Impact of the Antarctic benthic fauna on the enrichment of biopolymer degrading psychrophilic bacteria.

Stenothermic cold adaptation was a predominant growth characteristic among biopolymer degrading bacteria from Antarctic shelf sediments. Psychrophilic decomposers of protein (gelatin), chitin, and cellulose accounted for up to 84, 93, and 68%, respectively, of 0°C-isolates from selected compartments of the sediments. Macroinvertebrates were recognized as a selective pressure on these fast-growing (zymogenous) psychrophiles. Psychrophilic properties of growth and biopolymer degradation coincided most in the case of proteolytic isolates. On the other hand, the majority of psychrophilic chitin- and cellulose-decomposers showed less efficient biopolymer degradation at environmental temperatures (0°C). Temperature optima of the activities of pertinent depolymerizing enzymes (e.g., scleroprotease) exceeded by far the temperature optima for growth (between 4 and 12°C). Therefore, it appears likely that enhanced rates of enzyme synthesis at low temperatures play a crucial role for the degradation of detrital organic matter in this permanently cold environment.