The nitrifying bacteria Nitrosomonas is a:

Options

A. photoautotroph
B. chemoautotroph
C. anaerobic
D. symbiotic

Answer

**Step-by-Step Solution:**

1. **Understanding the Question:**
The question asks about the classification of the nitrifying bacteria Nitrosomonas. We need to identify which category it falls into from the given options.

2. **Analyzing the Options:**
The options provided are:
- Option 1: Photoautotroph
- Option 2: Chemoautotroph
- Option 3: Anaerobic
- Option 4: Symbiotic

3. **Defining Nitrosomonas:**
Nitrosomonas is a genus of gram-negative bacteria that plays a crucial role in the nitrogen cycle. It is known for converting ammonia into nitrites, which is an essential process in soil and aquatic ecosystems.

4. **Identifying the Energy and Carbon Source:**
Nitrosomonas uses ammonia as both its energy source and carbon source. This means it derives energy from the oxidation of ammonia.

5. **Evaluating Each Option:**
- **Photoautotroph:** These organisms use light as their energy source and carbon dioxide as their carbon source. Since Nitrosomonas uses ammonia, this option is incorrect.
- **Chemoautotroph:** These bacteria obtain their energy from the oxidation of inorganic compounds (like ammonia) and can use these compounds as their carbon source. This matches the characteristics of Nitrosomonas, making this option correct.
- **Anaerobic:** Anaerobic bacteria do not require oxygen for growth. However, Nitrosomonas requires oxygen to oxidize ammonia, so this option is incorrect.
- **Symbiotic:** Symbiotic bacteria form a mutual relationship with plants. Nitrosomonas does not form such relationships, so this option is also incorrect.

6. **Conclusion:**
After evaluating all the options, the correct classification for Nitrosomonas is that it is a **chemoautotroph**.

**Final Answer:**
The nitrifying bacteria Nitrosomonas is a **chemoautotroph**.

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