B FRAGILIS OXYGEN STRESS RESPONSE AND INFECTION

描述（改编自申请人的摘要）：厌氧的 脆弱拟杆菌对有毒的 氧和其他氧化应激的影响。这种阻力可以是 氧化应激反应（OSR）的诱导， 反应将进行研究，以记录其在发病机制中的作用， 脆弱拟杆菌感染。预计新的机制， 自由基保护和新的抗氧化防御策略将 被发现。这一观点得到以下事实的支持：B。脆弱拟 很早就从其他真细菌中分化出来， 长时间暴露在氧气中生存的能力此外，由于这 是一种厌氧生物，它可能对氧气有严格的要求。 保护导致了独特的高度发展 保护性抗氧化剂。这项研究的长期目标是 了解基本的生理和遗传过程，负责 B的公差。脆弱的氧化应激，并确定如何这些 有助于致病。本提案的目标是：1）定义 并在蛋白质和遗传水平上表征OSR。起初， 注意力将集中在OSR的一个子集，对H2O2的耐受性， 过氧化物（HPR）。一组HPR基因将被克隆和分析， 这些数据将用于建立表达HPR蛋白的目录， 在氧化应激过程中。2)HPR调节子的调节 将初步研究使用模型系统采用过氧化氢酶 基因、katB.这将集中在转录调控和 氧化应激调节分子的鉴定。系统将 扩大到包括HPR基因，因为它们变得可用。第三章 确定HPR控制基因中的特定突变对 氧化应激的存活率。这些基因中的一个或多个的突变将 通过等位基因交换构建并测试其能力 在各种形式的氧化应激中存活。突变体将受到 各种生化测试，以确定其机制， 保护，例如DNA修复或大分子保护。4)调节器 负责控制HPR调节子的基因将被克隆， 将确定总体OSR。

DESCRIPTION (Adapted from the Applicant's Abstract): The anaerobic organism, Bacteroides fragilis is exceptionally resistant to the toxic effects of oxygen and other oxidative stress. This resistance can be attributed to induction of an oxidative stress response (OSR) and this response will be studied to document its role in the pathogenesis of Bacteroides fragilis infection. It is expected that new mechanisms of free radical protection and novel antioxidant defense strategies will be uncovered. This idea is supported by the fact that B. fragilis diverged very early from other eubacteria and has independently evolved the ability to survive extended exposure to oxygen. Further, since this is an anaerobe, it is likely to have stringent requirements for oxygen protection that have resulted in the development of unique highly protective antioxidants. The long term goals of this research are to understand the basic physiological and genetic processes responsible for tolerance of B. fragilis to oxidative stress and to determine how these contribute to virulence. The objectives for this proposal are: 1) Define and characterize the OSR at the protein and genetic levels. Initially, attention will focus on a subset of the OSR, resistance to H2O2 and peroxides (HPR). A set of HPR genes will be cloned and analyzed, and these data will be used to establish a catalog of HPR proteins expressed during the course of oxidative stress. 2) Regulation of the HPR regulon will be studied initially using a model system employing the catalase gene, katB. This will focus on transcriptional regulation and the identification of oxidative stress regulatory molecules. The system will be expanded to include the HPR genes as they become available. 3) Determine the effect of specific mutations in HPR-controlled genes on survival to oxidative stress. Mutants in one or more of these genes will be constructed by allelic exchange and tested for their ability to survive various forms of oxidative stress. Mutants will be subjected to a variety of biochemical tests to determine their mechanism of protection e.g. DNA repair or macromolecule protection. 4) The regulator responsible for control of the HPR regulon will be cloned and its role in the overall OSR will be determined.