Antibiotic resistance gene (ARG) transmission poses significant threats to human health. The effluent of wastewater treatment plants is demonstrated as a hotspot source of ARGs released into the environment. In this study, a synthetic microbiome containing nuclease-producing Deinococcus radiodurans was constructed to remove extracellular ARGs. Results of quantitative polymerase chain reaction (qPCR) showed significant reduction in plasmid RP4-associated ARGs (by more than 3 orders of magnitude) and reduction of indigenous ARG sul1 and mobile genetic element (MGE) intl1 (by more than 1 order of magnitude) in the synthetic microbiome compared to the control without D. radiodurans. Metagenomic analysis revealed a decrease in ARG and MGE diversity in extracellular DNA (eDNA) of the treated group. Notably, whereas eight antibiotic-resistant plasmids with mobility risk were detected in the control, only one was detected in the synthetic microbiome. The abundance of the nuclease encoding gene exeM, quantified by qPCR, indicated its enrichment in the synthetic microbiome, which ensures stable eDNA degradation even when D. radiodurans decreased. Moreover, intracellular ARGs and MGEs and pathogenic ARG hosts in the river receiving treated effluent were lower than those in the river receiving untreated effluent. Overall, this study presents a new approach for removing extracellular ARGs and further reducing the risk of ARG transmission in receiving rivers.
Keywords: antibiotic resistance genes; extracellular DNA; extracellular nuclease; horizontal gene transfer; synthetic microbiome.