Electroplating Wastewater Treatment System: An Overlooked Reservoir of Antibiotic Resistance Genes

Abstract

The global electroplating industry generates huge amounts of metal-laden wastewater annually, necessitating a significant number of treatment plants to manage this waste. Metals can induce the expression of antibiotic resistance genes (ARGs) through multiple pathways, making metal-rich electroplating wastewater treatment systems potential overlooked ARG reservoirs. Given that antibiotic resistance is an increasing global threat to human health, exploring the distribution of ARGs and their enrichment mechanisms in electroplating wastewater treatment systems is important for controlling the risk of ARG transmission. This study focused on the largest electroplating wastewater treatment plant in South China, and utilized metagenomic techniques and statistical analysis to elucidate that the enrichment of ARGs (mainly Multidrug, Sulfonamide, and Bacitracin) in the electroplating wastewater treatment system was caused by metal accumulation in sludge and biomembranes, and by the co-selection of metal resistance genes. Co-occurrence relationship analyses suggested that the abundance of ARGs was highly correlated with the abundance of mobile genetic elements; thus, the system may be at risk of horizontal ARG gene transfer. Variation partitioning analysis and partial least squares path modeling analyses confirmed that metals were the most significant factors influencing changes in ARGs abundance. This study revealed, for the first time, the distribution of ARGs and their correlations with metals, metal resistance genes, mobile genetic elements, and microbes in an electroplating wastewater treatment system, thereby refreshing the knowledge of ARGs reservoirs, which is of great significance for controlling the risk of ARGs.