Earthworm gut microbiome promotes biodegradation of albendazole in soil

The excretion of the anthelmintic drug albendazole (ALB) from treated animals into the soil, as well as its widespread application as a fungicide, poses a serious ecological risk to the soil environment. In this study, we investigated the degradation of ALB in soil and its bioaccumulation in earthworms, changes in the microbiome and degradation genes, and the effect of zinc oxide nanoparticles on the degradation and enrichment behaviors of ALB and microbial community structure and function. Our findings showed that ALB selectively enriched specific albendazole degradation genes (i.e., hmr and ami) in the earthworm, preferentially activating the pathways associated with sulfur reduction, amination of ALB sulfone, and hydroxylation of ALB. Metagenomic analysis revealed that the relative abundances of ppo, xylA, cutC, and nfsl in the earthworm gut were 0.19-52.64-fold higher in the ALB treatment than in the control, indicating their potential dominance in ALB biodegradation. Network analysis further identified potential bacterial hosts carrying biodegradation genes and albendazole degradation genes. Notably, Sphaerobacter, Saccharothrix, Actinomadura, and Nocardia were recognized as potential dual hosts of biodegradation genes and albendazole degradation genes, displaying a 0.05-1.32-fold elevation in relative abundance in ALB-treated earthworm guts compared to the control. Additionally, ZnO nanoparticles were found to reduce ALB bioaccumulation in earthworms and accelerate its dissipation in soil. These findings provide novel insights into the bioremediation mechanisms of pesticides in soil-earthworm ecosystems.