PROTEOLYTIC ACTIVITY OF SOME COLD-TOLERANT BACTERIA FROM ARCTIC SEDIMENTS

Abstract

A number of Gram-negative cold-tolerant bacteria capable of growth on agar at 0 °C but not at 25 °C were isolated from Arctic littoral and marine sediment samples. Eight of these organisms able to hydrolyze gelatin were chosen for study. Taxonomically these organisms consisted of an unidentified but closely related group of seven cultures and a single Pseudomonas strain. Culture supernatants of these Arctic organisms contained proteinases that hydrolyzed gelatin, casein, and β-lactoglobulin, but not bovine plasma albumin. When casein was the substrate, the proteinases were most active at pH 7.0 to 8.0 between 30° and 40 °C and were inhibited by ethylenediaminetetraacetic acid. The proteinases were relatively heat-labile; the activity of the most heat-labile was reduced by 90% in 20–30 minutes at 40 °C and that of the most heat-stable by 90% in 45 minutes at 50 °C. Proteinases of the unnamed group of Arctic organisms were characterized by a low temperature characteristic and possession of high enzymic activity at low temperatures. Presumably such organisms can convert protein to simple nitrogenous compounds in the Arctic environment.