Pigment composition of two pigment-protein complexes derived from anaerobically and semi-aerobically grown Rubrivivax gelatinosus, and identificationof a new keto-carotenoid, 2-ketospirilloxanthin

Pigments of two light-harvesting (LH) pigment-protein complexes, LH 1 and L H 2, isolated from the purple bacterium, Rubrivivax gelatinosus, grown anae robically and semi-aerobically in the light mere investigated. In the anaer obic culture, pigment compositions of both LH 1 and LH 2 complexes were app roximately equal; OH-spheroidene was the major carotenoid accompanying sphe roidene and spirilloxanthin. In the semi-aerobic culture, pigment compositi ons of both complexes again were approximately equal; an oxidized carotenoi d, OB-spheroidenone, was the major component accompanying spheroidenone and 2,2'-diketospirilloxanthin. A novel carotenoid of 2-ketospirilloxanthin, a n intermediate between spirilloxanthin and 2,2'-diketospirilloxanthin, was found in both LH complexes from the semi-aerobic culture. Based on these re sults, we propose the presence of both the spheroidene and the normal spiri lloxanthin pathways as the biosynthetic pathway of carotenoids in this bact erium. The oxidation procedure of spirilloxanthin by CrtA was also discusse d.