Membrane rigidity regulates E. coli proliferation rates

Abstract

Combining single cell experiments, population dynamics and theoretical methods of membrane mechanics, we put forward that the rate of cell proliferation in E. coli colonies can be regulated by modifers of the mechanical properties of the bacterial membrane. Bacterial proliferation was modelled as mediated by cell division through a membrane constriction divisome based on FtsZ, a mechanically competent protein at elastic interaction against membrane rigidity. Using membrane fuctuation spectroscopy in the single cells, we revealed either membrane stifening when considering hydrophobic long chain fatty substances, or membrane softening if short-chained hydrophilic molecules are used. Membrane stifeners caused hindered growth under normal division in the microbial cultures, as expected for membrane rigidifcation. Membrane softeners, however, altered regular cell division causing persistent microbes that abnormally grow as long flamentous cells proliferating apparently faster. We invoke the concept of efective growth rate under the assumption of a heterogeneous population structure composed by distinguishable individuals with diferent FtsZcontent leading the possible forms of cell proliferation, from regular division in two normal daughters to continuous growing flamentation and budding. The results settle altogether into a master plot that captures a universal scaling between membrane rigidity and the divisional instability mediated by FtsZ at the onset of membrane constriction.