Nitrifying bacteria are

Options

A. autotrophs
B. chemoautotrophs
C. phototrophs
D. heterotrophs

Answer

**Step-by-Step Solution:**

1. **Definition of Nitrifying Bacteria:**
Nitrifying bacteria are a group of bacteria that play a crucial role in the nitrogen cycle by converting ammonia into nitrites and then into nitrates.

2. **Process of Nitrification:**
The process of nitrification occurs in two main steps:
- In the first step, ammonia (NH₃) is oxidized to nitrite (NO₂⁻) by bacteria such as **Nitrosomonas**.
- In the second step, nitrite (NO₂⁻) is further oxidized to nitrate (NO₃⁻) by bacteria such as **Nitrobacter**.

3. **Types of Nitrifying Bacteria:**
Common examples of nitrifying bacteria include:
- **Nitrosomonas**: Converts ammonia to nitrite.
- **Nitrobacter**: Converts nitrite to nitrate.
- **Nitrococcus**: Another example involved in the nitrification process.

4. **Nutritional Classification:**
Nitrifying bacteria are classified as **chemoautotrophs**. This means they obtain energy by oxidizing inorganic substances (like ammonia) and use this energy to fix carbon dioxide into organic compounds.

5. **Comparison with Other Bacteria:**
- **Autotrophs**: Organisms that can produce their own food from inorganic substances.
- **Heterotrophs**: Organisms that cannot synthesize their own food and rely on other sources of organic carbon.
- **Phototrophs**: Organisms that obtain energy from light.