Flexibility of gram-negative bacterial cell wall

Addition of salts (NaCl and MgCl2) to isolated cell wall of E. coli cause appreciable contraction in volume. This contraction in volume of the cell walls is probably due to binding of the ions to wall polymers, including the peptidoglycan layer and the concomitant release of protons. The peptidoglycan layer of the cell wall is thus an elastic rather than a rigid layer.