Decoding Microplastic-Induced Adaptive Strategies in Electroactive Biofilms: Stress Resistance Pathways and Enhanced Extracellular Electron Transfer

Elucidating how electroactive biofilms (EABs) maintain robust extracellular electron transfer (EET) functionality under prolonged microplastic (MP) exposure, this study addresses a critical knowledge gap in their stress resistance repertoire. Through integrated electrochemical profiling, physiological assessment, and microbial structure analysis, we demonstrate MP-type-specific microbial adaptation strategies. Notably, polyvinyl (PVC) MPs, with a zeta potential of −18.87 mV, induced metabolic adaptation through NAD-malate dehydrogenase (NAD-MDH) upregulation (+42.33%) and cytochrome c (c-Cyts) synthesis (+24.14%), enhancing the electron flux in metabolism. Prolonged exposure to polypropylene (PP) MPs, characterized by strong hydrophobicity (contact angle of 129°), heightened bacterial viability, as indicated by a 2.53% increase in the proportion of living cells. Polyethylene terephthalate (PET) MPs drove ecological selection for Geobacter dominance (71.58% abundance) with adaptive extracellular polymeric substance (EPS) production (1734.64 μg/mg protein), reinforcing electroactivity and microbial stability. Correlation analysis identified c-Cyts and cell viability as reliable indicators of the electroactivity of EABs across MP types. These findings refine our understanding of EAB stress tolerance, advancing environmental monitoring, bioremediation strategies, and the design of evolutionarily robust microbial electrochemical technologies.