Superoxide dismutase activity during recovery of thermally stressed Staphylococcus aureus MF-31

Superoxide dismutase (SOD) activity was determined during the growth cycle of unheated and heat-injured cells of Staphylococcus aureus MF-31. SOd activity levels dropped in unheated cells during the lag phase, increased during logarithmic phase, and became constant in the stationary phase. Cells which were sublethally heated (52 degrees c, 20 min) in 100 mM phosphate buffer and subsequently allowed to recover in tryptic soy broth demonstrated an 85% decrease in SOD activity upon inoculation into recovery medium. As the injured cells repaired the heat-induced lesions and entered logarithmic growth, SOD levels rapidly increased. Heat-injured cells allowed to recover in tryptic soy broth plus 10% NaCl showed similar decreases in SOD activity levels. However, no subsequent increase was observed when specific activity was calculated based on milligrams of protein.