Regulation of S. aureus Colonization by NO.

 描述（由申请人提供）：全球约有20亿人感染了金黄色葡萄球菌，但其中只有少数人会出现侵袭性感染。本申请集中于一氧化氮（NO*）的作用，一氧化氮是一种分子介质，通过靶向蛋白质硫醇和金属中心来调节细菌生理学，在S.金黄色。我们将检验NO* 抑制毒力和调节S.金黄色。我们的初步观察表明，NO* 是一个关键的决定因素是否S。金黄色葡萄球菌与宿主存在稳定的寄生关系或成为入侵性病原体。具体目的是：（1）研究S.通过NO* 抑制金黄色葡萄球菌毒力基因-我们已经发现NO* 抑制侵袭性感染所需的毒力基因的表达。遗传和生物化学方法将确定外源NO* 如何抑制毒力基因表达，重点是AgrA、MgrA、SarR和SarS，这四种被NO* S-亚硝基化的中心转录调节因子。一种新的小鼠鼻腔定植模型将用于确定宿主来源的NO* 对S。金黄色葡萄球菌毒力基因的体内表达。(2)分析了S.金黄色葡萄球菌的微氧生理和NO* - S的定殖。金黄色葡萄球菌通过表达与哺乳动物NO* 氧化酶相关的酶（saNOS）产生其自身的NO*。我们已经发现，saNOS是需要从有氧呼吸到硝酸盐呼吸的微需氧过渡期间的氧化还原传感和小鼠的鼻腔定植。这一目标将使用表达和生物化学测定来测试一种新的机制模型，其中细菌衍生的NO* 转移电子传递到硝酸还原酶时，O2浓度是有限的。我们的小鼠模型将用于评估宿主和细菌来源的NO* 对S。金黄色葡萄球菌在体内定植。这些研究将确立NO* 作为一个至关重要的信号分子，使S。金黄色葡萄球菌适应宿主环境中的氧限制条件，同时通过调节毒力基因表达将其维持在一种可耐受的状态。

 DESCRIPTION (provided by applicant): Approximately two billion people are colonized with Staphylococcus aureus worldwide, but only a minority of these individuals will develop invasive infections. This application focuses on the role of nitric oxide (NO*), a molecular mediator that modulates bacterial physiology by targeting protein thiols and metal centers, during nasal colonization by S. aureus. We will test the hypothesis that NO* inhibits virulence and regulates microaerobic respiration in S. aureus. Our preliminary observations suggest that NO* is a critical determinant of whether S. aureus exists in a stable commensal relationship with the host or becomes an invasive pathogen. Our specific aims are to: (1) Assess the mechanism of S. aureus virulence gene inhibition by NO* - We have found that NO* inhibits the expression of virulence genes required for invasive infection. Genetic and biochemical approaches will determine how exogenous NO* inhibits virulence gene expression, focusing on AgrA, MgrA, SarR and SarS, four central transcriptional regulators that are S- nitrosylated by NO*. A novel murine nasal colonization model will be used to determine the effects of host-derived NO* on S. aureus virulence gene expression in vivo. (2) Analyze the regulation of S. aureus microaerobic physiology and colonization by NO* - S. aureus produces its own NO* by expressing an enzyme (saNOS) related to mammalian NO* synthases. We have discovered that saNOS is required for redox sensing during the microaerobic transition from aerobic respiration to nitrate respiration and for nasal colonization in mice. This aim will use expression and biochemical assays to test a novel mechanistic model in which bacterial-derived NO* diverts electron transport to nitrate reductase when O2 concentrations are limiting. Our mouse model will be used to assess the contribution of host- and bacterial-derived NO* to S. aureus colonization in vivo. These studies will establish NO* as a critically important signaling molecule that allows S. aureus to adapt to oxygen-limited conditions within the host environment while maintaining it in a commensal state by modulating virulence gene expression.