Flavobacterium Gliding Motility:From protein secretion to cell surface movements

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Gliding motility is a form of movement by which certain bacteria commonly found both inside and on the surface of the body are able to move themselves over solid surfaces. Gliding motility relies on an apparatus composed of unique proteins and this project will explore two fundamental cellular processes (protein secretion and cell movement) and the interactions between them that underlie gliding motility. Graduate and undergraduate students as well as postdoctoral fellows will be actively engaged in the project, and will gain experience in interdisciplinary research involving genetics, molecular biology, and microscopic and mathematical modeling. They will also receive training in scientific writing and presentation. Results of the project will be reported by students at national meetings and published in the scientific literature, and genetic tools that are developed will be made available to the scientific community. Results of this research will be incorporated into undergraduate laboratory exercises and public lectures will be presented to convey the excitement of scientific discovery. The research will address 3 specific aims related to the functioning of the type IX secretion system (T9SS) responsible for delivering surface adhesin SprB which is responsible for the gliding motility apparatus. The goals are: (1) to characterize using biochemical and genetic approaches the mechanism by which secreted proteins are targeted to the T9SS; (2) to define the moving components of the motility machinery by fusing fluorescent proteins to components of the motility apparatus to identify those that move rapidly over long distances (mathematical analyses of these movements will be used to construct models to explain gliding); and (3) to distinguish between the T9SS and the gliding motility apparatus to determine which proteins function primarily in secretion, in motility, or in both processes. This will help determine if the T9SS and the gliding motility apparatus are two independent machines or different aspects of a single machine. Cells with mutations in T9SS genes will be examined to determine if they retain gliding motor function. Mutations that result in defects in either motility or secretion, but not both, will be isolated and analyzed to determine which proteins function primarily in secretion and which function in motility. Comparative analysis of the F. johnsoniae and Cellulophaga algicola T9SSs and their respective gliding machines will identify conserved features and highlight the roles of individual proteins in secretion or motility. The bacteria studied belong to the understudied phylum, Bacteroidetes. Bacteriodetes is one of the largest bacterial phyla where the proteins that make up the T9SS and the gliding motility apparatus are common. However, these proteins are not found in other groups of bacteria. A more complete understanding of the T9SS and the gliding machinery will expand our understanding of mechanisms of bacterial protein secretion, dynamic protein movements within cells, and cell movements over surfaces.