Structure and Synthesis of a Lipid‐Containing Bacteriophage

Enzymes of glycerophosphatide biosynthesis and degradation have been characterized using membrane fractions of Pseudomonas BAL‐31, the host cell of the lipid‐containing bacteriophage PM2. Inner and outer membrane fractions were investigated. Whereas the outer membrane con‐tained more phosphatidylethanolamine and less phosphatidylglycerol than the inner membrane, the fatty acid composition was almost the same for both membranes. The pathway for glycerophos‐phatide biosynthesis was the same as that for Escherichia coli and Bacillus megaterium . The biosyn‐thesis of phosphatidylserine and phosphatidylglycerol was shown to proceed via CDP‐diglyceride as a common intermediate. Phospholipase A hydrolyzed phosphatidylethanolamine more efficiently than phosphatidylglycerol. All of the enzymatic activities were stimulated by Triton X‐100. Phos‐phatidylserine synthetase was stimulated by Na 2 SO 4 and inhibited by Mg 2+ . Phosphatidylserine decarboxylase was completely inhibited by NH 2 OH. Phosphatidylglyceror synthetase was stimulated by Mg 2+ . Phospholipase A was stimulated by Ca 2+ . Phosphatidylserine decarboxylase and phosphatidylglycerol synthetase were localized in the inner membrane fraction. Phosphatidylserine synthetase and phospholipase A were found in both outer and inner membrane fractions. Effects of virus infection on these enzymes were studied. Phosphatidylglycerol synthetase and phospholipase A activity against phosphatidylethanolamine were activated early post‐infection. Phosphatidylserine synthetase and decarboxylase remained unaltered. At later times post‐infection, phosphatidylglycerol synthetase and phosphatidylserine decarboxylase were inactivated and phos‐ phatidylserine synthetase was activated. There was little alteration in phospholipase A activity against phosphatidylglycerol after infection.