Disrupting bacterial cytoskeletal protein interaction partners modulates geometric localization and alters cell shape.

The shape a bacterial cell assumes is an essential component in its ability to interact with its physical environment. For many bacterial species, shape is genetically encoded in the action of a small number of cell shape determining proteins. These proteins guide the building of a rigid peptidoglycan cell wall of a given geometry. We use a computational imaging framework to reconstruct the 3D shape of individual cells from fluorescence microscopy images and determine where a secondary fluorescent probe is enriched. In the straight-rod bacterium Escherichia coli, the bacterial actin MreB is enriched in areas with low Gaussian curvature, avoiding the poles. Disrupting MreB's interactions with the transmembrane protein RodZ alters MreB's geometric localization and cells lose their characteristic rod-like morphology. In the helical-rod bacterium Helicobacter pylori, the bactofilin CcmA is preferentially enriched at regions of small positive Gaussian curvature along the outer or major helical axis. Disrupting CcmA interaction partners results in less CcmA on the membrane, altered geometric localization of CcmA, and loss of the characteristic helical morphology of cells. These results are consistent with a model of cell shape determination that includes proper geometric localization of bacterial cytoskeletal proteins.