“Bacterial conjugation is a process of genetic transfer between bacteria that allows them to
exchange genetic material, such as plasmids or other mobile genetic elements.”
It is one of the mechanisms of horizontal gene transfer, which enables bacteria to acquire new
traits and genetic diversity.
During conjugation, two bacterial cells establish physical contact through a specialized structure
called a sex pilus. The sex pilus is produced by the donor cell, which possesses a conjugative
plasmid containing the genes necessary for conjugation. The plasmid carries the genetic
information to be transferred, such as antibiotic resistance genes or virulence factors.
PRINCIPLE OF BACTERIAL CONJUGATION
The process of bacterial conjugation is based on the principle that the plasmid or any
other genetic material is transferred from the donor cell to the recipient cell through
close physical contact.
Of all the conjugative plasmids, the F (fertility) plasmid of E. coli was the first
discovered and is one of the best-studied.
, The F plasmid is present in one or two copies per cell and is very large (about 100
kilobases). E. coli harboring the F plasmid are referred to as donor (F + or male) cells and
E. coli lacking the F plasmid are referred to as recipient (F – or female) cells. Only donor
cells are capable of transferring the F plasmid to recipient cells.
For transfer of the F plasmid from donor to recipient, intimate contact between cells,
resulting in mating-pair formation, is required.
The transfer of genetic material is then brought by membrane fusion of the two cells by
the action of different enzymes.
Following the membrane fusion, the replication of donor DNA occurs and is transferred
into the recipient cell.
STEPS OF BACTERIAL CONJUGATION
The process of conjugation involves several steps:
1. Attachment:
The sex pilus of the donor cell attaches to the recipient cell, bringing the
two cells into close proximity.
2. Formation of a conjugation bridge:
The sex pilus retracts, pulling the two cells together
and forming a bridge between them.
3. DNA transfer:
The donor cell transfers a copy of its genetic material, usually in the form
of a plasmid, through the conjugation bridge into the recipient cell. The plasmid is
replicated within the recipient cell, and the donor cell retains a copy of the plasmid.
4. Disruption of the bridge:
After DNA transfer is complete, the conjugation bridge is
broken, and the cells separate.