Which of the following is a facultative anaerobe?

Options

A. Clostridium
B. Pseudomonas
C. Chlorobium
D. Bacillus subtilis

Answer

To determine which of the given options is a facultative anaerobe, we need to understand what a facultative anaerobe is and then analyze each of the options provided.

### Step-by-Step Solution:

1. **Define Facultative Anaerobe**:
- A facultative anaerobe is an organism that can grow in both the presence and absence of oxygen. They typically prefer to use oxygen for aerobic respiration when it is available, but can switch to anaerobic respiration or fermentation when oxygen is not present.

2. **Analyze the Options**:
- The options provided are:
- Clostridium
- Pseudomonas
- Chlorobiont
- Bacillus subtilis

3. **Identify Each Organism's Oxygen Requirement**:
- **Clostridium**: This genus consists of obligate anaerobes, meaning they cannot survive in the presence of oxygen.
- **Pseudomonas**: This genus is known to be a facultative anaerobe. It can grow in both aerobic and anaerobic conditions.
- **Chlorobiont**: This term generally refers to green algae, which are typically photoautotrophic and can perform photosynthesis; however, they are not classified as facultative anaerobes.
- **Bacillus subtilis**: This organism is also known to be a facultative anaerobe, similar to Pseudomonas.

4. **Select the Correct Answer**:
- Among the options, both **Pseudomonas** and **Bacillus subtilis** are facultative anaerobes. However, since the question asks for one facultative anaerobe, we can conclude that **Pseudomonas** is a well-known example of a facultative anaerobe.

### Final Answer:
The facultative anaerobe among the given options is **Pseudomonas**.

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