Cell surface biogenesis in Streptococcus pneumoniae

项目摘要 病原菌的细胞表面含有许多关键的毒力因子，这些毒力因子被用来与病原菌相互作用。 主持人细胞表面聚合物还含有由先天免疫系统识别的分子特征， 激活防御反应，表面分子或其生物合成途径是重要的靶点 我们许多最有效的疫苗和抗生素疗法。更好地理解机制 因此，负责细菌表面组装的基因将影响致病机理研究的几乎所有领域， 为开发新的感染治疗方法提供信息。尽管细胞表面组装的某些方面可以 虽然这些模型不能从非致病性生物体的研究中推断出来，但模型的结果永远不会完全具有预测性。 该模型的结果可能对链球菌等病原体特别明显 肺炎链球菌（Sp），采用不同的（卵形）形态，并通过不同的机制从杆状生长 像大肠杆菌和枯草芽孢杆菌这样的生物，传统上对细胞表面组装的研究 被调查了在幼儿和老年人中，sp是威胁生命的疾病的主要原因， 这种微生物的抗药性感染的发生率正在上升。多价Sp的功效 疫苗也在下降，因为出现了表面多糖改变的菌株， 疫苗诱导免疫因此，重要的是要找到新的方法来抑制Sp的生长。为此，我们 已经启动了一项计划，以调查细胞表面组装在Sp，利用联合专业知识的 鲁珀特和伯恩哈特实验室在细胞壁生物发生，革兰氏阳性生物学，显微镜，生物化学， 和遗传学。重要的是，我们的方法并不局限于研究细胞的同源物的特性。 杆状模式生物的形态发生因子。相反，我们正在利用前进 由现代测序方法提供动力的基因筛选，以发现新的参与者和生物机制 参与sp的生长。我们初步的基因分析发现了两种新的青霉素调节剂- 这些是在革兰氏阳性菌中发现的第一组因子， 这些关键细胞壁脱氢酶的活性。该项目的第一个目标是通过以下方式调查该机制： 这些因子调节PBP活性并将这些酶的功能与其他组分联系起来 形态发生系统。除了控制PBP活性之外，适当的表面组装还需要 调节切割细胞壁的酶。控制这些酶活性的因素很差， 在所有细菌中都是如此。我们的第二个目标将建立在有希望的结果，我们已经确定了一个监管 称为脂磷壁酸（LTA）的表面聚合物在控制细胞壁水解酶活性中的作用 LytA负责β-内酰胺处理后的Sp细胞裂解。总的来说，我们的研究结果有望揭示新的 阻断细胞壁组装或引发自溶以用于治疗开发的方法。

PROJECT SUMMARY The cell surface of pathogenic bacteria contains many key virulence factors that are used to interface with the host. Cell surface polymers also contain the molecular signatures recognized by the innate immune system to activate a defensive response, and surface molecules or their biogenesis pathways serve as important targets for many of our most effective vaccine and antibiotic therapies. A better understanding of the mechanisms responsible for bacterial surface assembly will therefore impact virtually all areas of pathogenesis research and inform the development of new treatments for infections. Although some aspects of cell surface assembly can be inferred from studies of non-pathogenic organisms, results from the models will never be entirely predictive. Departures from the model are likely to be especially pronounced for pathogens like Streptococcus pneumoniae (Sp) that adopt a different (ovoid) morphology and grow via distinct mechanisms from rod-shaped organisms like Escherichia coli and Bacillus subtilis where studies of cell surface assembly have traditionally been investigated. Sp is a major cause of life-threatening disease in young children and older adults, and the incidence of drug-resistant infections with this organism is on the rise. The efficacy of the polyvalent Sp vaccine is also declining due to the emergence of strains with altered surface polysaccharides that escape vaccine-induced immunity. It is therefore important to identify new ways of disabling Sp growth. To do so, we have initiated a program to investigate cell surface assembly in Sp that leverages the joint expertise of the Rudner and Bernhardt laboratories in cell wall biogenesis, gram-positive biology, microscopy, biochemistry, and genetics. Importantly, our approach is not limited to the characterization of homologs of well-studied cell morphogenesis factors from the rod-shaped model organisms. Instead we are taking advantage of forward genetic screens powered by modern sequencing methods to discover new players and biological mechanisms involved in Sp growth. Our preliminary genetic analyses have uncovered two novel regulators of the penicillin- binding proteins (PBPs) of Sp. These are the first set of factors identified in gram-positive bacteria that control the activity of these critical cell wall synthases. The first aim of the project will investigate the mechanism by which these factors modulate PBP activity and connect the function of these enzymes with other components of the morphogenetic system. In addition to controlling PBP activity, proper surface assembly also requires the regulation of enzymes that cleave the cell wall. The factors governing the activity of these enzymes are poorly understood in all bacteria. Our second aim will build on promising results where we have identified a regulatory role for surface polymers called lipoteichoic acids (LTAs) in controlling the activity of the cell wall hydrolase LytA responsible for Sp cell lysis following beta-lactam treatment. Overall, our results promise to uncover new ways of either blocking cell wall assembly or triggering autolysis for therapeutic development.