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1 March 2004 The Role of Carotenoids in the Photoadaptation of the Brown-colored Sulfur Bacterium Chlorobium phaeobacteroides
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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 ϕ-end groups such as isorenieratene and β-isorenieratene and the second is carotenoid with one or two β-end groups such as β-zeacarotene, β-carotene and 7,8-dihydro-β-carotene. The latter 7,8-dihydro-β-carotene was found to be a novel carotenoid in nature. OH-γ-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 ϕ-end group maintained the same ratio to BChl e, whereas that with the β-end group increased with increasing light intensity. The cells cultured under low-light intensity contained more ϕ-end carotenoids than β-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.

Hiroki Hirabayashi, Takasada Ishii, Shinichi Takaichi, Kazuhito Inoue, and Kaku Uehara "The Role of Carotenoids in the Photoadaptation of the Brown-colored Sulfur Bacterium Chlorobium phaeobacteroides," Photochemistry and Photobiology 79(3), 280-285, (1 March 2004).
Received: 9 October 2003; Accepted: 1 December 2003; Published: 1 March 2004

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