Disruption of sucA, which encodes the E1 subunit of alpha-ketoglutarate dehydrogenase, affects the survival of Nitrosomonas europaea in stationary phase.

Although Nitrosomonas europaea lacks measurable alpha-ketoglutarate dehydrogenase activity, the recent completion of the genome sequence revealed the presence of the genes encoding the enzyme. A knockout mutation was created in the sucA gene encoding the E1 subunit. Compared to wild-type cells, the mutant strain showed an accelerated loss of ammonia monooxygenase and hydroxylamine oxidoreductase activities upon entering stationary phase. In addition, unlike wild-type cells, the mutant strain showed a marked lag in the ability to resume growth in response to pH adjustments in late stationary phase.