Microbial community structure, function and environmental drivers of the urban soil plastisphere in a typical...

The plastisphere in urban soils remains poorly understood despite its potential ecological significance. Here, 42 samples, including 21 soil samples and 21 plastisphere samples, were collected from seven functional zones in Nanjing, and metagenomic sequencing, bioinformatics, and quantitative modeling with multisource geographic and soil data were employed to investigate the community structure, function and environmental drivers of the soil plastisphere in this typical megacity, China. Fungi, particularly Ascomycota and the genus Fusarium (LDA score = 4.73), exhibited stronger selective enrichment in the plastisphere than bacteria did, with this pattern being consistent across all functional zones, suggesting that the intrinsic properties of microplastics (MPs) govern taxonomic assembly. Plastisphere co-occurrence networks were simpler, more modular, and less robust than soil networks were, indicating that the structurally vulnerable microbial community was shaped predominantly by stochastic assembly (R² > 0.2). Functional analysis further revealed significant alterations in the characteristics of denitrification genes (napA, norB, and narH/narY/nxrB), suggesting modified nitrogen cycling potential. Critically, pollutants, especially MPs themselves, partially overrode geospatial and edaphic factors as direct drivers of plastisphere communities, representing fundamental decoupling from the natural environmental matrix governing bulk soil. Pollutants strongly negatively affected fungal compositions and networks in the plastisphere, amplifying the ecological hazards of coexisting contaminants. These findings revealed that MP pollution modified microbial community assembly in urban soils, creating a decoupled, pollutant-driven microbial system. Integrating these effects into urban environmental risk assessments is therefore urgently needed.