Localization of the Escherichia Coli Divisome by Nucleoid Occlusion and Membrane Curvature

Abstract

Cell division in typical rod-shaped bacteria such as Escherichia coli shows a remarkable plasticity in being able to adapt to a variety of irregular cell shapes. Here, we investigate the roles of the Min system and nucleoid occlusion mechanism in supporting this adaption. We study ‘squeezed’ E. coli in shallow nanofabricated channels [1], which despite their highly irregular shapes and large areas, are able to divide into two almost equally sized daughters and we compare this phenotype to normal rod-shaped cells, and mutants carrying deletions in Min and nucleoid occlusion systems. Fluorescently labeled MinD proteins in aberrant cell shapes show an irregular pattern of movement and do generally not generate a reliable signal for localization of the cell division proteins. By contrast, we establish that nucleoid occlusion provides a robust molecular mechanism which is not sensitive to perturbations in cell shapes. We also find that membrane curvature is important in selecting the nucleation site for the divisome. Progressive FtsZ arcs form only in those positions on the circumference of the squeezed E. coli where their line curvature is maximized. Our study underscores the importance of two so far poorly understood mechanisms - nucleoid occlusion and membrane curvature, which E. coli uses to localize their cell division apparatus in multiple of phenotypes.[1] J. Mannik, R. Driessen, P. Galajda, J.E. Keymer and C. Dekker, Proc. Natl. Acad. Sci. USA. 106 (2009) 14861.