Which of the following is an obligate aerobe

Options

A. E.coli
B. Closteridium tetani
C. Bacillus subtilis
D. None of these

Answer

To determine which of the given organisms is an obligate aerobe, we will analyze each option provided in the question.

### Step-by-Step Solution:

1. **Understand the Definition of Obligate Aerobes:**
- Obligate aerobes are organisms that require oxygen for their survival and growth. They cannot grow in environments devoid of oxygen.

2. **Evaluate the First Option: E. coli**
- E. coli is known to be a facultative anaerobe. This means it can grow in both the presence and absence of oxygen. Therefore, E. coli is not an obligate aerobe.

3. **Evaluate the Second Option: Clostridium tetani**
- Clostridium tetani is classified as an obligate anaerobe, meaning it cannot survive in the presence of oxygen. Thus, this organism is also not an obligate aerobe.

4. **Evaluate the Third Option: Bacillus subtilis**
- Bacillus subtilis is a facultative anaerobe, similar to E. coli. It can grow in both aerobic and anaerobic conditions. Therefore, this option is also not an obligate aerobe.

5. **Evaluate the Fourth Option: None of these**
- Since none of the previous options are obligate aerobes, this option is also incorrect.

6. **Conclusion:**
- After evaluating all the options, it appears that none of the provided organisms are obligate aerobes. Therefore, the correct answer is "None of these."

### Final Answer:
None of the options provided are obligate aerobes.

---