Elucidating applied voltage on the fate of antibiotic resistance genes in microbial electrolysis cell: Focusing on its transmission between anolyte and biofilm microbes.

Microbial electrolysis cell (MEC) system to treat wastewater containing antibiotics has been researched actively in past years. However, the fate of antibiotic resistant genes (ARGs) in MEC is not fully revealed. The effect of applied voltage on the migration of ARGs between anolyte and biofilm microbes via examining the microbial physiology and abundances of macrolide resistance genes (MRGs) and mobile genetic elements (MGEs) was elucidated in this research. Results showed that the abundance of MRGs and MGEs was decreased in the anolyte, but their abundances were increased on the electrode biofilm, indicating their transmission from anolyte to biofilm microbes. Increased applied voltage enhanced adenosine triphosphate (ATP), reactive oxygen species (ROS), and cell membrane permeability of electrode microorganisms. The structure of the electrode microbial community was shifted through applied voltage, and the abundance of electroactive microorganisms (Geobacter, Azospirillum and Dechlorobacter) was significantly improved. Network analysis revealed that Geobacter and Geothrix were potential hosts for MRGs. Therefore, the horizontal and vertical gene transfer of ARGs could be increased by the applied voltage, leading to the enriched ARGs at the electrode biofilm. This study provides evidence and insights into the transmission of ARGs between anolyte and biofilm microbes in MEC system. SYNOPSIS: This study revealed the effect of applied voltage on ARGs in MEC and the potential migration mechanism of ARGs.