Mechanism of Asymmetric Growth of the Bacterial Plant Pathogen Agrobacterium tumefaciens

细菌细胞通过细胞壁的扩张而生长。由于细菌细胞壁是一个重要的抗生素靶点，并引发免疫反应，因此了解细菌生长具有广泛的根本利益。这项工作将揭示植物病原体根癌农杆菌生长的分子机制。A.根癌农杆菌是数百种开花植物冠瘿病的病原体，并且是苗圃植物如苹果、李和樱桃的特别问题。值得注意的是，A.根癌农杆菌表现出细菌生长的非典型形式，其中新的生长被限制在细胞的一端（不对称生长）。不对称的细菌细胞生长相对知之甚少，但在不同的土壤栖息细菌中经常观察到。因此，拟议的科学工作预计将提供有关细菌生长机制的关键见解，这可能导致重要的应用，如限制冠瘿病。最后，与科学教育专家合作，将开发一个关于细菌抗生素耐药性出现的动手，基于调查的实验室模块。本单元将为高中生提供一个参与研究的机会，并将提供对进化过程的理解。许多重要的问题仍然是关于细胞壁生物发生的机制和调控。细胞壁的生物发生是如何在时间和空间上控制的？如何保持单元格的长度和宽度？这些问题主要在模型细菌中得到解决，例如大肠杆菌和枯草芽孢杆菌，它们利用细胞壁生长的分散模式。将细菌细胞生长的分析扩展到具有不对称生长的生物体，将揭示细胞壁生物合成的生物合成、组装和调节的新机制。本研究的目的是利用A. tumefaciens作为模型。以下问题将用于指导这项工作。在伸长过程中，细胞壁的生物发生是如何被限制在新的极上的？细胞壁生物发生是如何重定向到中细胞以使细胞分裂并使新的两极成为细胞壁生物发生的活性位点的？细胞壁生物发生成像的最新进展将被用来探测单极生长的机制。使用系统的方法，候选蛋白质的生物合成，组装或细胞壁生物发生的调节的作用将被表征。基因筛选将用于揭示参与细菌细胞生长过程的其他蛋白质。拟议的研究将提高目前对细胞壁生物发生如何在空间和时间上受到调节的理解，并将为相对未探索但普遍的细菌细胞生长模式提供关键见解。

Bacterial cells grow through expansion of their cell walls. Since the bacterial cell wall is an important antibiotic target and triggers immune responses, understanding bacterial growth is of broad fundamental interest. The proposed work will reveal the molecular mechanisms underlying growth of the plant pathogen, Agrobacterium tumefaciens. A. tumefaciens is the causative agent of crown gall disease in hundreds of flowering plants and is a particular problem for nursery plants such as apple, plum, and cherry. Remarkably, A. tumefaciens exhibits an atypical form of bacterial growth, in which new growth is restricted to one end of the cell (asymmetric growth). Asymmetric bacterial cell growth is relatively poorly understood, but has been observed frequently in diverse soil dwelling bacteria. Thus, the proposed scientific work is expected to provide key insights regarding mechanisms of bacterial growth, which may lead to important applications such as limiting crown gall disease. Finally, in collaboration with experts in science education, a hands-on, inquiry based lab module on the emergence of antibiotic resistance in bacteria will be developed. This module will provide high school students with an opportunity to participate in research and will provide an understanding of evolutionary processes.Many important questions remain about the mechanism and regulation of cell wall biogenesis. How is cell wall biogenesis controlled in time and space? How are cell lengths and widths maintained? These questions have been primarily addressed in model bacteria, such as Escherichia coli and Bacillus subtilis, which utilize a dispersed mode of cell wall growth. Expanding the analysis of bacterial cell growth into organisms with asymmetric growth will reveal new mechanisms for the biosynthesis, assembly, and regulation of cell wall biogenesis. In this project, the objective is to elucidate the mechanisms underlying unipolar growth of bacteria belonging to the Rhizobiales clade of Alphaproteobacteria using A. tumefaciens as a model. The following questions will be used to guide this work. How is cell wall biogenesis restricted to the new pole during elongation? How is cell wall biogenesis redirected to mid-cell to enable cell division and prime the new poles to serve as active sites for cell wall biogenesis? Recent advances in imaging cell wall biogenesis will be used to probe the mechanism of unipolar growth. Using a systematic approach, the role of candidate proteins in the biosynthesis, assembly, or regulation of cell wall biogenesis will be characterized. Genetic screens will be utilized to reveal additional proteins involved in bacterial cell growth processes. The proposed studies will improve the current understanding of how cell wall biogenesis is spatially and temporally regulated and will provide key insights into a relatively unexplored, but prevalent mode of bacterial cell growth.