PHAGE-ENCODED FUNCTIONS IN ENTEROHEMORRHAGIC E.COLI

说明(改编自应用程序) 这项研究的长期目标是了解温带的作用 噬菌体，以及噬菌体编码基因产物对 肠出血性大肠杆菌(EHEC)的毒力。EHEC正在出现 引起胃肠道大规模暴发的食源性病原体 在过去的二十年里，发达国家的疾病。肠道 感染可导致腹泻、出血性结肠炎或更严重的全身性 并发症，如溶血性尿毒症综合征。志贺酒的生产 EHEC菌株的毒素在重症肺炎的发生发展中起着重要作用 肠出血性大肠杆菌感染后的并发症。两种免疫学上截然不同的志贺菌 在临床大肠埃希菌中发现了毒素，命名为STX1和STX2 多种血清型的分离物。大肠杆菌中两种志贺毒素类型的基因都有 已被证明是在溶原性Lambdoid噬菌体上编码的。这些志贺 编码毒素的噬菌体在传播STX中发挥了重要作用 基因在产生STX的肠道病原体的进化过程中，并继续 参与志贺毒素基因向新宿主的持续传播。在……里面 此外，最近的研究表明，毒素基因似乎是 整合到这些噬菌体的裂解环路中 诱导导致毒素基因表达增加和伴随的释放 毒素由宿主细胞裂解。其中概述的实验的一个目的是 应用程序的目的是更清楚地定义噬菌体编码功能在 毒素基因的表达和毒素的释放。该应用程序的第二个目标是 研究其他噬菌体编码的基因，推测它们在 溶源转换。这些基因的产物可能会影响过程，例如 殖民或免疫逃避，这可能会导致 溶原菌。使用Stx2编码的噬菌体933W，它已经 全部测序后，个别基因的定向突变将被 建造的。这些突变对志贺毒素产生或其他的影响 与宿主细胞的相互作用将在体外进行评估，并对 使用小鼠模型系统的毒力将被确定。

DESCRIPTION (adapted from the application) The long-term goal of this research is to understand the role of temperate phages in, and the contribution of phage-encoded gene products to, the virulence of enterohemorrhagic Escherichia coli (EHEC). EHEC are emerging foodborne pathogens that have caused large-scale outbreaks of gastrointestinal illness in developed countries during the past two decades. Intestinal infection can lead to diarrhea, hemorrhagic colitis or more severe systemic complications, such as hemolytic uremic syndrome. The production of Shiga toxins by EHEC strains plays an important role in the development of serious complications following EHEC infection. Two immunologically distinct Shiga toxins, designated Stx1 and Stx2, have been identified among clinical E. coli isolates of many serotypes. Genes for both Shiga toxin types in E. coli have been shown to be encoded on lysogenic lambdoid bacteriophages. These Shiga toxin-encoding phages have played an important role in transmitting the stx genes during the evolution of Stx-producing enteric pathogens, and continue to be involved in ongoing dissemination of Shiga toxin genes to new hosts. In addition, recent studies have shown that the toxin genes appear to be integrated into the lytic circuitry of these phages in such a way that prophage induction leads to increased toxin gene expression and concomitant release of toxin by host cell lysis. One aim of the experiments outlined in this application is to define more clearly the roles of phage-encoded functions in toxin gene expression and toxin release. A second aim of the application is to investigate other phage-encoded genes that are postulated to play roles in lysogenic conversion. The products of these genes may affect processes, such as colonization or immune evasion, that could contribute to the virulence of lysogenic bacteria. Using the Stx2-encoding phage 933W, which has been sequenced in its entirety, directed mutations in individual genes will be constructed. The effects of these mutations on Shiga toxin production or other interactions with host cells will be assessed in vitro, and effects on virulence using a mouse model system will be determined.