Green and brown colour effects in tremellaceous yeast fungi on Staib agar

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Abstract
Fifty‐eight species of basidiomycetous yeast fungi were examined for green and brown colour effects (GCE, BCE) on Staib agar (Guizotia abyssinica creatinine agar). In addition to 9% of Cryptococcus laurentii strains tested, only Cryptococcus podzolicus was GCE‐positive. Out of 14 strains of this species, 13 showed a GCE and four showed a BCE. All GCE‐positive strains utilized creatinine and creatine as a source of nitrogen but not of carbon. None of these strains could grow at 37 °C. Unlike Cr. laurentii, no strains of Cr. podzolicus assimilated glycine as a source of carbon. No association was found to exist between GCE and killer activity. Some tremellaceous creatinine‐negative species (Cryptococcus gastricus) showed a BCE whereas some sporidiobolaceous creatinine‐positive yeasts (Leucosporidium, Rhodotorula) produced neither GCE nor BCE.