Elevated CO₂ Drives the Enrichment of Multidrug Resistance Genes in Paddy Soils

Antibiotic resistance genes (ARGs) are becoming a global issue due to the emergence of superbugs. However, the impact of elevated CO₂ (eCO₂) on the soil antibiotic resistome remains largely unknown. Here, using a free-air CO₂ enrichment platform, we employed high-throughput quantitative PCR and 16S rRNA gene sequencing to investigate the effect of eCO₂ (ambient + 200 ppm) on soil ARGs and bacterial communities in a paddy ecosystem at harvest. The results showed that eCO₂ had no significant effect on rice biomass. A LEfSe analysis identified a clear taxonomic shift, with taxa such as c_Clostridia, g_Dehalobacter and g_Syntrophus being significantly enriched under eCO₂. The total relative abundance of ARGs increased 1.5-fold under eCO₂, driven by a 2.8-fold increase in multidrug resistance genes. The correlation and network analyses revealed that the proliferation of specific potential host bacteria was the primary driver of the observed ARG enrichment under eCO₂. Together, this study offers new insights into the eCO₂-driven alterations of soil antibiotic resistomes, highlighting the elevated dissemination potential of multidrug resistance genes within paddy ecosystems and their potential implications for food safety.