Geobacter-dominated electroactive biofilms exhibit stable electricity generation under high-level heavy metal and organochlorine stress

Bioelectrochemical systems (BESs) are promising technologies for wastewater treatment and resource recovery, but their stable operation can be compromised by toxicant loading. Here, a Geobacter -dominated electroactive biofilm was developed and its resilience was evaluated under stepwise exposure to six toxicants: Cd 2+ , Hg 2+ , Cu 2+ , trichloroethylene (TCE), 1,2,4-trichlorobenzene (TCB), and trichloromethane (TCM). Electrochemical performance was monitored throughout the sequential exposure, followed by analyses of microbial community structure and metagenomic functional profiles. At nominal doing concentrations up to 300 mg/L, the biofilm retained about 50% of its current output. Metagenomic analysis showed limited community divergence from the control, with Geobacter remaining dominant (>80% at the genus level), while Geobacter sulfurreducens and Geobacter soli together accounted for >50% at the species level. Genes associated with metabolic pathways and detoxification functions, including nonribosomal peptide synthesis and ATP-binding cassette transport, showed increased abundance under pollutant stress. Resistance-related genes associated with transmembrane efflux, redox detoxification, and antioxidant defense also showed increased abundance. Approximately 80% of these enriched genes were retrieved in Geobacter genomes, including more than 60% in G. sulfurreducens . These results demonstrate that Geobacter -dominated electroactive biofilms exhibit strong resilience under toxicant loading, supporting stable bioelectrochemical process operation.