Antibiotic resistance genes, bacterial communities, and functions in microbial fuel cell constructed wetlands: Response to co-stress of antibiotic and zinc
The effects of continuous accumulation of Zinc (Zn) on the fate of ARGs in microbial fuel cell constructed wetland (CW-MFC) remain unclear. In this study, the impacts of Zn addition and circuit mode on antibiotic removal, occurrence of ARGs, bacterial community, and bacterial functions were investigated in three groups of CW-MFC. Continuous Zn exposure enriched the target ARGs in the initial process, while excessive Zn accumulation decreased antibiotic removal and the abundance of ARGs. Principal component analysis demonstrated that ARGs and bacterial community distribution characteristics were significantly impacted by mass accumulation of antibiotics and Zn as well as circuit mode. Redundancy analysis, Partial Least Squares Path Modeling, and Procrustes analysis revealed that the accumulation of antibiotics and Zn, the composition of bacterial community, circuit mode and the abundance of intI associated with horizontal gene transfer can jointly contribute to the distributions of ARGs in electrodes and effluent. Moreover, the continuous exposure to Zn can decrease bacterial diversity and change the composition and function of the bacterial community predicted by PICRUSt tool. Co-occurrence of ARGs, their potential hosts and bacterial functions were further revealed by network analysis. Variation partition analysis also showed that accumulation of target pollutants and circuit mode greatly impacted bacterial community composition and functions. Therefore, the interaction among ARGs, the bacterial community, bacterial functions and pollutants accumulation in CW-MFC was complex, and the study will provide useful implications for the application of CW-MFC in the treatment of wastewater contaminated with antibiotics and heavy metals.