Microbiology

Members of the family Mycoplasmataceae are small pleomorphic bacteria that characteristically lack a cell wall. Shapes range from filamentous to spherical, with diameters up to 0.8 µm. The genus Ureaplasma is biochemically unique in that all members possess urease and therefore hydrolyze urea to produce adenosine triphosphate. Ammonia also is produced, and it increases the pH and limits growth in culture. Ureaplasma urealyticum was first described in 1950 by Shepard, who noted minute colonies growing amid larger Mycoplasma colonies in specimens taken from the urethra and urine of men with nongonococcal urethritis.1 These bacteria were initially called “T-strain” Mycoplasma because of their tiny colony size. Urease production led to the name Ureaplasma urealyticum.

U. urealyticum, a human pathogen, has historically been divided into 14 serotypes, which are divided into 2 distinct biovars on the basis of biochemical and genetic features. Genetic study suggests that the 2 biovars represent 2 separate species; U. urealyticum biovar 1 (Ureaplasma parvum) includes serovars 1, 3, 6, and 14, and U. urealyticum biovar 2 is further divided into 3 subtypes. Subtype 1 includes serovars 2, 5, 8, and 9. Subtype 2 includes serovars 4, 10, 12, and 13, and subtype 3 includes serovars 7 and 11.2 The entire genome of U. urealyticum has been sequenced.3 It is the smallest sequenced prokaryotic genome, except for Mycoplasma genitalium, and it consists of only 75 DNA kilobase pairs. The function of at least 50% of the 652 identified genes remains unknown. The description of the genome facilitates improved understanding of the mechanism of disease caused by these elusive organisms.