Printed in U.S.A. Mutants of Escherichia coli Defective in Membrane Phospholipid Synthesis: Mapping of sn-Glycerol 3-Phosphate

plsB mutants of Escherichia coli are sn-glycerol 3-phosphate auxotrophs which owe their requirement to a Km defect in sn-glycerol 3-phosphate acyltransferase, the first enzyme in the phospholipid biosynthetic pathway. We have located the plsB gene at minute 69 of the E. coli genetic map, far removed from the gene defined by mutants with a temperature-sensitive sn-glycerol 3-phosphate acyltransferase. The plsB gene was cotransduced with the dctA locus, and the transduction data indicated that the clockwise gene order is asd, plsB, dctA, xyl. plsB- is recessive to plsB+ and all acyltransferase Km mutants tested lie very close to the plsB locus. Effective supplementation ofplsB mutants was shown not to require a defective glpD gene. Isolation and characterization of mutants of Escherichia coli defective in membrane synthe-sis have inaugurated a series of investigations into the structural and functional importance of phospholipids in biological membranes (8). sn