Characterization of a Novel Anaerobic Ammonium-Oxidizing Bacterium Enriched under Alkaline-Saline Conditions

Anaerobic ammonium-oxidizing (anammox) bacteria, which anaerobically convert ammonium and nitrite to dinitrogen, are key players in the global nitrogen cycle. They form a monophyletic lineage within the phylum Planctomycetes, with niche differentiation at the group or species level across various anoxic environments. Despite the increasing number of anammox genera proposed from environmental genomes in recent years, their cultivation and physiological characterization remain limited. In this study, we successfully enriched a novel anammox species, Candidatus Loosdrechtia alkalitolerans, through long-term reactor operation under combined saline and alkaline stress conditions.