Ultrastructure of Mycoplasma laidlawii during culture development.

Mycoplasma laidlawii B has been studied by phase-contrast and electron microscopy (thin-section and negative staining). Exponential-phase cells are filaments with the following structures: surface unit membrane, nuclear material, ribosomes, and intracellular granular region. These cells appear to reproduce by binary fission. In stationary phase, the filamentous cells have numerous constrictions, giving them a beaded appearance. Nonviable death-phase cultures contain cellular debris: swollen cells, granular bodies, and other aberrant forms.