DETERMINATION OF THE ROLE OF Smu.833 IN THE FITNESS AND VIRULENCE OF CARIOGENIC STREPTOCOCCUS MUTANS

 描述(由申请人提供)：龋齿，通常被称为龋齿，是世界上最常见的传染病，尽管龋病研究取得了进展，但在幼儿中的患病率仍在增加。未经治疗的龋齿可能会导致严重的疼痛和进食障碍，导致营养摄入量减少和与饮食有关的健康问题，特别是对儿童和老年人。龋病的主要病原菌是变形链球菌，它能在牙齿表面形成生物膜，通过膳食糖的代谢产生乳酸，导致牙釉质脱矿和破坏。此外，变形链球菌还能合成胞外葡萄糖转移酶(GTFS)，该酶能够分解膳食中的蔗糖，并将葡萄糖亚基聚合成生物膜的粘性葡聚糖基质，这对形成坚固的三维生物膜是必不可少的。目前使用的龋病治疗方法不是针对特定物种的，会杀死致病物种和共生物种，这些物种可以防止形成致病生物膜。变形链球菌中有许多蛋白质的功能尚不清楚，但可能为变形链球菌的特异性抗龋治疗提供新的靶点。其中一种蛋白质是一种保守的、假定的糖基转移酶，该酶由变形链球菌UA159中的smu833基因编码。Smu.833在不同血清类型的变形链球菌中的同源物，已被证明能够糖基化一种重要的表面胶原结合蛋白，对感染性心内膜炎的细菌定植至关重要。因此，这种蛋白质是一个很好的候选蛋白，可以作为龋病治疗的靶点进行研究和分析。为了确定该蛋白在变形链球菌中的特性，我们创建了一个缺失突变体，并检测了细菌适合性和毒力的表型变化。初步研究表明，突变体中GTFS水平和随后的葡聚糖基质形成减少，以及其他有趣的表型，包括细菌链长和聚集增加，对氧化应激的敏感性增加，以及生物膜调节蛋白水平增加。到目前为止所取得的成果 已经导致了这样的假设，即Smu.833对于GTF的糖基化和稳定性以及对变形链球菌的额外作用都是必需的，变形链球菌更具全球性地影响细菌的适应性和毒力。至 为了验证这一假设，我们提出了三个具体的目标：目标1：确定Smu.833在GTF表达中的作用；目标2：确定Smu.833在细菌适合性和毒力中扮演的整体角色；目标3：确定Smu.833对细菌竞争力的影响。阐明Smu.833在变形链球菌中的作用将有助于解开控制这种细菌的适合性和毒力的复杂相互作用。此外，这一应用的结果可能为用于预防龋齿的治疗提供一个新的特定物种的目标。龋病是一种影响世界绝大多数人口的昂贵而痛苦的疾病。

 DESCRIPTION (provided by applicant): Dental caries, more commonly known as tooth decay, is the most common infectious disease worldwide and is increasing in prevalence among young children despite advancements in caries research. Untreated cavities can cause severe pain and impairment of eating, leading to reduced nutritional intake and diet-related ill health especially for children and the elderly. The main etiological agent of dental caries is Streptococcus mutans which can readily form a biofilm on the surface of teeth and produce lactic acid through the metabolism of dietary sugars which is largely responsible for the demineralization and subsequent destruction of tooth enamel. In addition, S. mutans synthesizes extracellular glucosyltransferases (Gtfs) capable of breaking apart dietary sucrose and polymerizing the glucose subunits into the sticky glucan matrix of the biofilm, imperative for the formation of robust, three-dimensional biofilms. Currently used caries therapies are not species-specific and kill pathogenic species as well as commensal species which are protective against the formation of pathogenic biofilms. There are a number of proteins in S. mutans whose function remains unknown but which could present new targets for S. mutans specific anti-caries treatment. One such protein is a conserved, putative glycosyltransferase encoded by the gene smu.833 in S. mutans strain UA159. A homologue of Smu.833 in a different serotype of S. mutans, has been shown to glycosylate an important surface collagen binding protein important for bacterial colonization in infective endocarditis. Thus, this protein makes a good candidate to be studied and analyzed for its potential as a target for caries therapies. In order o characterize this protein in S. mutans, we created a deletion mutant and assayed for phenotypic changes in bacterial fitness and virulence. Initial studies revealed decreased levels of Gtfs and subsequent glucan matrix formation within the mutant, as well as additional intriguing phenotypes including increased bacterial chain length and aggregation, increased sensitivity to oxidative stress, and increased levels of biofilm regulatory protein. The results obtained thus far have led to the hypothesis that Smu.833 is required both for Gtf glycosylation and stability and for an additional role in S. mutans which more globally effects bacterial fitness and virulence. To test this hypothesis, we propose three specific aims: Aim 1: Determine the role of Smu.833 in Gtf expression; Aim 2: Determine the global role Smu.833 plays in bacterial fitness and virulence ; Aim 3: Determine the effect of Smu.833 on bacterial competitiveness. Elucidating the role of Smu.833 in S. mutans will help unravel the complex interactions that govern the fitness and virulence of this bacterium. Furthermore, results from this application may present a new species-specific target for therapeutics used in the prevention of dental caries, a costly and painful disease which effects the vast majority of the world's population.