Candida kazuoi sp. nov. and Candida hasegawae sp. nov., two new species of ascomycetous anamorphic yeasts isolated from insect frass in Thailand

Isolation and identification of Wickerhamiella tropicalis from blood culture by MALDI-MS

Wickerhamiella is a genus of budding yeast that is mainly isolated from environmental samples, and 40 species have been detected. The yeast isolated from human clinical samples usually only contain three species: W. infanticola, W. pararugosa and W. sorbophila. In this study, we isolated W. tropicalis from a blood sample of a six-year-old female with a history of B-cell precursor lymphoblastic leukemia in Japan in 2022. Though the strain was morphologically identified as Candida species by routine microbiological examinations, it was subsequently identified as W. tropicalis by sequencing the internal transcribed spacer (ITS) of ribosomal DNA (rDNA). The isolate had amino acid substitutions in ERG11 and FKS1 associated with azole and echinocandin resistance, respectively, in Candida species and showed intermediate-resistant to fluconazole and micafungin. The patient was successfully treated with micafungin. Furthermore, matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) detected three novel peaks that are specific for W. tropicalis, indicating that MALDI-MS analysis is useful for rapid detection of Wickerhamiella species in routine microbiological examinations.

Phylogenomic delineation of two new species of ascomycetous yeasts, Wickerhamiella koratensis sp. nov. and Wickerhamiella limtongiae sp. nov., and proposal of two synonyms, Wickerhamiella infanticola and Wickerhamiella tropicalis

Two novel ascomycetous yeast species of the genus Wickerhamiella are proposed based on isolates obtained in Thailand from food waste and the fruiting body of a polypore fungus, and on a combination of conventional DNA-barcode sequence analyses and whole-genome phylogenies. We focus on a particular subclade of the genus Wickerhamiella that contains species found in anthropic environments and describe Wickerhamiella limtongiae sp. nov. (DMKU-FW31-5T=PYCC 9022T=TBRC 15055T), found on food waste samples. In an adjacent clade, we describe Wickerhamiella koratensis sp. nov. (DMKU-KO16T=PYCC 8908T=TBRC 14869T), which represents the closest relative of Wickerhamiella slavikovae and was isolated from the fruiting body of Bjerkandera sp. In the subclade of W. limtongiae sp. nov., we propose that Wickerhamiella infanticola should be regarded as a synonym of Wickerhamiella sorbophila and that Wickerhamiella tropicalis should be regarded as a synonym of Wickerhamiella verensis.

Wickerhamiella shivajii sp. nov., a thermotolerant yeast isolated from distillery effluent

Ethanol production at high temperatures has garnered much interest in recent years and a key factor is the availability of thermotolerant yeasts. During an investigation on the diversity of thermotolerant yeasts from different habitats, a novel yeast species from the spent wash of a distillery unit associated with a sugar factory was isolated. Phylogenetic analysis of D1/D2 large subunit and ITS rRNA genes placed this species in the ascomycetous genus Wickerhamiella. The novel species can be distinguished from the closely related species Wickerhamiella pararugosa using these rRNA gene regions. The cells of the new species are ovoid to ellipsoid with a diameter of 3.5-6.0×2.4-3.10 µm, while W. pararugosa cells are cylindrical with a cell diameter of 1.5-3.0×6-23 µm. This novel species represents, together with Wickerhamiella cacticola, one of the two most thermotolerant yeast species in the genus Wickerhamiella, able to grow at 42 °C. Wickerhamiella shivajii sp. nov. is proposed during this study.

W ickerhamiella siamensis f.a., sp. nov., an endophytic and epiphytic yeast species isolated from sugar cane leaf

Six strains representing a novel yeast species were isolated from tissue (DMKU-SE106T, DMKU-SE110, DMKU-SE112 and DMKU-SE132) and the external surface (DMKU-SP335 and DMKU-SP406) of sugar cane leaves collected in Thailand. On the basis of morphological, biochemical, physiological and chemotaxonomic characteristics, and sequence analysis of the D1/D2 region of the LSU rRNA gene and the internal transcribed spacer (ITS) region, the six strains were found to represent a single novel species of the genus Wickerhamiella although the formation of ascospores was not observed. The sequences of the D1/D2 region of the LSU rRNA gene and ITS region of the six strains differed from each other by 0–2 and 2–3 nt substitutions, respectively. The novel species was related most closely to Candida infanticola but with 4.5–4.6 % nucleotide substitutions in the D1/D2 region of the LSU rRNA gene and 6.6–7.1 % nucleotide substitutions in the ITS region. The name Wickerhamiella siamensis f.a., sp. nov. is proposed. The type strain is DMKU-SE106T ( = BCC 61185T = NBRC 109697T = CBS 13331T).

Wickerhamiella kiyanii f.a., sp. nov. and Wickerhamiella fructicola f.a., sp. nov., two yeasts isolated from native plants of Atlantic rainforest in Brazil

Two novel species, Wickerhamiella kiyanii f.a., sp. nov. (type strain FB1-1DASPT = CBS 12905T = CBMAI 1613T) and Wickerhamiella fructicola f.a., sp. nov. (type strain H10YT = CBS 12902T = CBMAI 1614T) are proposed in the Wickerhamiella clade (Saccharomycetes, Saccharomycetales) to accommodate three strains isolated from flowers and fruits typical of the Brazilian Atlantic rainforest. The novel status of these yeast species was established by sequence divergence observed in the D1/D2 domains of the LSU rRNA gene from the most closely related, described species as well as by phylogenetic analysis. Wickerhamiella kiyanii sp. nov. differs from its nearest phylogenetic neighbours W. pagnoccae CBS 12178T, Candida jalapaonensis CBS 10935T and Candida drosophilae CBS 8459T by 2.2–4.2 % in the D1/D2 sequences. By contrast, a sequence divergence of 13.2–13.8 % was observed between W. fructicola sp. nov. and its closest, described phylogenetic relative Candida kazoui JCM 12558T and Candida hasegawae JCM 12559T. Taxonomic descriptions of the two novel species are given.

Candida potacharoeniae sp. nov. and Candida spenceri sp. nov., two novel galactose-containing ascomycetous anamorphic yeast species isolated in Thailand

Fifteen strains of anamorphic yeasts isolated from various natural substrates collected in various places in Thailand were found to represent two novel species of anamorphic yeast genus Candida based on the sequence analysis of the D1/D2 domain of the large subunit rRNA genes, chemotaxonomic and conventional properties used for the classification of yeasts. These strains are located in the clade including Candida etchellsii and Candida magnoliae. Fourteen strains represented by ST-490(T) (BCC 15176(T)=NBRC 106439(T)= CBS 11674(T)) are closely related to Candida sorbosivorans in the D1/D2 sequences but 11 nucleotides (2.4%) were substituted. The remaining strain, ST-594(T) (=BCC 15278(T)=NBRC 106446(T)=CBS 11673(T)) showed a close relationship to Candida geochares but 21 nucleotides (4.7%) were substituted. Apparently, these strains represent two novel Candida species of the Starmerella clade. The two species are described as Candida potacharoeniae sp. nov. and Candida spenceri sp. nov. in the present paper. Like the most species of this clade, the two species contain galactose in the cells in addition to glucose and mannose and have high mol% G + C of 54.4-55.9 and 54.9, respectively.

Candida kanchanaburiensis sp. nov., a new ascomycetous yeast species related to Pichia nakazawae isolated in Thailand

Three yeast strains, ST-633, ST-634 and ST-635, isolated from the fruit body of a mushroom, Coprinus sp., and rotted fruit of guava collected in the western region of Thailand, were found to represent a hitherto undescribed species. This yeast is related to Pichia nakazawae var. akitaensis, P. nakazawae var. nakazawae and Pichia philogaea in the D1/D2 domain of 26S rDNA but 12 (2.3%), 13 (2.5%) and 15 (2.8%) nucleotides are different from these taxa, respectively, suggesting the distinctness of the Thai strains at species level. Since ascospore formation was not detected, it is described as a new species of Candida, Candida kanchanaburiensis. This species is distinguished from P. nakazawae by the ability to assimilate 2-ketogluconic acid and L-lysine, and inability to assimilate soluble starch.