Cytopathic Effects and Ultrastructure of Mycoplasma agalactiae var. bovis (Donetta strain).

An electron microscopic examination of the pathogenic Donetta strain mycoplasma (tentatively Mycoplasma agalactiae var. bovis), in broth and cell cultures, revealed that this organism possessed considerable pleomorphism. A membranelined space occurred in a number of the organisms, and some of these were considered to represent deep, cuplike invaginations of the outer limiting membrane. In cell cultures, the mycoplasmas were located almost exclusively in extracellular locations but often in close association to the host-cell membrane. The cytopathic effects (CPE) were not considered to be caused primarily by cytoplasmic invasion. Serum was necessary for the development of the CPE and multiplication of the mycoplasmas in cell cultures. An effort to determine the basic cause of the CPE was unsuccessful but did eliminate causes previously reported for other strains of mycoplasma.