Destroys superoxide anion radicals which are normally produced within the cells and which are toxic to biological systems. Catalyzes the dismutation of superoxide anion radicals into O2 and H2O2 by successive reduction and oxidation of the transition metal ion at the active site. Also contributes to the inhibition of lipid oxidation. Manganese-preferring enzyme, less active with iron than with manganese. 2 H(+) + 2 superoxide = H2O2 + O2 Binds 1 Mn(2+) or Fe(3+) ion per subunit. Homodimer. Transcription increases slightly by internally generated superoxide stress. The levels of SOD activity and sodA expression were growth-phase dependent, occurring most during stationary phase. Expression is not affected by manganese. Is not essential for aerobic growth in complex medium. Belongs to the iron/manganese superoxide dismutase family.