十字花科黑腐病菌聚量感應誘發致病因子之機制研究

ASIA unversity > 醫學暨健康學院 > 生物科技學系 > 科技部研究計畫 > Item 310904400/9466

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題名:	十字花科黑腐病菌聚量感應誘發致病因子之機制研究
作者:	胡若梅
貢獻者:	健康學院生物科技學系
日期:	2006
上傳時間:	2010-05-07 07:44:08 (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。本計劃即基於此策略，藉由了解Xcc 聚量感應系統來尋找有效抑制Xcc 聚量感應的分子。其工作目標重點如下: (1) 確認聚量感應在細菌獨立生存以及感染狀態下對致病因子表現的調控角色; (2) 研究相類似菌種聚量感應之溝通訊息物質(即自誘導因子，DSF)在不同菌種間的作用情形; (3) 尋找有效抑制Xcc 聚量感應的訊息分子; (4) 研究此類物質作為防制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 isthe causal agent of black rot in crucifers. Xcc produces a range of extracellular enzymes andan extracellular polysaccharide known as xanthan gum. Extracellular enzymes and xanthanare 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 isimplicated 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, aphenomenon 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 andxanthan, 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 systemmight 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 sensingquenching molecules. The aims of this project are to (1) characterize the role ofquorum-sensing in the expression regulation of virulence factors in free-living Xcc or inbacteria under interaction with their host plants; (2) study the activity of exogenous signalingfactors (i.e. autoinducer or DSF) in different Xanthomonas species; (3) search for putative Xcc DSF-quenching molecules; (4) evaluate the DSF-quenching molecules as a diseaseprevention 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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