Seasonal dynamics of plastic-degradation-associated microbiomes in an anthropogenically impacted Pearl River Estuary: A genome-resolved metagenomic study

Estuarine sediments are important sinks for plastic debris and potential reservoirs of microbial functions involved in plastic transformation. Here, metagenomic sequencing and genome-resolved analyses were used to characterize the seasonal distribution and environmental associations of microbial taxa and genes potentially associated with plastic degradation in the Pearl River Estuary. The screened taxa differed between wet and dry seasons, with Priestia and Staphylococcus showing higher relative abundances in the dry season, whereas Vibrio, Photobacterium, Methylobacterium, and Ralstonia were more abundant in the wet season. Microbial community dynamics were associated with variation in organic matter, pH, temperature, and nitrogen variables, with the leading environmental predictors differing between microbial communities and seasons. Genome-resolved analysis recovered 150 non-redundant medium- to high-quality metagenome-assembled genomes (MAGs), of which 42 carried putative plastic-degradation-associated gene homologs identified through comparison with PlasticDB. Approximately 60% of these 42 MAGs belonged to Pseudomonadota, and three Burkholderiaceae MAGs harbored multiple candidate homologs. KEGG annotations further identified genes related to alkane oxidation, fatty acid degradation, ester hydrolysis, and aromatic-compound metabolism, providing a broader metabolic context for these genomes. Together, these findings characterize seasonal variation in the screened microbial communities and identify candidate microbial hosts and genes for investigating plastic transformation in estuarine sediments.