Abstract
Phototrophic purple bacteria produce many kinds of acyclic carotenoids, which are rare in organisms. Some carotenoids are specific to some classes, families or genera, and some are not related to phylogenetic classification. Around half species produce spirilloxanthin as the final product. Others produce different carotenoids, which may be due to modification or deletion of four enzymes of spirilloxanthin synthesis and/or addition of a new enzyme.
Rhodobacterales produces spheroidene and spheroidenone, which might be due to modification of CrtI and additional CrtA. All of four species of Phaeospirillum produce hydroxylycopene (rhodopin) or dihydroxylycopene glucosides, which might be due to inactivity of CrtD and additional glucosyltransferase. All of five species of Roseospira produce 3,4-didehydrorhodopin as major carotenoid, which might be due to low activity of CrtF. Rhodoplanes contains five species. Two species produce spirilloxanthin, and one produces rhodopin as major carotenoid. One produces rhodopin as major carotenoid and tetrahydrospirilloxanthin. These might be due to different characteristics of four enzymes in each species among one genus.
