For understanding the role of LCFAs in maintaining the fluidity of a realistic cell membrane under drastic cooling, we have simulated a model lipid membrane of E. coli bacteria consisting of 14 different types of lipids from all-atom (AA) and coarse-grained (CG) resolution. To elucidate specific advantages of LCFAs, we have also simulated two additional membranes with modified lipidome by replacing all the cyclopropane rings with either C-C single bond or C=C double bonds. The fully hydrated membranes are simulated at 6 different temperatures: 250, 270, 290, 310, 330, and 350 K.