Catalyzes the reduction of superoxide to hydrogen peroxide, using electrons from NADH and NADH:rubredoxin oxidoreductase (NROR) and rubredoxin (Rd) as electron transport intermediaries between NADH and Dfx. Is a key factor in the superoxide reductase dependent part of a pathway for detoxification of reactive oxygen species (ROS) in C.acetobutylicum, an obligate anaerobic bacterium. 2 H(+) + reduced [rubredoxin] + superoxide = H2O2 + oxidized [rubredoxin] Binds 1 Fe(2+) ion per subunit. In contrast to some other SORs, does not bind a second iron ion. Up-regulated after exposure to oxygen stress (at both transcript and protein levels). Repressed by PerR. The SOR reaction is believed to be advantageous to anaerobic bacteria, in comparison to SOD (superoxide dismutase), because SOR produces no oxygen by reducing superoxide. Belongs to the desulfoferrodoxin family.