The bacterium (Clostridium botulinum) that causes botulism is

Options

A. A facultative anaerobe
B. An obligate anaerobe
C. A facultative aerobe
D. An obligate aerobe

Answer

To determine the classification of the bacterium Clostridium botulinum that causes botulism, we need to analyze the characteristics of this organism.

### Step-by-Step Solution:

1. **Understand Botulism**:
- Botulism is a serious illness caused by a toxin produced by Clostridium botulinum. It affects the nervous system, leading to symptoms such as muscle paralysis and difficulty in breathing.

**Hint**: Remember that botulism is linked to a toxin that affects the nervous system.

2. **Identify the Characteristics of Clostridium botulinum**:
- Clostridium botulinum is described as a gram-positive, rod-shaped, spore-forming bacterium.

**Hint**: Focus on the shape and spore-forming ability of the bacterium.

3. **Determine Oxygen Requirements**:
- The key to answering the question lies in understanding the bacterium's oxygen requirements. Clostridium botulinum is known to grow in the absence of oxygen, indicating it is an anaerobic organism.

**Hint**: Consider what it means for an organism to be anaerobic.

4. **Differentiate Between Types of Anaerobes**:
- There are two types of anaerobes:
- **Facultative Anaerobes**: These can grow in both the presence and absence of oxygen, switching between aerobic respiration and fermentation.
- **Obligate Anaerobes**: These cannot survive in the presence of oxygen and will die if exposed to it.

**Hint**: Recall the definitions of facultative and obligate anaerobes.

5. **Classify Clostridium botulinum**:
- Since Clostridium botulinum cannot survive in the presence of oxygen, it is classified as an obligate anaerobe.

**Hint**: Think about the survival conditions of Clostridium botulinum when making your final classification.

### Final Answer:
The bacterium Clostridium botulinum that causes botulism is an **obligate anaerobic** bacterium.