Anja Hemschemeier

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The unicellular green alga Chlamydomonas reinhardtii possesses a [FeFe]-hydrogenase HydA1 (EC, 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)
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 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)
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 a special type of anaerobic metabolism that is quite unusual for eukaryotes. It has two oxygen-sensitive [Fe-Fe] hydrogenases (EC that are coupled to photosynthesis and, in addition, a formate- and ethanol-producing fermentative metabolism, which was proposed to be initiated by pyruvate(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)
Sealed Chlamydomonas reinhardtii cultures evolve significant amounts of hydrogen gas under conditions of sulfur depletion. However, the eukaryotic green alga goes through drastic metabolic changes during this nutritional stress resulting in cell growth inhibition and eventually cell death. This study aimed at isolating C. reinhardtii transformants which(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)
We have found the transcript of one of at least six ferredoxin encoding genes of the green alga Chlamydomonas reinhardtii, FDX5, strongly accumulating in anaerobiosis, indicating a vital role of the encoded protein in the anaerobic metabolism of the cells. According to absorption and electron paramagnetic resonance spectroscopy, Fdx5 is a plant-type(More)