Swarming motility and the regulation of flagellar biosynthesis in Bacillus subtilis

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ABSTRACT Many bacteria are motile by synthesizing corkscrew-like flagella which when rotated propel bacteria through the environment. Each bacterium synthesizes a species-specific number of flagella and inserts the flagella in a species-specific pattern on the cell surface. Flagella are complex nanomachines assembled from dozens of different proteins and how each bacterial species controls flagellar number and patterning is poorly- understood. Moreover, the number of flagella per cell increases when cells come into contact a solid surface to initiate a form of surface motility called swarming. The Kearns lab uses classical forward genetics, super- resolution microscopy, and biochemistry to study flagellar biosynthesis and swarming motility of the Gram positive bacterium Bacillus subtilis. The goals of the project are to understand flagellar biosynthesis in the context of growing cell architecture. First, we will determine how flagellar number is controlled by the poorly- understood master regulator of flagellar biosynthesis SwrA and a response regulator DegU. Second, we will explore how the surface contact response is transduced to inhibit the adaptor-mediated regulatory proteolysis of SwrA and increase flagellar number. Third, we will learn how the flagellar rod insertion through peptidoglycan occurs, and how rod length is controlled to match the thickness of peptidoglycan. Fourth, flagella are synthesized in a grid-like pattern and we will study how flagellar patterning is interpreted and updated in time during cell growth, and coordinated with peptidoglycan insertion. Ultimately, we want to achieve a holistic understanding of how a cell dynamically governs the initiation of flagellar biosynthesis at specific locations to insert the machine through the cell envelope. Our basic research is fundamental to how cells self-organize and is applicable to the spatiotemporal control of the assembly of transenvelope nanomachines involved in pathogenesis including flagella, pili and secretion systems like the injectisome.