Mycoplasma genitalium

Mycoplasma genitalium is a small parasitic bacterium which lives on the ciliated epithelial cells of the primate genital and respiratory tracts.
It has one of the smallest known genomes, and is one of the smallest bacteria. Other very small bacteria are the endosymbiont "Candidatus" Carsonella ruddii, and the recently discovered bacterium "Nanoarchaeum". The smallest known free living bacterium is "Pelagibacter ubique" with 1.3 Mb.
Origin and isolation.
"Mycoplasma genitalium" was originally isolated in 1980 from the urethras of two male humans with non-gonococcal urethritis. Infection by "M. genitalium" is fairly common, and is transmitted between partners during unprotected sexual intercourse. It can be treated with antibiotics. Much remains to be discovered about its role in sexual disease.
Genome.
"M. genitalium" has 525 genes. There are 482 protein-encoding genes in a circular chromosome of 582,970 base pairs. An initial study of the "M. genitalium" genome with shotgun sequencing was done by Peterson in 1993. It was then sequenced by Fraser and others. 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".