Flagellum-Dependent Pole Shape Asymmetry and Dynamics in Caulobacter crescentus

Abstract

The shape of most bacteria is determined by a peptidoglycan cell wall. In rod-shaped bacteria, this dynamic structure is rearranged along the length of the cell during growth or to maintain the shape of the bacterium. The two poles of these bacteria are widely considered inert with respect to cell wall dynamics and the associated changes in shape. Caulobacter crescentus is a rod-shaped bacterium that divides asymmetrically into morphologically distinct daughter cells. Examination of high-resolution images of Caulobacter cells led to the hypothesis that the stalked and flagellated poles havedifferent shapes. This observation, coupled with the fact that the swarmer progeny ofCaulobacter swaps its poles exactly once during each cell cycle, suggests the poles are both asymmetric with respect to one another and dynamic structures that can change shape. In this study, cell pole shapes were quantified to confirm and characterize this asymmetry. Pole shape asymmetry was found to be an inherent property in Caulobacter that is dependent on flagellar synthesis at the pole. Furthermore, temporal analysis of pole dynamics showed that the shape change of the flagellated pole coincides with the activation of flagellar synthesis. Future studies will attempt to elucidate the molecular mechanisms underlying these dynamics.