Lipids, Quinones and Fatty Acids of Anoxygenic Phototrophic Bacteria

Abstract

Differences in profiles of polar lipids and quinones distinguish major groups of phototrophic prokaryotes. Also the fatty acid composition of representative species of purple sulfur bacteria, purple nonsulfur bacteria, green sulfur bacteria, Chloroflexus aurantiacus and Heliobacterium and Heliobacillus species are significantly different. Phospholipids, and specifically PG, are present in all phototrophic bacteria. The presence of ornithine lipids and the sulfolipid SQDG has been clearly established only in purple nonsulfur bacteria. Various glycolipids are major components in Chloroflexus and green sulfur bacteria and are also common in Chromatiaceae, but absent from Ectothiorhodospiraceae and Heliobacterium; occasionally, they occur in purple nonsulfur bacteria. The presence of MGDG has only been established for green sulfur bacteria. The specific distribution of major quinones in anoxygenic phototrophic bacteria and the variety of hopanoid triterpene structures found in these bacteria are considered in this chapter. A major part of the chapter is concerned with polar lipids of Rhodobacter species because they have been most intensively studied in this chapter. Also biosynthesis, lipid transfer activities, and incorporation of lipids into different membrane fractions are discussed. Special attention is paid to the influence of growth conditions on lipid and fatty acid composition and to possible differences in the composition of cellular membrane fractions (CM, ICM, OM).