The Remediation Mechanism of Soil Atrazine Contamination by Vermicompost: A Metagenomic Perspective

Atrazine persistence poses serious environmental threats. This study used metagenomics and qPCR to elucidate the remediation mechanism of vermicompost in atrazine degradation pathways. Seven treatments were established: unsterilized soil (CKn); sterilized soil amended with 45 (SsV1), 60 (SsV2), and 75 (SsV3) days of vermicompost; and unsterilized soil with the same vermicompost (SnV1, SnV2 and SnV3). Vermicompost significantly restructured soil microbial communities. SsV1 exhibited the highest Proteobacteria abundance (51.38%), while SsV3 markedly increased Bacteroidetes abundance (10.34%). Functional annotation revealed that vermicompost enriched carbohydrate metabolism-related COG units and upregulated CAZymes (e.g., CE1 and CE10 families), providing energy support for degrading microbial communities. Regarding metabolic pathways, SnV2 exhibited the highest atrazine degradation abundance (2.94%), significantly enriching <i>Bauldia</i> (4.84 RPKM) for dechlorination. During cyanuric acid ring-opening, SnV3 significantly enriched <i>Pseudorhodoplanes</i> (12.14 RPKM). During terminal mineralization, SsV2 increased <i>Caenimonas</i> abundance (15.25 RPKM) and introduced the exogenous genus <i>Pseudorhodoplanes</i> (7.78 RPKM). qPCR confirmed SnV2's <i>trzN</i> (day 20) and <i>atzB</i> (day 40) reached 9.03 × 10⁴ and 6.95 × 10⁷ copies/g, respectively. These findings indicate vermicompost accelerated atrazine mineralization by enriching degradative microbial communities and promoting key functional gene expression, with 60-day vermicompost demonstrating superior performance. This study provides a robust theoretical framework for remediating atrazine-contaminated soil by vermicompost.