Enzymatic Activity of Psychrotolerant Antarctic Bacteria

Abstract

The Antarctic region has significant potential to study the biodiversity of microorganisms and to search for bacterial producers of glycolytic and proteolytic enzymes with new properties. The aim was to study the extracellular glycosidase and proteolytic activity of four bacteria strains isolated from black lichens of the cliffs of Galindez Island in the Antarctic. Methods. Cultures of bacteria were grown in submerged conditions at a temperature of 15 and 26oC for 48 h. The synthetic and natural substrates such as p-nitrophenyl-glycosides, soluble starch, gelatin, casein and Elastin-Congo red were used to study the enzymatic activity of bacteria. Results. All studied strains showed α-fucosidase activity. Microbacterium foliorum, Sporosarcina aquimarina and Rothia sp. exhibited α-, β-xylosidase, β-glucosidase or β-N-acetylglucosaminidase activity in different ratios. That may indicate the presence of the enzymatic complex of hydrolysis of lichenan and xylan, which are part of polysaccharides of plants and lichens. P. fluorescens and M. foliorum also showed gelatinase activity. The enzymatic activity of bacteria was noted to be higher in the case of cultivating at 15oC compared to 26oC. The α-xylosidase of M. foliorum was optimally active at pH 6.0 and 35oC, the α-xylosidase of Rothia sp. – at pH 6.5 and 35oC. High level of stability was shown for these enzymes in the pH range from 4.0 to 7.0 and temperature from 15 to 35оС during 24 h. Conclusions. Antarctic lichens can be a source of bacterial producers of polysaccharide degrading enzymes with new properties and low temperature optimum. The Antarctic cold environment provides the great opportunities to study the adaptive mechanisms of microorganisms and their enzymatic systems in order to develop new biotechnologies.