Global control of differentiation in Caulobacter

描述（由申请人提供）：致病菌的持续存在和使其感染宿主的过程需要多种信号的整合。了解细菌如何协调多个过程对于我们设计策略以抑制其在环境中的持久性和增殖的能力至关重要，包括宿主感染期间的病原体，并将导致公共卫生的改善。蛋白质和细胞器在细胞极点的定位是细菌与环境相互作用的重要组成部分；许多致病菌将毒力因子定位在它们的细胞株上。本研究的长期目标是利用模式生物新月形茎杆菌来了解细菌生长过程中细胞分裂、极性定位、形态变化和细胞生理是如何协调的。这种细菌在其不对称的生命周期中，以特定的顺序合成了许多极性细胞器，其中一个运动的簇生细胞分化为一个无梗的有柄细胞，然后分裂产生一个簇生细胞和一个有柄细胞。极性细胞器的合成是由一个复杂的信号转导网络调节的，其中多个输入是集成的。这些输入包括协调细胞器合成与细胞分裂和生理的检查点。极性发育的高潮是在极处形成一层薄薄的细胞包膜延伸，称为茎，这可以提高营养吸收。本研究的主要目的是确定极性发育与细胞分裂的偶联调控机制，并确定这种调控途径如何在茎合成中达到顶峰。抑制细胞分裂激活一个检查点，在鞭毛合成后停止新细胞极的发育：毛、支架和柄不合成。本研究的第一个目标是确定PodJ（一种发育调节因子）在细胞分裂检查点中的功能。在早期分裂前细胞中，全长形式的PodJ PodJL定位于茎对面的极点，并在细胞分裂时被加工成较短的形式PodJs。当细胞分裂被阻断时，PodJL加工被抑制。当细胞分裂被抑制时，所有已知的允许极性发育的突变体都恢复了PodJL的加工，这表明PodJL的加工提供了一个分子开关，标志着特定发育阶段的进展。PodJL加工的机制和调控及其在正常生长过程中极性发育中的作用将被确定。第二个目标是确定当细胞分裂被抑制时，抑制极性发育和PodJL加工所需的应答调节因子TacA的作用。调控TacA磷酸化的机制以及该途径如何调控PodJL加工将被确定。第三个目标是研究茎秆合成和调控所需的基因，包括TacA调控的基因，并利用电子冷冻层析技术对野生型和突变株茎秆合成进行详细的超微结构分析。我们的研究将为我们如何干扰和抑制病原菌感染所需的多个过程的执行提供见解。公共卫生相关性：致病菌依靠多种外部和内部信号的整合来对其环境作出反应并实现有效的宿主感染。本研究使用模式细菌新月形茎杆菌来确定细菌如何整合多种调控途径以产生特定的有利形态。了解细菌如何协调多个过程对于我们抑制它们的持久性、增殖和宿主感染的能力至关重要，并将导致公众健康的改善。

DESCRIPTION (provided by applicant): The persistence of pathogenic bacteria and the processes that enable them to infect their hosts require the integration of multiple signals. Understanding how bacteria orchestrate multiple processes is critical for our ability to design strategies to inhibit their persistence and proliferation in the environment, including pathogens during host infection, and will result in the improvement of public health. The localization of proteins and organelles at the cell poles is an important component of bacterial interaction with the environment; many pathogenic bacteria localize virulence factors to their cell poles. The long-term goal of this research is to use the model organism Caulobacter crescentus to understand how cell division, polar localization, morphological changes, and cell physiology are coordinated during bacterial growth. This bacterium synthesizes a number of polar organelles in a specific order during its asymmetric life cycle, in which a motile swarmer cell differentiates into a sessile stalked cell that then divides to produce a swarmer and a stalked cell. The synthesis of polar organelles is regulated by an elaborate signal transduction network, in which multiple inputs are integrated. These inputs include checkpoints that coordinate organelle synthesis with cell division and physiology. Polar development culminates in the morphogenesis of a thin cell envelope extension at the pole, known as the stalk, which improves nutrient uptake. The main objective of this research is to identify the regulatory mechanisms that couple polar development to cell division, and to determine how this regulatory pathway culminates in stalk synthesis. Inhibition of cell division activates a checkpoint that halts development of the new cell pole after flagellum synthesis: the pili, the holdfast, and the stalk are not synthesized. The first goal of this research is to determine the function of PodJ, a developmental regulator, in the cell division checkpoint. A full length form of PodJ, PodJL, localizes to the pole opposite the stalk in early predivisional cells, and is processed into a shorter form, PodJs, at the time of cell division. PodJL processing is inhibited when cell division is blocked. All known mutants that allow polar development when cell division is inhibited restore PodJL processing, suggesting that the processing of PodJL provides a molecular switch that signals the progression of specific developmental stages. The mechanisms and regulation of PodJL processing and their role in polar development during normal growth will be determined. The second goal is to determine the role of a response regulator, TacA, required for the inhibition of polar development and PodJL processing when cell division is inhibited. The mechanisms that regulate the TacA phosphorelay and how this pathway regulates PodJL processing will be determined. The third goal is to study genes required for stalk synthesis and regulation, including genes regulated by TacA, and to perform a detailed ultrasctucture analysis of stalk synthesis in wild-type and mutant strains using electron cryotomography. Our study will provide insight into how we can interfere with and inhibit the execution of the multiple processes required for the infection of pathogenic bacteria. PUBLIC HEALTH RELEVANCE: Pathogenic bacteria rely on the integration of multiple external and internal signals to respond to their environment and achieve effective host infection. This proposal uses the model bacterium Caulobacter crescentus to determine how bacteria integrate multiple regulatory pathways to produce specific advantageous morphologies. Understanding how bacteria orchestrate multiple processes is critical for our ability to inhibit their persistence, proliferation, and host infection, and will result in the improvement of public health.