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.