A Superoxide-Dismutase Mimic Protects SodA SodB Escherichia coli against Aerobic Heating and Stationary-Phase Death

Superoxide appears to be a major cause of stationary-phase death and heat kill. In support of this conclusion are the following observations: (a) Stationary-phase death was apparent in the sodA sodB, but not in the superoxide dismutase (SOD)-competent parental strain; (b) Stationary phase death in the sodA sodB strain was dioxygen-dependent; (c) A manganic porphyrin, which catalyzes the dismutation of superoxide, protected the sodA sodB strain against stationary-phase death; (d) Heating the sodA sodB strain to 42°C caused a loss of viability not seen with the SOD-competent parental strain and preventable by the manganic porphyrin. Exposure to aerobic conditions induced antibiotic resistance in the sodA sodB, but not in the parental strain and the manganic porphyrin prevented that induction. This again indicates its ability to substitute for SOD in Escherichia coli.