Citric acid cycle regulation of exopolysaccharide synthesis in staphylococci

描述(申请人提供)：金黄色葡萄球菌和表皮葡萄球菌是导致多种人类和动物疾病的机会致病菌。重要的是，金黄色葡萄球菌和表皮葡萄球菌是医院相关感染的两个主要原因，这显著增加了发病率和治疗成本。胞外多糖是葡萄球菌感染的重要介质，尤其是胞间粘附素(PIA)可促进生物膜的形成和免疫逃避，而胶囊则可促进免疫逃避、定植和持久性。葡萄球菌PIA是在三羧酸(TCA)循环活性被抑制后合成的。相反，金黄色葡萄球菌荚膜多糖的合成需要TCA循环活性。有趣的是，PIA和胶囊来自相同的氨基糖(即UDP-N-乙酰-氨基葡萄糖)。这两种胞外多糖的合成受营养物质、氧气和铁的供应的调节。同样，TCA循环活动受营养物质、氧气和铁的可用性以及某些压力诱导刺激(如热、乙醇和抗生素)的调节。TCA循环活性与胞外多糖合成的联系以及TCA循环对环境失活的敏感性使我们假设，葡萄球菌感知外部环境变化的一种机制是通过TCA循环活性的改变。TCA循环活性的这些变化改变了细菌代谢物增加或减少细胞内代谢物和辅因子的浓度，这些代谢物和辅因子被调节蛋白“感觉”，从而增加或减少胞外多糖的生物合成。这项建议的目的是确定控制胞外多糖合成的TCA循环代谢物，并确定哪些调节蛋白对这些TCA循环代谢物做出反应来调节胞外多糖的合成。为了实现这些目标，我们将使用系统生物学、生物化学、生物信息学和遗传学相结合的综合方法。拟议研究的基本原理是填补我们在理解环境条件如何影响细菌代谢状态以及代谢状态如何影响葡萄球菌胞外多糖生物合成方面的空白。了解这一点将有助于我们的长期目标，即设计针对葡萄球菌代谢和代谢反应调节因子的治疗策略，以促进抗生素和宿主免疫系统对细菌的杀灭。

DESCRIPTION (provided by applicant): Staphylococcus aureus and Staphylococcus epidermidis are opportunistic bacterial pathogens responsible for a wide array of human and animal diseases. Importantly, S. aureus and S. epidermidis are the two leading causes of hospital-associated infections, which significantly increase morbidity and treatment costs. Exopolysaccharides are important mediators of staphylococcal infections; specifically, polysaccharide intercellular adhesin (PIA) enhances biofilm formation and immune evasion, while capsule facilitates immune evasion, colonization, and persistence. Staphylococcal PIA is synthesized when tricarboxylic acid (TCA) cycle activity is repressed. In contrast, synthesis of the S. aureus capsular polysaccharide requires TCA cycle activity. Interestingly, PIA and capsule are derived from the same amino sugar (i.e., UDP-N-acetyl-glucosamine. Synthesis of both exopolysaccharides is modulated by the availability of nutrients, oxygen, and iron. Similarly, TCA cycle activity is regulated by the availability of nutrients, oxygen, and iron and by certain stress-inducing stimuli such as heat, ethanol, and antibiotics. The linkage of TCA cycle activity and exopolysaccharide synthesis and the susceptibility of the TCA cycle to environmental inactivation lead us to hypothesize that one mechanism by which staphylococci perceive external environmental change is through alterations in TCA cycle activity. These changes in TCA cycle activity alter the bacterial metabolome increasing or decreasing the intracellular concentrations of metabolites and co- factors that are "sensed" by regulatory proteins, which increase or decrease exopolysaccharide biosynthesis. The aims of this proposal are to identify the TCA cycle metabolites that control exopolysaccharide synthesis and determine which regulatory proteins are responding to these TCA cycle metabolites to regulate exopolysaccharide synthesis. To achieve these aims, we will use an integrated approach combining systems biology, biochemistry, bioinformatics, and genetics. The rationale for the proposed research is to fill the gap in our understanding of how environmental conditions affect the bacterial metabolic status and, in turn, how the metabolic status affects staphylococcal exopolysaccharide biosynthesis. Understanding this will aid in our long-term goal, which is to design therapeutic strategies targeting staphylococcal metabolism and metabolic responsive regulators that will facilitate bacterial killing by antibiotics and the host immune system.