Microplastics affect nitrogen cycling and antibiotic resistance genes transfer of sediment

Microplastics are prevalent in freshwater, coastal, and deep ocean sediments. However, the effects of microplastics on sedimentary microbial ecosystems have not been well reported. Using 16S rRNA gene and metagenomic sequencing, we investigated coastal sedimentary sludge microbial community structure, composition, function, assembly, and propagation of antibiotic resistance genes (ARGs) in response to different microplastics. The nitrifier, denitrifiers and ammonia oxidizer were significantly altered upon microplastics exposure. The concentrations of NO3−, NO2−, and NH4+ in PE and PET treated groups were in consistent with relative abundances of corresponding functional genera. The increased antibiotic efflux ARGs abundance in PE, PET, and PVC groups was directly related to the promoted efflux pump system. Reactive oxygen species (ROS) production, ROS-mediated DNA damage, and increased stress response induced by microplastics exposure might be the reason for the promotion of ARGs transfer. Assembly of dominate nitrogen degrading genus and ARGs hosts tended to be deterministic under the pressure of microplastics, indicating the selective effect of microplastics.