Metabolism of Phosphatidylglycerol and Lysyl Phosphatidylglycerol in Staphylococcus aureus

The metabolism of phosphatidylglycerol and lysyl phosphatidylglycerol was studied in Staphylococcus aureus under four conditions: growing at p H 7.0 and 5.2, and not growing (resting) at p H 7.0 and 5.2. Measurements of the amounts of phosphatidylglycerol and lysyl phosphatidylglycerol, as well as labeling and pulsechase experiments, revealed that the phosphate group of the former and the lysyl group of the latter were in a state of active turnover. A marked decline in the cellular level of phosphatidylglycerol observed when cells were resting at p H 5.2 was found to be caused by both a decrease in synthesis and an increase in catabolism. The level of lysyl phosphatidylglycerol was found to be relatively constant under the four incubation conditions, although the lysyl moiety was in a state of turnover. Experiments designed to test the possible role of lysyl phosphatidylglycerol as a lysyl group donor in biosynthetic processes or in lysine transport were negative; no evidence to support the hypothesis that lysyl phosphatidylglycerol serves as an intermediate was obtained.