With respect to bacterial pilus, which of the following statements is not true ?

Options

A. They are made up of pilin protein
B. They are shorter than flagella
C. They help in genetic recombination
D. They play an important role in movement

Answer

To determine which statement about bacterial pilus is not true, let's analyze each option step by step:

1. **Understanding Bacterial Pilus**:
- Bacterial pilus (or pili) are hair-like appendages found on the surface of bacteria. They are primarily made of a protein called pilin.
- Their main functions include adhesion to surfaces and other bacteria, and they can also play a role in genetic recombination.

2. **Evaluating Each Statement**:
- **Option A: They are made up of pilin protein.**
- This statement is true. Bacterial pili are indeed composed of pilin proteins.

- **Option B: They are shorter than flagella.**
- This statement is also true. Pili are generally shorter than flagella, which are longer and used for movement in bacteria.

- **Option C: They help in genetic recombination.**
- This statement is true as well. Pili, specifically sex pili, are involved in the process of conjugation, which is a form of genetic recombination in bacteria.

- **Option D: They play an important role in movement.**
- This statement is not true. While flagella are responsible for the movement of bacteria, pili do not play a significant role in movement. Their primary functions are adhesion and genetic exchange.

3. **Conclusion**:
- The statement that is not true regarding bacterial pilus is **Option D**: "They play an important role in movement."

### Final Answer:
The correct option is **D**: They play an important role in movement.