Heavy Metal-Induced Co-Selection for Antibiotic Resistance in Terrestrial Subsurface Soils

Abstract

Background: Terrestrial surface ecosystems are important sinks for antibiotic resistance genes (ARGs) due to the continuous discharge of contaminants from human-impacted ecosystems. However, factors determining the abundance and resistance types of ARGs in terrestrial subsurface soils remain largely unknown. In this study, we investigated the abundance and diversity of ARGs, and their correlations with metal resistance genes (MRGs), mobile genetic elements (MGEs), bacteria, and heavy metals in subsurface soils in a global scale using high throughput quantitative PCR and metagenomic sequencing approaches. Results: Abundant and diverse ARGs were detected with high spatial heterogeneity among the sampling sites. Vertically, there was no significant difference in the ARG profiles between the aquifer and non-aquifer soils. Heavy metals were the key factors shaping ARG patterns in soils with high heavy metal contents, while they induced no significant effect in low contents. Moreover, heavy metals could trigger the proliferation of antibiotic resistance by increasing MGE abundance or influencing bacterial communities. Metagenomic analysis also revealed the widespread co-occurrence of ARGs and MRGs, with heavy metals possibly aggravating the co-selection of ARGs and MRGs in soils with high heavy metal contents. Conclusions: This study highlighted the heavy metal-induced co-selection for ARGs and MRGs and revealed the occurrence of ARG pollution in terrestrial subsurface soils.

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“…The metagenomic analysis allows a correlation between antibiotic and biocide resistance genes, providing additional information on heavy metal-induced ARG co-selection (Wang et al, 2020). Cross-resistance and co-resistance are the main drivers for ARG co-selection.…”