Metabolism and Function of Bacterial Lipids

Abstract

In a previous communication (1) we have described some of the general features of the phospholipid metabolism of Escherichia coli B as revealed by experiments in which growing cultures of this organism were labeled with pulses of 32Pi. In such experiments, phosphatidylglycerol and phosphatidylethanolamine were found to be the principal labeled glycerophosphatides in the fraction of lipids readily extractable with chloroform-methanol. In cultures growing exponentially, 32P-labeled phosphatidylethanolamine is metabolically stable, while the kinetics of labeling of phosphatidylglycerol is consistent with a dynamic function for this phospholipid, requiring turnover or, alternatively, with a role as a metabolic intermediate. Upon very brief exposure of the cells to 32Pi, labeled phosphatidic acid and phosphatidylserine could also be detected among the first lipid products to be labeled. In this paper, the enzymatic synthesis of phosphatidylserine, phosphatidylethanolamine, and phosphatidylglycerol in cell-free extracts of E. coli will be described. All of these lipids have been found to be derived from cytidine diphosphate diglyceride. A preliminary report of some of this work has been published (2).