Membrane Lipids in Cyanobacteria

Abstract

Cyanobacteria, a large group of microorganisms in the prokaryotic kingdom, perform oxygenic photosynthesis using two photosystems that resemble those in the chloroplasts of eukaryotic plants. Cyanobacteria contain three glycolipids, monogalactosyldiacylglycerol, digalactosyldiacylglycerol and sulfoquinovosyldiacylglycerol, and a phospholipid, phosphatidylglycerol, as major glycerolipids. The lipid composition of most cyanobacteria is similar to that of the inner envelope membranes and thylakoid membranes of the chloroplasts of higher plants, and it is different from that of the membranes of most bacteria, which contain phospholipids as major glycerolipids. Cyanobacteria can be classified into four groups with respect to the composition of the fatty acids of their glycerolipids. Since some strains, such as Synechocystis sp. PCC 6803 and Synechococcus sp. PCC 7942, take up exogenous DNA autonomously, they are naturally transformable. Thus, molecular biological techniques, for example, transformation and gene targeting, can easily be applied to these strains and they provide useful systems for studying the molecular aspects of the biosynthesis of lipids and fatty acids, as well as of the functions of membrane lipids in oxygenic photosynthesis. Furthermore, since cyanobacteria respond to changes in a variety of environmental conditions by altering their membrane lipids, they are also useful systems for studying the acclimation of the photosynthetic machinery to environmental factors such as temperature.