ARGs under our feet

A new study reveals that urbanization is driving the emergence of increasingly sophisticated networks of antibiotic resistance genes (ARGs) in city soils. While bacterial diversity tends to decline in urban environments, the collection of resistance genes, known as the resistome, becomes richer, more interconnected, and more active.

Researchers, led by Cheng Gao at the Institute of Microbiology, Chinese Academy of Sciences, analyzed soil samples from 27 paired sites across China. Each pair compared relatively undisturbed forest soil with nearby land altered by human activity, including farmland, industrial zones, and urban areas. 

As human influence intensified, overall microbial diversity decreased and bacterial communities across different cities became more similar. However, the resistome followed the opposite trend: urban soils harbored significantly more diverse and complex resistance genes than forest soils.

The study also found evidence of heightened horizontal gene transfer — the process by which bacteria directly share genetic material, even across species. This mechanism allows resistance traits to spread rapidly. In urban soils, resistance-gene networks were denser and more robust, potentially making them harder to disrupt. A harmless soil bacterium carrying resistance genes could therefore transfer them to pathogenic species, increasing broader risks.

These findings highlight how urban development may create conditions that promote the accumulation and exchange of antibiotic resistance genes. While walking on city soil does not pose an immediate threat, the results underscore the role of urban environments in shaping the global resistome. With drug-resistant infections already causing over one million deaths annually, understanding and managing these underground networks will be critical for future public health strategies.

[Gao, C., et al. (2026). Urbanization drives increased complexity and connectivity of antibiotic resistance gene networks in soil. Communications Earth & Environment. DOI: 10.1038/s43247-026-03751-1]