POLIEXTREMOPHILIC YEASTS FROM PATAGONIA ARGENTINA AND ANTARTCTIC SEA

DE GARCÍA VIRGINIA; MARTINA TURK; ZALAR POLONA; GUNDE-CIMERMAN NINA; GIRAUDO MARIA ROSA

Vipava y Nova Gorica

Simposio; 31ST INTERNATIONAL SPECIALISED SYMPOSIUM ON YEAST; 2014

Microorganisms inhabiting cold environments have the ability to tolerate freezing since they are exposed to low temperatures, dehydration, which is caused by water being bounded to ice crystals, and to survive in ultraoligotrophic conditions. Cellular adaptations to low temperatures and high salinity are generally similar and the species that inhabit these environments have specialized mechanisms for stress tolerance (osmotic and oxidative). These conditions trigger the synthesis of various metabolites that help the cells to survive. Physiological adaptations of psychrophilic and psychrotolerant microorganisms include modifications of membrane lipid composition, the accumulation of cryoprotectants like polyols (glycerol, trehalose), synthesis of the enzymes that are active at low temperatures and the production of antifreeze proteins. The presence of yeasts in sea water and sea ice of Antarctic (Bellingshausen, Weddell and Scotia seas) was studied. From 26 samples (19 of sea water and 7 of sea ice), 281 yeast strains (65 species) were isolated and identified. On selected yeast strains (psychrophilic, psychrotolerant and halophilic) cellular stress was estimated by measuring phosphoglucomutase activity at various osmotic conditions and temperature (at 5 and 15 °C, with 3 % NaCl (w/v) and without NaCl). Results showed that strains have a higher phosphoglucomutase activity at 15 °C with 3 % NaCl (w/v). We also studied the capability of yeasts to grow on media with urea as the only carbon source at 4 °C, were only basidiomycetous yeasts were able to grow. Furthermore we have searched for the presence of antifreeze protein genes in psychophilic yeasts (Glaciozyma, Mrakia and Rhodotorula), and for all genera positive results were obtained. The results contribute to the general knowledge of the diversity, ecology, and biotechnological potential of these yeasts and will help to identify the impact of stress conditions on the major metabolic pathways of poliextremophilic yeasts from the marine environments of Patagonia and the Antarctic seas.