Genetic and biochemical characterization of yeasts isolated from Antarctic soil samples

The Polish Arctowski Station is situated in the maritime Antarctic on the western shore of Admiralty Bay and encompasses terrestrial habitats which are not permanently covered by ice, in contrast to more than 90% of the island's surface area. Over the past several decades, studies exploring the soils of those habitats have revealed a considerable diversity of bacteria, filamentous fungi, and, to a lesser extent, yeasts; however, characterization of this complex microbiome, especially at the molecular level, is still far from satisfactory. The isolates were assigned to their respective genera and species based on genetic analysis of the D1/D2 and ITS1-5.8S-ITS2 regions of rDNA. In the studied soil samples, the most abundant microorganisms belonged to the genera Cryptococcus, Rhodotorula, and Debaryomyces. Physiological and biochemical analysis of Cryptococcus gilvescens (pro tempore Goffeauzyma gilvescens) and Rhodotorula mucilaginosa showed only a limited level of intraspecies diversity. Cellular DNA content and karyotypes were determined using flow cytometry and pulsed-field gel electrophoresis for several selected strains. For the first time, genome size and electrophoretic karyotypes were investigated in C. gilvescens (pro tem G. gilvescens), Cryptococcus saitoi (pro tem Naganishia globosa), Cryptococcus gastricus (pro tem Goffeauzyma gastrica), and Cryptococcus albidus (pro tem Naganishia albida). In addition, plate tests showed Antarctic yeasts to be a potential source of biotechnologically important enzymes. This study in biodiversity, presenting physiological and molecular characterization of psychrotolerant yeast strains isolated from the soils of western Admiralty Bay, contributes to a better understanding of the microbial ecology of this unique ecosystem.