Swarming motility and the regulation of flagellar biosynthesis in Bacillus subtilis

ABSTRACT Many bacteria are motile by synthesizing corkscrew-like flagella which when rotated propel bacteriathrough the environment. Each bacterium synthesizes a species-specific number of flagella and inserts theflagella in a species-specific pattern on the cell surface. Flagella are complex nanomachines assembled fromdozens 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 toinitiate 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 Grampositive bacterium Bacillus subtilis. The goals of the project are to understand flagellar biosynthesis in thecontext 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 willexplore how the surface contact response is transduced to inhibit the adaptor-mediated regulatory proteolysisof SwrA and increase flagellar number. Third, we will learn how the flagellar rod insertion throughpeptidoglycan occurs, and how rod length is controlled to match the thickness of peptidoglycan. Fourth, flagellaare synthesized in a grid-like pattern and we will study how flagellar patterning is interpreted and updated intime during cell growth, and coordinated with peptidoglycan insertion. Ultimately, we want to achieve a holisticunderstanding of how a cell dynamically governs the initiation of flagellar biosynthesis at specific locations toinsert the machine through the cell envelope. Our basic research is fundamental to how cells self-organize andis applicable to the spatiotemporal control of the assembly of transenvelope nanomachines involved inpathogenesis including flagella, pili and secretion systems like the injectisome.