Growth (OD565) and magnetic response (Cmag) of WT MSR-1 and the Δnap, ΔnorCB, and ΔnosZ mutants under different conditions. Under aerobic conditions, the Cmag values were always zero and not shown. (A) Aerobic, ammonium medium; (B) aerobic, nitrate medium; (C) microaerobic, ammonium medium; (D) microaerobic, nitrate medium; (E) anaerobic, nitrate medium. Results from representative experiments were measured in triplicate, and values are given as means and standard deviations.