TEMPERATURE SHIFT-INDUCED CHANGES IN THE ANTIOXIDANT ENZYME-SYSTEM OFCYANOBACTERIUM-SYNECHOCYSTIS PCC-6803

1. Effect of controlled up- and down-shifts of growth temperature on t he antioxidant enzymes activities and lipid peroxidation were investig ated in intact cells of Cyanobacterium synechocystis PCC 6803 acclimat ed at different growth temperature. 2. Algal cells grown at 36-degrees -C were treated at 20 and 43-degrees-C as down- and upward-shifts of g rowth temperature for 24 hr, respectively. At the down-shift of growth temperature the superoxide dismutase, catalase and glutathione peroxi dase were significantly increased with concomitant decrease in protein content. 3. These parameters showed similar temperature dependencies in the up-shift of growth temperature, they were decreased significant ly. 4. The increased hydroxyl (HO.) radical and malonyldialdehyde (MDA ) formation, when algal cells exposed to down-shift of growth temperat ure, supposedly due to stimulated production of superoxide radicals (O 2-) and hydrogen peroxide (H2O2) at lower temperature.