The Role of Lactate in the ???Metabolic Evolution??? of Staphylococcus aureus

描述（由申请人提供）：金黄色葡萄球菌能够承受宿主先天免疫的几乎所有方面，包括一氧化氮（NO）的产生。否。-耐药性在其他细菌中不明显，包括密切相关的凝固酶阴性葡萄球菌（CNS）。我们已经发现金黄色葡萄球菌NO的关键。-抵抗力是生物体唤起代谢状态的能力，以乳酸代谢为中心，基本上对NO免疫。金黄色葡萄球菌含有三种乳酸脱氢酶，其中一种（Ldh1）在中枢神经系统中不存在，在金黄色葡萄球菌no -耐药性中起关键作用。本提案的重点是了解乳酸代谢在金黄色葡萄球菌毒力和免疫逃避中的作用。具体目标建立Lqo作为一氧化氮循环的一部分，这是金黄色葡萄球菌毒力的重要途径。我们鉴定了一个编码乳酸金黄色葡萄球菌醌氧化还原酶（Lqo）的基因，并证明了它在毒力中的作用。在这里，我们测试的假设解释了为什么第四乳酸利用酶在金黄色葡萄球菌是如此关键的发病机制。我们将建立NOX循环，这是一种依赖Ldh1和Lqo的代谢途径，实际上允许金黄色葡萄球菌利用宿主NO。用于能源生产。我们还将从结构和生化方面对Lqo进行表征，Lqo是仅在葡萄球菌中发现的新酶家族的创始人。具体目标2。揭示乳酸代谢在金黄色葡萄球菌发病机制中的多重作用。与中枢神经系统不同，金黄色葡萄球菌在NO期间表现出乳酸“对映体偏好”。-应激并产生大量的l -异构体，这是唯一能够参与NOX循环的乳酸形式。我们将定义导致ldh1峰值表达的调控机制，ldh1是金黄色葡萄球菌特异性乳酸脱氢酶，负责“对映体偏好”。我们还将测试旨在解释L-乳酸和d -乳酸的生产是金黄色葡萄球菌毒力所必需的奇怪观察的假设。我们观察到，参与金黄色葡萄球菌乳酸代谢的基因在中枢神经系统中要么不存在，要么受到差异调节。因此，参与金黄色葡萄球菌乳酸代谢的基因的新获取和改变调控为新出现的病原体的“代谢进化”提供了一个模型。这些渐进式的进化变化为金黄色葡萄球菌提供了在具有免疫能力的宿主内繁殖所必需的代谢灵活性，并且必须与这种病原体出现的典型毒力因子的获得相一致。

DESCRIPTION (provided by applicant): S. aureus is capable of withstanding nearly every facet of host innate immunity, including the production of nitric oxide (NO.) NO.-resistance is not apparent in other bacteria, including closely related coagulase negative staphylococci (CNS). We have found that the key to S. aureus NO.-resistance is the ability of this organism to evoke a metabolic state, centered around lactate metabolism, that is essentially immune to NO. S. aureus harbors three lactate dehydrogenases, one of which (Ldh1) is not present in CNS and plays a critical role in S. aureus NO.-resistance. The focus of this proposal is to understand the role of lactate-metabolism in S. aureus virulence and immune evasion. Specific Aim 1. Establish Lqo as part of the NOX-cycle, an essential pathway for S. aureus virulence. We identified a gene encoding the S. aureus lacate:quinone oxidoreductase (Lqo) and demonstrated its role in virulence. Here we test hypotheses explaining why a fourth lactate-utilizing enzyme in S. aureus is so critical to pathogenesis. We will establish the NOX cycle, a metabolic pathway relying on both Ldh1 and Lqo that actually allows S. aureus to use host NO. for energy production. We will also structurally and biochemically characterize Lqo, the founder of a new family of enzymes found only among the staphylococci. Specific Aim 2. Unravel the multiple roles for lactate metabolism in S. aureus pathogenesis. Unlike CNS, S. aureus exhibits lactate "enantiomer preference" during NO.-stress and produces copious amounts of the L-isomer, the only form of lactate able to participate in the NOX cycle. We will define the regulatory mechanisms resulting in peak expression of ldh1, the S. aureus-specific lactate dehydrogenase responsible for "enantiomer preference". We will also test hypotheses aimed at explaining the curious observation that both L- and D-lactate production are required for S. aureus virulence. We have observed that genes involved in S. aureus lactate metabolism are either not present or are differentially regulated in CNS. Thus, the new acquisition and altered regulation of genes involved in S. aureus lactate-metabolism provides a model for the "Metabolic Evolution" of an emerging pathogen. These incremental evolutionary changes provided S. aureus with the metabolic flexibility necessary to thrive within an immunocompetent host and must have coincided with the acquisition of canonical virulence factors for this pathogen to emerge. PUBLIC HEALTH RELEVANCE: Staphylococcus aureus, the organism responsible for MRSA infections, is one of the most dangerous and costly bacterial pathogens afflicting Americans today. In order to resist the effects of our immune system and cause disease, this bacterium must adopt a unique form of metabolism involving lactate, an organic acid commonly associated with spoiled milk. We propose that a thorough understanding of lactate-metabolism in S. aureus will lead to new targets for the development of antibiotics used to combat this important human pathogen.