Novel YcbQ Pili of Enterohemorrhagic E. coli O157:H7

描述（由申请人提供）：肠出血性大肠杆菌（EHEC） O157:H7被认为是一种重要的新兴病原体，负责在人类中产生出血性结肠炎和溶血性尿毒症综合征（HUS）。肠出血性大肠杆菌O157:H7菌株产生一种强效志贺毒素，这种毒素与溶血性尿毒症的发病机制有关。在O157:H7菌株中尚未发现可重复的菌毛，因此，菌毛是否在其天然牛或偶然的人类宿主的肠道定植中发挥作用仍然是一个谜。我们最近鉴定并纯化了由EHEC菌株EDL933和其他O157:H7菌株产生的一种新的菌毛结构。这些毛由一个18 kDa的毛蛋白亚基组成，其氨基末端与EDL933染色体中含有的ycbQ基因的预测产物一致。序列比较分析表明，这些毛被称为YcbQ，属于毒力相关毛家族，由多种动物和人致病性大肠杆菌菌株中的F17、K99和G毛以及铜绿假单胞菌的CupA毛组成。通过序列同源性分析，EDL933基因组中有4个与F17家族亲缘关系基因同源的基因（ycbQ、ycbR、ycbS、ycbT），其中ycbQ为结构基因。总的来说，本研究的目的是通过阐明EHEC O157:H7粘附于培养的人上皮细胞的机制来推进对EHEC发病机制的了解。将梳理包括分子生物学、细胞生物学、高功率电子显微镜超微结构分析、生化和抗原分析在内的多学科方法，以扩展我们目前对肠出血性大肠杆菌O157:H7与宿主靶细胞相互作用的了解。这一建议的结果将为肠出血性大肠杆菌疾病的诊断和O157:H7在食物来源和储藏库中的检测提供重要意义。获得的信息将对肠出血性大肠杆菌感染的预防和控制策略具有重要意义。本研究的核心目标是：1)确定YcbQ菌毛生物发生所需的基因；2)明确YcbQ菌群的作用；3)研究ycb基因的转录表达。

DESCRIPTION (provided by applicant): Enterohemorrhagic E. coil (EHEC) O157:H7 is recognized as an important emerging pathogen responsible for producing hemorrhagic colitis and the hemolytic uremic syndrome (HUS) in humans. EHEC O157:H7 strains elaborate a potent Shiga toxin, which has been associated with the pathogenesis of HUS. No pili have yet been reproducibly identified in O157:H7 strains and therefore, it is still an enigma as to whether pili play a role in colonization of the intestine of their natural bovine or accidental human hosts. We have recently identified and purified a novel pilus structure produced by EHEC strain EDL933 and other O157:H7 strains. These pili are composed of an 18- kDa pilin subunit and its amino terminus shows identity to the predicted product of the ycbQ gene contained in the EDL933 chromosome. Sequence comparison analysis revealed that these pili, herein called YcbQ, belong to the virulence-associated pili family composed of F17, K99, and G pili found in several animal and human pathogenic E. coli strains, and CupA pili of Pseudomonas aeruginosa. Four genes (ycbQ, ycbR, ycbS, ycbT) with homology to F17 family piliation genes were identified by sequence homology in the genome of EDL933, being ycbQ the structural gene. Overall, the objective of this proposal is to advance knowledge of EHEC pathogenesis by elucidating the mechanism(s) of adherence of EHEC O157:H7 to human epithelial cells in culture. Several multidisciplinary approaches involving molecular biology, cell biology, ultrastructural analysis by high power electron microscopy, and biochemical and antigenic analysis will be carded out to extend our current knowledge on the interaction of EHEC O157:H7 with host target cells. The outcome of this proposal will provide important implications for diagnosis of EHEC disease and detection of O157:H7 in food sources and reservoirs. The information obtained will be important for prevention and control strategies of EHEC infections. The central focus of this proposal lies in the following specific aims: 1) To define the genes required for YcbQ pili biogenesis; 2) Define the role of YcbQ pili; and 3) Study transcriptional expression of ycb genes.