Texture and Neonicotinoid Exposure Shape Bacterial Assemblages and Functions in Agricultural Soils: Responses Over Prolonged Exposure.

The physical and chemical properties of soil fundamentally shape its microbial communities. In a controlled 28-day microcosm experiment, we assessed bacterial community responses to imidacloprid in three soils with differing textures and classifications: a loamy sand (11 g/100 g clay; red Luvisol), a sandy loam (16 g/100 g clay; red Luvisol) and a clay soil (56 g/100 g clay, Vertisol). Analyses included 16S rRNA gene amplicon sequencing, indicator species analysis, co-occurrence network analysis and PICRUSt2-based functional prediction. Imidacloprid exposure elicited soil-specific shifts in bacterial community structure, primarily altering evenness rather than richness; however, overall diversity patterns were more strongly governed by soil texture and sampling time. Indicator species analysis identified distinct sensitive and tolerant taxa in each soil texture, with a core set of taxa remaining largely unchanged. Co-occurrence network analysis showed decreased network complexity and increased modularity under imidacloprid, particularly in loamy sand and clay soils, suggesting altered bacterial interaction patterns. Predicted functional profiles showed upregulation of stress-response pathways and downregulation of energy/nutrient metabolism pathways, implying a community-level shift toward stress adaptation. Although taxonomic richness remained relatively stable, these reorganisations of community interactions and functional potential suggest changes in bacterial resilience and biogeochemical cycling, which may have implications for long-term soil health.