GENETIC REGULATION OF S GORDONII GLUCOSYLTRANSFERASE

戈登链球菌在高浓度之间表现出可逆的相变， (Spp+）和低（Spp-）水平的葡糖基转移酶（GTF）活性。 的 这种相位变化的分子基础是未知的，但可能涉及 在调控区的DNA的移码或重排。 关于gtfR 区域，紧邻gtfG结构基因的上游， 参与调节gtfG表达水平。 拟议 研究将使用分子遗传学技术来检测 在Rec-粪肠球菌背景中的gtfR和gtfR。 基因表达 将使用lacZ转录融合来监测。 涉及的DNA区域 在lacZ表达调控中的作用将被表征，测序， 与S.戈登氏菌Spp+和Spp-菌株， 试图确定这些相位变化的分子基础， 有机体 如果S.发现戈登氏菌 如果这些区域的克隆不参与gtfR和/或gtfG表达，则将克隆这些区域的克隆。 表征了 适当的构建体将转化回S。 Gordonii菌株为了确定各种培养条件的影响， 已知产生GTF活性的定性和定量变化，可 对gtfR和gtfG表达的影响。 GTF酶及其葡聚糖产物 与介导口腔细菌相互作用有关。 体外 研究表明，早期菌斑微生物的Spp+和Spp-菌株 S. gordonii，对各种口腔表面显示出不同的亲和力， 在不同的环境条件下， 这些表面，表明在体内GTF相位变化可能允许 口腔部位的差异定植。 希望能达成谅解 参与GTF活性调节的基因将提供 深入了解口腔微生物生态学和牙齿健康。

Streptococcus gordonii exhibits reversible phase variation between high (Spp+) and low (Spp-) levels of glucosyltransferase (GTF) activity. The molecular basis for this phase variation is unknown, but may involve frameshifts or rearrangements of DNA in a regulatory region. The gtfR region, immediately upstream from the gtfG structural gene has been implicated in regulating the level of gtfG expression. The proposed studies will use molecular genetic techniques to examine the expression of gtfR and gtfR in a Rec- Enterococcus faecalis background. Gene expression will be monitored using lacZ transcriptional fusions. DNA regions involved in the regulation of lacZ expression will be characterized, sequenced and compared to comparable regions in S. gordonii Spp+ and Spp- strains to attempt to determine the molecular basis for phase variation in these organisms. If additional chromosomal regions of S. gordonii are found to be involved in gtfR and/or gtfG expression, clones of these regions will be characterized. Appropriate constructs will be transformed back into S. gordonii strains to determine the effects that various culture conditions, known to produce qualitative and quantitative changes in GTF activity, may have upon gtfR and gtfG expression. The GTF enzyme and its glucan products have been implicated in mediating oral bacterial interactions. In vitro studies have shown that Spp+ and Spp- strains of the early plaque organism S. gordonii, display different affinities for various oral surfaces under different environmental conditions and use different mechanisms to colonize these surfaces, suggesting that in vivo GTF phase variation may allow differential colonization of oral sites. It is hoped that an understanding of the genes involved in the regulation of GTF activity will provide insight into oral microbial ecology and dental health.