Question

Explain about pili and fimbriae.

Answer 1

Hint:- Bacteria are microscopic organisms and the cells are prokaryotic cells. These cells are not very developed but are capable of all biological processes such as reproduction. Several species of bacteria are pathogenic in nature and are known to infect other cells. The bacterial cell membrane or surface contains a number of structures which are used for attachment, adhesion and genetic exchange.

Complete step-by-step solution:-
The bacterial cell membrane contains thin tubular structures which are made of proteins and these originate from the cytoplasmic membrane. These structures are known as pili and fimbriae. They are present in all Gram-negative bacteria but not in many Gram-positive bacteria. The structure of the pili and fimbriae are elongated structures that extend from the surface of the cell wall.
Pili or a pilus is a hair-like structure present on the surface of many bacteria and is made up of proteins known as pilin proteins. They are comparatively long filamentous structures and are limited in number. The pili act as a receptor for some viruses. The pili consists of a shaft composed of the protein pilin. At the end of the shaft an adhesive tip like structure is present. This tip bears a shape which corresponds to the specific glycoprotein or glycolipid receptors present on the host cell.
Pili are of two types which are short attachment pili and long conjugation pili. The long conjugation pili is also known as F or sex pili. They are few and longer in shape. They enable us to complete the process of conjugation. In the process of conjugation transfer of genetic material from a donor or male bacterium processing a sex pilus to the other bacterium known as the recipient or female bacterium.
The short type of pili is known as the fimbriae or the attachment pili. It is short and more numerous. It enables the bacteria to infect different cells and colonize other surfaces as well as resist flushing. The attachment of the bacteria to the infected cells through the fimbriae occurs due to the shape of the tip of the shaft. The pili is able to bind with the host cell and make more intimate contact.

Note:-
Pili and fimbriae are thin filamentous structures arising from the cell wall of the bacteria. They are present in the Gram-negative bacteria. pili are long structures and are few and are associated with the process of conjugation of the bacteria. Fimbriae are short pili and more numerous in number and they are associated with the infecting of other cells by the bacterial cells.