Denitrification and ammonia oxidation by Nitrosomonas europaea wild-type and NirK- and NorB-deficient mutants.

The phenotypes of three different Nitrosomonas europaea strains - wild-type, nitrite reductase (NirK)-deficient and nitric oxide reductase (NorB)-deficient strains - were characterized in chemostat cell cultures, and the effect of nitric oxide (NO) on metabolic activities was evaluated. All strains revealed similar aerobic ammonia oxidation activities, but the growth rates and yields of the knock-out mutants were significantly reduced. Dinitrogen (