Microbial biodegradation of polyethylene in estuarine sediments: metabolic pathways of Pseudomonas under denitrifying...

Estuarine sediments are major sinks for micro-polyethylene (mPE). Given the prevalence of anoxic, denitrifying conditions in these habitats, aerobic mPE biodegradation is likely inhibited. However, the microorganisms and metabolic pathways responsible for anaerobic mPE biodegradation under denitrifying conditions remain largely unknown. Here, we employed multiple approaches integrating microcosm incubations, microbial community profiling, pure-culture validation, and metabolomics to elucidate these mechanisms. Microcosm experiments revealed that nitrate amendment significantly enhanced mPE degradation and reshaped the plastisphere community, enriching denitrifiers like Pseudomonas spp. Community analysis identified Pseudomonas as a core plastisphere taxon. Consequently, we isolated Pseudomonas sp. C1 from plastics, confirming its ability to mineralize mPE under denitrifying conditions. Untargeted metabolomics indicated that Pseudomonas sp. C1 undergoes extensive metabolic reprogramming for mPE biodegradation, marked by significant enrichment in key pathways including biotin metabolism, pantothenate and CoA biosynthesis, and β-alanine metabolism. These findings decipher the key microbial taxa and biochemical mechanisms of denitrifying mPE biodegradation, providing novel insights into the environmental fate of plastics in estuaries and informing future bioremediation strategies.