Stable ammonium assimilation mediates the metabolic adaption of halophilic microbiome to hypo-osmotic stress

Salinity barrier shapes distinct microbial ecology on earth, and applications of microbiomes are frequently hindered by trans-osmotic challenges. As a central nutrient metabolism, nitrogen transformations may contribute to conquering osmotic perturbations in microbiomes, and thus understanding the nitrogen metabolic responses to non-isosmotic exposure is crucial. Here we uncover that ammonium assimilation mediates the maintenance of physicochemical properties in a marine-derived halophilic microbiome when adapting to hypo-osmotic stress from salinity of 3% to 0.5% and recovery.