Lake plastisphere as a new biotope in the Anthopocene: potential pathogen colonization and distinct microbial functionality

The not-homogenous microplastics (MPs) distribution in freshwaters results in distinct microbial communities. Yet knowledge regarding plastisphere in metabolic pathways and element cycling behaviors remains limited. In this study, we collected MPs from 15 sampling sites in the Taihu Lake in China, and found that MPs were widely distributed in this freshwater lake, and dominantly composed of fibrous polyethylene terephthalate. Based on the metagenomic analysis, we found that MPs were colonized by Bacteroidia, Alpha-Proteobacteria, and Bacilli as a filter, but depleted in Verrucomicrobiae. Potential pathogens of plant eudicots and monocots were significantly enriched in plastisphere. Predicted functional profiles involved in the metabolism of other amino acids, biosynthesis of other secondary metabolites, and glycan biosynthesis and metabolism were overrepresented in plastisphere. Regarding elemental cycling, functional genes related to nitrogen fixation and nitrification showed 39.6% and 67.5% decline in plastisphere, whereas the genes involved in denitrification and nitrate reduction were significantly enriched. For sulfur cycles, the plastisphere exhibited higher sulfate reduction and sulfur oxidation system activities. Additionally, the taxonomic compositions and predicted functions in the plastispheres were mainly driven by the stochastic processes, while the deterministic processes were more important for the planktonic communities. The distinction in the microbial composition, the predicted functionality, and the underly mechanisms between plastisphere and planktonic communities illustrated the unique ecology of the new anthropogenic-related plastisphere ecosystems. Considering ever-increasing microplastic pollution in freshwater system, the impact of plastisphere on pathogens recruitment and biogeochemical cycling merits in-depth exploration. This study provides metagenomic insights into the enrichment of potential pathogens of eudicots and monocots in plastisphere communities, indicating their risks to ecological safety. Clarifying the importance of stochastic and deterministic processes for the assembly of taxonomic compositions and predicted functions greatly contributes to the understanding of ecological drivers controlling the plastisphere communities. The distinct communities, metabolic functions, and driving mechanisms for the microbiome in microplastics highlighted the unique ecological patterns of this new anthropogenic ecosystem system.