New insights on municipal solid waste (MSW) landfill plastisphere structure and function.

Plastisphere plays crucial role in global carbon and nitrogen cycles and microplastics formation. Global Municipal Solid Waste (MSW) landfills contain 42 % plastic waste, therefore representing one of the most significant plastispheres. MSW landfills are also the third largest anthropogenic methane sources and the important anthropogenic NO source. Surprisingly, knowledge of microbiota and the associated microbial carbon and nitrogen cycles of landfill plastispheres is very limited. In this study, we characterized and compared the organic chemicals profile, bacterial community structure and metabolic pathway on plastisphere and the surrounding refuse in a large-scale landfill using GC/MS and 16S rRNA genes high-throughput sequencing, respectively. Landfill plastisphere and the surrounding refuse differed in organic chemicals composition. However, abundant phthalate-like chemicals were determined in both environments, implying the plastics additives leaching. Bacterial colonizing on the plastics surface had significantly higher richness than that in the surrounding refuse. Plastic surface and the surrounding refuse had distinct bacterial community composition. Genera of Sporosarcina, Oceanobacillus and Pelagibacterium were detected on the plastic surface with high abundance, while Ignatzschineria, Paenalcaligenes and Oblitimonas were rich in the surrounding refuse. Typical plastics biodegradation genus Bacillus, Pseudomonas and Paenibacillus were detected in both environments. However, Pseudomonas was dominant in plastic surface (up to 88.73 %), whereas Bacillus was rich in the surrounding refuse (up to 45.19 %). For the carbon and nitrogen cycle, plastisphere was predicted to had significant (P < 0.05) higher functional genes involved in carbon metabolism and nitrification, indicating more activated carbon and nitrogen microbial activity on the plastics surface. Additionally, pH was the main driver in shaping the bacterial community composition on plastic surface. These results indicate that landfill plastispheres serve as unique niches for microbial community habitation and function on microbial carbon and nitrogen cycles. These observations invite further study of the landfill plastispheres ecological effect.