Bacillus subtilis are

Options

A. Hay bacteria
B. Nitrifying bacteria
C. Ammonifying bacteria
D. Intestinal bacteria.

Answer

**Step-by-Step Solution:**

1. **Identify the Organism**: The question asks about "Bacillus subtilis". This is a specific type of bacterium, and it is important to understand its classification and characteristics.

2. **Understand the Naming**: "Bacillus" is the genus name and "subtilis" is the species name. This naming convention is important in biology for identifying organisms.

3. **Research Characteristics**: Bacillus subtilis is known for being a soil bacterium. It is also classified as an obligate aerobe, meaning it requires oxygen to survive. It cannot thrive in anaerobic (without oxygen) conditions.

4. **Identify Unique Features**: Bacillus subtilis has the ability to degrade plant polysaccharides and pectin, which is a unique characteristic that distinguishes it from other bacteria.

5. **Review the Options**: The options given are:
- Option 1: Hay bacteria
- Option 2: Nitrifying bacteria
- Option 3: Ammonifying bacteria
- Option 4: Intestinal bacteria

6. **Evaluate Each Option**:
- **Hay Bacteria**: This is a common name for Bacillus subtilis, making this option likely correct.
- **Nitrifying Bacteria**: These bacteria convert ammonia into nitrates, which does not describe Bacillus subtilis.
- **Ammonifying Bacteria**: These bacteria convert organic nitrogen into ammonia, which is also not applicable to Bacillus subtilis.
- **Intestinal Bacteria**: These are bacteria that live in the intestines of mammals, which does not apply to Bacillus subtilis.

7. **Select the Correct Answer**: Based on the evaluation, the correct answer is Option 1: Hay bacteria.

8. **Conclusion**: Bacillus subtilis is primarily known as hay bacteria due to its presence in soil and its ability to degrade plant materials.

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