Edaphic Gradients Reshape Microbial Microenclaves Assembly within Plastispheres

Microplastics create unique microbial habitats known as plastispheres, functioning as embedded "micro-enclaves" in soil ecosystems. However, their assembly mechanisms and ecological implications remain poorly understood. Here, we sampled microplastics and adjacent soils at 27 urban wetland sites in Changsha, China, to sequence bacterial communities and assess their assembly processes and environmental drivers. Plastispheres selectively recruit soil bacteria, with bacterial richness representing only 51.6-69.3% of that in adjacent soils despite positive correlations with source communities. Improved nutrient availability and favorable hydrothermal conditions within plastispheres reduce dispersal limitation while enhancing homogenizing selection. Network analysis indicates stronger positive correlations and greater structural robustness, reflecting niche consolidation in these confined microhabitats. Moreover, KEGG-based functional predictions reveal intensified redox-driven metabolism, where degradation of recalcitrant organics (e.g., xenobiotics, lipids and phosphonates) is inferred to supply electrons for nitrate/nitrite reduction─a coupling amplified under nitrate-enriched, well-aerated conditions. These findings collectively establish plastispheres as self-contained "micro-enclaves", where local environmental and edaphic factors reshape microbial community and functions. They deepen our understanding of plastisphere-mediated biogeochemical processes and pollution mechanisms, thereby providing a scientific basis for conserving and managing wetland ecosystem health.