Production of nitric oxide in nitrosomonas europea by reduction of nitride.

Nitrosomonas europea and Nitrosovibrio sp. produced NO and N sub 2 O during nitrification of ammonium. Less than 15 % of the produced NO was due to chemical decomposition of nitrite. Production of NO and especially of N sub 2 O increased when the bacteria were incubated under anaerobic conditions at decreasing flow rates of air, or at increasing cell densities. Low concentrations of chlorite (10 myM) inhibited the production of NO and N sub 2 O, but not of nitrite indicating that NO and N sub 2 O were not produced during the oxidative conversion of ammonium to nitrite. NO and N sub 2 O were produced during reduction of nitrite with hydrazine as electron donor in almost stoichiometric quantities indicating that reduction of nitrite was the main source of NO and N sub 2 O.