Proteomics and comparative genomics of Nitrososphaera viennensis reveal the core genome and adaptations of archaeal ammonia oxidizers

Ammonia-oxidizing archaea (AOA), key players in global biogeochemical cycles, represent a heterogeneous group with a broad environmental distribution. Understanding their activity and physiology is of great importance due to the impact of the overuse of agricultural fertilizers on the N cycle and the production of the greenhouse gas N₂O during nitrification. Despite their prominent ecological role, little is known about the fundamental metabolic processes of AOA. Here, we show that AOA of marine and terrestrial environments share unique and well-conserved pathways of carbon and nitrogen metabolism, and we raise hypotheses about missing steps in these pathways. Our approach also highlights the extensive environmental adaptations of the soil clade, including the capacity for cell surface modifications, carbohydrate conversions, detoxification, and biofilm formation.