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.
