Cell surface biogenesis in Streptococcus pneumoniae

项目概要 病原菌的细胞表面含有许多关键的毒力因子，用于与细菌相互作用。 主机。细胞表面聚合物还含有先天免疫系统识别的分子特征 激活防御反应，表面分子或其生物发生途径作为重要目标 用于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细菌实际上将影响发病机制研究的所有领域 为感染新疗法的开发提供信息。尽管细胞表面组装的某些方面可以 从非病原生物的研究可以推断，模型的结果永远不会完全具有预测性。 对于链球菌等病原体来说，与模型的偏离可能尤其明显 肺炎杆菌 (Sp) 采用不同的（卵圆形）形态，并通过与杆状不同的机制生长 传统上，对大肠杆菌和枯草芽孢杆菌等生物体的细胞表面组装的研究 被调查。 Sp 是幼儿和老年人中危及生命的疾病的主要原因，并且 这种生物体的耐药性感染的发生率正在上升。多价Sp的功效 由于表面多糖发生改变的菌株的出现，疫苗的使用也在减少 疫苗诱导的免疫。因此，找到抑制 Sp 生长的新方法非常重要。为此，我们 启动了一项研究 Sp 细胞表面组装的计划，该计划利用了 鲁德纳和伯恩哈特实验室从事细胞壁生物发生、革兰氏阳性生物学、显微镜、生物化学、 和遗传学。重要的是，我们的方法不仅限于充分研究的细胞同系物的表征 来自杆状模型生物的形态发生因子。相反，我们正在利用前进的优势 由现代测序方法支持的遗传筛选，以发现新的参与者和生物机制 参与 Sp 的生长。我们的初步遗传分析发现了青霉素的两种新型调节因子—— Sp 的结合蛋白 (PBP)。这些是在革兰氏阳性菌中确定的第一组控制因素 这些关键细胞壁合酶的活性。该项目的首要目标是通过以下方式研究该机制： 这些因素调节 PBP 活性并将这些酶的功能与其他成分联系起来 的形态发生系统。除了控制 PBP 活性外，正确的表面组装还需要 调节裂解细胞壁的酶。控制这些酶活性的因素很差 在所有细菌中都可以理解。我们的第二个目标将建立在有希望的结果之上，我们已经确定了监管 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 Sp 细胞的裂解。总的来说，我们的结果有望发现新的 阻止细胞壁组装或触发自溶以进行治疗开发的方法。

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.