Suraya Hamid (2009) Inhibition of quorum sensing controlled virulence factors in escherichia coli 0157-H7 by dietary plant extracts. Masters thesis, Universiti Malaysia Sabah.
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Abstract
Quorum sensing (QS) is a cell-to-cell communication mechanism in bacteria that regulates gene expression in response to cell population density, mediated by signal molecules known as autoinducers. Pathogenic bacteria such as Escherichia coli O157:H7 utilize quorum sensing to regulate virulence genes, contributing to infection processes. This study screened several ethanol-based plant extracts—namely garlic (Allium sativum), sand ginger (Kaempferia galanga), pandan leaves (Pandanus amaryllifolius), and kaffir lime leaves (Citrus hystrix)—for potential quorum sensing inhibition. Using the acyl-homoserine lactone (AHL) reporter strain Chromobacterium violaceum, all extracts demonstrated the ability to inhibit or modulate violacein production at sub-lethal concentrations, suggesting interference with quorum sensing-regulated phenotypes. The extracts significantly reduced E. coli O157:H7 swarming motility and modulated biofilm formation, indicating a quorum sensing inhibitory effect. However, quantitative expression analysis revealed that extracts from betel leaves (Piper betle), garlic, sand ginger, and lemongrass (Cymbopogon citratus) induced luxS and QseC gene expression by 2- to 12-fold. These genes are associated with AI-2 synthase and AI-3 sensor kinase, respectively. This suggests that the active compounds likely target alternative genes within the quorum sensing regulatory network rather than directly inhibiting AI-2 or AI-3 pathways. These findings highlight the potential of certain plant-based compounds as natural QS modulators for therapeutic or food safety applications.
| Item Type: | Thesis (Masters) |
|---|---|
| Keyword: | Quorum sensing, Escherichia coli, Autoinducers, Chromobacterium violaceum |
| Subjects: | Q Science > QR Microbiology > QR1-502 Microbiology > QR75-99.5 Bacteria |
| Department: | INSTITUTE > Biotechnology Research Institute (BRI) |
| Depositing User: | DG MASNIAH AHMAD - |
| Date Deposited: | 29 Apr 2025 11:19 |
| Last Modified: | 29 Apr 2025 11:19 |
| URI: | https://eprints.ums.edu.my/id/eprint/43597 |
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