Disrupting manure-to-soil transmission of antibiotic resistance genes: the role of gamma irradiation and hydrogen peroxide co-treatment

The application of untreated livestock manure poses significant risks for disseminating antibiotic resistance genes (ARGs) in agricultural ecosystems, yet the mechanisms underlying risk mitigation through manure pretreatment remain poorly understood. Here, we systematically evaluated the synergistic effects of gamma irradiation and hydrogen peroxide on ARG dynamics in chicken manure and it amended soils. Integrated metagenomic analysis and soil microcosm experiments revealed that the combined treatment achieved the greatest reductions in both the abundance and diversity of ARGs and mobile genetic elements (MGEs), outperforming individual treatments. Specifically, in the fertilizer, the ARGs and MGEs in the combined treatment were reduced by 29.47% and 24.25%, respectively, compared to control. The intervention selectively depleted ARG-harboring taxa, including Cellvibrio, Alicyclobacillus, and Chitinophaga, while concurrently suppressing microbial functions critical to ARG dissemination-particularly biofilm formation, membrane transport (ABC transporter genes), and SOS response pathways. Soil application of pretreated manure maintained ARG suppression via reconstructuring of functional pathways, with structural equation modeling identifying microbial community shifts as the primary driver. These findings provide a mechanistic basis for physical-chemical manure pretreatment, highlighting gamma irradiation/hydrogen peroxide co-treatment as an effective strategy to disrupt manure-to-soil ARG transmission while preserving agricultural value.