Plastic-mediated alterations in soil microbial networks and their role in sulfamethazine degradation

The spatiotemporal co-accumulation of plastics and antibiotics in the environment drives structural changes in soil microbial communities, thereby affecting their antibiotic resistance and metabolic functionality. However, the selection and colonization of microorganisms with antibiotic-degrading capabilities in soil plastisphere remain insufficiently understood. In this study, we utilized high-throughput sequencing and DNA-stable isotope probing (DNA-SIP) to examine the influence of polyethylene (PE) on the biodegradation of sulfamethazine (SMZ) and to identify the taxonomic affiliations of SMZ-degrading bacteria in plastisphere. Our results revealed that the presence of plastic reduced soil bacterial diversity, significantly altered microbial community composition (P < 0.01), and weakened the stability of the soil ecological network. Proteobacteria and Actinobacteria were selectively enriched in the plastisphere, resulting in a 25.05 % increase in soil SMZ residues. A total of 38 genera were identified as potential SMZ degraders in the plastisphere, including Nocardioides, Oryzihumus, and Streptomyces. Of these, nine genera-such as Methylobacterium-Methylorubrum, unclassified Nocardioidaceae, and Myxococcaceae were uniquely active in SMZ degradation in the plastisphere. These findings demonstrate that plastisphere-associated microbial colonizers influence antibiotic degradation in soil, emphasizing their ecological significance and highlighting the broader impact of plastic pollution on the environmental fate of antibiotics.