Enhanced microbial synergy and electron transfer in Feammox: mechanisms driven by streamlined continuous flow systems

Feammox is a promising low-carbon nitrogen removal process, yet constrained to low activity and efficiency of functional microorganisms due to unclear microbial mechanisms caused blind regulation. Herein, we elucidated the driving mechanisms of the microbial community using multi-omics approaches. By establishing streamlined continuous flow systems that imposed a substrate steady‑state and ultrasound‑enhanced cell permeability, directionally enhanced functional microbial interactions and electron transfer efficiency, ultimately improving microbial activity and performance. The Feammox process was predominantly driven by a multifunctional consortium comprising ammonia‑oxidizing bacteria, iron‑reducing bacteria, nitrate‑dependent ferrous‑oxidizing bacteria, and denitrifiers. The steady-state system increased the abundance and synergistic interactions of core functional microorganisms, leading to a twofold enhancement in functional microbial activity. Key electron transfer pathways were promoted, including the synthesis of c-type cytochromes, riboflavin metabolism, and biofilm formation, resulting in a 50% reduction in charge-transfer resistance. Enhanced cell membrane permeability increased intracellular iron metabolic flux by 30%. This synergistically activated quorum sensing, membrane transport, and nitrogen metabolism pathways, further targeting and intensifying microbial activity and electron transfer efficiency in the Feammox system. These findings deepen the understanding of iron‑based autotrophic nitrogen removal mechanisms and provide a theoretical and technical basis for the targeted optimization of Feammox in low‑carbon wastewater treatment.