Exophiala dermatitidis and Sarcinomyces phaeomuriformis: ITS1-sequencing and nutritional physiology

The internal transcribed spacer 1 (ITS1) sequences of the nuclear rRNA gene (approximately 200 bp) of 33 strains of the Exophiala dermatitidis complex were determined; two similar species were added for comparison. A core group (I), including the type strain CBS 207. 35, contained 20 identical strains which had previously been found to have introns in their small sub-unit (SSU) rDNA. Eleven remaining strains identified as E. dermatitidis (groups II-V) differed from the core group in 1-4 nucleotide positions (plus a deletion in one strain); most of them lacked introns in their SSU ribosomal genes. The type strain of the meristematic species Sarcinomyces phaeomuriformis CBS 131.88 was found to differ significantly from E. dermatitidis. One strain had the annellidic morphology of E. dermatitidis, but the ITS1 sequence of S. phaeomuriformis. Strain CBS 709.95, an E. dermatitidis reported to have a meristematic synanamorph, was found to have ITS1 identity to the type strain of E. dermatitidis, although SSU sequences established previously suggested a close relationship with S. phaeomuriformis. Slight physiological differences were found between E. dermatitidis and S. phaeomuriformis. An oligonucleotide probe specific for E. dermatitidis was designed, thus able to discriminate this species from closely related black yeasts.