Overproduction of superoxide dismutase does not protect Escherichia coli from stringency-induced growth inhibition by 1mM paraquat.

Two plasmid-containing Escherichia coli strains which overproduce manganese superoxide dismutase by 4- to 5-fold and iron superoxide dismutase by about 7-fold were not more resistant than parent strains to 1 mM paraquat (a known generator of superoxide) as measured by effects on growth, survival and induction of stringency. These results indicate that overproduction of superoxide dismutase does not mitigate the growth-inhibitory effects of 1 mM paraquat, including those which are expressed through induction of the stringency mechanism.