ROLE OF B.FRAGILIS OXYGEN STRESS RESPONSE IN INFECTION

描述（由申请人提供）：厌氧生物，脆弱拟杆菌对氧气的毒性作用具有特别的抵抗力。这种抗性可归因于氧化应激反应（OSR）的诱导，该反应将被研究以证明其在拟杆菌感染发病机制中的作用。我们期待着新的自由基保护机制和新的抗氧化防御策略的发现。脆弱芽孢杆菌很早就从其他真细菌中分化出来，并独立进化出了长时间暴露于氧气中的生存能力，这一事实支持了这一观点。此外，由于这是一种厌氧菌，它可能对氧气保护有严格的要求，这导致了独特的高保护性抗氧化剂的发展。本研究的长期目标是了解脆弱芽孢杆菌氧耐受性的基本生理和遗传过程，以及这些过程如何影响毒力。本研究的具体目标是：1)描述调控OxyR表达和功能的新机制。OxyR是一种氧化还原敏感的转录调节剂，控制OSR的表达。这一目的提出了追求独特的机制，通过氧r调节基因表达的分析。此外，我们将验证脆弱芽孢杆菌硫氧还蛋白系统是维持细胞氧化还原平衡的主要系统，因此它控制氧化应激反应调节蛋白（如OxyR）的氧化还原状态。2)表征Fur同源物在控制OSR中的作用。这一目的将验证脆弱芽孢杆菌中三个Fur同源物在氧化应激过程中需要保护的假设，因为它们调节金属（铁）稳态和其他OSR基因。3)阐明OSR在脆弱芽孢杆菌感染中的作用。这一目标将解决OSR对于感染的开始和在宿主中的持续是必要的假设。我们的方法由两个阶段组成，将在模拟感染的两个不同阶段的动物模型中检查OSR突变对生存的影响。了解氧耐受性可能有助于鉴定治疗脆弱芽孢杆菌感染的新抗生素靶点。例如，完全依赖硫氧还蛋白来控制氧化还原可能是一个弱点，可以被靶向硫氧还蛋白还原酶的药物所利用。

DESCRIPTION (provided by applicant): The anaerobic organism, Bacteroides fragilis is exceptionally resistant to the toxic effects of oxygen. 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 infections. 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 has diverged 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 B. fragilis oxygen tolerance and how these contribute to virulence. Specific objectives for this proposal are: 1) Delineate novel mechanisms that regulate expression and function of OxyR. OxyR is a redox sensitive transcriptional regulator that governs expression of the OSR. This aim proposes to pursue analysis of unique mechanisms through which OxyR regulates genes expression. In addition we will test the hypothesis that the B. fragilis thioredoxin system is the predominant system for maintaining the cellular redox balance and as such it controls the redox state of oxidative stress responsive regulatory proteins such as OxyR. 2) Characterize the role of Fur homologs in control of the OSR. This aim will test the hypothesis that the three Fur homologs in B. fragilis are required for protection during oxidative stress due to their regulation of metal (Fe) homeostasis and other OSR genes. 3) Elucidate a role for the OSR in B. fragilis infections. This aim will address the hypothesis that the OSR is necessary for initiation of infection and for persistence in the host. Our approach is composed of two phases that will examine the effect of OSR mutations on survival in animal models that mimic the two different stages of infection. Understanding oxygen tolerance may lead to identification of new antibiotic targets effective for treatment of B. fragilis infections. For example, exclusive dependence on thioredoxins for redox control may be a weakness that can be exploited by drugs targeted against thioredoxin reductase.