Metahyphopichia suwanaadthiae sp. nov., an anamorphic yeast species in the order Saccharomycetales and reassignment of Candida silvanorum to the genus Metahyphopichia

Seven yeast strains, representing a single novel anamorphic species, were isolated in Thailand. They consisted of five strains (DMKU-MRY16(T), DMKU-SK18, DMKU-SK25, DMKU-SK30 and DMKU-SK32) obtained from five different mushrooms, and two strains (ST-224 and 11-14.2) derived from insect frass and soil, respectively. The pairwise sequence analysis indicated that all seven strains had identical sequences in the D1/D2 domains of the large subunit (LSU) rRNA gene and the internal transcribed spacer (ITS) region. Metahyphopichia silvanorum was the most closely related species, but with 11.9-12.4% nucleotide substitutions in the D1/D2 domains of the LSU rRNA gene and 13.1-13.3% nucleotide substitutions in the ITS region. The phylogenetic analyses based on the concatenated sequences of the ITS region and the D1/D2 domains of the LSU rRNA gene showed that the seven strains form a well-separated subclade in a clade containing M. silvanorum and Metahyphopichia laotica with high bootstrap support. A phylogenetic analysis of a multilocus dataset including the small subunit (SSU) rRNA gene, the ITS region, the D1/D2 domains of the LSU rRNA gene, translation elongation factor 1-alpha gene, actin gene and the RNA polymerase II subunit 2 gene, confirmed the presence of the monophyletic clade that also includes M. silvanorum and M. laotica, and strongly supported the phylogenetic isolation of the seven strains from its neighbouring species. Therefore, the seven strains were assigned as a single novel species of the genus Metahyphopichia, according to their phylogenetic relationships. The name Metahyphopichia suwanaadthiae sp. nov. is proposed to accommodate the seven strains. The holotype is DMKU-MRY16(T) (TBRC 11775(T)=NBRC 114386(T)=PYCC 8655(T)). The MycoBank number of the novel species is MB 841280. In addition, Candida silvanorum is reassigned to the genus Metahyphopichia. The MycoBank number of M. silvanorum comb. nov. is MB 841279.