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

项目简介：变形链球菌是产生多种毒力因子的主要致病菌。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的口腔细菌的特定相互作用。我们推测，不仅仅是变形链球菌的定植决定了斑块的最终致龋性，而且病原体与其他生物膜细菌的相互作用也影响了毒力。存在于牙菌斑中的其他细菌可能调节有机体毒力特性的群体感应依赖性表达。这一假设基于以下观察：1)变形链球菌的能力刺激肽（CSP）和信号转导系统介导多种毒力特性：生物膜形成、细菌素产生、耐酸性、抗菌敏感性和自然遗传转化。消除CSP或其信号转导系统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，本研究的实验重点将是确定其他早期定植菌（如naeslundii放线菌）和后来的厌氧定植菌（如Porphyromonas龈卟啉单胞菌）对变形链球菌群体感应的影响，以及确定这些生物对变形链球菌毒力相关特性的影响。具体目标是：为了确定早期的定植者，S. gordonii或A. naeslundii是否会拮抗S. mutans的定植效率和耐酸反应。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突变体在预成型的gordonii Challis或a.s naeslundii生物膜上的定殖。ii)通过活细胞计数评估变形链球菌及其与gordonii Challis或naeslundii混合的耐酸反应。具体目标2。确定晚期殖民者如牙龈假单胞菌、密螺旋体和连翘Tannerella是否能拮抗变形链球菌的群体感应特性。i)将通过测定指示菌株的杀伤百分率来监测变形链球菌的细菌素在变形链球菌和变形链球菌与牙龈假单胞菌、齿状假单胞菌或连翘假单胞菌的混合物中的产生。ii)将评估变形链球菌在单一培养和与牙龈假单胞菌、牙齿假单胞菌或连翘假单胞菌混合培养中的转化效率。iii)变形链球菌和与牙龈假单胞菌、齿状假单胞菌或连翘假单胞菌混合的耐酸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酶是否能灭活变形链球菌的CSP。

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.