To provide more insight into the spatial arrangement of the lipids in xy-plane we present, in Figure , the lateral density profiles (LDP) of lipids in the three membranes NM, MMU, and MMS at 250 K. It is observed that the NM and MMU membranes remain fluid, while the MMS is gel at 250 K, consistent with the drastic changes in the packing density and fluidity between 290 and 300 K (see Figure ). Closer inspection reveals that a small portion of the MMS membrane remains fluid. As shown in Figure , this fluid domain is mainly composed of mono-and di-unsaturated lipids. The Voronoi-based spatial profiles of membrane thickness at different temperatures (Figure ) shows that the size of the fluid domain increases with increasing temperature such that at 300 K the membrane becomes entirely fluid. Figure presents the area per lipid and thickness values for different lipids, grouped by the type of acyl chain (cyclopropane ring containing, unsaturated, and fully saturated). Clearly, for NM, all lines coincide with each other suggesting a uniformity in the cooling response of the lipids. On the other hand, for MMS, the saturated lipids respond more strongly towards cooling than the unsaturated lipids. This is due to the closer packing of saturated lipids than the unsaturated lipids. In MMU membrane the tri-unsaturated lipids occupy more area although the thickness is same throughout the lipid types. In brief, Figure indicates that cyclopropane rings in the lipid acyl chains maintain packing density and fluidity of the cell membrane of E. coli very similar to what unsaturated acyl chain containing lipid does. However, the specific purpose of cyclopropanation of the lipid acyl chain is not clear from the CG resolution. The area and thickness of lipids with different headgroups are not distinguishable from each other from the present CG-based simulation (see Figures ).