Catalase and superoxide dismutase activities after heat injury of Listeria monocytogenes

Abstract

Four strains of Listeria monocytogenes were examined for catalse (CA) and superoxide dismutase (SOD) activities. The two strains having the highest CA activities (LCDC and Scott A) also possessed the highest SOD activities. The CA activity of heated cell extracts of all four strains examined decreased sharply between 55 and 60°C. SOD was more heat labile than CA. Two L. monocytogenes strains demonstrated a decline in SOD activity after heat treatment at 45°C, whereas the other two strains demonstrated a decline at 50°C. Sublethal heating of the cells at 55°C resulted in increased sensitivity to 5.5% NaCl. Exogenous hydrogen peroxide was added to suspensions of L. monocytogenes; strains producing the highest CA levels showed the greatest H2O2 resistance.