Page 24 - MNU microbiology theoritical 2025

General Microbiology & Immunology (PM 401) Second level Semester 4 2024/2025

Pili and fimbriae

• They are small appendages hair like structures present on the surface of the
cell wall of many bacteria.

• They are shorter than Flagella and more in number.

• They are fibrous structures made of pilin protein

Fimbriae (short attachment pili) are a shorter version of pili.

- Fimbriae help bacteria in adherence to the host tissue (through adhesins)

- Number: 200-400 per cell

Sex pilus, appendages involved in bacterial conjugation (transfer of genetic
information from one cell to another)

- longer and fewer (up to 10 in each cell) in number than fimbriae.

General Microbiology & Immunology (PM 401) theoretical handbook Page 13