Oral streptococcal-enterococcal peptide-mediated intercellular communication

描述(申请人提供)：戈登链球菌，一种重要的口腔共生细菌，可与牙源性感染和感染性心内膜炎有关。粪肠球菌是肠道微生物区系的主要组成部分，已成为一种机会性病原体，已知携带编码临床上重要毒力因子和抗生素耐药性的多个质粒。粪肠球菌也在口腔中发现，在牙髓感染中具有特别重要的意义，在牙髓治疗失败和持续感染的牙髓管中通常可以恢复。戈登氏链球菌和粪肠球菌之间的移动DNA元件的转移已经在体外和体外牙齿模型中得到证实。由于这两种细菌都生活在口腔中，并且已经从顽固性牙髓感染中恢复过来，这种DNA转移有可能在体内发生。粪肠球菌分泌多种七肽和八肽信息素，在含有特定结合质粒家族的肠球菌中诱导交配反应。这些多肽在携带质粒的应答细胞中诱导聚集/交配反应，涉及参与细胞间聚集和DNA转移功能的细胞表面蛋白的表达，从而促进细胞间的接触和质粒的转移。这一过程在含质粒肠球菌供体和无质粒肠球菌受体之间得到了很好的研究。PAM373是一种与其同源信息素cAM373反应的肠球菌结合质粒，cAM373由无质粒肠球菌分泌。对包括万古霉素在内的多种抗生素具有耐药性的PAM373的衍生物也对cAM373有反应。PAM373是一种新型的载体，因为它还能响应戈登链霉菌的信息素样信号。我们最近已经确定了编码戈登氏链球菌七肽gordonii-cAM373的基因camg。合成的Gordonii-cAM373能在粪肠球菌中诱导出丛集反应，并诱导质粒从粪肠球菌转移到S.gordonii。这是第一次证明来自链球菌的多肽可以作为粪肠球菌的交配信号，并促进属间的质粒转移。这些结果对链球菌信息素样肽在属间DNA转移中的潜在作用具有有趣的意义，并表明这种肽可以提供信号，通过这些信号粪肠球菌可能有助于在共生口腔菌群中储存毒力和耐药性决定因素。相反，这一诱导粪肠球菌假定毒力因子表达的链球菌信号的证明表明，多菌感染中口腔链球菌的存在可能增加粪肠球菌的致病潜力。我们建议通过以下具体目标来进一步研究这种新的属间细胞间的通信：1)进一步表征戈登氏链球菌CAMG表达和加工所涉及的分子机制，并确定有利于或不利于其表达的环境条件；2)监测粪肠球菌毒力基因在接触戈尔登氏链球菌信息素产生细胞和gordonii-cAM373肽时的反应。 与公共卫生相关：肠球菌可能具有使它们对几乎所有已知抗生素产生抗药性的基因。携带这些基因的DNA质粒可以由多肽发出信号，以转移到新的肠球菌细胞。我们建议研究一种新发现的来自一种通常在口腔中发现的链球菌的多肽，它可以信号肠球菌将其质粒转移到链球菌，从而潜在地影响口腔感染的严重程度和治疗。

DESCRIPTION (provided by applicant): Streptococcus gordonii, a prominent commensal bacterium of the human oral cavity, can be associated with odontogenic infections as well as infective endocarditis. Enterococcus faecalis, predominantly a component of gut microflora, has emerged as an opportunistic pathogen, known to carry multiple plasmids encoding clinically significant virulence factors and antibiotic resistance. E. faecalis is also found in the oral cavity and is of particular significance in endodontic infections where it is commonly recovered from pulp canals with failed endodontic treatment and persistent infection. Transfer of mobile DNA elements between S. gordonii and E. faecalis has been demonstrated in vitro and in an ex vivo tooth model. Since both organisms inhabit the oral cavity and have been recovered from recalcitrant endodontic infections, such DNA transfer has the potential to occur in vivo. E. faecalis secretes multiple hepta- and octameric peptide pheromones that induce a mating response in enterococci harboring specific families of conjugative plasmids. The peptides induce a clumping/mating response in plasmid-carrying responder cells, involving expression of cell-surface proteins involved in inter-cellular aggregation and DNA transfer functions, thereby facilitating inter-cellular contact and plasmid transfer. This process is well-studied between plasmid-bearing enterococcal donors and plasmid-free enterococcal recipients. Plasmid pAM373 is an enterococcal conjugative plasmid that responds to its cognate pheromone cAM373 secreted from plasmid-free enterococci. Derivatives of pAM373 that carry resistance to multiple antibiotics including a vancomycin, are also cAM373-responsive. Plasmid pAM373 is novel in that it also responds to pheromone-like signals from S. gordonii. We have recently identified the gene, camG, that encodes the S. gordonii heptapeptide gordonii-cAM373. Synthetic gordonii-cAM373 was able to induce a clumping response in E. faecalis and induce plasmid transfer from E. faecalis to S. gordonii. This is the first demonstration that a peptide from a streptococcal species can act as an E. faecalis mating signal and facilitate intergeneric plasmid transfer. These results have intriguing implications for a potential role of streptococcal pheromone-like peptides in intergeneric DNA transfer, and suggest that such peptides could provide signals by which E. faecalis could contribute to the reservoir of virulence and resistance determinants in the commensal oral flora. Conversely, this demonstration of a streptococcal signal that induces expression of E. faecalis putative virulence factors suggests that the presence of oral streptococci in polymicrobial infections may increase the pathogenic potential of E. faecalis. We propose to further investigate this novel intergeneric cell-to-cell communication via the following Specific Aims: 1) to further characterize the molecular mechanisms involved in S. gordonii camG expression and processing and determine environmental conditions that favor or disfavor its expression; 2) To monitor the response of E. faecalis virulence genes when exposed to S. gordonii pheromone-producing cells and gordonii-cAM373 peptide. PUBLIC HEALTH RELEVANCE: Enterococci can have genes that make them resistant to virtually all known antibiotics. The DNA plasmids that carry these genes can be signaled by peptides to transfer to new enterococcal cells. We propose to investigate a newly-discovered peptide from a streptococcus bacterium normally found in the mouth that can signal enterococci to transfer their plasmids to streptococci, potentially affecting the severity and treatment of oral infections.