Question

What is the benefit to the bacteria donating DNA in conjugation? What causes it to occur?

Answer 1

Bacterial conjugation is one of the three major known modes of genetic exchange between bacteria, the other two being transduction and bacterial transformation. Of these three modes, conjugation is the only one that involves cell-to-cell contact.

The phenomenon was first reported in 1946 by J. Lederberg and E. L. Tatum using Escherichia coli, as the result of a conscious effort to find sexual recombination in bacteria.

Bacterial conjugation is a sexual mode of genetic transfer in the sense that chromosomal material from two sexually distinct types of cells are brought together in a defined and programmed process.

However, in bacterial conjugation the process involves only a portion (usually small) of the genome of one of the cells (the donor) and the complete genome of its sexual partner (the recipient), as opposed to sexual union in most higher organisms which involves an interaction between the entire set of chromosomes from both of the parental cells.

Thus, genetic transfer in bacterial conjugation is partial, and it is in most cases polar, wherein genetic material moves unidirectionally from the donor cell into the recipient cell followed by separation of the cells and further changes in the organization or recombination of the combined genetic material within the recipient cell.

With a few conjugational transfer systems, some transfer can also occur from the recipient strain into the donor strain. This is known as retrotransfer. The transfer of genetic material can take several minutes or more (up to several hours).

Bacterial conjugation is the bacterial equivalent of sexual reproduction or mating. To perform conjugation, one bacterium has to carry a transferable plasmid (referred to as either an F+ or an R+ plasmid), while the other must not. The transfer of plasmid DNA occurs from the F-positive bacterial cell to the F-negative bacterium (making it F+ once transfer is complete).

Conjugation is used in nature to share beneficial genetic material between bacteria, such as antibiotic resistance.

Bacteria that undergo conjugation are better able to survive when conditions become less than ideal because they are connected by a pilus and have a greater chance of getting favorable genes from both parents to survive. antibiotic resistance occurs because of a genetic mutation.