Psychrotolerant yeasts from glacial environments of Patagonia, Argentina: biodiversity and extracellular enzyme production

DE GARCIA V.; BRIZZIO S. ; VAN BROOCK MARÍA ROSA GIRAUDO

Ljubljana

Congreso; 4th International Conference on Polar and Alpine Microbiology.; 2011

FEMS - Ljubljana University

Extremely cold environments (i.e. ice, snow, and sea ice) are frequently colonized by extremophilic microorganisms known as PSYCHROTOLERANT and psychrophiles. They can use complex biopolymers as energy sources, synthesizing extracellular enzymes active at low temperatures. Psychrophilic yeasts play an essential role in nutrient cycling and biomass production processes in cold ecosystems. These microorganisms have been isolated from cold environments in the entire world. Patagonian Andes in Southwestern Argentina offer interesting and unexplored glacial environments, such as Mount Tronador (Nahuel Huapi National Park) and Patagonian icefields (Los Glaciares, National Park). The latter are the largest temperate ice masses in the Southern Hemisphere accounting for more than 60% of the Southern Hemisphere’s glacial area outside Antarctica. First studies on the occurrence of cold-adapted yeasts in glacial environments in Patagonia are from melt-water rivers of Mount Tronador. Occurrence of yeasts in ice from Frías glacier (Mount Tronador) and Perito Moreno glacial (Patagonian icefields) has been studied for the first time and are reported here. Ice samples were melted aseptically at room temperature and then filtered; filters incubated at 10 ºC in MYP agar for up to 1 month. Total of 115 strains were isolated, characterized and identified by biochemical and molecular techniques. Isolates were tested for their capability to produce extracellular enzymes (amylase, esterase, protease, protease, pectatelyase, pectinase, cellulose) at 5 and 20 °C. Basidiomicetous yeasts represented 90 % of the isolates, 16 genera and 33 species were identified, 21 % represent possible new species, 2 have been formally described (Cryptococcus spencermartinsiae sp. nov.and Wickerhamomyces patagonicus sp. nov.). Psychrophilic yeasts accounted for 25 % of all isolates, while the rest 75 % were psychrotolerant; 85 % of all isolated showed at least one enzymatic activity. Statistic analysis of multiple correspondences and cluster classification allows finding a relationship among isolated genera and enzymatic activities. Sporobolomyces isolates produced amilases, Leucosporidiella and Udeniomyces produced proteases, cellulase, pectinase and esterase, Cryptococcuscellulase, Dioszegia esterase, Mrakia protease, esterase and pectinase at 5 °C, and genera Rhodotorula and ascomycetous yeasts did not showed any relation with enzymatic production. Results presented here showed all isolated yeasts are adapted to cold environments and are able to hydrolyze natural compounds at low temperatures. The above data suggest a significant ecological role, as organic matter decomposers and nutrient cyclers; yeasts occurring in these extreme cold habitats could be used for metabolic and ecological studies, and application in biotechnological process at low temperatures.