Feng-Yan Bai

Reclassification of the Sporobolomyces roseus and Sporidiobolus pararoseus complexes, with the description of Sporobolomyces phaffii sp. nov.

More than 50 ballistoconidium-forming yeast strains, isolated from plant leaves collected in Yunnan, China, were identified as Sporobolomyces roseus Kluyver & van Niel by conventional methods. However, comparison of the internal transcribed spacer (ITS) region and 265 rDNA D1/D2 domain sequences indicated that these strains represented more than one species. Type or authentic strains of the synonyms of Sporobolomyces roseus and the closely related species Sporidiobolus pararoseus Fell & Tallman were employed in the rDNA sequence comparison. Sporobolomyces boleticola Ramírez, Sporobolomyces pollaccii Verona & Ciferri, Sporobolomyces roseus var. madurae Janke and Torulopsis somala Verona were confirmed to be conspecific with Sporobolomyces roseus. Another synonym of this species, Sporobolomyces salmoneus Derx, was located together with Sporobolomyces marcillae Santa Maria in a separate clade. Two synonyms of Sporidiobolus pararoseus, Sporobolomyces carnicolor Yamasaki & Fujii (nom. inval.) and Sporobolomyces japonicus Iizuka & Goto, were revealed to represent two distinct species. The name Sporobolomyces carnicolor is validated, with strain CBS 4215(T) as the type strain. A novel species represented by five of the selected Yunnan strains was confirmed, for which the name Sporobolomyces phaffii sp. nov. is proposed (type strain CH 2.052(T) = AS 2.2137(T) = JCM 11491(T) = CBS 9129(T)). This study also indicates that yeast species with similar ITS sequences may have quite different D1/D2 sequences.

Phylogenetic analysis of strains originally assigned to Bullera variabilis: descriptions of Bullera pseudohuiaensis sp. nov., Bullera komagatae sp. nov. and Bullera pseudoschimicola sp. nov.

Twenty strains previously assigned to the species Bullera variabilis Nakase & Suzuki were reclassified using a molecular taxonomic approach. The strains were regrouped first by nucleotide sequence comparison of the rDNA internal transcribed spacer (ITS) regions, including the 5.8S gene. Phylogenetic positions of B. variabilis strains with different ITS region sequences were then analysed based on their 18S rDNA sequences. The taxonomic status of the original Bullera variabilis strains was clarified further by DNA-DNA hybridization experiments. Of the 20 strains studied, five remained in the species B. variabilis, six strains were reassigned to the species Bullera mrakii and three novel species were proposed for eight of the nine remaining strains, namely Bullera pseudohuiaensis sp. nov. (one strain; type strain JCM 5984T = AS 2.2203T), Bullera komagatae sp. nov. (one strain; type strain JCM 5983T = AS 2.2202T) and Bullera pseudoschimicola sp. nov. (six strains; type strain JCM 391ST = AS 2.2201T). The remaining strain, JCM 6140, was closely related to B. pseudoschimicola. However, differences in ITS region sequences between strain JCM 6140 and strains of B. pseudoschimicola, and the intermediate DNA-DNA relatedness to representative strains of B. pseudoschimicola did not allow a definite taxonomic decision to be made for strain JCM 6140.

Bullera anomala sp. nov. and Bullera pseudovariabilis sp. nov., two new ballistoconidium-forming yeast species from Yunnan, China

Two ballistoconidium-forming yeast strains, CH 2.504 and CH 2.509, were isolated from the wilting leaves of Parthenocissus sp. collected in Yunnan, China in 1996. These two strains were assigned to the genus Bullera Derx by the characteristics of forming rotationally symmetric ballistoconidia, containing xylose in the cell hydrolysates and having Q-10 as the major ubiquinone. Molecular phylogenetic analysis based on small subunit ribosomal RNA gene (18S rDNA) and internal transcribed spacer (ITS) region sequences revealed that CH 2.504 is closely related to B. variabilis Nakase & Suzuki, while CH 2.509 is located in a clearly separate clade among the described Bullera species and related taxa. The results indicated that CH 2.509 represents a new species, for which Bullera anomala sp. nov. is the proposed name (type strain AS 2.2094T). Further DNA-DNA reassociation data showed that CH 2.504 also represents a distinct species, for which the name Bullera pseudovariabilis sp. nov. is given (type strain AS 2.2092T).

Sporobolomyces yunnanensis sp. nov., a Q-10(H2)-containing yeast species with a close phylogenetic relationship to Erythrobasidium hasegawianum.

A ballistoconidia-forming yeast strain, CH 2.141T, isolated from a semi-dried leaf sample collected in Yunnan, China, was found to have Q-10(H2) as its major ubiquinone. Molecular phylogenetic analysis based on the nucleotide sequences of small subunit (18S) rDNA and the internal transcribed spacer region (including 5.8S rDNA) indicated that the strain was closely related to the two described Q-10(H2)-containing yeast species, Erythrobasidium hasegawianum and Sporobolomyces elongatus, with a closer relationship to the former. A DNA-DNA reassociation experiment showed that strain CH 2.141T represents a new yeast species, for which the name Sporobolomyces yunnanensis sp. nov. is proposed.

Rhodotorula oryzae sp. nov., a novel basidiomycetous yeast species isolated from paddy rice

A basidiomyetous yeast strain RO-203, which formed orange-red colored colonies, was isolated from a sample of paddy rice crops at the ripe stage in Japan. Morphological, physiological and biochemical characterization indicated that this strain belonged to the genus Rhodotorula. Molecular taxonomic analysis based on the 26S rDNA D1/D2 domain and internal transcribed spacer (ITS) region sequences showed that RO-203 represents an undescribed yeast species, for which the name Rhodotorula oryzae sp. nov. is proposed (type strain: AS 2.2363T = MAFF 516128T). The new species clustered in a branch together with Sakaguchia dacryoidea in phylogenetic trees based on the D1/D2 and ITS sequences. These two species differed by 2.3% and 12% nucleotide divergences in the D1/D2 and ITS regions, respectively.