Culturable heterotrophic nitrification-aerobic denitrification bacterial consortia with cooperative interactions for removing ammonia and nitrite nitrogen in mariculture effluents

Nitrogen pollution from ammonia and nitrite has been a significant environmental concern in the aquaculture industry. Current studies mostly focus on the characteristics of heterotrophic nitrification and aerobic denitrification (HNAD) bacteria isolated from freshwater environments such as domestic wastewaters, whereas HNAD bacteria in mariculture have yet to be well understood. Herein, this study aimed to investigate the interactions between culturable HNAD bacteria from mariculture environments by combining high-throughput sequencing and traditional cell culture method, in order to develop potential microbial consortia for high-efficiency nitrogen removal in mariculture effluents. By twenty-five species of halophilic HNAD bacteria co-cultured in the synthetic mariculture effluent (ammonia: 20 mg/L, C/N: 5), ammonium removal was mainly driven by the cooperative interactions between strains from Marinomonas, Marinobacterium, Halomonas, and Cobetia. Due to the interspecific coexistence, three novel bacterial consortia of Marinomonas communis & Halomonas titanicae, Marinomonas aquimarina & Halomonas titanicae, and Marinomonas aquimarina & Cobetia marina exhibited significantly better ammonium removal efficiency and stability than single strains. Meanwhile, Marinomonas communis & Halomonas titanicae showed the highest nitrite removal rate of 0.76 mg NO2--N/L/h. Importantly, these microbial consortia could convert more inorganic-N into bacterial biomass by assimilation and dissimilation instead of the increased nitrogen lost by denitrification. These findings will contribute to understanding and developing the culturable HNAD bacterial consortia for controlling inorganic-N pollution in mariculture effluents or other saline wastewaters.