Heavy metals potentially drive co-selection of antibiotic resistance genes by shifting soil bacterial communities in paddy soils along the middle and lower Yangtze River

Abstract

Heavy metals (HMs) and antibiotic resistance have become serious environmental problems affecting soil and human health. Soil microorganisms play key roles in pollutant degradation and biogeochemical cycling processes; however, the interactions among HMs, soil microbial communities, and antibiotic resistance genes (ARGs) in agricultural soils remain unclear. Using quantitative real-time polymerase chain reaction and NovaSeq sequencing, we evaluated heavy metal contents, abundances of ARGs, soil bacterial community structure and functions, and their correlations in paddy soils at 43 sampling sites along the middle and lower reaches of the Yangtze River, central and eastern China. Our results showed the co-occurrence of HMs, ARGs, and HM resistance genes across all paddy soils. Additionally, significant positive associations were detected between HMs and resistance genes. Cadmium, czcA, and int1 were positively correlated with bacterial community diversity. The Mantel test showed that bacterial community composition and functions were significantly associated with HMs and resistance genes, such as Cd, Cr, Zn, copA, czcA, int1, and sul1. Moreover, HMs and ARGs were the major factors shaping soil bacterial communities; thus, HMs triggered proliferation of HM and antibiotic resistances by influencing the mobile genetic element (int1) and soil microbial communities. Our study revealed that HMs potentially drive the co-selection of ARGs by shifting soil bacterial community structure and functions, thereby increasing the potential risks to human health as well as ecological environment in the paddy soils along the middle and lower reaches of the Yangtze River.