: These bacteria convert nitrates into free nitrogen. An example is Thiobacillus denitrificans.

4. **Nitrogen Fixing Bacteria**: These are the same as ammonifying bacteria, converting atmospheric nitrogen into a form usable by plants.

### Step 3: Identify the Correct Answer
From the analysis, we see that the bacteria that specifically convert nitrates into free nitrogen are the **Denitrifying Bacteria**.

### Conclusion
The correct answer to the question is **Denitrifying Bacteria**.

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