Phenotypic changes in colonial morphology of Neisseria gonorrhoeae

Phenotypic changes in the colonial morphology of four opacity variants of Neisseria gonorrhoeae strain F62 occurred upon growth in the presence of 14 mM pyruvate. Each of the naturally occurring opacity variants, a transparent, an opaque, and two deeply opaque, became more opaque; in addition, colonies of the opaque variants became rougher. Pyruvate did not appear to have a direct function in these colonial changes. Its effects were due to the ability of pyruvate to retard the oxidation of cysteine that was added to the medium in a defined supplement. Sodium dodecyl sulfate--polyacrylamide gel electrophoresis (SDS-PAGE) of outer membranes showed that the opacity-associated proteins of the naturally occurring variants were not affected by growth in the presence of pyruvate; therefore, the induced opacity changes appear to have another basis. However, other proteins were affected. SDS-PAGE of the outer membranes, as well as of cell fractions composed predominantly of cytosol and of cytoplasmic membranes, revealed quantitative differences in the protein profiles after growth in the presence of pyruvate of each variant.