Resumo

Yeasts have been isolated from almost every aquatic environments of the world. In particular marine yeasts have been reported to be truly versatile agents of biodegradation; they participate in a range of ecologically significant processes in the sea, especially in estuarine and near-shore environments. Among such activities, decomposition of plants substrates, nutrient-recycling, biodegradation of oil/recalcitrant compounds and parasitism of marine animals are important. Eighty percent of the biosphere is at low temperatures (3 - 7 °C) and 90 % of marine habitats are lower than 5 °C. In this regard Southern Ocean is home to a diverse and rich community of life that thrives in an environment dominated by glaciations and strong currents. In Antarctic waters, sea ice formation creates cold, dense, salty water that sinks to the seafloor pushing the global ocean’s nutrient-rich, helping to create areas of high primary productivity. In these extreme cold environments psychrotolerant and psychrophilic yeasts had been found, they show numerous strategies to maintain sufficient metabolic activities to survive in this harsh conditions. Occurrence of cold-adapted yeasts in marine water and ice from Antarctic Sea (Bellingshausen, Scotia and Weddell Sea) were studied. In February-March of 2012, 25 samples were collected, 19 water samples (9 from Bellingshausen, 6 from Scotia and 4 from Weddell Sea) and 6 ice samples (2 from Bellingshausen and 4 from Scotia Sea); 300 mL of each sample were filtrated; filters were placed in MYP agar and incubated at 5 ºC, for up to 2 month. Yeasts viable counts (CFU L–1) varied from 2 ± 2 to 883.3 ± 385.3 in water samples, while varied from 62.7 ± 32.57 to 843.8 ± 452.27 in ice samples. A total of 209 strains were isolated, 46 different species were identified. Cosmopolitan species Rhodotorula mucilaginosa, Cryptococcus victoriae, Aureobasidium pullulans and Debaryomyces hansenii were isolated. From ice samples known psychrophilic species were isolated Mrakia frigida, Glaciozyma martinii, Rh. glacialis and psychrotolerant species Dioszegia fristingensis. All identified species are in agreement with others occurrence yeast reports from marine environments of the world, also possible new species have been found. Cold extreme environments are potential source of yeasts with desirable characteristics, which could be explored further for metabolic and biotechnological properties. It also contributes to understanding global warming consequences. Microorganisms present in sea environments may be released from glacial environments (polar areas) and complement/change existing microbial communities therein.