Iron reduction byAquaspirillum magnetotacticum

Iron reductase activity in cell extracts ofAquaspirillum magnetotacticum strain MS-1 (wild type) or nonmagnetotactic mutant strain NM-1A was located primarily in the periplasm. Cytoplasm contained 20%–35% and membrane fractions 3% of total iron reductase activity detected. Iron reduction was reversibly inhibited by oxygen, required -NADH, and was enhanced by flavins. Reduced disulfide bonds and uncomplexed sulfhydryl groups were necessary for reductase activity. Respiratory inhibitors did not appreciably affect iron reductase activity. Iron complexed with quinic acid, dihydroxybenzoic acid, acetohydroxamic acid, citric acid, or deferrioxamine B was reduced by soluble iron reductases of strain MS-1.