Rather than killing bacteria directly, the extracts interfered with bacterial quorum sensing—the signaling system that enables pathogens to coordinate biofilm formation, virulence, and gene transfer.
The use of manure is essential for sustaining soil fertility and crop yields, yet it can introduce human bacterial pathogens (HBPs) into farmland. These microbes may carry ARGs and virulence factor genes (VFGs), which can spread through mobile genetic elements (MGEs) such as plasmids. Once established in soil, HBPs can migrate into crops and the food chain, posing risks to ecosystems and human health. Existing mitigation approaches—such as biochar or engineered nanoparticles—can be effective, but they are often expensive or raise environmental concerns. Plant extracts, widely studied for soil remediation and plant protection, offer a promising natural alternative, though their effects on soil-borne human pathogens and gene transfer have remained largely unexplored.
A study (DOI:10.48130/biocontam-0025-0009) published in Biocontaminant on 26 November 2025 by Meizhen Wang’s team, Zhejiang Gongshang University, reveals that natural plant extracts can substantially reduce the risks posed by human bacterial pathogens in agricultural soils by disrupting how these microbes communicate and share harmful traits.
Using manure-amended soil microcosms combined with metagenomic profiling, targeted gene quantification, pure-culture assays, and molecular docking analyses, this study systematically examined how plant extracts influence HBPs and their associated risks in agricultural soils. A total of 323 HBPs were first identified from a curated pathogen database, and changes in their abundance, community composition, and diversity were assessed following treatment with three representative plant-derived compounds—curcumin (CUR), andrographolide (AG), and thymol (THY). In parallel, VFGs, ARGs, and MGEs were quantified to evaluate pathogenicity and transmission potential, supported by co-occurrence network analysis to identify high-risk pathogens co-hosting resistance and virulence traits. To elucidate mechanisms, quorum sensing (QS)–related genes and signal molecules were analyzed using metagenomic data, chemical measurements, and gene expression assays, while additional experiments quantified virulence factor secretion, biofilm formation, and conjugative gene transfer; molecular docking and binding affinity analyses were further applied to resolve interactions between plant compounds and QS receptor proteins. Corresponding to these approaches, the results showed that plant extracts reduced total HBP abundance by approximately 25–28% and selectively suppressed Actinobacteria- and Proteobacteria-associated pathogens, while overall richness declined without significant changes in alpha diversity. Key risk indicators were simultaneously attenuated, with ARGs reduced by about 20–27%, VFGs by 6–11%, and MGEs by 25–34%, and strong positive correlations observed among these elements. Network analysis revealed pronounced declines in high-risk HBPs co-hosting ARGs and VFGs. Mechanistically, plant extracts disrupted QS by lowering QS gene abundance and acyl-homoserine lactone signal concentrations, leading to downregulation of QS-regulated genes. These disruptions translated into reduced virulence factor secretion, up to 40% inhibition of biofilm formation, and as much as 90% suppression of conjugative ARG and VFG transfer. Molecular docking confirmed that plant compounds bind the QS receptor LasR with higher affinity than native signal molecules, competitively blocking signal recognition and bacterial communication, demonstrating that plant extracts mitigate soil-borne pathogen risks primarily by disrupting microbial communication and gene exchange rather than direct bactericidal effects.
The findings suggest that plant extracts could serve as environmentally friendly soil amendments to curb microbial health risks associated with manure use. Unlike antibiotics or nanomaterials, these compounds act by disarming pathogens rather than killing them, reducing selective pressure for resistance.
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References
DOI
10.48130/biocontam-0025-0009
Original Source URL
https://doi.org/10.48130/biocontam-0025-0009
Funding information
We acknowledge the financial support from the 'Leading Goose' R&D Program of Zhejiang (Grant No. 2024C03131), the National Key R&D Program of China (Grant No. 2022YFC3704600), and the National Natural Science Foundation of China (Grant Nos 22122607, U21A20292, 22376097, and 22306164).
About Biocontaminant
Biocontaminant is a multidisciplinary platform dedicated to advancing fundamental and applied research on biological contaminants across diverse environments and systems. The journal serves as an innovative, efficient, and professional forum for global researchers to disseminate findings in this rapidly evolving field.