Somjit Am-In

Wickerhamomyces xylosica sp. nov. and Candida phayaonensis sp. nov., two xylose-assimilating yeast species from soil.

Two strains (NT29(T) and NT31(T)) of xylose-assimilating yeasts were obtained from soils collected in northern Thailand. On the basis of morphological, biochemical, physiological and chemotaxonomic characteristics, and sequence analysis of the D1/D2 domain of the large subunit rRNA gene and the internal transcribed spacer region, the two strains were found to represent two novel ascomycete yeast species. Strain NT29(T) was assigned to the genus Candida belonging to the Pichia clade as a representative of Candida phayaonensis sp. nov.; the type strain is NT29(T) (=BCC 47634(T)=NBRC 108868(T)=CBS 12319(T)). Strain NT31(T) represented a novel Wickerhamomyces species, which was named Wickerhamomyces xylosica sp. nov.; the type strain is NT31(T) (=BCC 47635(T)=NBRC 108869(T)=CBS 12320(T)).

Candida saraburiensis sp. nov. and Candida prachuapensis sp. nov., xylose-utilizing yeast species isolated in Thailand.

Four strains of two novel xylose-utilizing yeast species were obtained from samples collected in Thailand from decaying corncobs (strains KU-Xs13(T) and KU-Xs18), a decaying grass (KU-Xs20) and estuarine water from a mangrove forest (WB15(T)). On the basis of morphological, biochemical, physiological and chemotaxonomic characteristics and sequence analysis of the D1/D2 domain of the large subunit rRNA gene, the four strains were found to represent two novel species of the genus Candida in the Candida albicans/Lodderomyces elongisporus clade. Three strains (KU-Xs13(T), KU-Xs18 and KU-Xs20) were assigned as a single novel species, which was named Candida saraburiensis sp. nov. The type strain is KU-Xs13(T) (=CBS 11696(T)=NBRC 106721(T)=BCC 39601(T)). Strain WB15(T) represented another novel species of the genus Candida that was named Candida prachuapensis sp. nov. The type strain is WB15(T) (=CBS 11024(T)=NBRC 104881(T)=BCC 29904(T)).

Kluyveromyces siamensis sp. nov., an ascomycetous yeast isolated from water in a mangrove forest in Ranong Province, Thailand.

Seven strains of a novel Kluyveromyces species were isolated from seven water samples collected from a mangrove forest. Analysis of the D1/D2 domain of the large subunit (LSU) rRNA gene sequences revealed that the sequences of five strains (RS8(T), RS20, RS54, RV42 and RV89) were identical and differed from the other two strains (RS65 and RV153) by only one nucleotide substitution in 544 nucleotides (nt). The closest species in terms of pairwise sequences similarity was Kluyveromyces aestuarii, but the level of nucleotide substitution (six to seven nucleotide substitutions in 544 nt) was sufficient to justify the description of a separate species. The phylogenetic tree based on the sequence of the D1/D2 domain of the LSU rRNA gene rather suggested that the new species is a sister species of K. aestuarii and forms a clade with the other six recognized species of Kluyveromyces. Sequence analysis of the internal transcribed spacer (ITS1-5.8S rRNA gene-ITS2) region supported their distinct status as a species. The phenotypic characteristics of the seven strains were typical of the genus Kluyveromyces. On this basis, the seven strains were assigned to a single novel species of the genus Kluyveromyces, for which the name Kluyveromyces siamensis sp. nov. is proposed. The type strain is RS8(T) (BCC 25962(T)=NBRC 103859(T)=CBS 10860(T)).

Candida andamanensis sp. nov., Candida laemsonensis sp. nov. and Candida ranongensis sp. nov., anamorphic yeast species isolated from estuarine waters in a Thai mangrove forest.

Five strains (RV5(T), RV140, R31(T), RS17 and RS28(T)) representing three novel anamorphic ascomycetous yeast species were isolated by membrane filtration from estuarine waters collected from a mangrove forest in Laem Son National Park, Ranong Province, Thailand, on different occasions. On the basis of morphological, biochemical, physiological and chemotaxonomic characteristics, sequence analysis of the D1/D2 domain of the large-subunit rRNA gene and the internal transcribed spacer region and phylogenetic analysis, three strains were found to represent two novel Candida species. Two strains (RV5(T) and RV140) represented a single novel species, for which the name Candida laemsonensis sp. nov. is proposed. The type strain is RV5(T) (=BCC 35154(T) =NBRC 105873(T) =CBS 11419(T)). Strain R31(T) was assigned to a novel species that was named Candida andamanensis sp. nov. (type strain R31(T) =BCC 25965(T) =NBRC 103862(T) =CBS 10859(T)). On the basis of morphological, biochemical, physiological and chemotaxonomic characteristics, sequence analysis of the D1/D2 domain of the large-subunit rRNA gene and phylogenetic analysis, strains RS17 and RS28(T) represented another novel species of Candida, for which the name Candida ranongensis sp. nov. is proposed. The type strain is RS28(T) (=BCC 25964(T) =NBRC 103861(T) =CBS 10861(T)).

Candida xylanilytica sp. nov., a xylan-degrading yeast species isolated from Thailand.

Xylan is a major component of hemicellulose, which constitutes about 40 % of plant biomass. Hydrolysis of xylan into simple sugars is one of the important steps in the conversion of lignocellulosic material to value-added products. During an investigation of cellulose- and xylan-degrading yeasts, two yeast strains that were able to use cellulose and xylan as sole carbon source were found to represent a phylogenetically distinct species in the Spathaspora clade. The closest species in terms of pairwise sequence similarity in the D1/D2 domain of the LSU rRNA gene was Candida subhashii. The novel species can be distinguished from the other species in the Spathaspora clade based on the ability to assimilate methanol and raffinose, growth in medium containing 60 % glucose, and growth at 42 °C. It ferments glucose but not other carbohydrates. The name Candida xylanilytica sp. nov. is proposed for this species. The type strain is KU-Xn11(T) ( = NBRC 106499(T)  = BCC 34694(T)  = CBS 11761(T)).

Hannaella siamensis sp. nov. and Hannaella phetchabunensis sp. nov., two new anamorphic basidiomycetous yeast species isolated from plants

Eight strains, representing two novel anamorphic yeast species, consisted of five strains isolated from the external surfaces of rice leaves (DMKU-RP72(T), DMKU-RP109, DMKU-RP119, YE-124 and YE-156) and one from a corn leaf (DMKU-CP430(T))4 collected in Thailand, and one strain isolated from each of a composite flower (11-1114) and a fallen dead leaf (12-301); the latter two were collected in Belize. On the basis of sequence analysis of the D1/D2 region of the large subunit rRNA gene and the internal transcribed spacer (ITS) region, they were suggested to be two novel species of the genus Hannaella. Seven strains (DMKU-RP72(T), DMKU-RP109, DMKU-RP119, YE-124, YE-156, 11-1114 and 12-301) differed from each other by 0-3 nt substitutions in the D1/D2 region and by 0-1 nt substitutions in the ITS region. In terms of pairwise sequence similarities of the D1/D2 region these seven strains were closest to Hannaella zeae, but with 1.2-1.7% (7-9) nucleotide substitutions. The sequences of the ITS region of these seven strains differed from H. zeae by 3.7-3.9% (16-17) nucleotide substitutions. Therefore, they were assigned to a single novel species and the name Hannaella siamensis sp. nov. has been proposed. The type strain is DMKU-RP72(T) ( = BCC 69493(T) = NBRC 110425(T) = CBS 13533(T)). Strain DMKU-CP430(T) represents the second novel species and was also most closely related to H. zeae, but with 1.0% (6) nucleotide substitutions in the D1/D2 region and 3.2% (14) nucleotide substitutions in the ITS region. It was assigned to the proposed novel species, Hannaella phetchabunensis sp. nov. (type strain DMKU-CP430(T) = BCC 69492(T) = NBRC 110424(T) = CBS 13386(T)).

Trichosporon siamense sp. nov. isolated from insect frass in Thailand

A strain of yeast isolated from insect frass collected in Thailand was found to represent a hitherto undescribed species of a basidiomycetous anamorphic genus Trichosporon. It is described as Trichosporon siamense. In the phylogenetic tree based on the D1/D2 region sequences of 26S rDNA, this yeast constitutes a cluster with several Q-9 having species of Trichosporon including T. otae and T. brassicae but is clearly differentiated from these species by 1.8% or more base substitutions. In the internal transcribed spacer region (ITS1 and ITS2), this species differs from T. scarabaeorum, the nearest species, by 6.5% base substitution.

Pichia nongkratonensis sp. nov., a new species of ascomycetous yeast isolated from insect frass collected in Thailand

A yeast strain isolated from insect frass collected in Thailand was found to represent a new species of the genus Pichia. It is described as Pichia nongkratonensis sp. nov. In the phylogenetic tree based on the D1/D2 domain sequences of 26S rDNA, this yeast constitutes a cluster with Pichia dryadoides with high bootstrap confidence level; however, it differs from the latter species by 5.6% base substitutions. Pichia nongkaratonensis resembles P. dryadoides also in the phenotypic characteristics but is distinguished from this species by the assimilation of several carbon and nitrogen compounds.

Yamadazyma insecticola f.a., sp. nov. and Yamadazyma epiphylla f.a., sp. nov., two novel yeast species.

Two yeast strains representing two novel yeast species were isolated from frass of an unidentified insect (ST-78(T)) and the external surfaces of rice leaves (YE170(T)) collected in Thailand. The two strains were genetically, morphologically and phenotypically distinct from recognized species and were found to represent two novel species of the genus Yamadazyma although formation of ascospores was not observed. In terms of pairwise sequence similarity of the D1/D2 region of the large subunit rRNA gene, the closest relative of strain ST-78(T) was Candida lessepsii CBS 9941(T) but with 3.8% nucleotide substitutions, while the closest relative of strain YE170(T) was strain ST-78(T) but with 4.3% nucleotide substitutions. Analysis of the sequences of the internal transcribed spacer 1 and 2 (ITS1-2) regions revealed that strain ST-78 differed from C. lessepsii CBS 9941(T) by 8.8% nucleotide substitutions and from strain YE170(T) by 9.4% nucleotide substitutions. The result of pairwise sequence similarity of the D1/D2 and ITS1-2 regions together with phylogenetic analysis indicated that strains ST-78(T) and YE170(T) represented two novel species within the Yamadazyma clade. The names Yamadazyma insecticola f.a., sp. nov. (type strain ST-78(T) = BCC 8314(T) = NBRC 110421(T) = CBS 13382(T); MycoBank no. MB810546) and Yamadazyma epiphylla f.a., sp. nov. (type strain YE170(T) = BCC 63466(T) = NBRC 110423(T) = CBS 13384(T); MycoBank no. MB810547) are proposed for the two novel yeast species.

Limtongia gen. nov. for Zygozyma smithiae (Lipomycetaceae)

Teleomorphic species of the genus Zygozyma and anamorphic species of the genus Myxozyma were examined phylogenetically. In phylogenetic trees based on 18S rRNA-, 26S rRNA-, mitochondrial small subunit rRNA- and EF-1α-gene sequences and concatenated sequences of the latter four regions, derived from the neighbor-joining method, the four species of the genus Zygozyma constituted four clusters, respectively, with low bootstrap values, indicating that all four species can be distinguished from one another at the generic level. The name of Limtongia was newly suggested for Zygozyma smithiae, and Limtongia smithiae was proposed as new combination.