Research led by Meizhen Wang from Zhejiang Gongshang University has discovered that natural plant extracts can effectively reduce the risks posed by human bacterial pathogens (HBPs) in manure-amended soils. Published on 26 November 2025 in the journal Biocontaminant, the study reveals that these extracts interfere with bacterial quorum sensing, a critical communication process that enables pathogens to coordinate their harmful activities.
The application of manure is a common agricultural practice to maintain soil fertility and enhance crop yields. However, this practice carries the risk of introducing HBPs, which may harbor antibiotic resistance genes (ARGs) and virulence factor genes (VFGs). These genes can spread through mobile genetic elements (MGEs), leading to potential risks for both ecosystems and human health. Current mitigation strategies, including biochar and engineered nanoparticles, can be effective but often come with high costs and environmental concerns.
Plant extracts, known for their roles in soil remediation and plant protection, present a promising alternative. Despite their potential, the impact of these extracts on soil-borne human pathogens has been largely unexplored until now.
Study Findings and Methodology
Wang’s team conducted a systematic examination using manure-amended soil microcosms, metagenomic profiling, and targeted gene quantification. The study identified a total of 323 HBPs from a curated pathogen database and analyzed changes in their abundance, community composition, and diversity after treatment with three plant-derived compounds: curcumin (CUR), andrographolide (AG), and thymol (THY).
The researchers also quantified ARGs, VFGs, and MGEs to evaluate pathogenicity and transmission potential. Co-occurrence network analysis identified high-risk pathogens that co-host resistance and virulence traits. The study revealed that the plant extracts reduced total HBP abundance by approximately 25–28% and selectively suppressed pathogens associated with Actinobacteria and Proteobacteria.
In parallel, the analysis indicated significant reductions in key risk indicators: ARGs decreased by about 20–27%, VFGs by 6–11%, and MGEs by 25–34%. These findings highlight a strong correlation among these elements, with network analysis showing marked declines in high-risk HBPs that co-host ARGs and VFGs.
Mechanisms of Action
The mechanisms by which plant extracts exert their effects were elucidated through a detailed analysis of quorum sensing (QS) related genes and signal molecules. The results demonstrated that plant extracts disrupted QS by reducing the abundance of QS genes and concentrations of acyl-homoserine lactone signals. This led to downregulation of QS-regulated genes, resulting in decreased virulence factor secretion, a 40% inhibition of biofilm formation, and up to 90% suppression of conjugative ARG and VFG transfer.
Molecular docking studies confirmed that the plant compounds bind to the QS receptor LasR with higher affinity than native signal molecules, effectively blocking bacterial communication. This suggests that the extracts mitigate risks associated with soil-borne pathogens primarily through disruption of microbial communication and gene exchange rather than direct bactericidal effects.
The findings of this research open a new avenue for environmentally friendly soil amendments that can help reduce the health risks associated with manure use. By disarming pathogens instead of killing them, these plant extracts may lower the selective pressure for antibiotic resistance, presenting a sustainable alternative to conventional methods.
Overall, this study provides critical insights into the role of plant-derived compounds in enhancing soil health and safeguarding food systems. The application of such natural solutions could significantly impact agricultural practices and public health strategies globally.
