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.

Description of four Apiotrichum and two Cutaneotrichosporon species isolated from guano samples from bat-inhabited caves in Japan

Four new yeast species belonging to the genus Apiotrichum and two new yeast species belonging to Cutaneotrichosporon are described for strains isolated from guano samples from bat-inhabited caves in Japan. In 2005, we reported these isolates as Trichosporon species based on sequence analyses of the D1/D2 domain of large subunit (LSU) rRNA genes according to available basidiomycetous yeast classification criteria; however, to date, they have not been officially published as new species with descriptions. Their phylogenetic positions have been reanalysed based on comparison of internal transcribed spacer (ITS) region sequences (including the 5.8S rRNA gene) and the D1/D2 domain of the LSU rRNA gene with those of known species; we confirmed clear separation from previously described species. Physiological and biochemical properties of the isolates also suggest their distinctiveness. Therefore, we describe Apiotrichum akiyoshidainum (holotype JCM 12595T), Apiotrichum chiropterorum (JCM 12594T), Apiotrichum coprophilum (JCM 12596T), Apiotrichum otae (JCM 12593T), Cutaneotrichosporon cavernicola (JCM 12590T) and Cutaneotrichosporon middelhovenii (JCM 12592T) as new species. C. cavernicola showed particularly distinctive morphology including large inflated anomalous cells on the hyphae and germination from the cells, although clear clamp connections on the hyphae were not confirmed. Further study is needed to elucidate the morph of this species.

Papiliotrema maritimi f.a. sp. nov., a new tremellaceous yeast species associated to macrophytes in a Marshland of South Brazil

One new yeast species, Papiliotrema maritimi sp. nov., is being proposed to be suitable into the Rhynchogastremataceae family, belonging to the Tremellales clade. This new species is related to six others from the Papiliotrema genus: P. taeanensis, P. siamense, P. perniciosus, P. nemorosus, P. bandonii, P. japonica and P. fuscus. The novel species is proposed based on the phylogenetic species concept through analysis of the D1/D2 region, part of the large subunit (LSU) rRNA gene and the internal transcribed spacer (ITS) region. A total of 11 strains of Papiliotrema maritimi sp. nov. were obtained from macrophytes leaves collected in south Brazil. Papiliotrema maritimi sp. nov. differs by 12, 15, 25, 25, 25 and 29 substitutions in the D1/D2 domain from the related species P. fuscus, P. japonica, P. siamense, P. nemorosus, P. bandonii, and P. perniciosus, respectively. Concerning the ITS region, there are 11 substitutions and 52 or more substitutions when compared to P. teanensis and its closest relatives. The type strain of Papiliotrema maritimi sp. nov. is UFMG-CM-Y6048. The MycoBank number for Papiliotrema maritimi sp. nov. is MB 835603.

BIODIVERSITY OF YEASTS ISOLATED FROM CON DAO ISLAND – BA RIA VUNG TAU

During the study on yeast diversity from natural samples in Viet Nam, we have collected 38 samples of flowers, fruits, leaves, litter and soils in Con Dao Island and isolated 54 yeast strains. They were identified based on morphology observation and sequences of D1/D2 domain of 26S rDNA. The results showed that they belonged to 13 genera, 28 species, of which 15 strains were suspected as 13 new species. Thirty-nine strains were identified as Ascomycetes belonging 7 genera, 11 species, and the fifteen remaining strains belonged to Basidomycetes, 6 genera and 13 species. The results also showed that four Ascomycetous and nine Basidomycetous isolated were suspected to be new species. The results also showed that Candida was the genus with highest number isolates- 26 strains, and half of these were Candida rugosa. The most diverse species in this study was found in Cryptococcus genus with 7 species from 8 isolates only, and all of them were suspected to be new species. This study also proved that the samples had differences in yeast diversity and species composition among them. Therefore, Con Dao Island is multi potential to discover and publish new yeast species in Vietnam.