Phospholipid composition and cardiolipin synthesis in fermentative and nonfermentative marine bacteria

Twenty biochemically distinct isolates of marine bacteria, comprising a collection of gram-negative, motile, straight and curved rod-shaped organisms, were separated into fermentative and nonfermentative groups. The isolates were analyzed fro phospholipid composition and the activities of the enzymes, cardiolipin synthetase, and a phosphilipase were determined. The phospholipid compositions of all isolates were generally similar. Phosphatidylethanolamine and phosphatidylglycerol were the major phospholipid classes detected. The absence of cardiolipin in most of the nonfermentative isolates was the most striking observation noted. This was verified chromatographically and by the absence of cardiolipin synthetase activity. In isolates which had cardiolipin, it apparently was synthesized by the condensation of two molecules of phosphatidylglycerol, a mechanism similar to that observed in terrestrial bacteria. Possible correlations between the presence of cardiolipin and Mg-2+ requirements for growth are discussed.