FIG 1.

Membrane phospholipids of Escherichia coli. (A) Native lipid biosynthesis in E. coli. Genes encoding the following enzymes and associated with each biosynthetic step are listed next to the arrows. Lipid abbreviations are as follows: DAG, diacylglycerol; PS, phosphatidylserine; PA, phosphatidic acid; PE, phosphatidylethanolamine; PG, phosphatidylglycerol; CL, cardiolipin. Enzymes are indicated as follows: 1, CDP-DAG synthetase; 2, PS synthase; 3, PS decarboxylase; 4, PGP synthase; 5, PGP phosphatases; 6, CL synthases; 7, PG:membrane-derived oligosaccharide sn-glycerol-1-P transferase; 8, DAG kinase. Boxed phospholipids are the major phospholipids of E. coli; phospholipids in red are anionic lipids. (B) TLC analysis of total lipid extracts from WT and phospholipid-altered strains grown to mid-exponential phase in M9 minimal medium supplemented with 2% glucose and SC amino acids. (C) Histograms depict the lipid compositions determined by total phosphate assay after scraping off each lipid spot for the various strains. Error bars show the standard deviations (SD); n = 3.