Integration of Stress Tolerance in Competence Development

描述(申请人提供)：人类口腔中的环境波动有利于致龋菌数量的增加，包括变形链球菌，它是龋齿的病原体。龋齿是儿童中最常见的慢性疾病，极大地影响生活质量，在工业化国家占医疗保健支出的5%-10%。变形链球菌的毒力存在于三个核心属性中：它能够 在牙齿表面形成生物膜，从广泛的碳水化合物中产生大量有机酸，以及其耐受环境压力的能力。有趣的是，在胁迫耐受性、生物膜形成和自然遗传能力(或从环境中吸收外部DNA的能力)之间存在着非常强的相关性。需要更多地了解这些过程是如何联系在一起的，以及它们如何使有机体受益。本研究探讨了一种主要的应激反应途径及其对能力发展的影响。初步数据表明，(P)ppGpp合成酶/水解酶relA的缺失显著降低了生物体对能力刺激肽XIP的反应，导致转化频率不足。这项拟议的研究将确定通过丢失relA酶来降低能力诱导的机制，以及该酶在选择性sigma因子comX表达的单峰/双峰转换中的作用。此外，最近发现rcrRPQ操纵子可以调节一种名为ComX2的新蛋白的表达，该蛋白完全在comX基因内编码。需要对该蛋白进行进一步的细胞生理学描述，因为它是治疗干预的潜在靶点。提出了两个目标：1)研究双功能(P)ppGpp合成酶/水解酶relA调节毒力和感病基因表达的作用和机制；2)进一步鉴定新蛋白ComX2及其在感病发展中的作用。这项研究支持了NIDCR的目标，即调查致龋性生物，以确定有助于腐烂过程的基因和途径。此外，这项研究也是博士论文项目的基础。因此，这项奖学金申请将有助于培训对口腔健康研究感兴趣的学生成为一名独立的调查员。

DESCRIPTION (provided by applicant): Environmental fluctuations in the human oral cavity favor an increase in the amount of cariogenic bacteria, including Streptococcus mutans the etiological agent of dental caries. Dental caries is the most common chronic disease in children, can greatly impact quality of life, and represents 5-10% of healthcare expenditures in industrialized nations. The virulence of S. mutans resides in three core attributes: its ability to form biofilms on the tooth surface, to produce large quantities of organic acids from a wide range of carbohydrates, and its ability to tolerate environmental stressors. Of interest, a very strong correlation exists between stress tolerance, biofilm formation and natural genetic competence [or the ability to uptake external DNA from the environment]. Greater understanding of how these processes are connected and how they benefit the organism is needed. This study investigates a primary stress response pathway and its affects on competence development. Preliminary data indicates that a deletion of the (p)ppGpp synthetase/hydrolase enzyme RelA significantly reduces the organism's response to the competence stimulating peptide XIP, leading to deficiencies in transformation frequency. The proposed investigation will determine the mechanism by which competence induction is diminished through loss of the RelA enzyme, as well as the role of the enzyme in unimodal/bimodal switching of alternative sigma factor comX expression. Also, the rcrRPQ operon was recently found to modulate the expression of a novel protein termed ComX2 encoded entirely within the comX gene. Further description of this protein on cell physiology is needed as it serves as a potential target for therapeutic intervention. Two aims are proposed: 1) Examine the role of, and mechanisms by which, the bi-functional (p)ppGpp synthetase/hydrolase enzyme RelA modulates virulence and competence gene expression and 2) Further characterize the novel protein ComX2 and its role in competence development. This research supports the NIDCR goal to investigate cariogenic organisms to identify genes and pathways that contribute to the decay process. Additionally this research represents the basis of a doctoral dissertation project. Hence, this fellowship application will assist in training a studet with an interest in oral health research to become an independent investigator.