Research led by Meizhen Wang and his team at Zhejiang Gongshang University has revealed that plant-derived compounds can significantly reduce the risk posed by human bacterial pathogens (HBPs) in manure-amended soils. Published in the journal Biocontaminant on November 26, 2025, this study highlights a novel approach to managing pathogens without resorting to traditional bactericidal methods.
The issue at hand is the introduction of HBPs into agricultural lands through manure, which is critical for maintaining soil fertility and enhancing crop yields. These pathogens can carry antibiotic resistance genes (ARGs) and virulence factor genes (VFGs), leading to potential risks for ecosystems and human health. Current mitigation strategies, including biochar and engineered nanoparticles, are often costly or raise environmental concerns. Therefore, exploring natural solutions has become increasingly important.
Plant extracts have long been recognized for their potential in soil remediation and plant protection. This study systematically examined the effects of three representative plant-derived compounds—curcumin (CUR), andrographolide (AG), and thymol (THY)—on HBPs. Researchers used manure-amended soil microcosms, employing methods such as metagenomic profiling, targeted gene quantification, pure-culture assays, and molecular docking analyses to assess the impact of these extracts.
The team first identified a total of 323 HBPs from a curated pathogen database. Following treatment with the plant compounds, they observed a reduction in the total abundance of HBPs by approximately 25 to 28 percent. The study specifically noted a decline in pathogens associated with Actinobacteria and Proteobacteria, while overall richness decreased without significant changes in alpha diversity.
In addition to assessing pathogen abundance, the researchers quantified ARGs, VFGs, and mobile genetic elements (MGEs). They found that ARGs were reduced by about 20 to 27 percent, VFGs by 6 to 11 percent, and MGEs by 25 to 34 percent. The analysis also revealed strong positive correlations among these elements, indicating a complex interplay between resistance and virulence traits.
To uncover the mechanisms behind these effects, the team analyzed quorum sensing (QS)–related genes and signal molecules through a combination of metagenomic data, chemical measurements, and gene expression assays. Their findings demonstrated that plant extracts disrupted bacterial communication by lowering QS gene abundance and acyl-homoserine lactone signal concentrations. This led to downregulation of QS-regulated genes, which ultimately resulted in decreased virulence factor secretion and biofilm formation. Notably, the study reported up to 40 percent inhibition in biofilm formation and as much as 90 percent suppression of conjugative ARG and VFG transfer.
Molecular docking studies confirmed that the plant compounds bind to the QS receptor LasR with greater affinity than native signal molecules, effectively blocking signal recognition and disrupting bacterial communication. This innovative approach reduces the selective pressure for resistance associated with traditional antibiotics, highlighting the potential of plant extracts as environmentally friendly soil amendments.
The implications of this research are significant, suggesting that plant-derived compounds can serve as a sustainable alternative for managing microbial health risks linked to manure use. By disrupting microbial communication and gene exchange, these compounds offer a promising strategy to mitigate the threats posed by HBPs in agricultural soils without the adverse effects associated with chemical treatments.
This study was supported by funding from the ‘Leading Goose’ R&D Program of Zhejiang and the National Key R&D Program of China, among others. The findings not only advance our understanding of soil-borne pathogens but also pave the way for innovative agricultural practices that prioritize environmental health.
