Cloning/Characterization of S. mutans Iron Stimulation

描述（由申请人提供）：铁是细菌病原体及其哺乳动物宿主的必需微量营养素，因此对该元素的竞争是感染过程的组成部分。细胞外亚铁是生物学上不可用的入侵病原体，因为它主要是螯合宿主蛋白质，并在其游离形式迅速氧化为不溶性的三价铁状态。细菌通常通过开启铁清除系统和毒力决定因子来响应宿主的铁抑制系统，以促进细菌的存活和传播。革兰氏阳性菌中研究最广泛的金属离子依赖性调节剂是白喉棒状杆菌中的DNA结合蛋白DtxR，以及表皮葡萄球菌中的系统发育同源物SirR和金黄色葡萄球菌中的MntR。重要的是，这些金属调节因子作为转录因子，调节细菌毒力基因的表达和与毒力和氧化应激相关的高亲和力金属离子摄取系统。我们实验室对变形链球菌（人类牙菌斑的主要产酸成分）进行的研究揭示了一种DtxR同源物，可调节一系列基因，积累的证据与铁在变形链球菌中的作用一致。变形菌生物膜形成、氧化应激反应和耐酸性。事实上，参与这些和其他致病过程的基因的鉴定和表征是一个高度优先事项，因为它们可以被证明是未来的药物靶点。本研究计划的主要目标将集中在阐明铁依赖的基因调控及其在S。突变体诱发的龋齿。具体目标包括：1）鉴定属于推定的S.变异Dlg调节子; 2）克隆和表征变形链球菌中不受Dlg控制的其他铁依赖性基因;在接近人类口腔的环境中的变形链球菌Dlg-和铁-应答基因;和4）建立Dlg/铁-调节的基因表达和S.突变体诱发的龋齿。

DESCRIPTION (provided by applicant): Iron is an essential micronutrient for bacterial pathogens and their mammalian hosts, and hence competition for this element is an integral component of the infectious process. Extracellular ferrous iron is biologically unavailable to invading pathogens because it is largely sequestered to host proteins, and in its free form rapidly oxidizes to the insoluble ferric state. Bacteria often respond to the iron withholding system of the host by turning on iron scavenging systems and virulence determinants to promote bacterial survival and dissemination. Among the most extensively studied metal ion-dependent regulators in Gram-positive bacteria is DtxR, a DNA-binding protein, in Corynebacterium diphtheriae, and its phylogenetic homologs SirR in Staphylococcus epidermidis and MntR in Staphylococcus aureus. Importantly, these metalloregulators function as transcription factors that modulate the expression of bacterial virulence genes and high affinity metal ion uptake systems related to virulence and oxidative stress. Work conducted in our laboratory on Streptococcus mutans, the principal acidogenic component of human dental plaque, revealed a DtxR homolog that regulates a repertoire of genes, and accumulating evidence is consistent with a role for iron in S. mutans biofilm formation, the oxidative stress response, and acid tolerance. Indeed, the identification and characterization of genes involved in these and other pathogenic processes is a high priority since they can prove to be future drug targets. The major goal of this research proposal will focus on elucidating iron-dependent gene regulation and its role in S. mutans-induced cariogenesis. The specific aims include 1) characterizing iron-responsive genes that belong to a putative S. mutans Dlg regulon; 2) cloning and characterizing other iron-dependent genes in S.mutans that are not subject to Dlg control; 3) examining the expression of S. mutans Dlg- and iron-responsive genes in environments that approximate the human oral cavity; and 4) establishing a correlation between Dlg/iron-regulated gene expression and S. mutans-induced cariogenesis.