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( Bacterial conjugation)
Bacterial conjugation is the transfer of genetic material between bacteria through direct cell-to-cell contact.[1] Discovered in 1946 by Joshua Lederberg and Edward Tatum,[2] conjugation is a mechanism of horizontal gene transfer—as are transformation and transduction—although these mechanisms do not involve cell-to-cell contact.[3] Bacterial conjugation is often incorrectly regarded as the bacterial equivalent of sexual reproduction or mating. It is not actually sexual, as it does not involve the fusing of gametes and the creation of a zygote, nor is there equal exchange of genetic material. It is merely the transfer of genetic information from a donor cell to a recipient. In order to perform conjugation, one of the bacteria, the donor, must play host to a conjugative or mobilizable genetic element, most often a conjugative or mobilizable plasmid or transposon.[4][5] Most conjugative plasmids have systems ensuring that the recipient cell does not already contain a similar element. The genetic information transferred is often beneficial to the recipient cell. Benefits may include antibiotic resistance, other xenobiotic tolerance, or the ability to utilize a new metabolite.[6] Such beneficial plasmids may be considered bacterial endosymbionts. Some conjugative elements may also be viewed as genetic parasites on the bacterium, and conjugation as a mechanism that was evolved by the mobile element to spread itself into new hosts. The prototype for conjugative plasmids is the F-plasmid, also called the F-factor.[1] The F-plasmid is an episome (a plasmid that can integrate itself into the bacterial chromosome by genetic recombination) of about 100 kb length. It carries its own origin of replication, the oriV, as well as an origin of transfer, or oriT.[4] There can only be one copy of the F-plasmid in a given bacterium, either free or integrated (two immediately before cell division). The host bacterium is called F-positive or F-plus (denoted F+). Strains that lack F plasmids are called F-negative or F-minus (F-).
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