Mycoplasma and Ureaplasma - Microbiology

MICROBIOLOGY

The organisms have diameters of about 0.2 to 0.3 mm, but they are highly plastic and  pleomorphic  and  may  appear  as  coccoid  bodies,  filaments,  and  large  multinu- cleoid forms. They do not have a cell wall and are bounded only by a single triple- layered membrane (Fig 25 – 1) that, unlike other bacteria, contains sterols. The sterols are not synthesized by the organism but are acquired as essential components from the medium or tissue in which the organism is growing. Lacking a cell wall, Mycoplasma and Ureaplasmastain poorly or not at all with the usual bacterial stains. Their double- stranded DNA genome is small, probably because of lack of genes encoding a com- plex cell wall. M. pneumonia is an aerobe, but most other species are facultatively anaerobic.All grow slowly inenriched liquid culture medium  and on special Mycoplasma agar to produce minute colonies only after several days of incubation.The  center  of  the  M. pneumoniae colony  grows  into  the  agar  and  appears  denser, giving the appearance of an inverted “fried egg.” Growth in culture is inhibited by spe- cific antisera directed at the particular species. Colonies of M. pneumoniaebind red blood cells (RBCs) onto the surface of agar plate cultures (hemadsorption). This is due to binding by the mycoplasma to sialic acid – containing oligosaccharides present on the RBC surface.