Surface appendages or hairy structures present in some bacteria for attaching to one another are

Options

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

Answer

To answer the question "Surface appendages or hairy structures present in some bacteria for attaching to one another are," we will analyze the provided options step by step.

### Step-by-Step Solution:

1. **Understanding the Question**: The question is asking for a specific type of structure found on the surface of some bacteria that aids in their attachment to one another.

2. **Analyzing the Options**:
- **Option 1: Pili**: These are surface appendages that are hair-like structures found on the surface of some bacteria. Their primary function is to facilitate attachment between bacterial cells.
- **Option 2: Flagella**: These are whip-like structures that help in the movement of bacteria. They are not primarily for attachment.
- **Option 3: Cilia**: These are hair-like projections found on eukaryotic cells, not bacteria. They also assist in movement rather than attachment.
- **Option 4: Mesosome**: These are invaginations of the plasma membrane in some bacteria, but they do not serve the purpose of attachment between cells.

3. **Identifying the Correct Option**: Based on the analysis, the correct answer is **Option 1: Pili**. Pili are indeed the surface appendages that help bacteria attach to one another.

4. **Conclusion**: Therefore, the surface appendages or hairy structures present in some bacteria for attaching to one another are called **Pili**.