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6Fe9-hydrogenases in green algae: photo-fermentation and hydrogen evolution under sulfur deprivation

2002; Elsevier BV; Volume: 27; Issue: 11-12 Linguagem: Inglês

10.1016/s0360-3199(02)00095-2

1879-3487

Martin Winkler, Anja Hemschemeier, Cecilia Gotor, Anastasios Melis, Thomas Happe,

Nitrogen and Sulfur Effects on Brassica

Recent studies indicate that [Fe]-hydrogenases and H2 metabolism are widely distributed among green algae. The enzymes are simple structured and catalyze H2 evolution with similar rates than the more complex [Fe]-hydrogenases from bacteria. Different green algal species developed diverse strategies to survive under sulfur deprivation. Chlamydomonas reinhardtii evolves large quantities of hydrogen gas in the absence of sulfur. In a sealed culture of C. reinhardtii, the photosynthetic O2 evolution rate drops below the rate of respiratory O2 consumption due to a reversible inhibition of photosystem II, thus leading to an intracellular anaerobiosis. The algal cells survive under these anaerobic conditions by switching their metabolism to a kind of photo-fermentation. Although possessing a functional [Fe]-hydrogenase gene, the cells of Scenedesmus obliquus produce no significant amounts of H2 under S-depleted conditions. Biochemical analyses indicate that S. obliquus decreases almost the complete metabolic activities while maintaining a low level of respiratory activity.