The effect of inter-species interactions on the virulence of Streptococcus mutans

描述(申请人提供)：项目摘要：变形链球菌是产生多种毒力因子的主要致龋物。拟议研究的长期目标是表征变形链球菌与牙菌斑生物膜中口腔细菌的特定相互作用。我们假设，不仅是变形链球菌的定植决定了菌斑的最终致龋性，而且病原体与其他生物被膜细菌的相互作用也影响了毒力。牙菌斑中存在的其他细菌可能调节有机体毒力特性的依赖于群体感应的表达。这一假说基于以下观察：1)变形链球菌能力刺激肽(CSP)和一个信号转导系统介导了一系列毒力特征：生物被膜形成、细菌素产生、耐酸性、抗菌素敏感性和自然遗传转化。CSP或其信号转导系统的消失会导致所有这些毒力活动的改变。2)，其他口腔细菌，如共生的早期定植牙菌斑物种戈登链球菌，可以灭活变形链球菌CSP，从而干扰变形链球菌细菌素的产生。因此，这项提议的实验重点将是确定其他早期定殖物如奈斯伦迪放线菌和后来的厌氧定殖物如牙龈卟啉单胞菌对变形链球菌群体感应的影响，并确定这些微生物对变形链球菌毒力相关特性的影响。具体目标有：1.确定早期定殖者戈登链霉菌或内氏链霉菌是否拮抗变形链球菌的定殖率和耐酸反应。I)将通过放射性标记技术和共聚焦显微镜来评估变形链球菌WT及其comc突变体在戈登氏链球菌或内氏链球菌预制生物膜上的定植情况。Ii)变形链球菌和与戈登氏链球菌或内氏链球菌的混合物的耐酸性反应将通过活细胞计数来评估。具体目的2.确定晚期定殖者如牙龈假单胞菌、齿密螺旋体和连翘坦纳氏菌是否拮抗变形链球菌的群体感应特性。I)通过测定指示菌株的杀灭百分率，监测变形链球菌和变形链球菌与牙龈假单胞菌、齿状念珠菌或连翘混合培养物中的细菌素产量。Ii)将评估变形链球菌在单一培养物中的转化效率以及在与牙龈假单胞菌、齿状念珠菌或连翘混合培养中的转化效率。Iii)变形链球菌及其与牙龈假单胞菌、齿状念珠菌或连翘的混合物的耐酸性反应将通过活细胞计数来评估。IV)我们将确定牙龈假单胞菌的蛋白水解酶是否会使变形链球菌CSP失活。 项目简介：龋齿是一种常见的慢性传染病，影响着全球大部分人口。变形链球菌群体感应系统可能是干预减少龋齿的合适靶点。CSP依赖的调节的中断有可能减弱细菌，使其毒力降低。

DESCRIPTION (provided by applicant): Project summary: Streptococcus mutans is the primary cariogen that produces several virulence factors. The long-term goal of the proposed studies is to characterize specific interactions of S. mutans with oral bacteria in the dental plaque biofilm. We hypothesize that it is not merely colonization by S. mutans that determines the ultimate cariogenicity of plaque, but the interaction of the pathogen with other biofilm bacteria that affect virulence. Other bacteria present in dental plaque may modulate quorum sensing-dependent expression of virulence properties of the organism. This hypothesis is based on observations that: 1) S. mutans competence-stimulating peptide (CSP) and a signal transduction system mediate a variety of virulence characteristics: biofilm formation, bacteriocin production, acid tolerance, antimicrobial sensitivity, and natural genetic transformation. Elimination of CSP or its signal transduction system results in alterations in all of these virulence activities. 2), other oral bacteria, such as the commensal early-colonizing dental plaque species Streptococcus gordonii, can inactivate S. mutans CSP thereby interfering with S. mutans bacteriocin production. Therefore, the experimental focus of this proposal will be to determine the effects of other early colonizers such as Actinomyces naeslundii and later anaerobic colonizers such as Porphyromonas gingivalis on quorum-sensing in S. mutans and to determine the effects of these organisms on the virulence-associated properties of S. mutans. The Specific Aims are: Specific Aim 1. To determine if early colonizers, S. gordonii or A. naeslundii, antagonize colonization efficiency and the acid tolerance response in S. mutans. i) Colonization of S. mutans WT and its comC mutant on preformed biofilms of S. gordonii Challis or A. naeslundii will be assessed by both radioactive labeling techniques and confocal microscopy. ii) The acid tolerance response of S. mutans and mixtures with S. gordonii Challis or A. naeslundii will be assessed by viable cell counts. Specific Aim 2. To determine if late colonizers such as P. gingivalis, Treponema denticola, and Tannerella forsythia antagonize quorum-sensing properties in S. mutans. i) S. mutans bacteriocin production in broth monocultures of S. mutans and mixtures of S. mutans with P. gingivalis, T. denticola, or T. forsythia will be monitored by determining killing percentages of an indicator strain. ii) The transformation efficiencies of S. mutans in monocultures and in mixtures with P. gingivalis, T. denticola, or T. forsythia will be assessed. iii) The acid tolerance response of S. mutans and mixtures with P. gingivalis, T. denticola, or T. forsythia will be assessed by viable cell counts. iv) We will determine if the proteinases of P. gingivalis inactivate the S. mutans CSP. Project Narrative: Dental caries is a common chronic infectious disease affecting much of the worldwide population. The S. mutans quorum-sensing system may be an appropriate target for interruption to reduce dental caries. The disruption of CSP-dependent regulation has the potential to attenuate the bacterium so that it is less virulent.