title: The role of carotenoids in the photoadaptation of the brown-colored sulfur bacterium Chlorobium phaeobacteroides.
abstract: The brown-colored sulfur bacterium Chlorobium (Cb.) phaeobacteroides 1549 (new name, Chlorobaculum limnaeum 1549) contains many kinds of carotenoids as well as bacteriochlorophyll (BChl) e. These carotenoids were identified with C18-high-performance liquid chromatography, absorption, mass and proton nuclear magnetic resonance spectroscopies and were divided into two groups: the first is carotenoid with one or two phi-end groups such as isorenieratene and beta-isorenieratene and the second is carotenoid with one or two beta-end groups such as p-zeacarotene, beta-carotene and 7,8-dihydro-beta-carotene. The latter 7,8-dihydro-beta-carotene was found to be a novel carotenoid in nature. OH-gamma-Carotene glucoside laurate and OH-chlorobactene glucoside laurate were also found as minor components. The distribution of BChl e homologs in Cb. phaeobacteroides cultivated under various light intensities did not change, but the carotenoid to BChl e ratio changed markedly: carotenoid with the phi-end group maintained the same ratio to BChl e, whereas that with the beta-end group increased with increasing light intensity. The cells cultured under low-light intensity contained more phi-end carotenoids than beta-end. In Cb. phaeobacteroides the wavelength of the Qy band of BChl e aggregates did not change. We suggested that Cb. phaeobacteroides photoadapts to light intensity by changing the carotenoid composition.
authors.affiliation: Research Institute for Advanced Science and Technology, Osaka Prefecture University, Sakai, Osaka, Japan.
authors.forename: Hiroki
authors.initials: H
authors.lastname: Hirabayashi
authors.forename: Takasada
authors.initials: T
authors.lastname: Ishii
authors.forename: Shinichi
authors.initials: S
authors.lastname: Takaichi
authors.forename: Kazuhito
authors.initials: K
authors.lastname: Inoue
authors.forename: Kaku
authors.initials: K
authors.lastname: Uehara
mesh_terms: D001429:Bacteriochlorophylls / Q000502:physiology; D002338:Carotenoids / Q000096:biosynthesis / Q000502:physiology* / Q000528:radiation effects; D041883:Chlorobium / Q000254:growth & development / Q000502:physiology*; D002851:Chromatography, High Pressure Liquid; D004307:Dose-Response Relationship, Radiation; D008027:Light; D018462:Photobiology; D013053:Spectrophotometry
chemical_list: D001429:Bacteriochlorophylls; D002338:Carotenoids