[Profiling of Antibiotic Resistance Genes in Different Croplands]

Soil is the primary interface of Earth's critical zone and plays an important role in food security and sustaining environmental balance. Antibiotic resistance genes (ARGs) pose significant threat to human health and ecosystems, with croplands being intensively affected via planting patterns and the application of fertilizers. The transmission of ARGs in croplands remains largely unknown. Using high throughput quantitative Polymerase Chain Reaction (HT-qPCR) techniques, we investigated the occurrence and diversity of ARGs and their association with heavy metals in different croplands in China. A total of 187 ARGs were identified, ranging from 89 to 159 in agricultural soils. The abundance of ARGs ranged from 6.47×10⁹ to 1.41×10¹⁰ copies·g^-1 with multidrug resistance genes being the most abundant. Heavy metals including As, Co, Cr, Mo, Ni, and Pb were correlated with ARGs using the R package 'evnfit'. Furthermore, redundancy analysis (RDA) revealed that the heavy metals explained 59.3% of the variability of ARGs in the different croplands, indicating that heavy metals might exert an important influence on the composition and transmission of ARGs. Croplands soils act as a vital reservoir and reaction media for ARGs. Different crop cultivation coupled with selection pressure of heavy metals from fertilizers could have potential impacts on the prevalence, diversity, and distribution of ARGs.