Saturnispora sinensis sp. nov., a new ascomycetous yeast species from soil and rotten wood

A yeast strain (CGMCC 2.6937T) belonging to the ascomycetous yeast genus Saturnispora was recently isolated from soil collected in Xinghuacun, Shanxi Province, PR China. The strain produces one or two ellipsoid or spherical ascospores in asci formed by the conjugation between a cell and its bud. Phylogenetic analyses of the internal transcribed spacer (ITS) region and the D1/D2 domain of the large subunit rRNA gene suggest that this strain is conspecific with strains NYNU 14639 isolated from rotten wood collected in Funiu Mountain, Henan province and ES13S05 from soil collected in Nantou County, Taiwan. The CGMCC 2.6937T group is most closely related to Saturnispora dispora and Saturnispora zaruensis. However, strain CGMCC 2.6937T differs from S. dispora by 17 (3.2 %, 13 substitutions and four gaps) and 77 (18.8 %, 52 substitutions and 25 gaps) mismatches, and from S. zaruensis by 15 (2.9 %, 12 substitutions and three gaps) and 64 (15.6 %, 44 substitutions and 20 gaps) mismatches, in the D1/D2 domain and ITS region, respectively. The results suggest that the CGMCC 2.6937T group represents an undescribed species in the genus Saturnispora, for which the name Saturnispora sinensis sp. nov. is proposed. The holotype strain is CGMCC 2.6937T.

Yeasts from tropical forests: Biodiversity, ecological interactions, and as sources of bioinnovation

Tropical rainforests and related biomes are found in Asia, Australia, Africa, Central and South America, Mexico, and many Pacific Islands. These biomes encompass less than 20% of Earth's terrestrial area, may contain about 50% of the planet's biodiversity, and are endangered regions vulnerable to deforestation. Tropical rainforests have a great diversity of substrates that can be colonized by yeasts. These unicellular fungi contribute to the recycling of organic matter, may serve as a food source for other organisms, or have ecological interactions that benefit or harm plants, animals, and other fungi. In this review, we summarize the most important studies of yeast biodiversity carried out in these biomes, as well as new data, and discuss the ecology of yeast genera frequently isolated from tropical forests and the potential of these microorganisms as a source of bioinnovation. We show that tropical forest biomes represent a tremendous source of new yeast species. Although many studies, most using culture-dependent methods, have already been carried out in Central America, South America, and Asia, the tropical forest biomes of Africa and Australasia remain an underexplored source of novel yeasts. We hope that this review will encourage new researchers to study yeasts in unexplored tropical forest habitats.

Ecuadorian yeast species as microbial particles for Cr(VI) biosorption

Pollution caused by heavy metals is a prime concern due to its impact on human health, animals, and ecosystems. Cr(VI), generated in a range of different industries as a liquid effluent, is one of the most frequent contaminants. In the work presented herein, the adsorption efficiency of three species of native yeasts from Ecuador (Kazachstania yasuniensis, Kodamaea transpacifica, and Saturnispora quitensis) for Cr(VI) removal from simulated wastewater was assessed, taking Saccharomyces cerevisiae as a reference. After disruption of the flocs of yeast with a cationic surfactant, adsorption capacity, kinetics, and biosorption isotherms were studied. K. transpacifica isolate was found to feature the highest efficiency among the four yeasts tested, as a result of its advantageous combination of surface charge, individual cell size (4.04 μm), and surface area (1588.27 m²/L). The performance of S. quitensis was only slightly lower. The remarkable biosorption capacities of these two isolates (476.19 and 416.67 mg of Cr(VI)/g of yeast, respectively) evidence the potential of non-conventional yeast species as sorption microbial particles for polluted water remediation.

Saturnispora galanensis sp. nov., a yeast species isolated from rotting wood

Three strains of a novel yeast species were isolated from rotting wood in the Xishuangbanna Tropical Rainforest, Yunnan Province, PR China. Sequence analysis of the D1/D2 domains of the large subunit rRNA gene and the internal transcribed spacer (ITS) regions showed that the novel species represents a member of the genus Saturnispora. It differed from its closest known species, Saturnispora sekii CBS 10931^T, by 1.3 % nucleotide substitutions in the D1/D2 domains and by 2.2 % nucleotide substitutions in the ITS regions, respectively. In contrast to Saturnispora sekii, the novel yeast species was unable to assimilate glycerol, dl-lactate, succinate and citrate, and grow at 37 °C. The name Saturnispora galanensis sp. nov. is proposed to accommodate these strains, with NYNU 1797 as the holotype.

Saturnispora kantuleensis f.a., sp. nov., a novel yeast species isolated from peat in a tropical peat swamp forest in Thailand

Two strains (DMKU-PPS4-5^T and DMKU-EPS3-4) representing a single novel anamorphic yeast species were isolated from two peat samples collected in Kan Tulee peat swamp forest, Surat Thani Province, Thailand. The strains differed by two nucleotide substitutions in the sequences of the D1/D2 region of the large subunit (LSU) rRNA gene and only one nucleotide substitution in the internal transcribed spacer (ITS) region. Phylogenetic analysis based on the D1/D2 regions showed that the two strains represented a single species in the genus Saturnispora and were clearly distinct from other related species. Saturnispora sekii was the most closely related species, but with 1.7-2.1 % nucleotide substitutions in the D1/D2 region of the LSU rRNA gene, and 3.1-3.3 % nucleotide substitutions in the ITS region. They therefore represent a novel species of the genus Saturnispora, although the formation of ascospores was not observed. The name Saturnispora kantuleensis f.a., sp. nov. is proposed. The type strain is DMKU-PPS4-5^T (=CBS 15217^T=TBRC 7762^T).

Kazachstania yasuniensis sp. nov., an ascomycetous yeast species found in mainland Ecuador and on the Galápagos

Seven strains representing a novel yeast species belonging to the genus Kazachstania were found at several collection sites on both mainland Ecuador (Yasuní National Park) and the Galápagos (Santa Cruz Island). Two strains (CLQCA 20-132T and CLQCA 24SC-045) were isolated from rotten wood samples, two further strains (CLQCA 20-280 and CLQCA 20-348) were isolated from soil samples, and three strains (CLQCA 20-198, CLQCA 20-374 and CLQCA 20-431) were isolated from decaying fruits. Sequence analyses of the D1/D2 domains of the LSU rRNA gene and ribosomal internal transcribed spacer (ITS) region indicated that the novel species is most closely related to Kazachstania servazzii and Kazachstania unispora. Although the strains could not be distinguished from one another based upon their differing geographical origins, they could be differentiated according to their isolation source (fruit, soil or wood) by ITS sequencing. The species name Kazachstania yasuniensis sp. nov. is proposed to accommodate these strains, with CLQCA 20-132T ( = CBS 13946T = NCYC 4008T) designated the type strain.

Candida ecuadorensis sp. nov., an ascomycetous yeast species found in two separate regions of Ecuador

In the course of an on-going study aimed at cataloguing the natural yeast biodiversity found in Ecuador, two strains (CLQCA 13-025 and CLQCA 20-004T) were isolated from samples of cow manure and rotten wood collected in two separate provinces of the country (Orellana and Bolívar). These strains were found to represent a novel yeast species based on the sequences of their D1/D2 domain of the large-subunit (LSU) rRNA gene and their physiological characteristics. Phylogenetic analysis based on LSU D1/D2 sequences revealed this novel species to belong to the Metschnikowia clade and to be most closely related to Candida suratensis, a species recently discovered in a mangrove forest in Thailand. The species name of Candida ecuadorensis sp. nov. is proposed to accommodate these strains, with strain CLQCA 20-004T ( = CBS 12653T = NCYC 3782T) designated as the type strain.