Abstract
In the green sulfur bacteria, 5 genera including 15 species are known. From Chlorobium tepidum, all of carotenoids, entire genome, and a part of carotenogenesis genes have been identified: crtB, crtP, crtQ, crtH, crtC, crtU. Major carotenoids of this species are chlorobactene, γ-carotene and their 1,2-dihydro-derivatives, and OH-chlorobactene, OH-γ-carotene and their glucoside C12:0 esters. Therefore, additional lycopene cyclase, glucosyl transferase, C12:0 acyl transferase and 1,2-saturase must be present. C. phaeobacterioides, C. vibrioforme and C. limicola contain both the same and the different carotenoids. Additional minor carotenoids of 7,8-dihydro-β-carotene from C. phaeobacterioides and 7,8-dihydro-γ-carotene from C. vibrioforme must be produced from neurosporene by lycopene cyclase. Consequently diversity of carotenoids in these species might be due to different characteristics of the substrate specificity of the same enzymes, and presence or absence of enzyme(s). Recently a new taxonomy of the green sulfur bacteria has been proposed.
