Interaction of lipid vesicles with an heptoseless strain of Escherichia coli.
The conditions for uptake of lipid vesicles by the deep rough mutant of Escherichia coli, strain D21F2, and the parent strain, K12 were studied. A variety of lipids including phosphatidylcholine, phosphatidylethanolamine, diglyceride, cholesterol and palmitic acid were taken up much more readily by the deep rough mutant than the K12 strain. The uptake of lipid in the mutant strain was enhanced by Ca2+ at an optimal concentration of 2 mM, by alkaline pH and by growth of the cells up to the late exponential phase. With K12 cells, cholesterol and phosphatidylethanolamine were taken up from equimolar mixtures at similar rates thus suggesting the involvement of a fusion process. With D21F2 cells, the endogenous lipids of which had been labelled by growth in [3H] acetate, the uptake of exogenous [32P] phosphatidylethanolamine and [32P] lysophosphatidylethanolamine was not accompanied by a loss of endogenous lipid to the incubation medium. This precluded the involvement of an exchange mechanism. The absorbed exogenous lipid and the endogenous lipids of D21F2 cells displayed the same susceptibility to hydrolysis by added phospholipase C. This indicated that the exogenous lipid is inserted into lipid core of the membrane rather than adsorbed at the cell surface.
D002118:Calcium / Q000494:pharmacology; D002784:Cholesterol / Q000494:pharmacology; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism*; D006539:Heptoses / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D050356:Lipid Metabolism; D009154:Mutation; D010714:Phosphatidylethanolamines / Q000494:pharmacology; D010761:Phosphorus Radioisotopes; D013997:Time Factors; D010738:Type C Phospholipases / Q000494:pharmacology
D006539:Heptoses; D010714:Phosphatidylethanolamines; D010761:Phosphorus Radioisotopes; D002784:Cholesterol; D010738:Type C Phospholipases; D002118:Calcium