The dissimilatory nitrate/nitride reduction system in Staphylococcus aureus: its regulation and role in virulence

我们首次描述了编码葡萄球菌双组分调控系统的nreABC（氮调控）操纵子。它控制对氧气的异化硝酸盐/亚硝酸盐还原。NreB是一种具有4个n端半胱氨酸残基的胞质蛋白。在缺氧的情况下，可以观察到S. carnosus细胞质o2传感器NreB的自磷酸化。NreC作为磷酸化基团受体，磷酸化-NreC激活nir和nar操纵子以及narT基因的表达。由于牛肉豆S. cannosus¿nreABC缺失突变体无论硝酸盐或亚硝酸盐的存在都表现出普遍的生长缺陷，因此nreABC似乎不仅仅参与异化硝酸盐还原。在博士论文的框架内，我们计划构建并表征一个NreA缺失突变体，以研究NreA在调控系统中的作用，其与NreB和/或NreC的潜在相互作用以及与硝酸盐/亚硝酸盐的结合。我们将在金黄色葡萄球菌中创建一个nreABC缺失突变体，通过比较转录组分析来分析有多少基因和哪些基因受该规则控制。此外，我们想研究异化硝酸盐/亚硝酸盐减少在毒力和感染中的作用。我们计划在不同生长条件下，对野生型和相应的突变株进行细胞生物学比较研究，包括对吞噬杀伤的抗性，对氧化爆发过程中产生的活性氮分子的敏感性，或对抗菌肽的敏感性。在论文的最后一部分，博士生被邀请到巴塞尔大学的Landmann教授那里，在一个全身感染的小鼠模型中进行毒力的体内研究。

We described for the first time the nreABC (nitrogen regulation) operon that encodes a new staphylococcal two component regulatory system. It controls dissimilatory nitrate/nitrite reduction in response to oxygen. NreB is a cytosolic protein with four Nterminal cysteine residues. In the absence of oxygen, autophosphorylation of the cytoplasmic O2-sensor NreB of S. carnosus can be observed. NreC serves as the phosphoryl group acceptor, and phospho-NreC activates the expression of the nir and nar operons and the narT gene. Since an S. carnosus ¿nreABC deletion mutant shows a general growth defect irrespective of the presence of nitrate or nitrite, nreABC seem not only to be involved in dissimilatory nitrate reduction. In the frame of a PhD thesis we plan to construct and characterize an nreA-deletion mutant to study the role of NreA in the regulation system, its potential interaction with NreB and/or NreC and binding to nitrate/nitrite, respectively. We will create a nreABC deletion mutant in S. aureus to analyze by comparative transcriptome analysis how many and which genes are controlled by this regulon. Moreover, we want to study the role of dissimilatory nitrate/nitrite reduction in virulence and infection. We plan to carry out comparative cell biological studies with wild type and corresponding mutant strains with respect to resistance to phagocytotic killing, sensitivity to reactive nitrogen molecules created during oxidative burst, or antimicrobial peptide susceptibility under different growth conditions. For the last part of the thesis the PhD student is invited to Prof. Landmann, University Basel, to carry out in vivo studies for virulence in a murine model of systemic infection.