Fragility of the permeability barrier of Escherichia coli

An unsaturated fatty acid requiring auxotroph of Escherichia coli was grown with addition of various unsaturated fatty acids. The permeability of the cells for erythritol appeared to be strongly dependent on the fatty acid incorporated in the membrane lipid. Below certain temperatures, depending on the fatty acid incorporated into the lipids, the membrane of the cells became fragile. Mechanical stress on and also rapid cooling of the cells caused release of intracellular cations and small non-electrolyte molecules. By comparison of the cells with liposomes, prepared from synthetic lecithin, the fragility of the cells could be explained as being the consequence of the solidification of the paraffin core