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 ketocarotenoids spher oidenone and demethylspheroidenone constituted nearly half of the total car otenoids, even in strict anaerobic phototrophic cultures. Spheroidenone was , however, the sole carotenoid in aerobic cultures. Phototrophic cultures o f Rbc. bogoriensis were yellow in colour and quite distinct from the brown- red colour of cultures of Rhodobacter species. The carotenogenesis pathways of Rhodobaca and Rhodobacter species are compared with special reference t o two key enzymes of the spheroidene pathway, CrtA and CrtF, whose activiti es are thought to be responsible for the unusual carotenoid composition of Rhodobaca. This bacterium also contained bacteriochlorophyll ap and ubiquin one-10.