Drivers of metal resistance-virulence co-selection in landfill leachates

Metal resistance genes (MRGs) and virulence factor genes (VFGs) are driven by environmental factors and host immunity, respectively, and they are traditionally considered to evolve independently. However, their co-selection dynamics in landfill leachates remain poorly characterized. In this study, a multi-regional metagenomic assessment integrating environmental gradients was first presented to reveal how heavy metals shape MRG-VFG interactions and associated ecological risks in landfill leachates.

Landfill leachates were collected from 13 landfills spanning six regions in China. Multi-regional metagenomic sequencing combined with co-occurrence network analysis was applied to examine pathogen-gene relationships. The results revealed pronounced regional disparities in pathogen, MRG, and VFG distribution, alongside shared features. Staphylococcus aureus and Pseudomonas aeruginosa were identified as dominant pathogens. tufA and gyrA emerged as conserved VFGs, whereas arsB and copA represented dominant MRGs. Network analysis revealed Escherichia coli, Salmonella enterica, and Acinetobacter baumannii as central nodes carrying overlapping functional genes, forming a "metal resistance-virulence" synergy module. Redundancy analysis revealed that specific heavy metals (Cu, Zn, Cr, and As) were crucial for the formation and stability of "pathogen-MRG-VFG" functional assemblies.

This study addresses a critical knowledge gap by integrating multi-regional metagenomic evidence with environmental selection pressures. MRGs conferred survival advantages and synergized with VFGs to enhance pathogen infectivity. These findings provide insight into MRG-VFG co-selection mechanisms in landfill leachates and guide targeted monitoring to mitigate environmental and health risks.