Coordinate regulation of competence and pneumocin production in S. pneumoniae

描述（申请人提供）：肺炎链球菌（肺炎球菌）是一种重要的人类病原体，是细菌性脑膜炎、肺炎和中耳炎的最常见原因。虽然肺炎球菌可引起严重疾病，但它是正常鼻咽菌群的一部分。它吸收和结合外源DNA的能力使肺炎球菌能够通过提供遗传适应资源来抵抗清除的企图。基因组分析表明，该物种具有巨大的遗传多样性，主要来源于与其他链球菌DNA的重组。肺炎球菌的能力状态是由com系统控制的群体感应系统调节的，该系统驱动大量基因的产生，包括那些参与DNA摄取和重组的基因。有能力的肺炎球菌可以通过一种叫做“杀兄弟”的机制来分解非有能力的群体，释放出它们的DNA。释放的DNA被有能力的细胞吸收，并可以作为新的遗传物质的来源。参与杀兄弟和杀兄弟免疫的蛋白质在肺炎球菌和其他相关链球菌物种中高度保守，限制了裂解的目标群体为未能诱导能力的群体成员。从blp位点产生溶解性肺炎球菌细菌素（肺炎素）有可能扩大DNA释放的靶标范围。blp位点由一个平行的群体感应系统控制，以达到能力感应的要求。在早期能力诱导过程中，blp位点上的一些基因被证明是上调的，我们已经证明，在一些分离株中，能力的刺激会诱导肺炎素基因的转录。由于blp簇中编码的肺炎素及其免疫蛋白在不同菌株之间是可变的，因此它们可以促进多种肺炎球菌和相关链球菌的裂解，而不依赖于靶标的能力状态。我们假设，在能力状态下协调表达肺炎素将增加潜在的目标生物DNA释放和摄取。在本研究的目的中，我们将通过能力诱导研究肺炎素交叉刺激的机制。在Aim 2中，我们将确定调节蛋白CiaRH和HtrA在控制blp和com系统之间的串扰中的作用。在Aim3中，我们将通过证明产生肺炎素的菌株在获取外源DNA方面比仅依赖杀兄弟体的菌株具有优势，来验证协调blp/com调节增加了DNA释放的靶标范围。DNA交换事件将在优化条件下进行体外研究，并在小鼠鼻腔定植过程中进行体内研究。尽管正在进行清除宿主和周围菌群的尝试，但这种病原体的持久性证明了基因组多样性和适应性的力量。了解可变表达的肺炎素是如何促成这种多样性的，将使我们能够更好地预测，并可能阻止通过基因交换逃避控制措施的企图。

DESCRIPTION (provided by applicant): Streptococcus pneumoniae (pneumococcus) is an important human pathogen and the most common cause of bacterial meningitis, pneumonia and otitis media. Although it can cause significant disease, pneumococcus is part of the normal nasopharyngeal flora. Its ability to take up and incorporate foreign DNA has allowed pneumococcus to resist attempts at clearance by providing a resource for genetic adaptation. Genome analysis has demonstrated that this species is characterized by an enormous amount of genetic diversity largely derived from recombination with DNA from other streptococci. The competence state in pneumococcus is regulated by a quorum sensing system controlled by the com system which drives the production of a large number of genes including those involved in DNA uptake and recombination. Competent pneumococci can lyse non-competent members of the population releasing their DNA via a mechanism called fratricide. Released DNA is taken up by competent cells and can serve as a source of new genetic material. The proteins involved in fratricide and fratricide immunity are highly conserved among pneumococci and other related strep species limiting the target population for lysis to members of the population that have failed to induce competence. The production of lytic pneumococcal bacteriocins (pneumocins) from the blp locus has the potential to expand the target range for DNA release. The blp locus is controlled by a parallel quorum sensing system to that required for competence induction. A number of genes in the blp locus have been shown to be upregulated during early competence induction and we have demonstrated that stimulation of competence induces transcription of the pneumocin genes in some isolates. Because the pneumocins and their immunity proteins encoded in the blp cluster are variable from strain to strain, they can promote lysis of a wide range of pneumococci and related streptococcal species independent of the competence state of the target. We hypothesize that coordinate expression of pneumocins with the competence state will increase the potential target organisms for DNA release and uptake. In Aim1 of the proposal we will investigate the mechanism of cross stimulation of pneumocin by competence induction. In Aim 2 we will determine the role of the regulatory proteins CiaRH and HtrA in controlling the cross talk between the blp and com systems. In Aim3, we will verify that coordinate blp/com regulation increases the target range for DNA release by demonstrating that pneumocin producing strains have an advantage over strains that rely solely on fratricide in the acquisition of foreign DNA. DNA exchange events will be studied in vitro under optimized conditions and in vivo, during mouse nasal colonization. The persistence of this pathogen despite ongoing attempts at clearance from both the host and the surrounding flora is a testament to the power of genomic diversity and adaptation. Understanding how the variably expressed pneumocins contribute to this diversity will allow us to better anticipate and perhaps block attempts at escape from control measures via genetic exchange.