Supported Lipid Bilayers of Escherichia coli Extracted Lipids and Their Calcium Dependence

Formation of supported lipid bilayer (SLB) and additional structures of Escherichia coli (E. coli) lipids were investigated with fluorescence microscopy and atomic force microscopy. Ca2+ in the aqueous phase with concentration above 2 mM was necessary for the formation of SLB. Additional lipid structures, string-like structures, the second lipid bilayer, and multilayer stacking appeared on the first layer SLB depending on Ca2+ concentration. The bridging effect of Ca2+ between the negatively charged E. coli lipid bilayers and substrate is the dominant factor determining the two-dimensional and three-dimensional morphology of the E. coli lipid bilayer membranes.