Stationary Phase Behavior in Oral Streptococci

描述：变形链球菌是龋齿的主要病原体。我们认为，稳定期细菌对于牙菌斑生物膜中变形链球菌的行为和生存至关重要，因此也对其在龋齿中的作用至关重要。它们无疑是变形链球菌“盛宴或饥荒”生活方式的重要组成部分，因为饥荒会导致其进入静止期。然而，大多数对变形链球菌的研究都是针对呈指数增长的细菌。我们建议检验以下一般假设：生物膜中的静止期细菌的行为与营养细菌不同，并且在确定成熟生物膜的特性，特别是其持久性方面具有重要作用。我们建议使用流动池中形成的单一物种生物膜来检验这一假设。我们建议测试静止期细菌在生物膜中长期碳源饥饿中的生存情况，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个流动池中启动次级生物膜形成。我们建议使用荧光蛋白 GFPmut3b* 作为探针来定位表达已知稳定期特异性基因和表达营养期特异性基因的细菌。这将有助于阐明两种细菌类型之间的特性差异。我们将筛选新的稳定期表达基因。这些基因将能够测试是否存在具有不同抵抗力和对营养物不同反应的不同类型的静止期细菌。它们将指示稳定相期间表达的功能类型。我们建议测试这些基因的作用。我们建议鉴定和表征稳定期基因表达的调节因子。这些研究应该有助于更好地了解成熟牙菌斑生物膜中的变形链球菌如何持续存在并对其环境波动做出反应。

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.