The presence of psychrophilic yeasts in supra‐ and subglacial sediments, ice and meltwater collected from two glaciers of the Italian Alps (Forni and Sforzellina – Ortles‐Cevedale group) was investigated. After incubation at 4 °C, subglacial sediments contained from 1.3 × 103 to 9.6 × 103 CFU of yeasts g−1. The number of yeast cells in supraglacial sediments was c. 10–100‐fold lower. A significant proportion of isolated yeasts exhibited one or more extracellular enzymatic activities (starch‐degrading, lipolytic, esterolytic, proteolytic and pectinolytic activity) at 4 °C. Selected isolates were able to grow at 2 °C under laboratory‐simulated in situ conditions. In all, 106 isolated yeasts were identified by MSP‐PCR fingerprinting and 26S rRNA gene sequencing of the D1/D2 region as belonging to 10 species: Aureobasidium pullulans, Cryptococcus gilvescens (over 50% of the total), Cryptococcus terricolus, Mrakia gelida, Naganishia globosa, Rhodotorula glacialis, Rhodotorula psychrophenolica, Rhodotorula bacarum, Rhodotorula creatinivora and Rhodotorula laryngis. Four strains, all belonging to a new yeast species, yet to be described, were also isolated.

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Twenty-nine yeast strains were isolated from the ascocarps of black and white truffles (Tuber melanosporum Vitt. and Tuber magnatum Pico, respectively), and identified using a polyphasic approach. According to the conventional taxonomic methods, MSP-PCR fingerprinting and sequencing of the D1/D2 domain of 26S rDNA, the strains were identified as Candida saitoana, Debaryomyces hansenii, Cryptococcus sp., Rhodotorula mucilaginosa, and Trichosporon moniliiforme. All isolates assimilated L: -methionine as a sole nitrogen source and produced the volatile organic compounds (VOCs), 2-methyl butanol, 3-methyl butanol, methanethiol, S-methyl thioacetate, dimethyl sulfide, dimethyl disulfide, dimethyl trisulfide, dihydro-2-methyl-3(2H)-thiophenone and 3-(methylthio)-1-propanol (MTP). ANOVA analysis of data showed significant (P<0.01) differences in VOCs produced by different yeasts, with MTP as the major component (produced at concentrations ranging from 19.8 to 225.6 mg/l). In addition, since some molecules produced by the isolates of this study are also characteristic of truffle complex aroma, it is possible to hypothesize a complementary role of yeasts associated with this ecosystem in contributing to final Tuber spp. aroma through the independent synthesis of yeast-specific volatile constituents.

The electrophoretic karyotypes of strains of the ten species of the yeast genus Saccharomyces (sensu Vaughan-Martini & Martini 1992) were determined by the CHEF (contour-clamped homogeneous electric field) system of pulsed field gel electrophoresis. The number of bands was found to vary from 6 to 17 and the calculated molecular weights of haploid genomes ranged from 7.9 to 14.6 Mbp. The type strains of S. exiguus and the four species of the Saccharomyces sensu stricto complex (S. bayanus, S. cerevisiae, S. paradoxus and S. pastorianus) have genomes comprised of chromosomes of all three size classes: light (< 500 kb), medium (500-1000 kb) and heavy (> 1,000 kb). Saccharomyces kluyveri DNA has only heavy bands, while the remaining species exhibit medium and heavy chromosomes. When more than one strain of each species was examined, it was seen that while the species S. bayanus, S. castellii, S. cerevisiae, S. kluyveri, S. paradoxus and S. pastorianus showed uniform karyotypes, S. dairensis, S. exiguus, S. servazzii and S. unisporus comprise heterogeneous taxa.

Archaic speculations and firmly established legends regarding the origin of the yeast Saccharomyces cerevisiae and related species are revisited in light of past and recent ecological evidence pointing to a strict association with artificial, man-made environments such as wineries and fermentation plants. The nomenclature within this industrially important group is also discussed in view of the modifications imposed from application of molecular techniques to classification.