Pigment production by Cryptococcus neoformans from para and ortho diphenols: effect of the nitrogen source

Abstract

C. neoformans produced pigments when p diphenols were substrates in a glucose amino acid salts medium. The best substrates were 2,5 dihydroxybenzoic acid and 2,5 dihydroxybenzenesulfonic acid. In contrast to the cellular pigment production from o diphenols (hydroxyl groups in the 2,3 or 3,4 position of phenyl ring), the p diphenols (1,4 or 2,5 positions for the hydroxyl groups) produced large amounts of soluble pigments that diffused into the medium. When an optimal source of nitrogen (glutamine, glycine, and asparagine) was used, 89% of the C. neoformans strains produced pigments from p diphenols. In contrast, 0 to 67% of the strains produced pigments when a suboptimal nitrogen source (proline, ammonium sulfate, ornithine, and methionine) was used. When glutamine glycine asparagine was the nitrogen source, 100% of the C. neoformans strains produced pigments from o diphenols, whereas 77 to 100% of the strains produced pigment when proline ammonium sulfate ornithine methionine was the nitrogen source. Cryptococcus species other than C. neoformans and all tested Candida species failed to produce pigments from any of the substrates except when hydroquinone was used. A combination of glutamine glycine asparagine and 3,4 dihydroxyphenylalanine allowed differentiation of colonies of C. neoformans from C. albicans in 3 to 6 days. These data showed that pigment production from o and p diphenols served as an excellent biochemical test for the identification of C. neoformans.