Soil redox-adaptive anode potentials enhance microbial electroactivity through targeted enrichment of exoelectrogenic consortia in paddy soil

Exoelectrogenic bacteria (EEB) act as critical drivers in terrestrial and aquatic ecosystems, mediating pivotal biogeochemical processes. However, their low abundance in natural environments poses significant challenges for accurate identification and enrichment. Bioelectrochemical systems (BESs) have emerged as a promising tool for enriching EEB from environmental samples, yet the influence of applied potentials on shaping specific EEB populations remains poorly understood. Here, we developed an effective strategy to selectively enrich targeted exoelectrogenic consortia by adapting anode potentials to the redox conditions of paddy soil. Notably, in BESs inoculated with flooded soil, an applied potential of -0.28 V (simulating the redox conditions dominated by iron oxide-hydroxide reduction) preferentially enriched Geobacter-dominated EEB consortia. Metagenomic functional analysis indicated these EEB were primarily engaged in iron respiration. In contrast, drained soil-inoculated BESs required a higher potential (0.33 V, mimicking nitrate-reducing conditions) for optimal enrichment, resulting in Aeromonas as the predominant genus. The enriched community in this scenario exhibited chemoheterotrophic metabolism and nitrate reduction capabilities. The enrichment dynamics underscore how applied potentials modulate both taxonomic composition and functional specialization of EEB along soil redox gradients, with implications for targeted manipulation of microbial communities for environmental biotechnology applications.