Characterization of ComC export and processing in Streptococcus sanguinis

描述（由申请人提供）：血链球菌是草绿色链球菌的成员，是牙齿表面牙菌斑生物膜的最早定居者之一。在这一领域，S。血被认为通过与口腔中有害细菌的生长竞争而发挥有益的作用。然而，S.血吸虫也是感染性心内膜炎的主要原因，心内膜炎是心脏瓣膜的一种经常致命的感染。这项研究旨在确定有助于口腔和心脏环境适应性的基因。在这方面，我们最近开始描述S。血细胞调节子这种调节子最明显的功能是遗传能力-从环境中整合游离的外源DNA的能力。基于先前在肺炎链球菌和变形链球菌中的研究，我们假设，COM调节子也可能对心内膜炎毒力或生物膜形成很重要。我们的初步结果表明，COM调节子不增强心内膜炎的毒力，但它似乎有一个显着的生物膜形成的影响。这些发现表明，这种调节子可能是口腔竞争力的重要决定因素。提出了一种S.血链球菌是基于肺炎链球菌的良好表征系统构建的。In S.在肺炎链球菌中，感受态诱导前体肽ComC被切割成其活性形式，感受态刺激肽（CSP），并被分泌以充当群体感应信号，诱导DNA摄取。裂解发生在一个保守的网站，通过活性的ComA，一个ABC出口与肽酶活性。我们的结果表明S.血吸虫ComC也被加工和分泌为CSP。然而，在S. sanguinis ComC的同源物，并且没有鉴定出能够加工ComC的ComA直系同源物或其它蛋白质。尽管我们的进展，许多功能的S。sanguinis com调节子诱导尚不清楚。为了进一步描述这一重要系统的基本方面，S。我们提出三个目标：（1）分离并测定分泌型感受态刺激肽（CSP）的序列;通过筛选一系列确定的突变体（3），以检查S. sanguinis ComC的出口和加工系统。sanguinis ComC在异源宿主中的表达。总之，这些目标提供了一系列的方法来表征一个系统，可能有助于在多种方式的竞争力的S。血在嘴里。一旦该系统被更好地表征，我们的发现可能允许操纵com系统以增强S的有利性质。血在口腔中不会增强其对心内膜炎的毒力。 公共卫生相关性：血链球菌是牙菌斑的重要组成部分，可以通过与口腔中的有害细菌竞争而使人们受益。我们正在描述血链球菌中的一个系统，该系统使其能够从周围环境中吸收DNA，并可能帮助其在口腔中存活。这项研究提出了这一重要系统的最基本组成部分的特点。

DESCRIPTION (provided by applicant): Streptococcus sanguinis is a member of the viridans streptococci and is among the earliest colonizers of the dental plaque biofilm on the tooth surface. Within this niche, S. sanguinis is believed to play a beneficial role by competing with the growth of harmful bacteria in the mouth. However, S. sanguinis is also a leading cause of infective endocarditis, an often lethal infection of the cardiac valves. This research aims to identify genes that contribute to fitness in both the oral and cardiac environments. In this regard, we have recently begun to characterize the S. sanguinis com regulon. The most apparent function of this regulon is genetic competence- the ability to incorporate free, exogenous DNA from the environment. Based on previous studies in Streptococcus pneumoniae and Streptococcus mutans, we hypothesized that the com regulon might also be important for endocarditis virulence or biofilm formation. Our preliminary results suggest that the com regulon does not enhance endocarditis virulence; however it appears to have a significant effect on biofilm formation. Such findings suggest that this regulon may be an important determinant of competitiveness in the mouth. A model of the competence regulon in S. sanguinis is being constructed based on the well characterized system of Streptococcus pneumoniae. In S. pneumoniae, the competence inducing precursor peptide, ComC, is cleaved to its active form, competence stimulating peptide (CSP), and secreted to serve as a quorum sensing signal, inducing DNA uptake. Cleavage occurs at a conserved site through the activity of ComA, an ABC exporter with peptidase activity. Our results suggest S. sanguinis ComC is also processed and secreted as CSP. However, the conserved cleavage site is lacking in S. sanguinis ComC and no ComA ortholog or other protein capable of processing ComC has been identified. Despite our progress, many features of S. sanguinis com regulon induction are not understood. To further characterize such fundamental aspects of this important system with S. sanguinis we propose three aims: (1) to isolate and determine the sequence of secreted competence stimulating peptide (CSP) (2) to identify the S. sanguinis ComC export and processing system by screening a collection of defined mutants (3) to examine export and processing of S. sanguinis ComC in a heterologous host. Together, these aims provide a range of approaches for characterization of a system that may contribute in multiple ways to the competitiveness of S. sanguinis within the mouth. Once this system is better characterized, our findings may allow manipulation of the com system to enhance favorable properties of S. sanguinis in the mouth without enhancing its virulence for endocarditis. Public Health Relevance: The bacterium Streptococcus sanguinis is an important component of dental plaque and may benefit people by competing against harmful bacteria in the mouth. We are characterizing a system in Streptococcus sanguinis that enables it to take up DNA from its surroundings and may also help it survive in the mouth. This study proposes to characterize the most fundamental components of this important system.