Regulation of S. aureus Colonization by NO.

 描述(申请人提供)：全球约有20亿人带有金黄色葡萄球菌，但这些人中只有一小部分人会发生侵袭性感染。这项应用侧重于一氧化氮(NO*)的作用，它是一种分子介体，通过靶向蛋白硫醇和金属中心来调节细菌生理，在金黄色葡萄球菌鼻腔定植期间。我们将检验这一假设，即NO*抑制金黄色葡萄球菌的毒力并调节微氧呼吸。我们的初步观察表明，NO*是金黄色葡萄球菌是否以稳定的共生关系存在或成为一种侵袭性病原体的关键决定因素。我们的具体目标是：(1)评估NO*抑制金黄色葡萄球菌毒力基因的机制-我们发现NO*抑制侵袭性感染所需的毒力基因的表达。遗传学和生物化学方法将确定外源NO*如何抑制毒力基因的表达，重点是AGRA、MGRA、SAR和SARS，这四个中央转录调控因子被NO*亚硝化。一种新的小鼠鼻腔定植模型将被用来确定宿主来源的NO*对体内金黄色葡萄球菌毒力基因表达的影响。(2)分析金黄色葡萄球菌微氧生理及NO对其定植的调节作用--金黄色葡萄球菌通过表达与哺乳动物NO*合成酶相关的酶(SANOS)产生自身的NO*。我们发现，在小鼠从好氧呼吸到硝酸盐呼吸的微需氧转变过程中，SANOS是氧化还原感觉所必需的，也是鼻部定植所必需的。这一目标将使用表达和生化分析来测试一种新的机制模型，在该模型中，当氧气浓度有限时，细菌来源的NO*将电子传递转移到硝酸还原酶。我们的小鼠模型将被用来评估宿主和细菌来源的NO*对金黄色葡萄球菌体内定植的贡献。这些研究将确定NO*是一种至关重要的信号分子，它允许金黄色葡萄球菌通过调节毒力基因的表达来适应宿主环境中的氧气限制条件，同时保持其共生状态。

 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.