Reproduction - Sexual Reproduction, Conjugation, Transformation, Transduction

Reproduction - Sexual Reproduction, Conjugation, Transformation, Transduction

While bacteria multiply chiefly by simple asexual division, they can also exchange genetic material between two cells in ways that resemble sexual reproduction in the sense that DNA from one cell (the donor) ends up combined with the DNA of another (the recipient), producing genetic recombination. Three such mechanisms are recognised in bacteria: conjugation, transformation and transduction.

Conjugation is a process of direct cell-to-cell contact in which a donor bacterial cell forms a sex pilus that draws it together with a recipient cell, and DNA (often on a plasmid) passes across this connection from the donor into the recipient. Conjugation was discovered by Joshua Lederberg and Edward Tatum in 1946, working with the bacterium Escherichia coli.

Transformation is the uptake, by a recipient bacterial cell, of 'naked' DNA fragments that are free in its surroundings (typically released by the breakdown of other bacterial cells), which the recipient then incorporates into its own genome. Transformation was discovered by Frederick Griffith in 1928, in his experiments with the bacterium Streptococcus pneumoniae (the pneumococcus).

Transduction is the transfer of DNA from one bacterial cell to another using a bacteriophage (a virus that infects bacteria) as the carrier: DNA belonging to a previously infected bacterium is accidentally packaged into a new phage particle, which then injects that DNA into the next bacterial cell it infects. Transduction was discovered by Norton Zinder and Joshua Lederberg in 1952, working with the bacterium Salmonella typhimurium. …