CONTROL OF THE FIM SWITCH IN ESCHERICHIA COLI

这项建议的总体目标是了解遗传和 I型菌毛表达的环境控制。第一类菌毛是 与尿路感染相关的毒力因子在大肠杆菌和 很吸引人研究，因为它们是由极好的油井生产的 特征菌株K-12。通过研究K-12，我们将利用 这种菌株有广泛的遗传工具可用。流苏介导的 附着于宿主细胞被认为是感染的重要步骤。 菌毛使细菌能够继续附着在营养丰富的宿主上。 上皮细胞，尽管液体的流量不变。然而，菌毛是 此外-极佳的免疫原，以及显著的代谢消耗 细菌。因此，控制菌毛表达的能力 恰如其分地，这本身就可能是一个致命因素。建议数 研究将集中在DNA倒置(Switch)的控制上 与1型菌毛表达的位相变化相关。反转 的FIM开关需要FIMB(开到关或关到开)或FIME (仅限开关倒置)，可能编码FIM开关的基因 重组酶。利用分子生物学方法，我们打算分析 遗传和环境因素对FIMB和FIME的影响 转录和翻译，并直接在FIM开关上。这部电影 Switch还受到全球调节蛋白H-NS和LRP的影响 (亮氨酸反应调节蛋白)，这两种蛋白质显示出影响 其他毒力决定因素的表达。这项工作中提出的 提案可能会提供一个模型，用来比较对FIM的控制 在临床分离株中。此外，这项研究应该提供一个洞察 用于协调控制的遗传和环境信号 毒力因素。

The overall objective of this proposal is to understand the genetic and environmental control of type I fimbriae expression. Type I fimbriae are a virulence factor associated with urinary tract infections in E. coli and are attractive to study because they are produced by the extremely well characterized strain, K-12. By studying K-12, we will utilize the extensive genetic tools available in this strain. Fimbrially-mediated attachment to host cells is considered an important step in infection. Fimbriae enable the bacteria to remain attached to the nutrient-rich host epithelium despite the constant flux of fluids. Nevertheless, fimbriae are also-excellent immunogens, and a significant metabolic drain on the bacterium. Therefore, the ability to control fimbrial expression appropriately is likely a virulence factor in itself. The proposed research will focus on the control of the DNA inversion (switch) associated with phase variation of type 1 fimbrial expression. Inversion of the fim switch requires fimB (ON-to-OFF or OFF-to-ON inversion) or fimE (ON-to-OFF inversion only), genes that likely encode the fim switch recombinases. Using molecular biological approaches, we intend to analyze the influence of genetic and environmental factors on fimB and fimE transcription and translation, and on the fim switch directly. The fim switch is also influenced by the global regulatory proteins H-NS and Lrp (Leucine-responsive regulatory protein), two proteins shown to influence the expression of other virulence determinants. The work suggested in this proposal is likely to provide a model with which to compare control of fim in clinical isolates. Moreover, this study should provide an insight into the genetic and environmental signals used to coordinately control virulence factors.