Patterns of substrate utilization in species of Capronia and allied black yeasts: ecological and taxonomic implications

Forty-one isolates representing 14 members of the ascomycete genus Capronia and 15 black yeasts belonging to the anamorph genera Exophiala, Cladospori um, Ramichloridium and Rhinocladiella were tested for their ability to degr ade amylose, casamino acids, casein, cellulose, chitin, gelatin, lignin, li pid, pectin and urea. The results of these tests were compared to assays fo r the breakdown of the same compounds by eight ascomycetes, basidiomycetes and zygomycetes that served as reference strains. Species of Capronia and b lack yeasts were unable to degrade amylose, cellulose, chitin, lignin and p ectin. The utilization of casein, casamino acids, lipid, gelatin and urea v aried among the taxa tested. These results indicate that plant-derived poly mers and chitin are inaccessible to the Herpotrichiellaceae in natural syst ems and support the hypothesis that the members of this family are saprobes of secondary or higher incidence (hypersaprobes). Clinical and nonclinical Herpotrichiellaceae could not be discriminated on the basis of their enzym atic capabilities. Of the 12 substrate utilization tests employed in this s tudy, only those used to assess the hydrolysis of casamino acids, casein an d lipid proved valuable for distinguishing members of the genera Capronia, Exophiala and Ramichloridium. A simple method for detecting chitinolytic ac tivity in fungi using chitin azure is described.