Production of Extracellular Polysaccharide in Cultures of Coccidioides Immitis

SUMMARY

Three strains of Coccidioides immitis which differed in virulence for white mice were studied with regard to growth rate and output of polysaccharide, nondialyzable nitrogenous substances and precipitinogen over an 18 week period. The three strains had a comparable growth rate over a 4 week period followed by a loss in mycelial weight between the fourth and tenth weeks. This loss in weight occurred concomitantly with the attainment and maintenance of maximum alkalinity, pH 8.4 to 8.7, and was most profound with strain “Venezuela Brown” (VB) which underwent extensive autolysis. The other two strains manifested a striking secondary growth between the tenth and eighteenth weeks. There appeared to be no correlation between virulence of the strains and production of extracellular polysaccharide, while the liberation of non-dialyzable nitrogenous substances appeared proportional to virulence. The formation of precipitinogen was most rapid in cultures of strain VB of intermediate virulence. The release of extracellular polysaccharide appeared to be greater under conditions of nitrogen limitation. The low pH in the growth menstruum resulting when NH₄Cl was the nitrogen source appeared to restrict the output of polysaccharide.

The possible significance of autolysis in the release of antigens by C. immitis was discussed.