Compositions of glycerolipids and fatty acid compositions of glycerolipids were compared among Synechocystis sp. PCC 6803 cells grown in the BG-11 medium containing different concentrations of glucose and Na2S2O3 in this study. It was found that Na2S2O3 can effectively increase the percentage of sulphoquinovosyl diacylglycerol (SQDG) and phosphatidylglycerol (PG) to total membrane lipids and the simultaneous application of glucose with Na2S2O3 can counteract the effect of Na2S2O3. In addition, Na2S2O3 can significantly increase the percentage of palmitic acid (C, 16:0) in fatty acid composition of monogalactosyl diacylglycerol (MGDG) and digalactosyl diacylglycerol (DGDG) and decrease the fatty acid unsaturation degree accordingly, and these effects can also be eliminated by glucose. These results indicate that Na2S2O3 can take as a reductant to make membrane lipids in a low unsaturated state, and the simultaneous application of glucose can decrease the reducing power of Na2S2O3. In addition, Na2S2O3 can take as a sulfur donor for the synthesis of SQDG.
A novel lipid occurred when cyanobacterium Synechocystis sp. PCC 6803 cells were grown in BG-11 medium with glucose applied. This lipid was determined to be a glycolipid, designated glycolipid-x (Glyco-x), by staining with alpha-naphthol and concentrated sulfuric acid. The occurrence of Glyco-x accompanies the disappearance of other lipids, especially DGDG. Glyco-x can also be observed in cells grown in BG-11 medium with the application of other carbon sources: fructose, maltose and lactose. Sodium thiosulfate, an effective scavenger of reactive oxygen intermediates, showed strong capability to inhibit glucose-induced occurrence of Glyco-x. In the presence of 0.3% sodium thiosulfate, Glyco-x could only be detected in cells grown in BG-11 medium with 100 mmol/L glucose applied in late-exponential phase. These results suggest that reactive oxygen species might be involved in the occurrence of Glyco-x in cyanobacterium Synechocystis sp. PCC 6803 cells grown in the presence of glucose.
