Stationary Phase Behavior in Oral Streptococci

描述：变形链球菌是引起龋齿的主要致病因素。我们认为，固定相细菌对变形链球菌在牙菌斑生物膜中的行为和生存至关重要，因此对其在龋病中的作用也是至关重要的。它们肯定是变种链霉菌要么大吃大喝，要么挨饿的生活方式的关键部分，因为饥荒会导致进入静止阶段。然而，大多数对变形链球菌的研究都是关于细菌呈指数增长的。我们建议检验这一一般假设，即生物膜中的固定相细菌的行为不同于营养细菌，并在决定成熟生物膜的性质，特别是在它们的持久性方面发挥重要作用。我们建议使用在流动细胞中形成的单一物种生物膜来检验这一假设。我们建议测试固定相细菌在生物膜中长期碳源饥饿的情况下如何生存，以及它们对营养恢复和酸休克的反应。我们将测试不同处理对固定相生物膜中细菌脱落的影响，并测试脱落的细菌如何有效地在第二流动细胞中启动二次生物膜的形成。我们建议使用荧光蛋白GFPmu3b*作为探针来定位表达已知的静止期特定基因的细菌和表达营养期特定基因的细菌。这将有助于澄清这两种细菌类型在性质上的差异。我们将筛选新的固定相表达的基因。这些基因将使测试是否存在不同类型的静止相细菌具有不同的抵抗力和对营养的不同反应。它们将给出在静止阶段表达的功能种类的指示。我们建议测试这些基因的作用。我们建议对稳定期基因表达的调控因子进行鉴定和表征。这些研究应该有助于更好地理解变形链球菌如何在成熟的牙菌斑生物膜中持续存在并对其环境的波动做出反应。

DESCRIPTION: Streptococcus mutans is the primary agent of Dental caries. We think that stationary-phase bacteria are critical to the behavior and survival of S. mutans in the Dental plaque biofilm, and hence to its role in Dental caries. They are surely a critical part of the feast-or-famine lifestyle of S. mutans, as famine causes entry into the stationary phase. Yet, most studies of S. mutans have been of exponentially growing bacteria. We propose to test the general hypothesis that stationary-phase bacteria in biofilms behave differently from vegetative bacteria and have an important role in determining the properties of mature biofilms, and in particular in their persistence. We propose using single-species biofilms formed in flow cells to test this hypothesis. We propose to test how well stationary-phase bacteria survive prolonged carbon-source starvation in biofilms and how they respond to nutrient restoration and acid shock. We will test the effect of different treatments on the shedding of bacteria from stationary-phase biofilms, and test how effectively the shed bacteria can initiate secondary biofilm formation in a second flow cell. We propose to use the fluorescing protein GFPmut3b* as a probe to locate bacteria expressing known stationary-phase-specific genes and those expressing vegetative-phase specific genes. This will help clarify the difference in properties between the two bacterial types. We will screen for new stationary-phase expressed genes. These genes will enable testing if there are different types of stationary-phase bacteria with different resistances and different responses to nutrient. They will give an indication of the sorts of function that are expressed during stationary phase. We propose to test the roles of these genes. We propose to identify and characterize the regulators of stationary phase gene expression. These studies should lead to a better understanding of how S. mutans in mature Dental plaque biofilm persists and responds to fluctuations in its environment.