The biology of Mycoplasma genitalium

Mycoplasma genitalium, discovered almost 20 years ago, is one of 14 mycopla smas of human origin and is found predominantly in the genital tract, being sexually transmitted. It is mainly flask-shaped, and the MgPa protein of t he narrow terminal portion 6 instrumental in its attachment to eukaryotic c ell surfaces. The terminal structure may also be involved in the gliding mo vement of M genitalium. It metabolises glucose but not arginine or urea and is susceptible to broad-spectrum antibiotics in a manner similar to M pneu moniae. The M genitalium genome, the smallest known for a self-replicating organism, namely 580 Kb, was the first to be fully sequenced. All the propo sed open reading frames of the genome are contained in the M pneumoniae gen ome, with the latter containing other specific genes. In addition, the MgPa adhesin gene of M genitalium has considerable sequence homology with the P 1 adhesin gene of M pneumoniae. Apart from adhesion, invasion of eukaryotic cells by M genitalium has been demonstrated, entrance being mediated appar ently by the terminal structure; intracellular location may promote chronic infection and enhance pathogenicity. Thus, apart from acute nongonococcal urethritis, M genitalium is associated with the chronic disease. M genitali um, lacking all the genes for amino acid synthesis, requires an exogenous s upply and this probably accounts for the difficulty of primary cultural iso lation. Reliable detection is made routinely by means of the polymerase cha in reaction (PCR), primers and probes fcr which are detailed, although PCR technology in combination with cell culture and mycoplasmal medium has resu lted in some isolates.