Screening and isolation of polyethylene microplastic degrading bacteria from mangrove sediments in southern China.

Mangrove sediments in southern China are a large reservoir for microplastics (MPs). In particular, polyethylene microplastics (PE-MPs) are environmentally toxic and have accumulated in large quantities in these sediments, posing a potential threat to the overall mangrove and the organisms that inhabit it. We screened sediments from 5 mangrove sites and identified a potential source of PE-MP degrading bacteria. We purified the bacterial strains Acinetobacter venetianus E1-1, Serratia marcescens E1-2, Chryseobacterium cucumeris E1-3 and Bacillus albus E1-4 from P1 that were able to reduce the mass of the 75 μm PE-MPs substrate by 3.67 to 6.59 %, respectively and use it as a sole carbon source. The degradation was accompanied by surface deformation of the MPs and introduction of polar oxygen-containing carbonyl and carboxylic acid functional groups thereby decreasing the hydrophobicity of the substrate. Whole-genome sequencing of S. marcescens E1-2, the most effective degrader, revealed it possesses a variety of enzymes and metabolic pathways related to PE degradation. Our results indicated that the PE-MP degrading bacteria isolated from screened mangrove sediments represent an effective strategy for in situ MP pollution remediation and uncovering mechanisms associated with PE degradation.