Cryptotrichosporon siamense sp nov., a ballistoconidium-forming yeast species in Trichosporonales isolated in Thailand

Two strains, which formed pink colonies and produced ballistoconidia and represented a novel anamorphic yeast species, were isolated from peat (DMKU-SPS1-2) and fern leaf (ST-145) collected in Thailand. Analysis of the sequences of the D1 /D2 domains of the large subunit (LSU) rRNA gene and the internal transcribed spacer (ITS) regions showed that the two strains were identical to the sequences of the D1/D2 domains of the LSU rRNA gene and differed by two nucleotide substitutions in the ITS regions. Phylogenetic analysis based on the combined sequences of the ITS and the D1/D2 regions confirmed that the two strains represented a single species in the genus Cryptotrichosporon that was distinct from the other known species of the genus. Cryptotrichosporon argae (CBS 14376 Tau) was the most closely related species, but with 22% nucleotide substitutions in the D1/D2 domains of the LSU rRNA gene, and 6.8-8.0 % nucleotide substitutions in the ITS regions. Therefore, the two strains were assigned as a novel species, for which we propose the name Cryptotrichosporon siamense sp. nov. The type is DMKU-SPS1-2 Tau. The MycoBank number of the novel species is MB82336.