Microbial-Mediated Degradation of Aflatoxin B1 in Agricultural Soil

Aflatoxin B1 (AFB1) is commonly present in agricultural soil and poses severe threats to soil ecosystems due to its high toxicity, yet its environmental fate and microbial-mediated degradation mechanisms remain insufficiently studied. In this study, the environmental behavior of AFB1 in an agricultural soil was investigated. Metagenomic analysis showed that exposure to a higher concentration of AFB1 (5.0 mg kg^-1) altered soil bacterial community structure and reduced community diversity. After 30 days of incubation, AFB1 was slowly removed from natural soil microcosms but persisted in sterilized soil microcosms, indicating that indigenous soil microorganisms make a major contribution to AFB1 dissipation. Exposure to high-concentration AFB1 significantly enriched the genus Nocardioides, and a novel AFB1-degrading strain, Nocardioides sp. N13 (phylum Actinomycetota), was isolated from the agricultural soil. Strain N13 harbors three genes encoding putative F₄₂₀H₂-dependent reductase (FDR) homologs, which are hypothesized to be involved in the initial degradation of AFB1. Bioinformatics analysis revealed that putative FDR homolog-carrying bacteria are mostly assigned to the phylum Actinomycetota and are widely distributed across diverse soil environments worldwide. These findings provide a theoretical basis and potential microbial resources for mitigating AFB1 contamination in soil ecosystems.