Low Temperature Polyethylene Biodeterioration by Freshwater Microplastics-Associated Bacteria

Microplastics (MPs) are emerging contaminants that threaten ecosystems and human health. These particles host microbial biofilms that may include plastic-degrading bacteria, yet inland freshwater systems remain understudied, particularly under cold, environmentally relevant conditions. Here, 14 bacterial strains were isolated from MPs collected from a boreal lake and a glacier-fed river and evaluated for their ability to degrade low-density polyethylene (LDPE) at a low temperature. Several isolates removed up to 25% LDPE (w/w), formed biofilms, and caused surface deterioration. Chemical analyses detected alkanes, plastic additives, and oxidation products, indicating partial depolymerization of LDPE. Isolates’ genomes revealed few homologs of known plastic- or hydrocarbon-degradation genes, suggesting novel pathways. For the first time, Sanguibacter and Cryobacterium are identified as plastic-degrading bacteria. These findings show that freshwater MPs harbour cold-adapted bacteria capable of LDPE biodeterioration, advancing our understanding of the fate of microplastics and offering new biotechnological avenues for low-temperature plastic-waste mitigation.