Quote:
Do bacteria indulge in sex?: Bacteria don’t have sex in the traditional sense of the term. They multiply asexually. However, they can reproduce sexually using a technique known as plasmid (rings of DNA) migration. They wander around, bump into each other and “talk” to each other as to whether they want each other’s genetic material. With mutual consent plasmid(s) are exchanged through the cell membrane. Usually, this is done for survival to fight antibiotics and other toxins that are detrimental to them. Vegetative bacteria unite by a conjugation bridge through which all or part of a male genome migrates into the female cell. The gametic cells then separate. The ex-conjugant male goes on to multiply unaltered, surviving by virtue of its remaining DNA. The ex-conjugant female generates a mixed clone, some its own original copy (unaltered) and others modified slightly by virtue of the conjugal event, but still all are immortal.

from: http://www.chennaionline.com/science/BiotechCorner/14biotech.asp