Acid Adaptation and Membrane Physiology

该计划项目的两个具体目标反映了减少牙菌斑致病性的两种方法。首先是增加我们对口腔细菌应激反应的认识。在牙菌斑中，细菌经常受到多种氧化和其他压力。特别是酸适应被认为是蛀牙细菌的关键毒力属性。第二个特定目标也是针对降低菌斑细菌的酸耐受性，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组成部分。一个来自我们最近的发现，口服链球菌的酸适应涉及细胞膜脂肪酸组成的变化，主要是向长，单不饱和脂肪酸的转变。这种转变可能会影响膜的质子渗透性，也会影响包括H+- atp酶在内的各种膜酶的工作，众所周知，H+- atp酶需要相关的脂质才能充分发挥活性。第二个子成分与口腔细菌在响应环境压力时产生伴侣蛋白有关。该研究延续了之前关于DnaK、HrcA和GroEL在酸适应中的作用的研究，并与其他研究项目联系起来，研究在弱酸胁迫和膜脂肪酸谱改变突变体中伴侣蛋白的产生。第三个子成分考虑了由斑块细菌产生的过氧化氢酶在氧化应激耐受中的作用。第二个具体目标与Bowen博士实验室关于使用弱酸控制龋齿和使氟化物作为抗龋齿剂更有效的研究相结合。我们的重点将放在细胞膜上，并更清楚地了解弱酸如何增加细菌膜和细胞的质子通透性。增强细菌膜和细胞的质子渗透性。质子渗透性的增强降低了耐酸性，并可能降低致癌性。我们对开发弱酸的可能性特别感兴趣，弱酸可以进入细胞膜的疏水区域，作为长效抗龋剂。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.