Earthworms accelerated the degradation of the highly toxic acetochlor S-enantiomer by stimulating soil microbiota in repeatedly treated soils

This study investigated the effects of earthworms on the enantioselective degradation of chloroacetamide her-bicide acetochlor with soil microorganisms in repeatedly treated soils. The S-enantiomer degraded more slowly and exerted stronger inhibition on soil microbial functions than the R-enantiomer in single soil system. A syn-ergistic effect was observed between soil microorganisms and earthworms that accelerated the degradation of both the enantiomers, particularly the highly toxic S-enantiomer, which resulted in the preferential degradation of S-enantiomer in soil-earthworm system. Earthworms stimulated five potential indigenous degraders (i.e. Lysobacter, Kaistobacter, Flavobacterium, Arenimonas, and Aquicell), induced two new potential degraders (i.e. Aeromonas and Algoriphagus), and also significantly strengthened the correlations among these seven dominant potential degraders and other microorganisms. Notably, the relative abundances of Flavobacterium and Aero-monas in soil treated with earthworms for S-enantiomer were higher than those for R-enantiomer. Furthermore, earthworms significantly stimulated overall soil microbial activity and improved three microbial metabolic pathways, and xenobiotics biodegradation and metabolism, signal transduction, cell motility, particularly for the S-enantiomer treatment with earthworms, which alleviated the strong inhibition of S-enantiomer on microbial community functions. This study confirmed that earthworms accelerated the degradation of the highly toxic acetochlor S-enantiomer in soil, providing a potential approach in chloroacetamide herbicide-polluted soil remediation.

Automated summary

Earthworms accelerated the degradation of the highly toxic acetochlor S-enantiomer in soil by synergistically promoting the degradation of both enantiomers with soil microorganisms. The presence of earthworms stimulated potential indigenous degraders and enabled the preferential degradation of the S-enantiomer in the soil-earthworm system, ultimately improving soil microbial activity and metabolic pathways.