Trends in yeast diversity discovery

Yeasts, usually defined as unicellular fungi, occur in various fungal lineages. Hence, they are not a taxonomic unit, but rather represent a fungal lifestyle shared by several unrelated lineages. Although the discovery of new yeast species occurs at an increasing speed, at the current rate it will likely take hundreds of years, if ever, before they will all be documented. Many parts of the earth, including many threatened habitats, remain unsampled for yeasts and many others are only superficially studied. Cold habitats, such as glaciers, are home to a specific community of cold-adapted yeasts, and, hence, there is some urgency to study such environments at locations where they might disappear soon due to anthropogenic climate change. The same is true for yeast communities in various natural forests that are impacted by deforestation and forest conversion. Many countries of the so-called Global South have not been sampled for yeasts, despite their economic promise. However, extensive research activity in Asia, especially China, has yielded many taxonomic novelties. Comparative genomics studies have demonstrated the presence of yeast species with a hybrid origin, many of them isolated from clinical or industrial environments. DNA-metabarcoding studies have demonstrated the prevalence, and in some cases dominance, of yeast species in soils and marine waters worldwide, including some surprising distributions, such as the unexpected and likely common presence of Malassezia yeasts in marine habitats.

Teunomyces basidiocarpi sp. nov. and Teunomyces luguensis sp. nov., two ascomycetous yeast species related to the Candida kruisii clade isolated in Taiwan

Four strains of anamorphic yeasts isolated from the fruiting bodies of mushrooms collected in Taiwan were found to represent two novel yeast species belonging to the genus Teunomyces, which was formally known as the Candida kruisii clade. Strains NY13M09^T and NY14M14 were related to the type strains of Teunomyces panamensis, T. pallodes, T. tritomae and T. lycoperdinae, and strains GG4M07^T and GG6M14 were related to T. kruisii NRRL Y-17087^T and T. cretensis NRRL Y-27777^T. However, strains NY13M09^T and NY14M14 differed from their closest phylogenetic neighbours by 2.9-3.7 % in the D1/D2 domain sequence of the LSU rRNA gene and by 6.6-13.7 % in the internal transcribed spacer (ITS); GG4M07^T and GG6M14 differed from their closest known species by 2.4 % in the D1/D2 domain sequence of the LSU rRNA gene and by 8.7-10.0 % in the ITS. Meanwhile, these strains were also clearly distinguished from their closest relatives based on the results of physiological tests. Based on the characteristics described above, the strains could be regarded as representing two novel species of the genus Teunomyces, for which the names Teunomyces basidiocarpi sp. nov. and Teunomyces luguensis sp. nov. are proposed. The holotypes are Teunomyces basidiocarpi BCRC 23475^T and Teunomyces luguensis BCRC 23476^T.

Pichia nanzhaoensis sp. nov. and Pichia paraexigua f.a., sp. nov., two yeast species isolated from rotting wood

Four yeast strains were isolated from rotting wood samples collected in the Baotianman Nature Reserve in Henan Province, Central China. On the basis of sequence analysis of the D1/D2 domains of the large subunit rRNA gene and the internal transcribed spacer regions, they were suggested to be two novel species of the genus Pichia. Pichia nanzhaoensis sp. nov. produces one to four spherical ascospores per ascus, and is most closely related to Candida pseudolambica. Pichia paraexigua f.a., sp. nov. is a sister taxa to Pichia exigua, but the formation of ascospores was not observed on various sporulation media. P. nanzhaoensis sp. nov. can weakly assimilate inulin, whereas P. paraexigua sp. nov. can weakly assimilate d-glucosamine. The type strain of Pichia nanzhaoensis is NYNU 178136^T (=CICC 33279^T=CBS 15346^T) and the type strain of Pichia paraexigua is NYNU 178135^T (=CICC 33278^T=CBS 15237^T).