Question

what purpose do fimbrae serve?

Answer 1

FIMBRIAE:

Fimbriae are short, fine, hair-like appendages that help in the bacterial adhesion; hence called the organ of adhesion. Special type of pili called (sex pili) also exists which helps in conjugation.

The fimbriae is made up of a protein called fimbrillin. Pili are made up of a protein called pilin. They are antigenic. The antibodies against pilin antigens are not protective.

They are not related to motility and can be found in both motile and non-motile organisms.

According to the functions, pili are of two types:

• common fimbriae or pili
• Sex pili

FIMBRIAE OR COMMON PILI:

• They help in bacterial adhesion to epithelial surface helping in colonization (hence called as colonization factor), to red blood cells (causing haemagglutination), and to surfaces of yeast and fungal cells.
• There are six types of common pili depending on their morphology, number per cell, adhesive properties, and antigenic nature.
• A single bacterium can have as many as 1000 fimbriae.
• They are present Gram-negative and some Gram-positive bacteria.

Sex or F (fertility) pili:

• Sex pili are special types of large fimbriae present 1- 10 per cell (e.g.. gonococcus).
• Sex pili help in bacterial conjugation. They are long, thick tubular structures.
• They are only found in Gram-negative bacteria. They are present in male bacterium; form the conjugation tube in the male bacterium and thereby help in the transfer of genetic material from male bacteria to the female bacteria through the conjugation tube.