In a 150-day microcosm experiment, simulated acid rain increased the persistence of Escherichia coli O157:H7 and triggered rapid genetic and phenotypic adaptation. The stress destabilized native microbial networks, weakening biotic resistance and creating ecological space for invasion. Surviving populations underwent major genomic remodeling, evolving into more persistent, more virulent strains with higher transmission potential.
Anthropogenic disturbances are reshaping ecosystems worldwide, generating selective pressures that can alter the ecology and evolution of environmental pathogens. Acid deposition is a globally distributed stressor known to disrupt soil chemistry, suppress microbial activity, and impair bacterial survival. Yet ecosystems are not passive: changes in pH also affect species interactions, potentially weakening the invasion resistance typically provided by complex native microbiomes. For emerging zoonotic pathogens such as E. coli O157:H7—commonly introduced into farmland through livestock manure—soil serves both as an environmental reservoir and a crucible for adaptation. Given these challenges, it is critical to investigate how acidification may influence pathogen persistence, evolutionary trajectories, and public-health risk.
A study (DOI:10.48130/newcontam-0025-0012) published in New Contaminants on 12 November 2025 by Peng Cai’s team, Huazhong Agricultural University, exposes an eco-evolutionary feedback loop through which pollution may generate more transmissible and lethal pathogens.
To uncover how environmental stress shapes the ecological success and evolutionary trajectory of E. coli O157:H7 in soil, the study first conducted a global-scale analysis of 2,874 soil metagenomes to identify environmental drivers of E. coli abundance, and then performed a 150-day soil microcosm experiment using simulated acid rain to track pathogen persistence, community responses, interaction-network restructuring, phenotypic evolution, genomic changes, and subsequent effects on plant transmission and host virulence. The metagenomic survey showed that E. coli occurs in nearly all soils worldwide and that pH is a key predictor of its ecological fitness, with abundance peaking in weakly acidic soils (pH ~5.0) and declining sharply toward alkaline conditions. Building on this macroecological pattern, microcosm experiments revealed that acid rain significantly slowed the decay of E. coli O157:H7 populations: pathogen abundance under mild acid rain remained up to 100-fold higher at day 30 and up to 7-fold higher by day 150 than under normal rainfall. Community sequencing demonstrated that acidification did not overhaul the phylum-level composition of native microbes, but co-occurrence network analyses showed pronounced simplification and destabilization of microbial interaction networks, including reduced nodes, edges, and modularity and increased negative correlations, indicating weakened biotic resistance and greater ecological opportunity for pathogen persistence. Phenotypic assays of isolates recovered after 150 days showed that acid rain selected for strains with shorter lag phases, altered metabolism, enhanced biofilm formation, and lineage-specific changes in motility, which together increased soil colonization by 6–450 fold. Gene-expression profiling further revealed coordinated upregulation of motility, biofilm, quorum-sensing, and virulence genes, while whole-genome sequencing identified large chromosomal inversions and deletions—including loss of the Rcs phosphorelay system—that likely accelerated adaptation. Finally, functional assays demonstrated that these evolved strains exhibited 5–8-fold greater transmission to lettuce and up to 5-fold higher lethality in mice, confirming that environmental stress simultaneously enhanced environmental persistence, cross-kingdom transmission, and pathogenicity.
The findings establish a direct mechanistic link between industrial pollution and the emergence of more dangerous pathogens. Acid rain does not simply stress microbial communities; it can restructure ecological networks in ways that promote pathogen invasion, accelerate adaptive evolution, and enhance cross-kingdom transmission. For agriculture, this suggests that soil acidification may increase the contamination risk of fresh produce. For public health, the research demonstrates that environmental reservoirs can act as training grounds where pathogens evolve enhanced virulence before reaching human hosts.
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References
DOI
10.48130/newcontam-0025-0012
Original Source URL
https://doi.org/10.48130/newcontam-0025-0012
Funding information
This work was financially supported by the National Natural Science Foundation of China (42225706, 42177281), and the Natural Science Foundation of Hubei Province of China (460324005).
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