Biodegradable microplastics induced the dissemination of antibiotic resistance genes and virulence factors in soil: A metagenomic perspective

Concerns about the ecological safety of both conventional and biodegradable microplastics have grown due to the inadequate end-of-life treatments of plastics. In this study, the effects of conventional and biodegradable microplastics on the spread of antibiotic resistance genes (ARGs) and virulence factors (VFs) were estimated in a soil microcosm experiment. The gene profiles and their respective bacterial hosts in soil were evaluated by metagenomic sequencing methods. The abundances of ARGs and VFs in polybutylene succinate (PBS) treated soils were statistically higher than the values in the control and conventional microplastic treatments. In comparison with the control, application of conventional microplastics showed negligible effects on ARG and VF profiles in the soil, while biodegradable microplastic amendments significantly changed the compositions of ARGs and VFs. The host-tracking analysis suggested application of microplastics broadened the bacterial hosts of ARGs and VFs in the soil. The percentage of Proteobacteria as ARG hosts increased from 38.5% in the control soils to 58.2% in microplastic exposed soil. The genus Bradyrhizobium was the dominant host of ARGs and VFs in biodegradable microplastic treatments, while conventional microplastics increased the percentages of Pseudomonas as the bacterial hosts. This study enhances the understanding of the effects of conventional and biodegradable microplastics on the propagation and hosts of ARGs and VFs in the terrestrial environment, providing essential insights into the risk assessment and management of plastics.