Yeasts from temperate forests.

Yeasts are ubiquitous in temperate forests. While this broad habitat is well-defined, the yeasts inhabiting it and their life cycles, niches, and contributions to ecosystem functioning are less understood. Yeasts are present on nearly all sampled substrates in temperate forests worldwide. They associate with soils, macroorganisms, and other habitats and no doubt contribute to broader ecosystem-wide processes. Researchers have gathered information leading to hypotheses about yeasts' niches and their life cycles based on physiological observations in the laboratory as well as genomic analyses, but the challenge remains to test these hypotheses in the forests themselves. Here, we summarize the habitat and global patterns of yeast diversity, give some information on a handful of well-studied temperate forest yeast genera, discuss the various strategies to isolate forest yeasts, and explain temperate forest yeasts' contributions to biotechnology. We close with a summary of the many future directions and outstanding questions facing researchers in temperate forest yeast ecology. Yeasts present an exciting opportunity to better understand the hidden world of microbial ecology in this threatened and global habitat.

Ecophysiological properties of cultivable heterotrophic bacteria and yeasts dominating in phytocenoses of Galindez Island, maritime Antarctica.

Antarctic plants are stable specific microenvironments for microbial colonization that are still less explored. In this study, we investigated cultivable heterotrophic bacteria and yeasts dominating in plant samples collected from different terrestrial biotopes near Ukrainian Antarctic Base on Galindez Island, maritime Antarctica. Phylogenetic analysis revealed affiliation of the bacterial isolates to genera Pseudomonas, Stenotrophomonas, Brevundimonas, Sporosarcina, Dermacoccus, Microbacterium, Rothia and Frondihabitans, and the yeast isolates to genera Rhodosporidium, Cryptococcus, Leucosporidiella, Candida and Exophiala. Some ecophysiological properties of isolated strains were determined that are important in response to different stresses such as psychro- and halotolerance, UV-resistance and production of hydrolytic enzymes. The majority of isolates (88 %) was found to be psychrotolerant; all are halotolerant. Significant differences in survival subsequent to UV-C radiation were observed among the isolates, as measured by culturable counts. For the bacterial isolates, lethal doses in the range 80-600 J m⁻² were determined, and for the yeast isolates--in the range 300-1,000 J m⁻². Dermacoccus profundi U9 and Candida davisiana U6 were found as most UV resistant among the bacterial and yeast isolates, respectively. Producers of caseinase, gelatinase, ß-glucosidase, and cellulase were detected. To the best of our knowledge, this is the first report on isolation of UV resistant strain D. profundi, and Frondihabitans strain from Antarctica, and on detection of cellulase activity in Antarctic yeast strain C. davisiana. The results obtained contribute to clarifying adaptation strategies of Antarctic microbiota and its possible role in functional stability of Antarctic biocenoses. Stress tolerant strains were detected that are valuable for ecological and applied studies.

Ogataea saltuana sp. nov., a novel methanol-assimilating yeast species.

Four ascosporulating strains of an undescribed methanol-assimilating yeast species were isolated from forest habitats in Hungary. Three were recovered from rotten wood and one from leaves of a sessile oak (Quercus petraea). An additional isolate of the undescribed species sharing similar phenotypic characters with the above-noted strains was recovered from the gut of an unidentified beetle collected from under the bark of a coniferous tree in Bulgaria. A closely related, but somewhat divergent strain was recovered from insect frass in a Ponderosa pine (Pinus ponderosa) collected in New Mexico, USA. Analysis of the D1/D2 sequences of the LSU rRNA gene placed the new species in the Ogataea clade. The ITS and the D1/D2 LSU sequences of the rRNA gene repeats were compared for the above-noted strains and that of the type strain of Ogataea zsoltii, the closest neighbour among currently recognized Ogataea species. Their relatedness was investigated by parsimony network analysis as well. As a result of the sequence analysis, it was concluded that the six strains isolated from tree associated habitats represent a single new yeast species. Ogataea saltuana sp. nov. is proposed to accommodate these strains. The type strain NCAIM Y.01833(T) (CBS 10795(T), NRRL Y-48448(T)) was recovered from rotten wood of Scotch pine (Pinus silvestris) in Hungary. The GenBank accession number for the D1/D2 domain nuclear large subunit rRNA gene sequence of strain NCAIM Y.01833(T) (CBS 10795(T), NRRL Y-48448(T)) is EU327033. The MycoBank number of the new species is MB 519966.

DNA barcoding revealed Nematodospora valgi gen. nov., sp. nov. and Candida cetoniae sp. nov. in the Lodderomyces clade.

During a yeast biodiversity survey conducted in 2009-2011 in Bulgaria (South Eastern Europe) five strains of a novel ascomycetous yeast species were isolated from the beetle Valgus hemipterus (Cetoniinae) collected from two localities, namely Osogovska Planina Mountain and Nature Park Zlatni Pyasatsi. Phylogenetic analysis using combined sequences of the D1/D2 domains of the large subunit ribosomal DNA (LSU rDNA) and the internal transcribed spacers 1 + 2 regions (ITS1+2) placed the novel species on a separate branch near the basal part of the Lodderomyces clade. The novel species has a unique ascospore morphology distinct from those of the closely related teleomorphic genus Lodderomyces. Based on phylogenetic analysis and morphology of the ascospores we propose Nematodospora valgi gen. nov., sp. nov. to accommodate these isolates (MB811804 D37S(T), MB802458). Two strains of a novel anamorphic yeast species were isolated from the beetles Cetonia aurata and Oxythyrea funesta (Cetoniinae) collected in East Rhodopies and Sofia city, respectively. DNA barcoding analysis placed the new yeast species within the Candida parapsilosis subclade. Here, we present the description of a new yeast species, Candida cetoniae sp. nov. (IMB1R2(T), MB803501) to accommodate these two strains. The ecology and biogeography of the insect-associated yeasts of the Lodderomyces clade is discussed.

Rapid screening of plasmid-encoded small hsp-genes in Streptococcus thermophilus.

A new rapid procedure for detection of small heat shock protein genes (shsp) was developed. Using PCR-based molecular approach, single colonies of 49 Streptococcus thermophilus industrial and artisanal starters were examined. Five strains contained plasmid-encoded shsp. The nucleotide sequence analysis revealed that the genes are very conservative, as only a few nucleotide substitutions were noticed. It was shown that all new isolated plasmids belong to the pC194 family of rolling circle replicating (RCR) plasmids. We concluded that shsp genes are always inherited together with pC194-type replicative region. The viability of plasmid-bearing and plasmid-free derivatives of S. thermophilus strain ST2980 under heat shock condition was studied.

The molecular diversity of freshwater picoeukaryotes from an oligotrophic lake reveals diverse, distinctive and globally dispersed lineages.

The recent discovery of a diverse phylogenetic assemblage of picoeukaryotes from environments such as oceans, salt marshes and acidic habitats, has expanded the debates about the extent and origin of microbial eukaryotes. However, the diversity of these eukaryote microorganisms, that overlap bacteria in size, and their environmental and biogeographical ubiquity remains poorly understood. Here we survey picoeukaryotes (microbial eukaryotes of 0.2-5 microm in size) from an oligotrophic (nutrient deficient) freshwater habitat using ribosomal RNA gene sequences. Three taxonomic groups the Heterokonta, Cryptomonads and the Alveolata dominated the detected diversity. Most sequences represented previously unsampled species, with several being unassignable to known taxonomic groups and plausibly represent new or unsampled phyla. Many freshwater phylogenetic groups identified in this study appeared unrelated to picoeukaryotic sequences identified in marine ecosystems, suggesting that aspects of eukaryote microbial diversity are specific to certain aquatic environments. Conversely, at least five phylogenetic clusters comprised sequences from freshwater and globally dispersed and often contrasting environments, supporting the concept that a number of picoeukaryotic lineages are widely distributed.