Comparative analysis of microbial colonization and degradation of low-density (LDPE) and high-density polyethylene (HDPE) microplastics

The global spread of microplastics (MPs) poses significant environmental risks, with polyethylene (PE) being the most common polymer found in ecosystems. While most research on MP contamination in agricultural soils focuses on pristine environments, microbial responses to PE-MPs under laboratory culture conditions with MPs as the sole carbon source remain poorly understood. This study examines the diversity, composition, and degradation potential of microbial communities colonizing low- and high-density polyethylene (LDPE and HDPE). Microbial diversity was initially lowest on LDPE but increased significantly over time, whereas HDPE sustained higher initial diversity that remained stable throughout the culture. Proteobacteria dominated all samples, with key plastic-degrading taxa such as Actinobacteriota and Bacteroidota playing critical roles. Co-occurrence networks indicated more complex microbial interactions on LDPE, suggesting stronger ecological cooperation. Degradation performance differed between polymers: HDPE showed more consistent removal and structural modification, facilitated by functional strains such as Stenotrophomonas maltophilia and Bacillus proteolyticus. These findings highlight how microbial community structure influences PE biodegradation and offer insights for bioremediation applications.