The motile bacteria are able to move by

Options

A. Pili
B. Fimbriae
C. Flagella
D. Cilia

Answer

**Step-by-Step Solution:**

1. **Understanding Motility in Bacteria:**
- Motile bacteria are those that can move from one place to another. This movement is essential for various functions, including finding nutrients, escaping harmful environments, and colonizing new habitats.

2. **Analyzing the Options:**
- The question provides four options: Pilae, Fimbriae, Flagella, and Celia. We need to determine which of these structures is responsible for the motility of bacteria.

3. **Evaluating Pilae:**
- Pilae (or pili) are hair-like structures on the surface of bacteria. They are primarily involved in the process of conjugation, which is the transfer of genetic material between bacteria. Therefore, Pilae do not facilitate movement.

4. **Evaluating Fimbriae:**
- Fimbriae are also small, hair-like structures that help bacteria adhere to surfaces, such as host tissues or other surfaces. They play a role in attachment rather than locomotion, so they are not responsible for bacterial movement.

5. **Evaluating Flagella:**
- Flagella are long, whip-like structures that protrude from the bacterial cell. They are the primary organelles responsible for motility in bacteria. Flagella can rotate, allowing the bacteria to swim through liquids. They are typically 15 to 20 micrometers long and consist of three parts: the filament, the basal body, and the hook.

6. **Evaluating Celia:**
- Celia (or cilia) are short, hair-like structures that can help in movement, but they are more commonly associated with eukaryotic cells rather than bacteria. They assist in small, coordinated movements rather than the primary motility of bacteria.

7. **Conclusion:**
- Based on the analysis, the correct answer is **Flagella**, as they are the structures that enable motility in bacteria.

**Final Answer:**
Motile bacteria are able to move by **Flagella**.

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