A COMPARISON OF THE OSMOTIC AND PASSIVE PERMEABILITY PROPERTIES OF MYCOPLASMA LAIDLAWII AND MYCOPLASMA HOMINIS

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Abstract
Turbidity variations induced by a variety of solutes at known levels of osmolality were determined in suspensions of Mycoplasma laidlawii and Mycoplasma hominis. Turbidity values were corrected for refractive index effects using Ficoll solutions. The two organisms differed in passive permeability properties, cell refractilities, estimated internal osmotic pressures, and cation stabilization effect. More specifically, M. laidlawii gave large turbidity responses, interpreted as caused by osmotic influences on cell volume, to potassium and sodium chlorides, sodium acetate, and sucrose. In addition a non-osmotic enhancement of turbidity was produced by potassium and sodium salts. Glucose, glycerol, and dimethylsulfoxide induced little turbidity variation. Of the above solutes, only glycerol and dimethylsulfoxide failed to induce maximum turbidity responses in M. hominis. M. laidlawii appeared to be more retractile and had higher estimated internal osmotic pressure values than M. hominis. These differences undoubtedly reflect properties of the enclosing cell membranes that are unlike in the two organisms. Their pertinence to saprophytic versus parasitic existence is obscure at the present time.