Ammonium Availability Affects the Ratio of Ammonia-Oxidizing Bacteria to Ammonia-Oxidizing Archaea in Simulated Creek Ecosystems

The ammonia-oxidizing microbial community colonizing clay tiles in flow channels changed in favor of ammonia-oxidizing bacteria during a 12-week incubation period even at originally high ratios of ammonia-oxidizing archaea to ammonia-oxidizing bacteria (AOB). AOB predominance was established more rapidly in flow channels incubated at 350 μM NH₄⁺ than in those incubated at 50 or 20 μM NH₄⁺. Biofilm-associated potential nitrification activity was first detected after 28 days and was positively correlated with bacterial but not archaeal amoA gene copy numbers.