Mycoplasma genitalium belongs to the class Mollicutes and is the smallest prokaryote capable of independent replication. It was originally isolated
from the urethras of two men with non-gonococcal urethritis (NGU). It has a number of characteristics which are similar to its genetically close relative,
Mycoplasma pneumoniae, which is an established pathogen of the respiratory tract. M. genitalium lacks a cell wall and has a characteristic pear/flask
shape with a terminal tip organelle. This organelle enables M. genitalium to glide along and adhere to moist/mucous surfaces, including host cells.
M. genitalium has minimal metabolism, and when compared to the other genital mycoplasmas, has the ability to metabolise glucose. The organism
is the smallest self-replicating prokaryote with a genome of only 580 kb pairs and was the second bacterium to have its genome fully sequenced. Its
DNA falls under the low G+C category and thus has a lower melting temperature during denaturation in polymerase chain reaction (PCR) assays. The
target genes for PCR assays include MgPa, rRNA and gap. M. genitalium has several virulence factors that are responsible for its pathogenicity. These
include the ability to adhere to host epithelial cells using the terminal tip organelle with its adhesins, the release of enzymes and the ability to evade
the host immune response by antigenic variation.