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Previously, we demonstrated that nitrate respiration increases the synthesis of iron-containing superoxide dismutase (Fe SOD) in anaerobically grown Escherichia coli cells. In this study, we developed a system with which the anaerobic induction of Fe SOD by nitrate respiration in E. coli was separated from the induction of the nitrate respiration system. The anaerobic induction of Fe SOD required the presence of both nitrate and an electron donor, and the induction of Fe SOD by nitrate respiration was inhibited by chloramphenicol or riphampicin. When glucose was used as the electron donor, carbonyl cyanide p-trifluoro-methoxyphenylhydrazone (FCCP) but not N,N'-dicyclohexylcarbodiimide (DCCD) inhibited the induction of Fe SOD by nitrate respiration, but when formate was used as the donor, both FCCP and DCCD inhibited the induction of Fe SOD by nitrate respiration.Superoxide dismutase (SOD), which catalyzes dismutation of the superoxide anion radical (02 -) into 02 and H2O2, is generally regarded as protecting the cells from oxygen toxicity.Escherichia coli has three types of SOD: iron-containing SOD (Fe SOD) (1), manganese-containing SOD (Mn SOD) (2), and a SOD with a protein moiety, this is a hybrid of Fe SOD and Mn SOD (hybrid SOD) (3).We have shown that E. coli cells, grown anaerobically by fermentation, had a low level of SOD and contained Fe SOD only (4). We also showed that E. coli cells, grown anaerobically by anaerobic respiration with an electron acceptor such as nitrate, fumarate, dimethyl sulfoxide (DMSO) or trimethylamine N-oxide (TMAO),

The effect of various metal ions on the anaerobic synthesis of superoxide dismutase (SOD) in Escherichia coli was examined. When cells were grown anaerobically by fermentation, adding CuSO4 in the culture medium resulted in the synthesis of manganese-containing SOD (Mn SOD), but adding CrCl3, CoCl2, NiSO4, ZnSO4 or Ga(N03)3 did not. The presence of nitrate in culture medium stimulated the anaerobic synthesis of Mn SOD by CuSO4. During the incubation of resting cells under anaerobic conditions, the addition of CuSO4 and KNO3 increased Mn SOD activity, which was inhibited by chloramphenicol. Adding CrCl3 or Ga(N03)3 with KNO3 increased Mn SOD activity during anaerobic incubation of resting cells, but adding MnCl2, (NH4)2Fe(S04)2, K3Fe(CN)6, CoCl2, NiSO4 or ZnSO4 with KNO3 did not increase Mn SOD activity. Instead, they decreased it. The increase of Mn SOD activity in resting cells by Cr ions or Ga ions with nitrate was inhibited by ferric citrate but that by Cu ions was not. When cells were grown anaerobically with CuSO4 or when resting cells were incubated anaerobically with CuSO4, a new activity band of SOD appeared in the polyacrylamide gel electrophoreogram, regardless of the operation of nitrate respiration. The SOD of the new activity band was insensitive to cyanide, H2O2 or diethyldithiocarbamate. This new SOD and Mn SOD had the same molecular size but had different charges.Escherichia coil has three types of superoxide dismutase (SOD): iron-containing SOD (Fe SOD) (20), manganese-containing SOD (Mn SOD) (7), and a SOD which consists of one of each of the subunits from the other two isozymes and contains both iron and manganese (Hybrid SOD) (2, 3).