Strong suppression of silver nanoparticles on antibiotic resistome in anammox process

This study comprehensively deciphered the effect of silver nanoparticles (AgNPs) on anammox flocculent sludge, including nitrogen removal performance, microbial community structure, functional enzyme abundance, antibiotic resistance gene (ARGs) dissemination, and horizontal gene transfer (HGT) mechanisms. After long-term exposure to 0-2.5 mg/L AgNPs for 200 cycles, anammox performance significantly decreased (P < 0.05), while the relative abundances of dominant Ca. Kuenenia and anammox-related enzymes (hzsA, nirK) increased compared to the control (P < 0.05). For antibiotic resistome, ARG abundance hardly changed with 0-0.5 mg/L AgNPs but decreased by approximately 90% with 1.5-2.5 mg/L AgNPs. More importantly, AgNPs effectively inhibited MGE-mediated HGT of ARGs. Additionally, structural equation model (SEM) disclosed the underlying relationship between AgNPs, the antibiotic resistome, and the microbial community. Overall, AgNPs suppressed the anammox-driven nitrogen cycle, regulated the microbial community, and prevented the spread of ARGs in anammox flocs. This study provides a theoretical baseline for an advanced understanding of the ecological roles of nanoparticles and resistance elements in engineered ecosystems. Silver nanoparticles (AgNPs) and antibiotic resistance genes (ARGs), as the most representative emerging contaminants, have exhibited growing global threat to public health and ecological safety. Anammox have been applied as an energy-efficient and carbon-neutral nitrogen removal technology in wastewater treatment processes. This study showed that AgNPs suppressed the anammox-driven nitrogen cycle and regulated the microbial community. Especially, AgNPs strongly inhibited the spread of ARGs via HGT mediated by MGEs, suggesting AgNPs could efficiently prevent the pollution of ARGs. Our finding highlighted a new insight into risk management of combined environment hazards from AgNPs and antibiotic resistome in engineered ecosystems.