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The unicellular green alga Chlamydomonas reinhardtii possesses a [FeFe]-hydrogenase HydA1 (EC 1.12.7.2), which is coupled to the photosynthetic electron transport chain. Large amounts of H2 are produced in a light-dependent reaction for several days when C. reinhardtii cells are deprived of sulfur. Under these conditions, the cells drastically change their(More)
In Chlamydomonas reinhardtii cells, H2 photoproduction can be induced in conditions of sulfur deprivation in the presence of acetate. The decrease in photosystem II (PSII) activity induced by sulfur deprivation leads to anoxia, respiration becoming higher than photosynthesis, thereby allowing H2 production. Two different electron transfer pathways, one PSII(More)
The unicellular green alga Chlamydomonas reinhardtii has a special type of anaerobic metabolism that is quite unusual for eukaryotes. It has two oxygen-sensitive [Fe-Fe] hydrogenases (EC 1.12.7.2) that are coupled to photosynthesis and, in addition, a formate- and ethanol-producing fermentative metabolism, which was proposed to be initiated by pyruvate(More)
Oxygenic photosynthesis uses light as energy source to generate an oxidant powerful enough to oxidize water into oxygen, electrons and protons. Upon linear electron transport, electrons extracted from water are used to reduce NADP(+) to NADPH. The oxygen molecule has been integrated into the cellular metabolism, both as the most efficient electron acceptor(More)
The green alga Chlamydomonas reinhardtii has a complex anaerobic metabolism characterized by a plastidic hydrogenase (HYD1) coupled to photosynthesis and a bacterial-type fermentation system in which pyruvate formate lyase (PFL1) is the central fermentative enzyme. To identify mutant strains with altered hydrogen metabolism, a C. reinhardtii nuclear(More)
The unicellular green alga Chlamydomonas reinhardtii has at least six plant-type ferredoxins (FDX). Besides the long-known photosynthetic ferredoxin PetF the isoforms Fdx2-Fdx6 have been identified. The FDX genes are differentially expressed under various environmental conditions such as the availability of oxygen, copper, iron and ammonium. Recently, the(More)
In anaerobiosis, the green alga Chlamydomonas reinhardtii evolves molecular hydrogen (H(2)) as one of several fermentation products. H(2) is generated mostly by the [Fe-Fe]-hydrogenase HYDA1, which uses plant type ferredoxin PETF/FDX1 (PETF) as an electron donor. Dark fermentation of the alga is mainly of the mixed acid type, because formate, ethanol, and(More)
Green algae are the only known eukaryotes with both oxygenic photosynthesis and a hydrogen metabolism. Recent physiological and genetic discoveries indicate a close connection between these metabolic pathways. The anaerobically inducible hydA genes of algae encode a special type of highly active [Fe]-hydrogenase. Electrons from reducing equivalents(More)
The unicellular green alga Chlamydomonas reinhardtii is able to use photosynthetically provided electrons for the production of molecular hydrogen by an [FeFe]-hydrogenase HYD1 accepting electrons from ferredoxin PetF. Despite the severe sensitivity of HYD1 towards oxygen, a sustained and relatively high photosynthetic hydrogen evolution capacity is(More)
The photosynthetic green alga Chlamydomonas reinhardtii is capable of performing a complex fermentative metabolism which is related to the mixed acid fermentation of bacteria such as Escherichia coli. The fermentative pattern includes the products formate, ethanol, acetate, glycerol, lactate, carbon dioxide and molecular hydrogen (H(2)). H(2) production is(More)