Which of the following microbes is a proteinaceous infectious agent?

Options

A. Fungi
B. Prions
C. Bacteria
D. Protozoa

Explanation

To determine which of the following microbes is a proteinaceous infectious agent, we need to analyze the options provided: fungi, prions, bacteria, and protozoa.

### Step-by-Step Solution:

1. **Understanding the Term "Proteinaceous Infectious Agent":**
- A proteinaceous infectious agent is a type of infectious agent that is primarily composed of protein and does not contain any nucleic acids (DNA or RNA).

2. **Evaluating the Options:**
- **Fungi:** Fungi are complex organisms that contain both DNA and RNA. They are not proteinaceous infectious agents.
- **Prions:** Prions are indeed proteinaceous infectious agents. They consist solely of misfolded proteins and lack any genetic material. Prions are known to cause neurodegenerative diseases in humans and animals.
- **Bacteria:** Bacteria are single-celled organisms that contain both DNA and RNA. They cannot be classified as proteinaceous infectious agents.
- **Protozoa:** Protozoa are also single-celled organisms that possess genetic material (DNA/RNA). Thus, they do not fit the definition of a proteinaceous infectious agent.

3. **Conclusion:**
- Based on the analysis, the only option that fits the description of a proteinaceous infectious agent is **prions**.

### Final Answer:
**Prions** are the proteinaceous infectious agents.

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