Novel Psychrophiles and Exopolymers from Permafrost Thaw Lake Sediments

Thermokarst lakes are one of the most abundant types of microbial ecosystems in thecircumpolar North. These shallow basins are formed by the thawing and collapse of ice-richpermafrost, with subsequent filling by snow and ice melt. Until now, permafrost thaw lakes havereceived little attention for isolation of microorganisms by culture-based analysis. The discoveryof novel psychrophiles and their biomolecules makes these extreme environments suitable sourcesfor the isolation of new strains, including for potential biotechnological applications. In this study,samples of bottom sediments were collected from three permafrost thaw lakes in subarctic Québec,Canada. Their diverse microbial communities were characterized by 16S rRNA gene ampliconanalysis, and subsamples were cultured for the isolation of bacterial strains. Phenotypic andgenetic characterization of the isolates revealed anities to the genera Pseudomonas, Paenibacillus,Acinetobacter, Staphylococcus and Sphingomonas. The isolates were then evaluated for their productionof extracellular enzymes and exopolymers. Enzymes of potential biotechnological interest included and-glucosidase, and-maltosidase, -xylosidase and cellobiohydrolase. One isolate, Pseudomonasextremaustralis strain 2ASCA, also showed the capability to produce, in the loosely bound cell fraction,a levan-type polysaccharide with a yield of 613 mg/L of culture, suggesting its suitability as a candidatefor eco-sustainable alternatives to commercial polymers.