Electron‑flow‑driven synergistic mineralization of naphthalene by an S‑N‑doped biochar‑bridged engineered consortium

Microbial synergy in naphthalene biodegradation is frequently constrained by the inefficiency of diffusion-based metabolite transfer. To address this limitation, we assembled immobilized engineered microbial systems (imGEMs) by co-anchoring engineered Pseudomonas stutzeri (overexpressing nahAc and nahB) and Rhodococcus rhodococcus (overexpressing nahH and catA) on S-N-doped biochar (S-N-BC). In this engineered consortium, Pseudomonas stutzeri acts as an oxidative bio‑anode that initiates naphthalene degradation and releases electrons. The S‑N‑BC matrix functions as an electron‑conductive interface, facilitating direct interspecies electron transfer (DIET) and enhancing extracellular electron transfer (EET). This directed electron flux is harnessed by Rhodococcus rhodococcus, serving as a reductive bio‑cathode, to drive its oxygenolytic ring‑cleavage catalysis. The resulting bioelectrochemical synergy achieved exceptional naphthalene removal (>98.3%) and mineralization efficiency (89.5%) by circumventing diffusive bottlenecks and minimizing intermediate accumulation. Electrochemical and multi‑omics analyses confirmed the establishment of this syntrophic circuit, demonstrating elevated electron flux, coordinated upregulation of catabolic genes, and reorganization of electroactive membrane components. Moreover, the immobilized system exhibited outstanding operational stability, maintaining high degradation efficiency over 30 days under varying environmental conditions. In conclusion, this work establishes a robust electron‑flow‑driven paradigm that integrates metabolic engineering with conductive material design for the efficient and sustainable bioremediation of persistent aromatic pollutants. SYNOPSIS: This analysis finds that Biochar-bridged engineered consortium mineralizes naphthalene via electron flux-driven DIET.