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Free Radicals onAging Microplastics Regulated thePrevalence of Antibiotic Resistance Genes in the Aquatic Environment:New Insight into the Effect of Microplastics on the Spreading of BiofilmResistomes

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Kaipeng Zhai (21353127), Keke Yin (19787777), Ying Lin (16144), Shu Chen (363692), Yuzhang Bi (21353130), Ruizhi Xing (8082527), Chenjia Ren (21353133), Ziyu Chen (1903933), Zhen Yu (203197), Zhi Chen (222749), Shungui Zhou (1659310)

Summary

Researchers investigated the effect of aged microplastics on antibiotic resistance gene dissemination in natural rivers, finding that aged MPs — which carry free radicals — suppressed ARG and mobile genetic element relative abundances on MP surfaces and in receiving water by approximately 21 to 42 percent over 30 days. The study provides new insight into how environmental aging of microplastics modifies their role as ARG 'hotspots' compared to pristine plastic particles.

The spread of antibiotic resistance genes (ARGs) by microplastics has received a great concern in coexisting “hotspots”. Despite most microplastics suffering from natural aging, little is known about the effect of aging microplastics (A-MPs) on ARGs dissemination. Here, we demonstrated significant suppression of A-MPs on ARGs dissemination in natural rivers. Although ARGs and mobile genetic elements (MGEs) were effectively enriched on A-MPs, the relative abundance of ARGs and MGEs on A-MPs as well as in receiving water decreased by approximately 21.4% to 42.3% during a period of 30 days of dissemination. Further investigation revealed that •OH was consistently generated on A-MPs with a maximum value of 0.2 μmol/g. Importantly, scavenging of •OH significantly increased the relative abundance of ARGs and MGEs both on A-MPs and in receiving water 1.4–29.1 times, indicating the vital role of •OH in suppressing ARGs dissemination. Microbial analysis revealed that •OH inhibited the potential antibiotic-resistant bacteria in surface biofilms, such as Pseudomonas and Acinetobacter (with a decrease of 68.8% and 89.3%). These results demonstrated that •OH was extensively produced on A-MPs, which greatly reduced both the vertical and horizontal gene transfer of ARGs. This study provided new insights into the dissemination of ARGs through microplastics in natural systems.

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