- Volume 72, Issue 7, 2022

This study describes Wickerhamomyces sinyiensis, a new anamorphic ascomycetous yeast species, four strains of which were isolated from soil and the fruiting body of a mushroom in Taiwan between 2006 and 2007. Analysis of the sequences of the large-subunit rRNA, small-subunit rRNA and elongation factor-1α identified this species as a member of the Wickerhamomyces clade. The yeast strains of W. sinyiensis exhibited a 0–3 nucleotide difference in the sequences of the D1/D2 domain of the large subunit rRNA when compared to one another and a 10 and 11 nucleotide difference when compared to Candida sp. BG99-11-14-10-4-1 and NRRL Y-7574, the closest undescribed species, respectively. The yeast strains differed by 77 and 78 nucleotides from W. orientalis and W. bispora, the close Wickerhamomyces species, respectively. The internal transcribed spacer sequences of the four isolates exhibited a divergence of 106–108 substitutions from the recognized species W. xylosivorus. No sexual reproduction was observed. The strains differed from those of related species in terms of their carbon and nitrogen assimilation patterns. Therefore, this study proposes W. sinyiensis f.a., sp. nov. to accommodate these four strains, with W. sinyiensis BCRC 23185T (isotype CBS 11432T; MycoBank number MB563484) as the holotype.

Establishing a solid taxonomic framework is crucial for enabling discovery and documentation efforts. This ensures effective communication between scientists as well as reproducibility of results between laboratories, and facilitates the exchange and preservation of biological material. Such framework can only be achieved by establishing clear criteria for taxa characterization and rank assignment. Within the anaerobic fungi (phylum Neocallimastigomycota), the need for such criteria is especially vital. Difficulties associated with their isolation, maintenance and long-term storage often result in limited availability and loss of previously described taxa. To this end, we provide here a list of morphological, microscopic, phylogenetic and phenotypic criteria for assessment and documentation when characterizing newly obtained Neocallimastigomycota isolates. We also recommend a polyphasic rank-assignment scheme for novel genus-, species- and strain-level designations for newly obtained Neocallimastigomycota isolates.