NITRATE REDUCTION II

Abstract

Escherichia coli strain Bn, selected for tolerance of nitrate and previously shown to grow with nitrate or nitrite as sole source of N, can similarly utilize hyponitrite, hydroxylamine, or nitrous oxide. The parental strain B in the presence of glucose reduces hydroxylamine nearly quantitatively to ammonia, but it fails to grow in the presence of hydroxylamine, even if an ammonium salt is added. Under an atmosphere of H2, strain Bn, but not strain B, reduces nitrite, hypo-nitrite and hydroxylamine to NH3. Strain Bn differs from the parental strain also in its luxuriant anaerobic growth with lactate as sole C source and nitrate as electron-acceptor. These results, together with rates of adaptation, support the hypothesis that nitrate, hydroxylamine, and hyponitrite or a closely related compound, but not nitrous oxide, are intermediates in the reduction of nitrate to ammonia.