文摘
Cold-adapted, complex polysaccharide-degrading marine bacteria have important implications in biogeochemical processes and biotechnological applications. Bacteria capable of degrading complex polysaccharide substrates, mainly starch, have been isolated from various cold environments, such as sea ice, glaciers, subglacial lakes, and marine sediments. However, the total diversity of polysaccharide-degrading culturable bacteria in Kongsfjorden, Arctic Ocean, remains unexplored. In the study reported here, we tested 215 cold-adapted heterotrophic bacterial cultures (incubated at 4 and 20 °C, respectively) isolated from Kongsfjorden, for the production of cold-active extracellular polysaccharide-degrading enzymes, including amylase, pectinase, alginase, xylanase, and carboxymethyl (CM)-cellulase. Our results show that 52 and 41% of the bacterial isolates tested positive for extracellular enzyme activities at 4 and 20 °C, respectively. A large fraction of the bacterial isolates (37% of the positive isolates) showed multiple extracellular enzyme activities. Alginase and pectinase were the most predominantly active enzymes, followed by amylase, xylanase, and CM-cellulase. All isolates which tested positive for extracellular enzyme activities were affiliated to microbial class Gammaproteobacteria. The four genera with the highest number of isolates were Pseudomonas, followed by Psychrobacter, Pseudoalteromonas, and Shewanella. The prevalence of complex polysaccharide-degrading enzymes among the isolates indicates the availability of complex polysaccharide substrates in the Kongsfjorden, likely as a result of glacial melting and/or macroalgal load. In addition, the observed high functional/phenotypic diversity in terms of extracellular enzyme activities within the bacterial genera indicates a role in regulating carbon/carbohydrate turnover in the Kongsfjorden, especially by reducing recalcitrance.
