Distribution of lipids in cytoplasmic and outer membranes of Escherichia coli K12.

The lipid composition of cytoplasmic and outer membranes of Escherichia coli K12 was studied. Compared with the cytoplasmic membrane, the outer membrane is enriched in both saturated fatty acids and phosphatidylethanolamine. This is also the case when the fatty acid composition of the phospholipids is changed, either by varying the growth temperature or by using mutants with alterations in their fatty acid metabolism. Phosphatidylethanolamine of the outer membrane contains relatively more saturated fatty acids than phosphatidylethanolamine of the cytoplasmic membrane.