ANALYSIS OF HYDROLYTIC PRODUCTS FROM CHOLINE-LABELED HOST-CELL PHOSPHOLIPIDS DURING GROWTH OF RICKETTSIA-PROWAZEKII

A phospholipase activity has been associated with the interaction of R ickettsia prowazekii with the surface of erythrocytes and competent ho st cells as well as during the growth of the rickettsiae within their host cells. Both fatty acid and lysophosphatides have been found in th e interaction of rickettsiae with the surface of eucaryotic cells; thi s finding provided strong evidence for the activity of a phospholipase A. However, fatty acids, but not lysophosphatides, were found during the growth of rickettsiae within cells in which the phospholipids had been radiolabeled with oleic acid; this observation left the type of p hospholipase activity in doubt. In this study, the water-soluble compo nents of phospholipid hydrolysis by phospholipase A plus lysophospholi pase and phospholipase C were determined following the growth of ricke ttsiae in host cells in which the phospholipids had been radiolabeled with choline. In infected cells relative to mock-infected cells, there was a loss of phosphatidylcholine with a corresponding increase not i n lysophosphatidylcholine but in the water-soluble components. There w as a large increase in glycerophosphorylcholine (185%) and a smaller i ncrease in phosphorylcholine (16%). These results indicate that both p hospholipase A activity (plus a lysophospholipase activity) and phosph olipase C were increased during infection by R. prowazekii and that th e former was the predominant activity.