New insights into microbial degradation of polyethylene microplastic and potential polyethylene-degrading bacteria in sediments of the Pearl River Estuary, South China

Microplastics (MPs) are widely distributed pollutants in various ecosystems, and biodegradation is a crucial process for removal of MPs from environments. Pearl River Estuary, one of the largest estuaries in China, is an important reservoir for MPs with polyethylene MPs (PE-MPs) as the most abundant MPs. Here, biodegradation of PE-MPs and the potential PE-degrading bacteria in sediments of eight major outlets of Pearl River Estuary were firstly investigated. Results showed that biodegradation extent of PE-MPs varied for different sourced sediments, with highest extent for Hongqimen sediment and lowest extent for Jitimen sediment. Selective enrichment of specific bacteria occurred on PE-MPs with Pseudomonadaceae as the predominant family. Potential PE-degrading bacteria of Pseudomonas, Vulcaniibacterium, Cupriavidus, Bacillus were selectively enriched on PE-MPs and their abundance showed positive correlations with degradation extent of PE-MPs, indicating a vital role of them in degrading PE-MPs. Diverse pure cultured strains affiliated to the genera Bacillus, Pseudomonas, Priestia, Lysinibacillus, Marinobacter, Stutzerimonas and Achromobacter isolated from the plastispheres were capable of degrading PE-MPs rapidly, and members in Bacillus showed highest efffeciency of PE-MPs degradation with 6.5 % weight loss of PE-MPs within 40 days. This study provides a new perspective on the natural degradation potential by microbial communities in sediments.