Artificial bio-cables of carbon fiber filaments bridge microbial electron flow and hydrocarbon degradation in soil

Low extracellular electron transfer (EET) efficiency and limited synergistic interactions of functional microbes are bottlenecks of in-situ bioremediation of petroleum hydrocarbon-contaminated soils. In this study, carbon fibers were used as conductive mediators to construct long-term "artificial bio-cable" in soil for 407 days. The results showed that carbon fibers substantially increased soil electron transport compared to the control, with 4.7 and 15-fold increases in electron flux and maximum power density, respectively. Moreover, the introduction of carbon fibers restructured bacterial, fungal, and archaeal communities, enriching electroactive and hydrocarbon-degrading taxa such as Desulfuromonas, Pseudomonas, and Methanothrix. Functional gene analysis revealed that carbon fibers stimulated glycolysis, the tricarboxylic acid (TCA) cycle, and nitrogen metabolism, and upregulated genes related to conductive pili, thereby accelerating EET. In essence, carbon fibers formed a conductive network within soil pores, functioning as "artificial bio-cables" that markedly reduced electron transfer resistance for long term. Electroactive bacteria such as Desulfuromonas, Pseudomonas, Geobacter, and Clostridium delivered electrons generated from hydrocarbon degradation directly to the fibers via conductive pili and outer membrane cytochromes (e.g., MtrA/B), thereby achieving efficient extracellular electron release. This study highlights a novel bioelectronic-guided strategy for in-situ remediation of organically polluted soils, supporting sustainable soil restoration and biogeochemical processes.