Biogenic FeS Reshapes microbial interactions to regulate acetogenesis in CO₂-Fed microbial electrosynthesis

Inefficient electron transfer and poorly coordinated microbial communities often limit stable CO₂-to-acetate conversion in microbial electrosynthesis (MES). Herein, Shewanella oneidensis MR-1 was introduced to induce in situ biogenic FeS formation at the cathode to regulate microbial interactions and enhance acetogenesis. Under the acetogenesis dominant condition (RAT: sludge to MR-1 ratio of 2:1, Fe/S = 5/10 mM, initial MR-1 inoculation), acetate production reached 1330.6 mg L^-1 with the carbon recovery efficiency of 62.9%. Community and metagenomic analyses showed that FeS selectively enriched acetogens and Fe/S transforming microorganisms while restructuring functional pathways related to redox metabolism and energy conservation. Co-occurrence network analysis further revealed that FeS promoted coordinated, function oriented microbial interactions rather than competitive associations. This study highlights the role of biogenic FeS in linking electron transfer with microbial cooperation, providing a mechanistic basis for improving MES performance through community level regulation.