Mycoplasma genitalium

Mycoplasma genitalium is a small parasitic bacterium which lives on the ciliated epithelial cells of the primate genital and respiratory tracts. M. genitalium is the smallest known free-living bacterium, and the second-smallest bacterium after the recently-discovered endosymbiont Carsonella ruddii. Until the discovery of Nanoarchaeum in 2002, M. genitalium was also considered to be the organism with the smallest genome (aside from viruses).

Mycoplasma genitalium was originally isolated in 1980 from urethral specimens of two male patients with non-gonococcal urethritis. Infection by M. genitalium seems fairly common, can be transmitted between partners during unprotected sexual intercourse, and can be treated with antibiotics; however, the organism's role in genital diseases is still unclear.

The genome of M. genitalium consists of approximately 580,000 base pairs, which are split into 74 fragments by the enzyme EcoRI. An initial study of the M. genitalium genome with random sequencing was performed by Peterson in 1993. It was then sequenced by Fraser and others (Science 270:397-403 (1995)). It was found to contain only 470 predicted coding regions, including genes required for DNA replication, transcription and translation, DNA repair, cellular transport, and energy metabolism. It was the second complete bacterial genome ever sequenced, after Haemophilus influenzae. The small genome of M. genitalium made it the organism of choice in The Minimal Genome Project, a study to find the smallest set of genetic material necessary to sustain life.

Synthetic life
In October of 2007, a team of scientists headed by controversial DNA researcher Craig Venter and Nobel laureate Hamilton Smith announced that they plan to create the first artificial life form in history by creating a synthetic chromosome which they plan to inject into the M. genitalium bacterium, potentially resulting in an artificial species dubbed Mycoplasma laboratorium.