Degradation of polystyrene microplastics mediated by intestinal microorganisms of earthworms and exploration of functional strain resources

PS, one of the most extensively used synthetic polymers, persists in terrestrial ecosystems owing to its high chemical stability and inherent resistance to degradation. Yet, the biological mechanisms for its degradation remain unclear. This study investigated the degradation of PS-MPs mediated by intestinal microorganisms from two earthworm species, Eisenia fetida and Perionyx guillelmi . An integrative approach combining SEM, GC-MS, and microbial diversity analysis was applied to characterize alterations, identify degradation intermediates, and assess gut microbial dynamics. The PS-MP content in soil decreased progressively, achieving degradation efficiencies of 2.33 % on day 7 and 56.67 % on day 28. Three bacterial strains , Bacillus cereus, Klebsiella variicola, and Citrobacter portucalensis , exhibited PS degradation efficiencies of 2.33 %, 2.48 %, and 2.60 %, respectively. Collectively, our findings provide compelling evidence that the earthworm intestinal microbiota actively mediate the biodegradation of PS-MPs. These results elucidate a microbial biodegradation pathway and highlight earthworm microorganisms as promising biocatalysts for sustainable plastic bioremediation.