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Temperature governs resistance assembly and dissemination in the freshwater plastisphere
Summary
Tiny plastic particles floating in rivers can become coated with bacteria, and this study found that water temperature strongly affects how much antibiotic-resistant bacteria grow on them and how easily they spread their resistance genes. Colder water tended to favor harmful bacteria, while warmer water—more common as climate change progresses—led to fewer disease-causing germs but made antibiotic resistance spread more efficiently among the bacteria that remained. This suggests that as rivers warm, the health risks from plastic pollution may change in complex ways rather than simply increasing or decreasing.
The enrichment of antibiotic resistance genes (ARGs) and pathogenic microorganisms on microplastics may pose potential risks to public health. In the context of ongoing global warming, however, the mechanisms governing the occurrence and dissemination of ARGs within the riverine plastisphere remain poorly understood. In this study, we investigated the effects of temperature on the plastisphere resistome by cultivating biofilms on PVC (φ = 3 mm) surfaces in river water at 5, 15, 25, and 35 °C. Our results demonstrate that temperature drives shifts in microbial community structure and thereby indirectly regulates ARG composition. Both increases and decreases in temperature enhanced the abundance and potential mobility of ARGs. At low temperatures, human-associated pathogens such as Pseudomonas fluorescens were enriched and predominantly carried ARGs associated with antibiotic efflux, contributing to elevated pathogenic risk. Under these conditions, ARG dissemination was largely governed by stochastic processes mediated by transposases. In contrast, higher temperatures favoured the enrichment of high-risk ARGs and promoted more stable dissemination through the increased prevalence of site-specific recombinases. Although pathogen diversity and abundance declined at elevated temperatures, the remaining hosts harboured ARGs spanning multiple resistance mechanisms. Collectively, these findings demonstrate that temperature is a key driver of both the composition and dissemination potential of the plastisphere resistome, and reveal a shift in ecological risk patterns under ongoing climate warming.