Reshaping the antibiotic resistance genes in plastisphere upon deposition in sediment-water interface: Dynamic evolution and propagation mechanism

Microplastics (MPs) could provide unique niches for microbiota and aggravate their gravity, leading to vertical travel from waters to sediments. Although the plastisphere functions as hotspots for antibiotic resistance genes (ARGs) enrichment, the dynamic evolution and mechanisms of ARGs remain poorly understood when MPs deposited at sediment-water interface (SWI). Herein, this study investigated the dynamic response and reshaping mechanism of ARGs in plastisphere across SWI. It reveals that in deep waters, the ARGs abundance in biodegradable polylactic acid (PLA) plastisphere was higher than non-biodegradable polyethylene terephthalate (PET). However, when plastisphere deposited at SWI from deep waters, the ARGs abundance in PET plastisphere was increased by 45.71-65.10 %, while that decreased by 52.15-53.25 % in PLA. The plastisphere across SWI possessed higher species richness and diversity, more complex interactions, and more key species regulating ARGs compared to deep waters. During sedimentation, the horizontal gene transfer potential was enhanced in PET plastisphere but inhibited PLA. In addition, the function response related to oxidative stress response, cell membrane permeability, and energy metabolism may be underlying mechanisms in regulating ARGs propagation during the travel of plastisphere across SWI. This study highlights the critical roles of SWI in regulating the ARGs propagation in the traveling plastisphere.