Endogenous iron activation driven by microbial competitive release enhances electrogenic petroleum hydrocarbon degradation via boosted oxygen influx at soil-water interface.

Abstract

Microbial extracellular electron transfer enhances the biodegradation of petroleum hydrocarbon (PH), however how the electron flow regulates iron cycling and PH removal remain unclear. This study confirmed a "competitive release" effect of biome that activated endogenous iron to create favorable conditions for subsequent colonization of electroactive bacteria. Sterilization, employed as a tool to simplify microbial community structure, triggered a "competitive release" effect by eliminating fast-growing competitors, which enriched electroactive bacteria and increased the cumulative electron flux by 27% (4157 C, 2.59 × 10²² e) over 203 days. This finding verified the role of microbial interactions in electrogenic removal (72-93% reduction). Furthermore, electron transfer shifted the in-situ soil redox potential from a reductive (< 100 mV) to an oxidative state (200-400 mV), and increased its diffusion depth and concentration at the soil-water interface, thereby enhancing the aerobic PH removal. In parallel, a consortium dominated by iron and oxygen redox was established, particularly in sterilized soil with more electron flux. Consequently, Desulfitibacter and Pseudomonas as capable taxa were enriched in sterilized soil while Guyparkeria and Salinimicrobium in non-sterilized soil. In conclusion, biocurrent-mediated iron redox established a superior electron transfer pathway to specialize PH removal in terms of the dissolved oxygen in soil.

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