Effects of Growth Condition Changes on the Photosynthetic Pigment Systems for Green Sulfur Bacteria. A Study on the Constituent of the Photosynthetic Pigment in Chlorosome.

Abstract

Green sulfur bacteria such as Chlorobium limicola f. thiosulfatophilum 6230 (Cb. limicola) have characteristic light-harvesting vesicles called chlorosome, which is surrounded by the mono-layer envelope of galactolipid¹). The chlorosomes contain bacteriochlorophyll (BChl) c, BChl d or BChl e molecules as a rod-like self-aggregates for light-harvesting. The BChls in chlorosomes of Cb. limicola consist of four major homologs possessing different alkyl groups at 8- and 12-position; [E,M]-, [E,E]-, [P,E]-, and [I,E]BChl (Fig.1) ²⁾. The homologation process increases the hydrophobic interactions between the BChl molecules, giving rise to larger aggregates³⁾. Nevertheless, it is not clarified why the BChls in the chlorosomes of green sulfur bacteria have so many different homologs.