Pigment Composition of Two Pigment-Protein Complexes Derived from Anaerobically and Semi-Aerobically Grown Rubrivivax gelatinosus, and Identification of a New Keto-Carotenoid, 2-Ketospirilloxanthin

Pigments of two light-harvesting (LH) pigment-protein complexes,LH 1 and LH 2, isolated from the purple bacterium, Rubrivivaxgelatinosus, grown anaerobically and semi-aerobically in thelight were investigated. In the anaerobic culture, pigment compositionsof both LH 1 and LH 2 complexes were approximately equal; OH-spheroidenewas the major carotenoid accompanying spheroidene and spirilloxanthin.In the semi-aerobic culture, pigment compositions of both complexesagain were approximately equal; an oxidized carotenoid, OH-spheroidenone,was the major component accompanying spheroidenone and 2,2'-diketospirilloxanthin.A novel carotenoid of 2-ketospirilloxanthin, an intermediatebetween spirilloxanthin, and 2,2'-diketospirilloxanthin, wasfound in both LH complexes from the semi-aerobic culture. Basedon these results, we propose the presence of both the spheroideneand the normal spirilloxanthin pathways as the biosyntheticpathway of carotenoids in this bacterium. The oxidation procedureof spirilloxanthin by CrtA was also discussed. ¹ This paper is dedicated to Prof. K. Harashima on the occasionof his 70th birthday and his retirement.