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Conjugation

Conjugation is a DNA transfer between cells through physical contacts via pili or adhesin. Conjugation involves a donor (F+) and a recipient (F-) cell. A donor has to carry genes that encode the machinery (e.g sex pili) required to perform the cell-to-cell contact. In most cases, these genes are encoded in conjugative or fertility (F) plasmid.

Gram-negative bacteria mainly perform conjugation using sex pili, while Gram-positive bacteria generally generates sticky molecules on its surfaces that brings two cells together.

Conjugation happens in steps.

First, a donor cell, which contains the conjugative plasmid, comes in contact with a recipient cell, which does not contain the conjugative plasmid. Then, the plasmid is replicated during the transfer of a single-stranded copy of the plasmid DNA to the recipient. Recipient's enzymes will synthesize a complementary strand for the transferred plasmid DNA.

Two bacteria cell in the process of conjugation. Cell on the left has a dark blue chromosome and two red circular plasmids. Cell on the right has Light blue chromosome and is in the process of acquiring the red plasmid from the cell on the left, pointed out by an arrow coming from the left cell, through the sex pili that is merging two cell together, pointing towards the red plasmid entering the cell on the left.

Figure 1. Conjugation involves donors carrying F factors (F+ cells) transfer the plasmid to recipients cells (F- cells), which become F+ cells as the results.

In some cells carrying F factors, the factor integrates into the chromosomes, converting F+ cells to Hfr (high frequency of recombination) cells.

Referred from:

Article
Horizontal gene transfer