Exploring the physiological role and mode of action of the small RNA LhrC of Listeria monocytogenes and a recently discovered sigmaB-regulated sRNA of Staphylococcus aureus to check for their possible involvement in pathogenicity

小RNA（sRNA）在所有生命王国中发挥着重要作用。它们通常通过与特定靶mRNA配对来改变其翻译和/或稳定性或影响蛋白质的活性。小RNA也是两种人类病原体单核细胞增生李斯特菌和金黄色葡萄球菌的调控网络的一部分，因此最有可能参与毒力机制。 最近发现了许多sRNAs。然而，在革兰氏阴性细菌中，最重要的是在大肠杆菌中，许多sRNA被赋予了功能性作用，而关于革兰氏阳性细菌的知识却落后于此。在这种情况下，sRNA LhrC在L.单核细胞增多症仍然需要功能分类。有趣的是，LhrC sRNA已被证明在血液中和β-内酰胺抗生素存在期间上调，表明参与毒力机制。在预期的研究项目中，LhrC功能将主要在蛋白质组水平上通过比较野生型和LhrC所有五个拷贝缺失的突变体来探索。更确切地说，蛋白质组学分析将涉及基于14 N/15 N同位素标记的蛋白质的代谢标记程序，并且将不仅包括细胞溶质蛋白质组，而且包括膜和细胞外蛋白质级分。因此，确定推定LhrC目标将备份和补充应用基于生物信息学和生化捕捞的进一步战略。在该项目的第二部分，另一种功能完全未知的sRNA将采用类似的实验方法进行研究。S.金黄色葡萄球菌显示是σ B调节的，表明在感染期间可能的作用。拟议的研究将有助于了解sRNA在致病性革兰氏阳性菌中的作用，并可能为新的抗菌策略提供基础。

Small RNAs (sRNAs) play an important role in all kingdoms of life. They often act by pairing with specific target mRNAs to change their translation and/or stability or act to influence the activity of proteins. Small RNAs are also part of regulatory networks of the two human pathogens Listeria monocytogenes and Staphylococcus aureus and therefore most likely involved in virulence mechanisms. Numerous sRNAs have been discovered recently. Whereas in Gram-negative bacteria, foremost in Escherichia coli, a functional role has been assigned to many sRNAs, the state of knowledge concerning Gram-positive bacteria is lagging behind. In this context, the sRNA LhrC which is present in five almost identical copies in L. monocytogenes still requires functional classification. Interestingly, LhrC sRNAs have been shown to be up-regulated in blood and during the presence of beta-lactam antibiotics pointing to an involvement in virulence mechanisms. In the intended research project LhrC function will be explored primarily on proteome level by comparison of wild type and a mutant deleted in all five copies of LhrC in a comprehensive quantitative approach. More precisely the proteomics analysis will involve a metabolic labeling procedure based on 14N/15N isotopically labeled proteins, and will comprise not only the cytosolic proteome but also the membrane and extracellular protein fraction. Thereby identified putative LhrC targets will be backed up and complemented applying further strategies based on bioinformatics and biochemical fishing. In a second part of the project another sRNA of completely unknown function will be investigated employing a comparable experimental approach. This sRNA of S. aureus was shown to be sigmaB-regulated indicating a possible role during infection. The proposed research will contribute to the understanding of sRNA action in pathogenic Gram-positive bacteria and may provide a basis for new antimicrobial strategies.