Low pH-mediated membrane biosynthesis in S. mutans.

描述（由申请人提供）：口腔感染性疾病仍然是现代牙科的主要挑战。龋齿和牙周病被认为是工业化世界中最普遍的疾病。主要的口腔传染病是由机会致病菌引起的，Philip Marsh已经综述了（Microbiology 149：279-294，2003）将牙科传染病视为生态灾难的主要例子的基础。疾病的发生是由于压力条件导致口腔生物膜群落发生变化的结果;因此，有利于具有所谓致病性人格的生物体。例如，高度耐酸的生物体或具有高能力诱导宿主的炎症反应的生物体可能在这些条件下茁壮成长。开发除抗生素之外的新型抗菌剂可能是目前预防和治疗口腔传染病最有前途的方法。我们已经表明，单不饱和膜脂肪酸（UFAs）的形成对S。变形杆菌在酸性环境中生存（Fozo和Quivey，2004 a和B）。此外，我们已经表明，不饱和脂肪酸的形成，在S。变形杆菌依赖于单一酶FabM（Fozo和Quivey，2004 b）。我们在“初步研究”部分包括了最近的数据，以表明FabM的缺失显著降低了S。变异体在老鼠身上致病。FabM酶目前仅在3种细菌属中鉴定：链球菌属。葡萄球菌和梭杆菌。因此，有关该酶在S.变异体将为其他重要的人类病原体提供线索。然而，我们目前缺乏关于膜生物合成酶的调节以及这些酶如何被S。变异体来控制膜稳态。我们假设S.变形杆菌响应外部酸化调节其膜组成，以维持膜流动性的稳态。我们提出了一系列实验，旨在完成我们早期的工作并验证我们的假设。[Our目的是达到对S.我们的具体目标如下：1）我们将完成我们的生化表征的pH依赖性变化的膜，以测量磷脂和支链脂肪酸的变化的目标; 2）我们将使用生物化学和分子工具，以确定机制的遗传调控的fab基因和fabR的作用，在调节的fab基因簇; 3）我们将使用生物化学和遗传学工具来阐明FabM和FabK与膜组成的关系; 4）我们将确定S.变形菌膜与流动性有关; 5）最后，我们将确定S.变形杆菌利用其Fab基因对膜破坏剂如浅蓝菌素和TT-法尼醇作出反应。

DESCRIPTION (provided by applicant): Oral infectious diseases remain major challenges in modern Dentistry. Caries and periodontal diseases are considered to be the most prevalent diseases in the industrialized world. The major oral infectious diseases are caused by opportunistic pathogens, and Philip Marsh has reviewed (Microbiology 149:279-294, 2003) the basis for considering Dental infectious diseases as prime examples of ecological catastrophes. Disease occurs as a result of shifts, due to stress conditions, in oral biofilm communities; thereby, favoring organisms that possess so-called pathogenic personalities. For example, highly aciduric organisms or those with high capacities to induce inflammatory responses of the host might thrive under these conditions. The development of new types of antimicrobials, other than antibiotics, is currently perhaps the most promising approach for preventing and treating oral infectious diseases. We have shown that the formation of mono- unsaturated membrane fatty acids (UFAs) is important for the ability of S. mutans to survive acidic environments (Fozo and Quivey, 2004a and b). Further, we have shown that the formation of unsaturated fatty acids in S. mutans is dependent on a single enzyme, FabM (Fozo and Quivey, 2004b). We include more recent data in the Preliminary Studies section to show that loss of FabM dramatically lowers the ability of S. mutans to cause disease in rats. The FabM enzyme is presently identified in only 3 bacterial genera: the Streptococci. Staphylococci, and Fusobacteria. Thus, knowledge about the role of the enzyme in S. mutans will shed light on other important human pathogens. Nevertheless, we are currently lacking information regarding the regulation of membrane biosynthesis enzymes, and how those enzymes are used by S. mutans to control membrane homeostasis. Our hypothesis is that S. mutans regulates its membrane composition in response to external acidification in order to maintain homeostasis in membrane fluidity. We propose a series of experiments designed to complete our earlier work and to test our hypothesis. [Our goal is to achieve a thorough understanding of the S. mutans membrane biosynthesis during growth at low pH. Our Specific Aims are as follows: 1) we will complete our biochemical characterization of pH-dependent changes in membranes, with the goal of measuring changes in phospholipids and branched chain fatty acids; 2) we will use biochemical and molecular tools to determine the mechanism of genetic regulation of fab genes and the role of fabR in regulating the fab gene cluster; 3) we will use biochemical and genetic tools to elucidate the relationship of FabM and FabK to membrane composition; 4) we will determine how pH-dependent changes in S. mutans membranes relate to fluidity; 5) finally, we will determine how S. mutans uses its fab genes to respond to membrane disrupting agents such as cerulenin and tt-farnesol.