Research led by Meizhen Wang at Zhejiang Gongshang University has revealed that plant-derived compounds can significantly reduce the risks posed by human bacterial pathogens in manure-amended soils. The study, published on November 26, 2025, in the journal Biocontaminant, highlights a novel method of interference with bacterial communication rather than directly killing bacteria.
Using manure is critical for maintaining soil fertility and boosting crop yields. However, it can introduce human bacterial pathogens (HBPs) into agricultural environments, which may carry antibiotic resistance genes (ARGs) and virulence factor genes (VFGs). These genes can spread through mobile genetic elements (MGEs) like plasmids, posing significant risks to ecosystems and human health. Traditional mitigation strategies, such as biochar or engineered nanoparticles, can be effective but often raise environmental concerns and are costly.
The study explored the effects of three representative plant-derived compounds—curcumin, andrographolide, and thymol. Using microcosms of manure-amended soil, the researchers combined metagenomic profiling, targeted gene quantification, pure-culture assays, and molecular docking analyses. They aimed to understand how plant extracts impact HBPs and their associated risks in agricultural soils.
A total of 323 HBPs were identified from a curated pathogen database. Following treatment with the plant extracts, the research team assessed changes in the abundance, community composition, and diversity of these pathogens. The results indicated that the extracts reduced total HBP abundance by approximately 25–28%, with a significant suppression of pathogens associated with Actinobacteria and Proteobacteria. The overall richness of microbial communities declined without significant changes in alpha diversity.
The study also quantified ARGs, VFGs, and MGEs to evaluate pathogenicity and transmission potential. Key findings showed that ARGs were reduced by about 20–27%, VFGs by 6–11%, and MGEs by 25–34%. Network analysis revealed a pronounced decline in high-risk HBPs that co-hosted ARGs and VFGs, demonstrating the effectiveness of plant extracts in mitigating microbial health risks.
Mechanistically, the plant extracts disrupted quorum sensing (QS), a critical communication system for bacteria. This disruption was evidenced by significant reductions in QS gene abundance and acyl-homoserine lactone signal concentrations, leading to a downregulation of QS-regulated genes. The study highlighted that the disruption resulted in 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 analyses confirmed that the plant compounds exhibited a higher affinity for the QS receptor LasR than native signal molecules. This competitive binding effectively blocked signal recognition and communication among bacteria. The findings suggest that plant extracts can serve as environmentally friendly soil amendments, addressing microbial health risks associated with manure use.
Unlike conventional antibiotics or nanomaterials, these plant-derived compounds operate by disarming pathogens rather than eliminating them. This approach reduces the selective pressure for resistance, offering a promising alternative for sustainable agricultural practices. The research underscores the potential of natural extracts in protecting soil health and mitigating the risks associated with HBPs.
This study was supported by funding from the ‘Leading Goose’ R&D Program of Zhejiang and the National Key R&D Program of China, alongside several grants from the National Natural Science Foundation of China. This research not only contributes to our understanding of soil health but also offers a pathway to safer agricultural practices.
