Species Accumulation Curves and Incidence-Based Species Richness Estimators to Appraise the Diversity of Cultivable Yeasts from Beech Forest Soils

Background: Yeast-like fungi inhabit soils throughout all climatic zones in a great abundance. While recent estimations predicted a plethora of prokaryotic taxa in one gram of soil, similar data are lacking for fungi, especially yeasts. Methodology/Principal Findings: We assessed the diversity of soil yeasts in different forests of central Germany using cultivation-based techniques with subsequent identification based on rDNA sequence data. Based on experiments using various pre-cultivation sample treatment and different cultivation media we obtained the highest number of yeasts by analysing mixed soil samples with a single nutrient-rich medium. Additionally, several species richness estimators were applied to incidence-based data of 165 samples. All of them predicted a similar range of yeast diversity, namely 14 to 16 species. Randomized species richness curves reached saturation in all applied estimators, thus indicating that the majority of species is detected after approximately 30 to 50 samples analysed. Conclusions/Significance: In this study we demonstrate that robust species identification as well as mathematical approaches are essential to reliably estimate the sampling effort needed to describe soil yeast communities. This approach has great potential for optimisation of cultivation techniques and allows high throughput analysis in the future

Trichosporon porosum comb. nov., an anarmorphoc basidiomycetous yeast inhabiting soil, related to the loubieri/laibachii group of species that assimilate hemicelluloses and phenolic compounds

Several isolates representing the genus Trichosporon were collected over a 6-year period from soils in The Netherlands. Based on classical growth tests with carbon and nitrogen compounds these were identical. Three of these (CBS 8396, CBS 8397 and CBS 8522) were subjected to molecular analysis of the D1/D2 region of the large subunit of rDNA. This confirmed that the three strains were identical, yet distinct from other members of the genus. Conspecificity was demonstrated with the type strain (CBS 2040) of Apiotrichum porosum Stautz (1931), with the exception that A. porosum, which had been isolated from exudate of a yew tree, differed morphologically from the soil strains. Based on the identity of DNA base sequences, morphology was not considered to be an adequate parameter to separate otherwise identical strains into two genera. Therefore, the new combination Trichosporon porosum is presented. Based on molecular sequence analysis, T. porosum may be related to T. sporotrichoides, within a weakly related clade that includes species such as Trichosporon laibachii and Trichosporon loubieri. The strains of T. porosum degrade phenolic compounds and hemicelluloses, which are characteristics with potential ecological importance in soil habitats. Characters distinguishing the nine species of the laibachii/loubieri group of species were listed. These include traditionally used tests as well as assimilation patterns of some aliphatic and phenolic compounds. Based on these tests, species such as Trichosporon multisporum and T. laibachii could be separated

Trichosporon guehoae sp.nov., an anamorphic basidiomycetous yeast

A morphological and physiological description of an anamorphic basidiomycetous yeast species, named Trichosporon guehoae (CBS 8521(T), is presented. The ability to assimilate several aliphatic and aromatic compounds as sole source of carbon and energy is reported. The phylogenetic position within the genus, based on nuclear base sequencing of the D1/D2 region of the large subunit of rDNA is discussed

Trichosporon guehoae sp.nov., an anamorphic basidiomycetous yeast

A morphological and physiological description of an anamorphic basidiomycetous yeast species, named Trichosporon guehoae (CBS 8521(T), is presented. The ability to assimilate several aliphatic and aromatic compounds as sole source of carbon and energy is reported. The phylogenetic position within the genus, based on nuclear base sequencing of the D1/D2 region of the large subunit of rDNA is discussed

Systematics of the anamorphic basidiomycetous yeast genus Trichosporon Behrend with the description of the five novel species: Trichosporon vadense, T. smithiae, T. dehoogii, T. scarabaeorum and T. gamsii

Phylogenetic trees of the anamorphic basichomycetous yeast genus Trichosporon Behrend, based on molecular sequence analysis of the internal transcribed spacer region and the D1/D2 region of the large subunit of ribosomal (26S) DNA, are presented. This study includes three novel species from soils, Trichosporon vadense sp. nov. (type strain, CBS 8901(T)), Trichosporon smithiae sp. nov. (type strain, CBS 8370(T)) and Trichosporon gamsii sp. nov. (type strain, CBS 8245(T)), one novel species from an insect, Trichosporon scarabaeorum sp. nov. (type strain, CBS 5601(T)) and one species of unknown origin, Trichosporon dehoogii sp. nov. (type strain, CBS 8686(T)). The phylogenetic positions and physiological characteristics that distinguish the new taxa from related species, based partly on growth tests that are not traditionally used in yeast taxonomy (uric acid, ethylamine, L-4-hydroxyproline, tyramine and L-phenylalanine as sources of carbon and nitrogen, and polygalacturonate, quinate, 4-ethylphenol, phloroglucinol, 2,3-dihydroxybenzoate and orcinol as sole carbon sources), are discussed. Assimilation of L-rhamnose and erythritol and maximum growth temperature were also used to delineate species

Cryptococcus statzelliae sp nov and three novel strains of Cryptococcus victoriae, yeasts isolated from Antarctic soils

A morphological and physiological characterization of yeast strains CBS 8908, CBS 8915, CBS 8920, CBS 8925(T) and CBS 8926, isolated from Antarctic soils, was performed. Phylogenetic analyses of the sequences of the D1/D2 regions and the adjacent internal transcribed spacer (ITS) regions of the large-subunit rDNA of these strains placed them into the Tremellales clade of the Hymenomycetes. The sequence data identified strains CBS 8908, CBS 8915 and CBS 8920 as belonging to the species Cryptococcus victoriae. Strains CBS 8925(T) and CBS 8926 were found to represent an unique clade within the Hymenomycetes, with Dioszegia crocea CBS 6714(T) being their closest phylogenetic relative. Fatty acid composition and proteome fingerprint data for these novel strains were also obtained. No sexual state was observed. A novel basidiomycetous species, Cryptococcus statzelliae, is proposed for strains CBS 8925(T) and CBS 8926

Trichosporon veenhuisii sp. nov., an alkane-assimilating anamorphic basidiomycetous yeast

A morphological and physiological description of an alkane-assimilating anamorphic basidiomycetous yeast species, named Trichosporon veenhuisii, is presented. The ability to assimilate several aliphatic and aromatic compounds as sole source of carbon and energy is reported. The phylogenetic position within the genus, based on nuclear base sequencing of the D1/D2 region of the large subunit of rDNA, is discussed. The type strain is CBS 7136(T)