Hierarchical in situ biomineralization-enhanced electroactive biofilm for high-efficiency antibiotic degradation

The low efficiency of extracellular electron transfer (EET) is a major bottleneck in bioelectrochemical water treatment. Here, we introduce an alternative strategy based on in situ biomineralization of conductive nanoparticles within a three-dimensional electroactive biofilm, creating an integrated "living conductive material". This self-engineered system achieves > 90 % chemical oxygen demand removal and up to 96.5 % tetracycline removal (79-97 % during long‑term operation) with sterilized controls confirming ∼64 % biologically mediated-several-fold higher than non-mineralized controls. Biogenic greigite (Fe₃S₄) nanoparticles form an in situ conductive network ("conductive armor") on the electrode surface. This armor establishes a multi-modal electron-transfer network that both mimics and mplifies native pathways, hypothetically functioning as (i) a cytochrome‑like transmembrane conduit, (ii) a nanowire-like percolation network for long‑range conduction, and (iii) a solid-state redox shuttles for rapid electron hopping. Direct validation of these individual roles remains an important goal for future research. Through integrated multi‑omics, electrochemical, and microscopic analyses, we further demonstrate that the emergent conductive niche selects for a streamlined, metabolically specialized consortium, resulting in a co‑adapted bio‑hybrid system with markedly enhanced electroactivity. Synthesizing these insights, we propose a hierarchical "conductive monomer‑to‑armor" model that links nanoscale biomineralization at the cellular interface to biofilm‑scale conductivity and reactor‑scale pollutant removal. This framework not only explains the dramatic improvements in antibiotic removal, but also provides a broadly applicable design principle for next‑generation, self‑engineering bioelectrochemical systems.