Production of indole pigments byCandida glabrata

Abstract

When provided as the sole nitrogen source tryptophan induces the production of several indole alkaloids, e.g., pityriacitrin, malasseziaindole, pityriaanhydride and pityriarubin with proven biological activity in the lipophilic yeast Malassezia furfur. So far these pigments seem to have been unique and only produced by highly specialized basidiomycetal yeasts of the genus Malassezia. Having surprisingly observed a brown pigmented Candida glabrata isolate as a contaminant on such a pigment inducing culture plate, we systematically analyzed whether this ascomycetal yeast can also synthesize the respective pigments. Therefore, 30 Candida glabrata strains, including the ex-type strain CBS 138, were cultured for 2 weeks on a pigment-inducing medium containing L-tryptophan. This culture medium along with the resultant biomass was then extracted with ethyl acetate. The extracted pigments were separated into six fractions by column chromatography. Each of these fractions was subjected to thin-layer chromatography (TLC) on silica gel and yielded identical pigment bands comparable to those observed with M. furfur. In the case of strain CBS 138, the individual TLC zones were further purified by HPLC and structural analysis of the pure metabolites was performed by mass spectrometry and proton nuclear magnetic resonance ((1)H-NMR), thereby proving the presence of pityriacitrin, malassezia indole, pityriaanhydride and pityriarubin C. Since lineage divergence of Basidiomycota and Ascomycota occurred approximately 600 million years ago, our findings demonstrate that the complex underlying biochemical pathway has not been exclusively evolved in the highly adapted basidiomycetes yeast M. furfur, but instead seems to be rather fundamental and archaic. Therefore, further investigations on the potential biological properties and the genetic regulation of these metabolites are needed to elucidate their hitherto unknown functions.