ELEVATION OF SUPEROXIDE-DISMUTASE IN HALOBACTERIUM-HALOBIUM BY HEAT-SHOCK

Exposure of Halobacterium halobium to 50-degrees-C for 2.5 h in an aerobic environment resulted in a greater than twofold increase in the activity of the manganese-containing superoxide dismutase. Nondenaturing polyacrylamide gels stained for enzymatic activity did not reveal any additional isozymes of superoxide dismutase induced by the heat shock. The maximal effect was observed at 50-degrees-C, and the elevated levels of activity remained constant during 5 h of recovery at 40-degrees-C. The induction of enzymatic activity was sensitive to protein synthesis inhibitors. The results are discussed relative to heat shock and stress-related proteins as well as alterations in metabolism brought about by elevated temperatures.