Polyvinyl chloride microplastic triggers bidirectional transmission of antibiotic resistance genes in soil-earthworm systems
Houpu Zhang, Xueyi Zhang, Hao Sun, Hong Ling, Rui Xie, Liancheng Fang, Min Guo, Xiangwei Wu
Abstract
• Earthworm inoculation elevated the diversity and abundance of ARGs in soils. • PVC-MPs increased the abundance of ARGs in soil-earthworm gut systems. • ARGs could be interactively transmitted between earthworm gut and the dwelling soils. • PVC-MPs stimulated bidirectional transmission of ARGs in soil-earthworm systems. The diffusion and distribution of ubiquitous microplastics and antibiotic resistance genes (ARGs) in soil ecosystems are easily influenced by earthworm activity. However, minimal research exists on the bidirectional dissemination of ARGs in the soil-earthworm ecosystems under microplastic stress. Focusing on the typical microplastic polyvinyl chloride (PVC) microspheres in simulated soil-earthworm ( Eisenia fetida ) systems, we characterized the PVC-triggered interactive transmission of ARGs between earthworm guts and their dwelling soils using shotgun metagenomics and qPCR methodologies. PVC exposure did not alter the diversity and relative abundance of ARGs in earthworm-uninoculated soils but significantly increased those in earthworm-inoculated soils. Meanwhile, the abundance of ARGs increased in the earthworm gut under PVC stress. Source tracking analysis showed a higher source proportion of soil-borne ARGs into earthworm gut under PVC treatments. Mechanistically, PVC-triggered increasing prevalence of ARGs was significantly related to both the bacterial community and mobile genetic elements-mediated horizontal transfer in the soils, whereas the bacterial community predominated the process in the earthworm guts. Overall, our findings reveal a PVC-triggered bidirectional transmission pattern of ARGs between earthworm guts and their dwelling soils and highlight the overlooked ecotoxicological risk of microplastics in soil-earthworm systems.