Accumulation of unusual carotenoids in the spheroidene pathway, demethylspheroidene and demethylspheroidenone, in an alkaliphilic purple nonsulfur bacterium Rhodobaca bogoriensis

Carotenoids extracted from cells of a novel alkaliphilic purple nonsulfur b acterium Rhodobaca bogoriensis strain LBB1 included unusual carotenoids in the spheroidene pathway; demethylspheroidene, demethylspheroidenone, neuros porene and spheroidenone. Spheroidene was present in only small amounts, an d the demethyl-carotenoids demethylspheroidene and demethylspheroidenone pr edominated in phototrophic cultures. Furthermore, the keto-carotenoids sphe roidenone and demethylspheroidenone constituted nearly half of the total ca rotenoids, even in strict anaerobic phototrophic cultures. Spheroidenone wa s, however, the sole carotenoid in aerobic cultures. Phototrophic cultures of Rbc. bogoriensis were yellow in colour and quite distinct from the brown -red colour of cultures of Rhodobacter species. The carotenogenesis pathway s of Rhodobaca and Rhodobacter species are compared with special reference to two key enzymes of the spheroidene pathway, CrtA and CrtF, whose activit ies are thought to be responsible for the unusual carotenoid composition of Rhodobaca. This bacterium also contained bacteriochlorophyll a(p) and ubiq uinone-10.