Question

How do pili help bacteria?

Answer 1

Pili are hair-like structures found on the surface of bacteria. They are thin, protein-like tubes originating from the membranes of many bacteria.

Complete answer:
Pili are shorter than the flagella and they are not involved in motility. They help the bacteria to stick to the surfaces. They are typically found in all Gram-negative bacteria and not in many Gram-positive bacteria. Dozens of these structures are found on the surface of bacteria and they are antigenic in nature. These structures facilitate infection and are a key virulence characteristic.

The pili are involved in conjugation. This is the transfer of genetic material between cells, and pili have a hollow core for this purpose. The conjugation pilus is also called sex pilus or F pilus. The sex pili make contact between two cells. Since they possess a hollow core, they act as a conjugation tube. The tip of the pilus recognizes the female (F–) cell through which the genetic material of the donor (F+) cell passes to the recipient (female) cell. Only F-pili (not I-pili) contains an axial hole. It has receptors to recognize recipient cells to receive the donor’s genetic material. The F pili are found on Escherichia coli. It functions by stabilizing bacteria during DNA transfer, which occurs via conjugation.

Note: Pili increase the bacterial ability to adhere to tissues and colonize by multiplying rapidly. Bacteria without pili are generally non-pathogenic. Pili are responsible for virulence through attachment. It also helps in the exchange of genetic material by conjugation.