An ammonifying bacterium is

Options

A. Bacillus mycoides
B. Nitrocystis
C. Nitrosomonas
D. Pseudomonas aeruginosa

Answer

### Step-by-Step Solution:

1. **Definition of Ammonifying Bacteria**:
- Ammonifying bacteria are a type of bacteria that play a crucial role in the nitrogen cycle. They are responsible for the conversion of organic nitrogen from dead organisms and waste products into ammonia.

2. **Process of Ammonification**:
- During ammonification, these bacteria break down organic matter and release ammonia (NH3) as a byproduct. This process is essential for recycling nitrogen in ecosystems.

3. **Types of Ammonifying Bacteria**:
- Ammonifying bacteria can be classified into two categories:
- **Symbiotic**: These bacteria form a symbiotic relationship with plants, particularly legumes, and are often found in root nodules. They help in nitrogen fixation and provide ammonia to the plants.
- **Non-symbiotic**: These bacteria do not have a symbiotic relationship with plants and exist freely in the soil.

4. **Examples of Ammonifying Bacteria**:
- An example of an ammonifying bacterium is *Bacillus mycoides*. This bacterium is known for its ability to convert organic nitrogen into ammonia.

5. **Conclusion**:
- Therefore, an ammonifying bacterium is defined as a bacterium that converts organic nitrogen into ammonia, and it can be either symbiotic or non-symbiotic. The correct answer to the question is that ammonifying bacteria include species like *Bacillus mycoides*.