Which of the following organisms is not an obligate aerobe ?

Options

A. Pseudomonas aeruginosa
B. Klebsiella pneumoniae
C. Mycobacterium tuberculosis
D. Bacillus sp

Answer

To determine which of the following organisms is not an obligate aerobe, we need to understand the definitions of obligate aerobes and facultative anaerobes.

### Step-by-Step Solution:

1. **Understand the Definitions**:
- **Obligate Aerobes**: These are organisms that require oxygen for their survival and metabolic processes. They cannot grow or survive in the absence of oxygen.
- **Facultative Anaerobes**: These organisms can grow in the presence of oxygen but can also switch to anaerobic metabolism when oxygen is not available.

2. **Analyze the Options**:
- **a. Pseudomonas aeruginosa**: This is an obligate aerobe. It requires oxygen for growth and metabolism.
- **b. Klebsiella pneumoniae**: This organism is a facultative anaerobe. It can grow in both the presence and absence of oxygen.
- **c. Mycobacterium tuberculosis**: This is also an obligate aerobe, as it requires oxygen for its metabolic processes.
- **d. Bacillus species**: Many Bacillus species are obligate aerobes, but some can also grow anaerobically.

3. **Identify the Correct Answer**:
- Among the options provided, **Klebsiella pneumoniae** is not an obligate aerobe; it is a facultative anaerobe. Therefore, it can survive without oxygen, unlike the obligate aerobes listed.

### Conclusion:
The organism that is not an obligate aerobe is **b. Klebsiella pneumoniae**.

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