| Co-Investigator(Kenkyū-buntansha) |
COX Raymond Odense University, Institute of Biochemistry, Associate Professor, 助教授
MILLER Mette Odense University, Institute of Biochemistry, Associate Professor, 助教授
MIMURO Mamoru Yamaguchi University, Faculty of Science, Professor, 理学部, 教授 (40142004)
NAGASHIMA Kenji Tokyo Metropolitan University, Department of Biolgy, Assistant Professor, 理学研究科, 助手 (80264589)
SHIMADA Keizo Tokyo Metropolitan University, Department of Biolgy, Associate Professor, 理学研究科, 助教授 (80112473)
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| Research Abstract |
Photosynthesis has been evalved under anaerobic environment, and thereafter adapted to oxidative environment. In this study, we have tried to clarify the effect of oxigen molecules in the environment on the excited energy transfer and the photosynthetic electron transfer in the absolute anaerobic green sulfur bacteria, Chlorobium, and the facultatively anaerobic green filamentous bacteria, Chloroflexus, as well as the facultatively anaerobic purple bacteria. Research was done as an international collaborative project among scientists of Japan, Denmark, France and Italy. Followings are main results we obtained.
(1)In the light-harvesting appratus of green sulfur bacteria, called chlorosomes, it was known the fluorescence from the photosynthetic pigments is changed by a factor of more than ten depending on the presence or absence of oxygen molecules in the environment. To clarify if this fluoresence changes really affect the efficiency of the photosynthetic electron transfer, we measured
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the light intensity dependence of the photosynthetic electron transfer by changing the redox potential in the environment. It was shown that oxygen regulates the efficiency of electron transfer by affecting the excitation energy transfer.
(2)In the green filamentous bacteria, such a regulation was not present. However, when artificial quinone was added to the chlororsomes or whole cells, a similar regulation was observed, indicating that quinone is responsible for the regulation.
(3)Such quinones were suggested to be interacted with bacteriochlorophyll c molecules.
(4)To clarify the adaptation of purple photosynthetic bacteria to the changes of redox conditions in the environment, cytochrome subunit bound to the photosynthetic reactio center was characterized in various species. We found in a species, Rhodovulum sulfidophilum, which well adapted to oxidative and reductive environment, only three hemes are bound to the subunit instead of the four hemes in the other many species. It was suggested the oxidative environment may have reduced the heme in the subunit evolutionary. Less
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