十字花科黑腐病菌聚量感應抑制物質之篩檢及應用

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題名:	十字花科黑腐病菌聚量感應抑制物質之篩檢及應用
作者:	胡若梅
貢獻者:	健康學院生物科技學系
關鍵詞:	十字花科黑腐病菌聚量感應擴散性訊息因子(DSF), rpf 基因串 Xanthomonas campestris quorum sensing diffusible signal factor (DSF) rpf cluster DSF-quenching molecule
日期:	2008
上傳時間:	2010-05-07 06:15:04 (UTC+0)
摘要:	十字花科黑腐病菌(Xcc)是一種桿狀、好氧性、能產生黃色素的革蘭氏陰性菌，它擁有一單極單鞭毛，是造成十字花科植物黑腐病的病原菌。Xcc 會分泌多種胞外酵素以及胞外黏多醣黃原膠。這兩類物質是細菌對植物感染的重要致病因子。黃原膠與胞外酵素的生成受到rpf 基因串的調控。rpf 基因串中的rpfF 基因可產生具擴散性訊息因子(DSF)到胞外，細菌族群內的個體可以偵測到DSF 的累積，並且依此來調節特定基因的表現，此現象稱為聚量感應。rpfG 和rpfC 基因產物則和聚量感應中的訊息傳遞有密切關係。 Xcc 主要的致病因子胞外酵素以及黃原膠的生產即受DSF 的正調控。rpfF的突變株失去產生DSF 的能力，同時喪失感染力。由這些資料可以推測抑制這種細菌間的溝通系統可以有效抑制細菌致病。本計劃前期已基於此策略，篩選有效抑制Xcc 聚量感應的天然萃取物，接下來一年將要並進一步測試此類物質的作用機制，以及其作為防治十字花科黑腐病菌藥物之可行性。 Xanthomonas campestris pv. campestris (Xcc) is a rod-shaped, aerobic, yellow-pigmented, gram-negative bacterium which possesses a single polar flagellum and is the causal agent of black rot in crucifers. Xcc produces a range of extracellular enzymes and an extracellular polysaccharide known as xanthan gum. Extracellular enzymes and xanthan are collectively required for bacterial pathogenicity. The production of these factors is regulated by a cluster of genes called rpf (for regulation of pathogenicity factors). rpfF is implicated in the synthesis of a diffusible regulatory molecule, DSF. Cells of the bacterial population can sense the accumulation of DSF and modulate expression of specific genes, a phenomenon called quorum sensing. RpfG and RpfC are involved in the signal transduction of DSF. Biosynthesis of the major Xcc virulence factors, such as extracellular enzymes and xanthan, are positively regulated by DSF. rpfF mutants can not produce DSF and lose the virulence. These data suggest that inhibition of this bacterial cell-cell communication system might efficiently block the microbial pathogenesis. Based on this strategy, we will find out the mechanism of Xcc quorum-sensing system and to identify effective Xcc quorum sensing quenching molecules. The preliminary result of the project showed that some plant extracts have anti-quorum sensing activity. The following work is to identify the mode of action of these extracts and evaluate the DSF-quenching molecules as a disease prevention drug of black rot in crucifers.
顯示於類別:	[生物科技學系] 科技部研究計畫

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