TEMPERATURE-DEPENDENCE OF GROWTH, ENZYME-SECRETION AND ACTIVITY OF PSYCHROPHILIC ANTARCTIC BACTERIA

Five psychrophilic Antarctic bacteria have been selected for their cap acity to secrete exoenzymes into culture medium. These strains are abl e to grow from 0 to about 25 degrees C. However, production of lipase from Moraxella, alpha-amylase from Alteromonas haloplanctis, beta-lact amase from Psychrobacter immobilis and protease from Bacillus is maxim al at temperatures close to that of their environment (-2 to 4 degrees C) and is strongly inhibited at higher temperatures. This thermal eff ect involves alterations in the secretory pathway in the upper range o f temperatures, losses due to the enzyme thermal lability and in some cases to reduction in cell development. The apparent optimal activity temperature of these enzymes is between 30 and 40 degrees C, i.e. abou t 20 degrees C lower than that of their mesophilic counterparts.