Acid Adaptation and Membrane Physiology

该方案项目的这一部分的两个具体目标反映了减少牙菌斑致龋性的两种方法。第一个涉及增加我们对口腔细菌的细菌应激反应的知识。在牙菌斑中，细菌经常受到多重氧化和其他压力。尤其是酸适应被认为是致龋菌的关键毒力属性。第二个具体目标也是为了降低菌斑细菌的耐酸性，特别是使用能够在低pH值下作为跨膜质子导体的弱酸。第一个具体目标有三个主要的子组成部分。一种来自我们最近的发现，口腔链球菌对酸的适应涉及细胞膜脂肪酸组成的变化，主要是向长的、单不饱和脂肪酸的转变。这种变化可能会影响膜的质子通透性，也会影响包括H-ATPase在内的各种膜酶的工作原理，众所周知，H-ATPase需要相关的脂类才能充分发挥作用。第二个亚组分与口腔细菌在应对环境压力时产生伴侣蛋白有关。它继续了以前关于DNAK、HrcA和GroEL在酸适应中的作用的工作，并与其他项目联系起来，考虑在弱酸胁迫下产生伴侣蛋白，以及在具有改变膜脂肪酸谱的突变体中。第三个亚组分考虑斑块细菌产生的过氧化氢酶在耐受氧化应激中的作用。第二个具体目标与鲍恩博士的实验室中有关使用弱酸控制龋齿并使氟化物作为防龋剂更有效的研究相辅相成。我们的重点将放在细胞膜上，并更清楚地了解弱酸是如何提高细菌膜和细胞的质子渗透性的。细菌膜和细胞质子渗透性的增强。质子渗透性的增强降低了对酸的耐受性，并可能降低致癌性。我们特别感兴趣的是开发弱酸的可能性，这种弱酸可以分割成细胞膜的疏水区域，作为长效防龋剂。拟议的研究受益于微生物遗传学和生理学方面的综合专业知识，以及与参与整个计划其他项目的人员的密切互动。

The two specific aims of this component of the program project reflect two approaches to reducing the cariogenicity of dental plaque. The first involves increasing our knowledge of bacterial stress responses of oral bacteria. In dental plaque, bacteria are regularly subjected to multiple oxidative and other stresses. Acid adaptation in particular is considered to be key virulence attribute of cariogenic bacteria. The second specific aim also is oriented to reducing acid tolerance of plaque bacteria, specifically be use of weak acids able to act as transmembrane proton conductors at low pH values. The first specific aim has three main subcomponents. One derives from our recent finding that acid adaptation by oral streptococci involves changes in fatty acid composition of the cell membrane, mainly a shift to long, mono-unsaturated fatty acids. This shift is likely to affect proton permeability of the membrane and also the workings of various membrane enzymes including the H+-ATPase, which is known to require associated lipids for full activity. The second subcomponent is concerned with production of chaperonins by oral bacteria in response to environmental stress. It continues previous work on the roles of DnaK, HrcA and GroEL in acid adaptation and connects to other projects in considering chaperonin production in response to weak-acid stress and in mutants with altered profiles of membrane fatty acids. The third subcomponent considers the role of catalase produced by plaque bacteria in tolerance of oxidative stress. The second specific aim interdigitates with studies in Dr. Bowen's laboratory on use of weak acids to control caries and to make fluoride more effective as an anti-caries agent. Our focus will be on the cell membrane and obtaining a clearer view of how weak acids act to increase proton permeabilities of bacterial membranes and cells. The enhancement of proton permeabilities of bacterial membranes and cells. The enhancement of proton permeabilities reduces acid tolerance, and presumably, carcinogenicity. We are particularly intrigued by the possibilities of developing weak acids that partition into hydrophobic regions of the cell membrane to act as long-acting anti- caries agents. The proposed research benefits from the combined expertise in microbial genetics and physiology and from the close interactions with those involved in other projects of the overall program.