Geometric localization of cell wall growth and shape determining proteins in Helicobacter pylori

The bacterial kingdom exhibits a wide variety of cell shapes. Our computational imaging framework allows us to extract 3D shapes of individual bacterial cells from fluorescence microscopy images. From these shapes we calculate geometric parameters such as local curvature, surface area, and the enrichment of fluorescent signals. The helical-rod shape of Helicobacter pylori, a human stomach pathogen, is important for its pathogenesis and is an ideal model system for studying complex bacterial cell shapes. In H. pylori, we have been investigating the geometric localization of the proteins and metabolic probes of cell wall growth. To propagate its helical shape, a cell must grow its longer, outer helical axis more than its inner one. Fluorescent, metabolic probes incorporated into the cell wall show enrichment of growth at both the outer and inner axes. Consistent with these labels, two of the proteins associated with cell wall homeostasis show geometric localization. MreB is enriched at regions of small and negative Gaussian curvature and CcmA is enriched at Gaussians curvatures of about 5 μm-², similar to the curvature of the outer axis. These data are consistent with a model of helical-rod like growth that takes the simple rod and elaborates it by defining a outer helical axis.