Enrichment of marine anammox bacteria in Hiroshima Bay sediments

摘要

Anaerobic ammonium oxidation (anammox) involves the microbiological oxidation of ammoniumnwith nitrite as the electron acceptor and dinitrogen gas as the main product. The Scalinduanspecies, an anammox genus that dominates natural habitats, plays an important role in catalysingnthe loss of nitrogen from marine environments. Until now, a few Scalindua species have beennreported to be enriched from sea sediments. The objective of this study is to enrich marinenanammox bacteria with coastal sediments in Hiroshima Bay as the inocula. The enrichment wasnachieved using a continuous upflow column reactor with synthetic sea water containingnammonium and nitrite. After 48 days of incubation, a simultaneous decrease in ammonium andnnitrite was observed. A total nitrogen removal rate of 1.16 kg-N mu00023 dayu00021 was attained aftern306 days of incubation when the nitrogen loading rate was 1.32 kg-N mu00023 dayu00021. Phylogeneticnanalysis revealed that the sequence similarity between the marine anammox-like bacteria in thisnreactor and the unidentified Candidatus Scalindua sp. was 96–98%. We successfully enrichednmarine anammox bacteria in the sediments of Hiroshima Bay by using synthetic sea water.nFurther studies are needed to investigate the characteristics of marine anammox bacteria,nincluding optimal pH, temperature, and nitrogen loading rate.