Different effects of heterocyclic compounds on the diversity and functions of soil microbiota

Heterocyclic compounds are extensively used in pharmaceuticals and agrochemicals, yet their persistence and bioavailability in soil may disrupt microbial functions and ecosystem health. To address these impacts, we performed a metagenomic sequencing to assess the impact of three such compounds--cefapirin, pyrimethanil, and quinclorac on soil microbial communities at 15 and 30 d exposure. Our results revealed distinct compound-specific and time-dependent effects. Cefapirin initially induced minimal changes at 15 days but significantly reduced eukaryotic diversity and functional potential by 30 days, while also enriching virulence factors. Pyrimethanil strongly perturbed the community at 15 days, suppressing metabolic pathways and elevating the abundance of antibiotic resistance genes (ARGs) and virulence factors, along with consistently enriching mobile genetic elements (MGEs) associated with these genes-though some effects diminished by 30 days. Quinclorac exerted comparatively milder inducing subtle shifts in virulence factor profiles and exerting limited influence on antibiotic resistance gene abundance. Spearman correlation analysis linked compound-induced shifts in dominant microbial phyla (notably Pseudomonadota and Actinomycetota) to the dynamics of ARGs and virulence factors. These results underscore that the ecological risks of heterocyclic compounds depend critically on both compound properties and exposure duration. Our findings provide valuable insights for guiding risk assessment and sustainable practices to mitigate the ecological risks of agrochemicals.