Silver nanoparticles alter the bacterial assembly and antibiotic resistome in biofilm during colonization

Abstract

Silver nanoparticles (AgNPs) are increasingly being discharged into freshwater systems, where they might encounter biofilm, and potentially affect the biofilm formation and structure. However, little is known about the effects of AgNPs on the microbial community assembly and antibiotic resistome during biofilm formation. In this study, we investigated the impacts of AgNP exposure on the microbial assembly and structure, and antibiotic resistance gene (ARG) profiles in the biofilm from microbial colonization to maturity. Both environmentally and clinically relevant levels of AgNPs significantly reduced the microbial community biomass and diversity during biofilm formation, particularly in the early stages of microbial colonization. In addition, AgNPs have the potential to profoundly accelerate the succession rate of microbiota and alter the microbial community structure during biofilm formation. Null model analyses indicated that the AgNP treatment tends to increase the ratio of the deterministic assembly process during the formation of biofilm microbial communities. Furthermore, exposure to AgNPs at a clinically relevant level (1 mg L⁻¹) could marginally change the overall profiles of ARGs and significantly increase the abundance of total ARGs in the biofilm. Procrustes analysis and structural equation models revealed a significant association between biofilm microbiota and ARGs. Taken together, these results indicate that AgNPs entering freshwater systems might have profound impacts on biofilm microbiota and antibiotic resistome, highlighting the potential ecological risks of nanoparticles.