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Poster Presentation 2-33
Photostimulation of H2 Production in Cyanobacteria and Green Algae upon Reversible Photoinhibition of Oxygen-evolving System
Josh Greenwood, Sergei A. Markov
Department of Biological Sciences, Marshall University400 Hal Greer Boulevard, Huntington, WV 25755
Telephone: (304) 696-2708; Fax: (304) 696-3243; E-mail: markov@marshall.edu
Brief exposure (7-15 min) of cyanobacterium Anabaena variabilis cells to high intensity light (more than 500 mmol s-1m-2) was accompanied by rapid suppression of photosynthetic O2 evolution, the extent of which depended on cell suspension density, culture age, and gas phase composition. The decline in the rate of O2 evolution was accompanied by stimulation of H2 production. Photostimulation of H2 evolution upon photoinhibition of O2-evolving system in green alga Chlamydomonas reinhardtii was observed as well. The effect of intense light was not observed when cyanobacterial cells were illuminated with far-red light of high intensity. The effect of high-intensity light on photosynthetic O2 evolution and H2 production was reversible. Illumination with light intensity of 5 mmol s-1m-2 for 2 hours restored initial rates of O2 and H2 evolution. Apparently, photoinhibition of photosynthetic O2 evolution led to anaerobiosis that is favorable for H2 production (both hydrogenase and nitrogenase, enzymes responsible for H2 production, are sensitive to oxygen).
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