Functional Significance of the Cu,ZnSOD inEscherichia coli

Diethyl dithiocarbamate (DDC) was used to inhibit the copper- and zinc-containing superoxide dismutase (Cu,ZnSOD) ofEscherichia coliin order to expose its physiological function. DDC inhibited the aerobic growth of asodA sodBmutant much more than it did the growth of a SOD-replete parental strain and this inhibitory effect was oxygen-dependent. The SOD mimic MnTMPyP markedly diminished the growth inhibitory effect of DDC. Transfer of thesodA sodBstrain from anaerobic to aerobic conditions induced fumarase C, which is a member of the soxRS regulon. DDC augmented this induction. These results indicate that the Cu,ZnSOD provides a defense against oxidative stress, which is more important to thesodA sodBmutant than to its SOD-replete parental strain.