Extreme climatic events drive consistent and predictable shifts in soil antibiotic resistance genes.

Abstract

Antimicrobial resistance (AMR) is a growing One Health challenge, and as climate warming intensifies extreme events, it remains unclear how these disturbances affect soil antibiotic resistance genes (ARGs). Here we analyzed the data from a controlled experiment using soils from 30 grassland sites across ten European countries, which simulated drought, flooding, freeze-thaw, and heatwaves to explore ARG dynamics. Overall, ARGs exhibited relatively small but highly consistent shifts across treatments. Heatwaves caused the strongest reductions in ARG abundance and in their linkages with mobile genetic elements (MGEs), a pattern that may reflect a hypothesized metabolic-genetic trade-off, in which microbial investment may shift from core metabolism toward stress signaling and structural maintenance. ARG dynamics during and after disturbance were governed by distinct soil physicochemical properties, with temperature and nutrient status determining acute responses, whereas soil moisture and seasonal variability in temperature and precipitation shaped longer-term legacy effects. Cross-validated random-forest models showed positive predictive performance for Bray-Curtis-based compositional responses within the environmental range represented by the 30 grassland sites. Our findings enhance the understanding of how soil ARGs respond to extreme climatic events and provide a step toward predicting extreme-event impacts on soil resistomes with relevance to One Health.