Definition
Conjugation is the direct transfer of genetic material between bacteria through cell-to-cell contact using a specialized structure called a pilus (sex pilus).
Mechanism of Conjugation
Formation of a Pilus: The donor bacterium (F⁺) extends a pilus to connect with the recipient bacterium (F⁻).
DNA Transfer: The plasmid DNA (usually the F-plasmid) is replicated and transferred to the recipient.
Recipient Becomes Donor: The recipient (F⁻) becomes an F⁺ cell after receiving the plasmid, enabling it to further transfer the plasmid to other bacteria.
Types of Conjugation
F-plasmid Conjugation
The donor cell (F⁺) contains an F-plasmid that encodes genes for conjugation.
Transfers the F-plasmid to an F⁻ recipient, converting it into an F⁺ donor.
Hfr Conjugation
The F-plasmid integrates into the bacterial chromosome, forming an Hfr (high-frequency recombination) cell.
Transfers part of the chromosomal DNA along with the plasmid.
Significance
Conjugation is a major mechanism for the spread of antibiotic resistance genes (e.g., R-plasmids carrying resistance genes).
Facilitates genetic recombination and evolution in bacterial populations.
