| dc.description.abstract | Motility helps bacteria explore different environments and promotes the chances of their survival. Motility is powered by the rotation of thin helical appendages called flagella. Each flagellum is rotated by a transmembrane flagellar motor. A flagellar motor consists of a rotor and several stator units that deliver torque. Switching in the direction of the motor rotation enables navigation in response to chemical signals – termed chemotaxis – which helps the cell swim to favorable surfaces. In addition, the flagellar motor has been implicated in tactile sensing of surfaces, which helps bacteria establish colonies on surfaces. Previous research indicated that physical obstruction of the rotation of the flagellar motor caused several stator units to be recruited in Escherichia coli. The role of stator recruitment in the signaling events that lead to bacterial colonization of surfaces is unknown. In this dissertation, I discuss our recent efforts to explain the mechanisms by which stator recruitment modulates the binding affinity of a major chemotaxis protein, CheY-P, to the flagellar motor. Our results indicate that the motor regulates its sensitivity to chemical signals by controlling the binding of CheY-P to the motor with mechanical force. These findings explain for the first time how bacteria are able to robustly target different niches irrespective of the fluctuations in the environmental conditions. To further delineate the link between environmental fluctuations and chemotaxis, we worked with a carcinogenic pathogen, H. pylori. The major technical challenge in H. pylori is the lack of suitable assays to probe the behavior of flagellar motors. Using particle-tracking approaches, we discovered that H. pylori cells swim faster when moving forward, and slower when swimming backward. Based on this finding, we developed a novel approach to determine the sensory output of the flagellar motors. This approach revealed that H. pylori employ a flagellar modulation strategy that is very similar to that employed by the model species, E. coli. These findings shed light on fundamental problems in chemotaxis and bacterial colonization, which are major biomedical challenges. | en |
