Wickerhamomyces corioli f.a., sp. nov., a novel yeast species discovered in two mushroom species

Two yeast strains, designated as 19-39-3 and 19-40-2, obtained from the fruiting bodies of Trametes versicolor and Marasmius siccus collected in Yunwu Mountain Forest Park, PR China, have been identified as representing a novel asexual ascomycetous yeast species. From the results of phylogenetic analyses of the sequences of the D1/D2 domains of the large subunit (LSU) rRNA, small subunit (SSU) rRNA and translation elongation factor 1-α (TEF1) genes, it was determined that these strains represent a member of the genus Wickerhamomyces, with Wickerhamomyces alni and Candida ulmi as the closest relatives. The novel species exhibited 6.6 and 6.7% differences in the D1/D2 domains compared with W. alni and C. ulmi, respectively. Additionally, distinct biochemical and physiological differences were observed between the novel species and its related counterparts. No sexual reproduction was observed in these strains, leading to the proposal of the name Wickerhamomyces corioli f.a., sp. nov. for this newly discovered species.

Diversity of Wickerhamomyces (Wickerhamomycetaceae, Saccharomycetales) in China with the description of four new species

Wickerhamomyces is a well-known genus of the family Wickerhamomycetaceae in the class Ascomycetes. These fungi can survive in a variety of substrates and environments and perform many valuable roles in both industrial processes and the natural ecosystems. During our investigation of yeast diversity associated with plant materials, 53 Wickerhamomyces isolates were obtained from rotting wood and plant leaves collected in Fujian, Guizhou, Henan, and Yunnan Provinces of China. Isolates were identified as 14 Wickerhamomyces species, including 1 species known previously to occur in China (W. anomalus), 9 new record species in China (W. arborarius, W. ciferrii, W. edaphicus, W. lynferdii, W. pijperi, W. subpelliculosa, W. xylosica, W. strasburgensis, and W. sydowiorum), and 4 novel species (W. guiyangensis sp. nov., W. paramyanmarensis sp. nov., W. quanzhouensis sp. nov., and W. phyllophilus sp. nov.). This study presents a detailed account of these new species, illustrating their morphology and analyzing their phylogenetic relationships with other Wickerhamomyces species. Our study is the first comprehensive study on Wickerhamomyces species associated with plant materials from tropical and subtropical China. The results of this study update our understanding of the phylogenetic relationships, systematics, and ecology of Wickerhamomyces.

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.

An Updated Global Species Diversity and Phylogeny in the Genus Wickerhamomyces with Addition of Two New Species from Thailand

Ascomycetous yeast species in the genus Wickerhamomyces (Saccharomycetales, Wickerhamomycetaceae) are isolated from various habitats and distributed throughout the world. Prior to this study, 35 species had been validly published and accepted into this genus. Beneficially, Wickerhamomyces species have been used in a number of biotechnologically applications of environment, food, beverage industries, biofuel, medicine and agriculture. However, in some studies, Wickerhamomyces species have been identified as an opportunistic human pathogen. Through an overview of diversity, taxonomy and recently published literature, we have updated a brief review of Wickerhamomyces. Moreover, two new Wickerhamomyces species were isolated from the soil samples of Assam tea (Camellia sinensis var. assamica) that were collected from plantations in northern Thailand. Herein, we have identified these species as W. lannaensis and W. nanensis. The identification of these species was based on phenotypic (morphological, biochemical and physiological characteristics) and molecular analyses. Phylogenetic analyses of a combination of the internal transcribed spacer (ITS) region and the D1/D2 domains of the large subunit (LSU) of ribosomal DNA genes support that W. lannaensis and W. nanensis are distinct from other species within the genus Wickerhamomyces. A full description, illustrations and a phylogenetic tree showing the position of both new species have been provided. Accordingly, a new combination species, W. myanmarensis has been proposed based on the phylogenetic results. A new key for species identification is provided.

Blastobotrys baotianmanensis sp. nov. and Blastobotrys xishuangbannaensis f.a., sp. nov., two novel yeast species associated with insects and rotting wood

Five yeast strains were isolated from the gut of the groundbeetle Pterostichus gebleri and rotting wood, which were collected from two different localities in China. These strains were identified as representing two novel species of the genus Blastobotrys through comparison of sequences in the D1/D2 domains of the LSU rRNA gene and other taxonomic characteristics. Blastobotrys baotianmanensis sp. nov. produces two to three spherical ascospores per ascus, and is most closely related to the type strains of B. elegans, B. capitulata, B. arbuscula, and an undescribed species represented by strain BG02-7-20-006A-3-1. Blastobotrys baotianmanensis sp. nov. differed from these strains by 3.6-8.4 % divergence (21-46 substitutions and 0-4 gaps) in the D1/D2 sequences. Blastobotrys xishuangbannaensis f.a., sp. nov. is closely related to B. nivea, B. elegans and B. aristata but the formation of ascospores was not observed on various sporulation media, and it differed from its relatives by 6.2-8.5 % divergence (34-43 substitutions and 2-6 gaps) in the D1/D2 sequences. The holotype of Blastobotrys baotianmanensis sp. nov. is NYNU 1581 and the holotype of Blastobotrys xishuangbannaensis f.a., sp. nov. is NYNU 181030.

Wickerhamomyces kurtzmanii sp. nov. An Ascomycetous Yeast Isolated From Crater Lake Water, Da Hinggan Ling Mountain, China

One novel ascomycetous yeast strain TF5-16-2 was isolated from water samples of Tuofengling crater lake located in Da Hinggan Ling Mountain, in the Inner Mongolia province of China. Morphological, physiological characteristics, as well as phylogenetic analyses of D1/D2 domains of the large subunit rRNA (LSU), ITS region, small subunit rRNA (SSU), and elongation factor-1α (EF-1α) were performed and finally confirmed the phylogenetic placement of strain TF5-16-2 in the genus Wickerhamomyces. Sequences analysis revealed that strain TF5-16-2 differed from its most closely related phylogenetic neighbors 'Candida' silvicultrix CBS 6269^T and Wickerhamomyces anomalus CBS 5759^T by 8.0% (including 2.3% gaps), 8.5% (including 2.4% gaps) divergences in D1/D2 domains of LSU, and 11% (including 4.3% gaps) and 13% (including 4.4% gaps) divergences in ITS region, respectively. As the considerable sequence divergence and distinguishable physiological characteristics, strain TF5-16-2 was proposed as a new species of the genus Wickerhamomyces, with the name Wickerhamomyces kurtzmanii sp. nov. (holotype = CGMCC 2.5597, Mycobank number is MB829959).

Metschnikowia baotianmanensis f.a., sp. nov., a new yeast species isolated from the gut of the rhinoceros beetle Allomyrina dichotoma

Four strains, NYNU 15610, NYNU 15612, NYNU 15613 and NYNU 15615, of a novel ascomycetous yeast were isolated from the gut of Allomyrina dichotoma (Coleoptera: Scarabeidae) collected from two different localities in Henan Province, Central PR China. The four strains shared identical sequences in both of the D1/D2 domains of the large subunit rRNA gene and the internal transcribed spacer regions. Sequence analyses revealed that this novel species represents a member of the genus Metschnikowia. It differed from its closest known species Metschnikowia zobellii, Metschnikowiaaustralis and Metschnikowia bicuspidata, by 8.4-9.2 % sequence divergence (33-40 nt substitutions and 7-12 gaps over 509 bases) in the D1/D2 sequences. The formation of ascospores was not observed on various sporulation media. In contrast to M. zobellii, M. australis and M. bicuspidata, the novel yeast species was unable to assimilate succinate, ethanol, ethylamine, cadaverine and 10 % NaCl plus 5 % glucose, but was able to grow in vitamin-free medium. The name Metschnikowia baotianmanensis f.a., sp. nov. is proposed to accommodate these strains, with NYNU 15613 as the holotype.

Wickerhamomyces menglaensis f.a., sp. nov., a yeast species isolated from rotten wood

Five strains, NUNU 16637, NYNU 16645, NYNU 1673, NYNU 1680 and NYNU 1689, of a novel ascomycetous yeast were isolated from the Xishuangbanna tropical rainforest, Yunnan Province, PR China. The five strains shared identical sequences in both of the D1/D2 domains of the large subunit rRNA gene and the internal transcribed spacer (ITS) regions. Sequence analysis showed that they represent undescribed yeast species belonging to the genus Wickerhamomyces. They differed from their closest known species, Wickerhamomyces xylosivorus NBRC 111553^T, by 3.4 % sequence divergence (14 substitutions and six gaps out of 584 bp) in the D1/D2 domains and by 9.6 % sequence divergence (28 substitutions and 24 gaps over 543 bp) in the ITS regions, respectively. The five strains of novel species reproduced asexually; no sexual reproduction could be found. In contrast to W. xylosivorus, the novel yeast species were able to assimilate l-arabinose, inulin, soluble starch, d-mannitol and citrate, and unable to assimilate trehalose, raffinose, 5-keto-d-gluconate, d-gluconate, ethanol, ethylamine and cadaverine. Growth was observed at 35 °C. The name Wickerhamomyces menglaensis f.a., sp. nov. is proposed to accommodate these strains, with NYNU 1673 as the holotype.

Three novel species of d-xylose-assimilating yeasts, Barnettozyma xylosiphila sp. nov., Barnettozyma xylosica sp. nov. and Wickerhamomyces xylosivorus f.a., sp. nov

This study describes three novel xylose-assimilating yeasts, which were isolated from decayed wood collected from Bung Hatta Botanical Garden in West Sumatra and Cibodas Botanic Garden in West Java, or from litter from Eka Karya Bali Botanic Garden in Bali, Indonesia. Phylogenetic analysis was performed based on the sequences of the D1/D2 domains of the large ribosomal subunit (LSU), the small ribosomal subunit (SSU), the internal transcribed spacer (ITS) and elongation factor-1α (EF-1α), and the three strains were found to represent three novel species belonging to genera Barnettozyma or Wickerhamomyces. The morphological, biochemical and physiological characteristics indicated that the strains were distinct from other closely related species. Strains 13Y206^T and 14Y196^T belonging to the Barnettozyma clade are described as the type strains of Barnettozyma xylosiphila sp. nov. (type strain 13Y206^T=NBRC 110202^T=InaCC Y726^T; MycoBank MB808598) and Barnettozyma xylosica sp. nov. (type strain 14Y196^T=NBRC 111558^T=InaCC Y1030^T; MycoBank MB819485). Strain 14Y125^T belonging to the Wickerhamomyces clade is described as the type strain of Wickerhamomyces xylosivorus f.a., sp. nov. (type strain 14Y125^T=NBRC 111553^T=InaCC Y1026^T; MycoBank MB819484).

Wickerhamomyces orientalis f.a., sp. nov.: an ascomycetous yeast species belonging to the Wickerhamomyces clade

Five closely related yeast strains were isolated from soil in Kharg Island, Persian Gulf, Iran, and from fallen fruits in Galle, Sri Lanka, during separate projects. Morphologically, the strains produced white-coloured yeast colonies, with cells that were ovoid to ellipsoidal, making branched, true hyphae and pseudohyphae. Ascospore formation was not observed. Biochemically, the strains were able to ferment d-glucose and weakly ferment d-galactose. The strains could use a wide variety of carbon sources except methanol and hexadecane. Phylogenetic analyses using combined sequences of the small ribosomal subunit and the D1/D2 domains of the LSU, as well as the internal transcribed spacer regions, suggested that these strains belong to the Wickerhamomyces clade and that together they form one strongly supported phylogenetic clade. Differences in their sequences, biochemistry and morphology suggest they are representatives of distinct species of the genus Wickerhamomyces. Therefore, the name Wickerhamomyces orientalis f.a., sp. nov. is proposed to accommodate these novel strains; the type strain is IBRC-M 30103^T (=CBS 13306^T). The MycoBank number is MB 807323.

Wickerhamomyces spegazzinii sp. nov., an ascomycetous yeast isolated from the fungus garden of Acromyrmex lundii nest (Hymenoptera: Formicidae)

A novel ascomycetous yeast species in the genus Wickerhamomyces was isolated from the fungus garden of an attine ant nest, Acromyrmex lundii (Hymenoptera: Formicidae), from Santa Fe province, Argentina. Pairwise sequence alignment of D1/D2 sequences in the GenBank (http://www.ncbi.nlm.nih.gov) database revealed that the novel species is related most closely to Wickerhamomyces subpelliculosus, Wickerhamomyces linferdii, Wickerhamomyces anomalus, Wickerhamomyces siamensis and Wickerhamomycesciferrii with 96% similarity to the first four. The species name Wickerhamomyces spegazzinii sp. nov. is proposed to accommodate this novel strain, which differs from the above species in melibiose, 5-keto-D-gluconate, succinate, and DL-lactate assimilation among others. The type strain is JLU025T (=CBS 12756T=CBMAI 1619T).

Trichosporon heliocopridis sp. nov., a urease-negative basidiomycetous yeast associated with dung beetles (Heliocopris bucephalus Fabricius)

Ninety-six yeast isolates associated with dung beetles (Heliocopris bucephalus Fabricius) were examined based on a culture-dependent method. A comparison of the colony morphology and PCR-fingerprints obtained by (GTG)₅ microsatellite-primed PCR indicated that 84 of these isolates belonged to one group. Five strains (DD1-1^T, DD2-33, DD4-11, DD5-15 and DD6-1) were selected as the representatives of this main group, where each of the five selected strains had been derived from a different dung beetle collected in northern Thailand. A comparison of the D1/D2 domain sequence of the large subunit rRNA gene (LSU D1/D2) and the internal transcribed spacer (ITS) sequences revealed that these five strains were the same and were related to the genus Trichosporon. Phylogenetic analysis based on the LSU D1/D2 plus ITS sequences placed this group within the Trichosporon brassicae clade, but it was clearly separated from any known species. In addition, physiological tests showed that this group had the unusual property of the inability to hydrolyse urea, which was distinctly different from the related taxon. Therefore a novel yeast species named Trichosporon heliocopridis sp. nov. (ex-type strain DD1-1^T = TISTR 5946^T = JCM 30786^T = CBS 14168^T) is proposed. The MycoBank number is MB812098.

Wickerhamiella allomyrinae f.a., sp. nov., a yeast species isolated from the gut of the rhinoceros beetle Allomyrina dichotoma

Two strains representing Wickerhamiella allomyrinae f.a., sp. nov. were isolated from the gut of Allomyrina dichotoma (Coleoptera: Scarabeidae) collected from the Baotianman National Nature Reserve, Nanyan, Henan Province, China. Sequence analyses of the D1/D2 domains of the LSU rRNA gene revealed that this novel species was located in the Wickerhamiella clade (Saccharomycetes, Saccharomycetales), with three described species of the genus Candida, namely Candida musiphila, Candida spandovensis and Candida sergipensis, as the most closely related species. The novel species differed from these three species by 9.3–9.8 % sequence divergence (35–45 nt substitutions) in the D1/D2 sequences. The species could also be distinguished from the closely related species, C. musiphila, C. spandovensis and C. sergipensis, by growth on vitamin-free medium and at 37 °C. The type strain is Wickerhamiella allomyrinae sp. nov. NYNU 13920T ( = CICC 33031T = CBS 13167T).

Molecular phylogenetic analysis reveals the new genus Hemisphaericaspora of the family Debaryomycetaceae

Four strains of a novel ascomycetous yeast species were recovered from the frass of wood-boring beetles collected from the Baotianman Nature Reserve and the Laojieling Nature Reserve in Henan Province, China. This species produced unconjugated and deliquescent asci with hemispheroid or helmet-shaped ascospores. Analysis of gene sequences for the D1/D2 domain of the large subunit (LSU) rRNA, as well as analysis of concatenated gene sequences for the nearly complete small subunit (SSU) rRNA and D1/D2 domain of the large subunit (LSU) rRNA placed the novel species in a small clade including only one recognised species, Candida insectamans, in the family Debaryomycetaceae (Saccharomycotina, Ascomycota). DNA sequence analyses demonstrated that the novel species was distinct from all currently recognised teleomorphic yeast genus. The name Hemisphaericaspora nanyangensis gen nov., sp. nov. is proposed to accommodate the novel genus and species. The new genus can be distinguished from closely related teleomorphic genera Lodderomyces and Spathaspora through sequence comparison and ascospore morphology. The ex-type strain of H. nanyangensis is CBS 13020^T ( = CICC 33021 = NYNU 13717). Furthermore, based on phenotypic and genotypic characteristics, C. insectamans is transferred to the newly described genus as Hemisphaericaspora insectamans comb. nov., in accordance with the changes in the International Code of Nomenclature for algae, fungi and plants.

Wickerhamomyces sylviae f.a., sp. nov., an ascomycetous yeast species isolated from migratory birds

In the present work, we investigated the phylogenetic position and phenotypic characteristics of eight yeast isolates collected from migratory birds on the island of Ustica, Italy. A phylogenetic analysis based on the D1/D2 region of the large-subunit rRNA gene showed that all isolates clustered as a single separate lineage within the Wickerhamomyces clade. They exhibited distinct morphological and physiological characteristics and were clearly separated from their closest relatives, Wickerhamomyces lynferdii, Wickerhamomyces anomalus and Wickerhamomyces subpelliculosus, in blastn searches. On the basis of the isolation source, physiological features and molecular strain typing carried out with randomly amplified polymorphic DNA (RAPD)-PCR and minisatellite-primed (MSP)-PCR analysis, the isolates were identified as strains of the same species. The name Wickerhamomyces sylviae f.a., sp. nov. is proposed to accommodate these novel strains; the type strain is U88A2(T) ( = PYCC 6345(T) = CBS 12888(T)). The MycoBank number is MB 804762.