Abstract
Green sulfur photosynthetic bacteria have extra-membraneous light-harvesting (LH) systems called chlorosomes. Comparing to usual LHs embedded in cytoplasmic membranes of various classes of photosynthetic organisms, chlorosomes are characterized by the following points: they are large micelle-like nano-architectures and the envelopes consist of glyco/phospholipids containing proteins. In the architectures, a huge number of photosynthetic pigments, estimated to 200,000 chlorophyll pigments per single chlorosomes, are capsulated. The green sulfur photosynthetic bacterium Chlorobium tepidum (currently referred to as Chlorobaculum tepidum), which grows at 45 degrees as its optimum temperature, mainly accumulated unique disaccharide rhamnosylgalactosyldiacylglyceride (RGDG) having a methylene-inserted palmitoleyl group together with the corresponding monosaccharide monogalactosyldiacylglyceride (MGDG). Here, we report changes in the structure and composition of the glycolipids dependent upon temperature and period of the cultivation. These results enable us to discuss the biosynthesis as well as the physiological meaning of unique glycolipids in green sulfur photosynthetic bacteria.
