Morphology and ultrastructure of human T-mycoplasmas

Four serologically distinct human T-mycoplasmas grown in liquid medium were studied in the electron microscope after ultrathin sectioning and negative staining. The morphology and ultrastructure of these strains was found to be essentially identical to that of other mycoplasmas; i.e., mainly spherical or ovoid cells were observed, but also short rod-shaped cells and filamentous, partly branched forms were noted. The cells were found to be enveloped by a triple-layered membrane, on the outer surface of which an electron-dense layer consisting of radiating hairlike structures was consistently present. In addition to ribosomes, now and then arranged in a regular geometric pattern, the ultrathin sections reveal vacuole-like structures in the interior of the cells.