References of "Franck, Fabrice"
     in
Bookmark and Share    
Full Text
See detailLa photosynthèse: aujourd'hui, hier et demain
Franck, Fabrice ULg

Conference (2012, November 30)

Detailed reference viewed: 32 (8 ULg)
Peer Reviewed
See detailAlternative photosynthetic electron pathways in symbiotic dinoflagellates of reef-building corals
Roberty, Stéphane ULg; Cardol, Pierre ULg; Franck, Fabrice ULg

Conference (2012, July 11)

The high productivity of coral reef ecosystems is largely attributed to the mutualistic symbiosis between reef-building corals and their intracellular dinoflagellate in the genus Symbiodinium. In the ... [more ▼]

The high productivity of coral reef ecosystems is largely attributed to the mutualistic symbiosis between reef-building corals and their intracellular dinoflagellate in the genus Symbiodinium. In the natural environment the holobiont have to cope with significant daily variations in light intensities that sometimes exceed Symbiodinium photosynthetic capacity. Fortunately, photosynthetic organisms possess regulatory features that help to ensure that high light intensities can be endured without the accumulation of photodamage. Thus, the regulation of photosynthesis can be viewed as a dynamic balance between photosynthetic efficiency (photochemical quenching) and photoprotection processes (i.e. non-photochemical quenching). In addition to the linear electron flow (LEF) operating during oxygenic photosynthesis, alternative electron flows (AEF) have been widely described in higher plants and microalgae but not in Symbiodinium. The present study aimed to highlight the existence of the Mehler ascorbate peroxidase pathway (reduction of oxygen by PSI), chlororespiration (oxidation by molecular O2 of the PQ pool) and cyclic electron flow around PSI. We report that the presence of particular AEF and/or their amplitude vary from one clade to another. These processes could play a key role under particular environmental conditions when sinks for photosynthetic electrons are scarce. Indeed, they could sustain significant levels of photosynthetic electron flux by initiating the ΔpH formation and of NPQ, regulating the ratio of ATP/NADPH to match the requirements of carbon reduction and reducing the excitation pressure over the photosynthetic apparatus. [less ▲]

Detailed reference viewed: 59 (12 ULg)
Full Text
See detailMetabolic plasticity of wild-type and AOX-deficient Chlamydomonas reinhardtii cells related to the inorganic nitrogen source (nitrate or ammonium), as revealed by a 2D-DIGE comparative proteomic analysis
Gerin, Stéphanie ULg; Mathy, Grégory; Franck, Fabrice ULg

Poster (2012, June 15)

In the model unicellular green alga Chlamydomonas reinhardtii, both nitrate and ammonium can be used as primary inorganic nitrogen sources. Interestingly, the expression of the mitochondrial alternative ... [more ▼]

In the model unicellular green alga Chlamydomonas reinhardtii, both nitrate and ammonium can be used as primary inorganic nitrogen sources. Interestingly, the expression of the mitochondrial alternative oxidase (AOX), an "energy-dissipating" ubiquinol-oxygen oxidoreductase of the mitochondrial electron transport chain, is under the control of the exogenous nitrogen source : it is activated in nitrate-grown cells and repressed in ammonium-grown cells at both transcriptional and translational levels. This regulation of AOX by nitrogen is Chlamydomonas-specific and currently its bioenergetic and metabolic significance is poorly understood. In order to get clues to this peculiar phenomenon, we characterized the global metabolic response of a wild-type strain (WT) and an AOX-deficient mutant (AOX-) obtained by RNA interference grown either on nitrate or ammonium. For this purpose, we used a highly accurate 2D electrophoresis-based comparative proteomic approach (2D-DIGE) to compare the cellular proteomes of nitrate and ammonium-grown WT and AOX- Chlamydomonas. The analysis was performed in the middle of the exponential growth phase in mixotrophic conditions. It revealed many proteomic modifications between WT and AOX- cells and a smaller number between nitrate and ammonium-grown cells. In nitrate-grown cells, we notably observed an important up-regulation of glutamine synthetase. Interestingly, in AOX- cells, we respectively detected a general down-regulation and a general up-regulation of mitochondrial and chloroplastic bioenergetic enzymes, and also an important up-regulation of glutathione-dependent oxidative stress defense systems together with a remarkable down-regulation of methionine synthase. Altogether these results and previous studies provide new features in understanding the metabolic adaptations occurring in response to the inorganic nitrogen source with emphasis on the role played by AOX. [less ▲]

Detailed reference viewed: 14 (1 ULg)
Full Text
See detailOptimization of an Haematococcus pluvialis medium by a Genetic Algorithm-based strategy
Fratamico, Anthony ULg; Tocquin, Pierre ULg; Franck, Fabrice ULg

Poster (2012, June 14)

The successful use of living organisms for the production of biomass or metabolites requires a careful control and optimization over growing conditions. However the range of interacting parameters makes ... [more ▼]

The successful use of living organisms for the production of biomass or metabolites requires a careful control and optimization over growing conditions. However the range of interacting parameters makes full optimization difficult and time-consuming. In this context, Genetic Algorithm-based (GA) methods emerge as promising strategies for optimization of biotechnological processes. However, the potential of GA in the microalgae field remains, today, poorly explored. As a proof-of-concept, we evaluated how GA could be applied for the optimization of a medium for high yield photoautotrophic growth of Haematoccocus pluvialis. [less ▲]

Detailed reference viewed: 62 (15 ULg)
Full Text
Peer Reviewed
See detailThe MicroH2 project:an association of four laboratories to improve theknowledge on biohydrogen production precesses
Beckers, Laurent ULg; Calusinska, Magdalena ULg; Hamilton, Christopher ULg et al

Poster (2012, June 04)

This poster presents a collaborative research project (MicroH2) held at the University of Liège (Belgium) since 2007 (www.microh2.ulg.ac.be) and involving four different research groups. The project aims ... [more ▼]

This poster presents a collaborative research project (MicroH2) held at the University of Liège (Belgium) since 2007 (www.microh2.ulg.ac.be) and involving four different research groups. The project aims to develop a center of excellence in the fields of photo- and dark- biohydrogen production. Our studies contribute to improve the knowledge of the processes involved in the microbiological production of hydrogen, from a fundamental and practical point of view. Some results are highlighted here. The research concerning photofermentation focuses on the interactions between respiration, photosynthesis and H2-producing pathways in algal microorganisms, by using mitochondrial mutants and genetically modified strains with modified ability for hydrogen production [1-2]. To study the metabolism of the hydrogen production by anaerobic bacteria, pure cultures and defined consortia are used and their production of biogas and soluble metabolites is measured. Moreover, we have developed and optimized molecular tools, like quantitative RT-PCR and FISH, to monitor the variations of bacterial populations in novel bioreactors for hydrogen production [3-4]. We have also mined the complete genomes of Clostridium spp. for putative hydrogenase genes and found a large diversity of them [5]. [less ▲]

Detailed reference viewed: 51 (12 ULg)
Full Text
Peer Reviewed
See detailFunction of the chloroplastic NAD(P)H dehydrogenase Nda2 for H(2) photoproduction in sulphur-deprived Chlamydomonas reinhardtii.
Mignolet, Emmanuel; Lecler, Renaud; Ghysels, Bart ULg et al

in Journal of biotechnology (2012), 162(1), 81-8

The relative contributions of the PSII-dependent and Nda2-dependent pathways for H(2) photoproduction were investigated in the green microalga Chlamydomonas reinhardtii after suphur-deprivation. For this ... [more ▼]

The relative contributions of the PSII-dependent and Nda2-dependent pathways for H(2) photoproduction were investigated in the green microalga Chlamydomonas reinhardtii after suphur-deprivation. For this purpose, H(2) gas production was compared for wild-type and Nda2-deficient cells with or without DCMU (a PSII-inhibitor) in the same experimental conditions. Nda2-deficiency caused a 30% decrease of the maximal H(2) photoevolution rate observed shortly after the establishment of anoxia, and an acceleration of the decline of H(2) photoevolution rate with time. DCMU addition to Nda2-deficient cells completely inhibited H(2) photoproduction, showing that the PSII-independent H(2) photoproduction relies on the presence of Nda2, which feeds the photosynthetic electron transport chain with electrons derived from oxidative catabolism. Nda2-protein abundance increased as a result of sulphur deprivation and further during the H(2) photoproduction process, resulting in high rates of non-photochemical plastoquinone reduction in control cells. Nda2-deficiency had no significant effect on photosynthetic and respiratory capacities in sulphur-deprived cells, but caused changes in the cell energetic status (ATP and NADPH/NADP+ ratio). The rapid decline of H(2) photoevolution rate with time in Nda2-deficient cells revealed a more pronounced inhibition of H(2) photoproduction by accumulated H(2) in the absence of non-photochemical plastoquinone reduction. Nda2 is therefore important for linking H(2) photoproduction with catabolism of storage carbon compounds, and seems also involved in regulating the redox poise of the photosynthetic electron transport chain during H(2) photoproduction. [less ▲]

Detailed reference viewed: 11 (2 ULg)
Full Text
Peer Reviewed
See detailFinding the bottleneck: a research strategy for improved biomass production
Bassi, Roberto; Cardol, Pierre ULg; Choquet, Yves et al

in Posten, Clemens; Walter, Christian (Eds.) Microalgal Biotechnology: integration and economy (2012)

Detailed reference viewed: 128 (30 ULg)
Full Text
Peer Reviewed
See detailUne brève histoire des centres réactionnels de la photosynthèse
Franck, Fabrice ULg

in Bulletin de la Société Royale des Sciences de Liège (2012), 81

Detailed reference viewed: 13 (6 ULg)
Full Text
Peer Reviewed
See detailScreening for a low-cost Haematococcus pluvialis medium reveals an unexpected impact of a low N:P ratio on vegetative growth
Tocquin, Pierre ULg; Fratamico, Anthony ULg; Franck, Fabrice ULg

in Journal of Applied Phycology (2012), 24(3), 365-373

Haematococcus pluvialis is the current better source of natural astaxanthin, a high-value carotenoid. Traditionally, the production process of astaxanthin by this algae is achieved by a two-stage system ... [more ▼]

Haematococcus pluvialis is the current better source of natural astaxanthin, a high-value carotenoid. Traditionally, the production process of astaxanthin by this algae is achieved by a two-stage system: during the first stage, vegetative “green” cells are produced and then converted, in the second stage, into cysts that accumulate astaxanthin. In this work, a medium screening strategy based on the mixing of a 3-component hydroponic fertilizer was applied to identify a new formulation optimized for the vegetative stage. A maximal and high cell density of 2 x 106 cells mL−1 was obtained in a medium containing a high level of phosphate relative to nitrate, resulting in a N:P ratio much lower than commonly used media for H. pluvialis. In this medium, cells remained at the vegetative and motile stage during a prolonged period of time. Both high cell density culture and motile stage persistence was proved to be related to the N:P feature of this medium. We conclude that the macrozoid stage of H. pluvialis is favored under high-P and low-N supply and that low-cost hydroponic fertilizers can be successfully used for achieving high density cultures of vegetative cells of H. pluvialis. [less ▲]

Detailed reference viewed: 271 (52 ULg)
Full Text
Peer Reviewed
See detailRegulation of the pigment optical density of an algal cell: filling the gap between photosynthetic productivity in the laboratory and in mass culture
Formighieri, Cinzia; Franck, Fabrice ULg; Bassi, Roberto

in Journal of Biotechnology (2012), 162

An increasing number of investors is looking at algae as a viable source of biofuels, beside Q3 cultivation for human/animal feeding or to extract high-value chemicals and pharmaceuticals. However ... [more ▼]

An increasing number of investors is looking at algae as a viable source of biofuels, beside Q3 cultivation for human/animal feeding or to extract high-value chemicals and pharmaceuticals. However, present biomass productivities are far below theoretical estimations implying that a large part of the available photosynthetically active radiation is not used in photosynthesis. Light utilisation inefficiency and rapid light attenuation within a mass culture due to high pigment optical density of wild type strains have been proposed as major limiting factors reducing solar-to-biomass conversion efficiency. Analysis of growth yields of mutants with reduced light-harvesting antennae and/or reduced overall pigment concentration per cell, generated by either mutagenesis or genetic engineering, could help understanding limiting factors for biomass accumulation in photobioreactor. Meanwhile, studies on photo-acclimation can provide additional information on the average status of algal cells in a photobioreactor to be used in modellingbased predictions. Identifying limiting factors in solar-to-biomass conversion efficiency is the first step for planning strategies of genetic improvement and domestication of algae to finally fill the gap between theoretical and industrial photosynthetic productivity. [less ▲]

Detailed reference viewed: 44 (10 ULg)
Full Text
Peer Reviewed
See detailFunction of the chloroplastic NADP(H) dehydrogenase NDA2 for the H2 photoproduction in sulphur-deprived Chlamydomonas reinhardtii
Mignolet, Emmanuel ULg; Lecler, Renaud ULg; Ghysels, Bart ULg et al

in Journal of Biotechnology (2012), 162

The relative contributions of the PSII-dependent and Nda2-dependent pathways for H2 photoproduction were investigated in the green microalga Chlamydomonas reinhardtii after suphur-deprivation. For this ... [more ▼]

The relative contributions of the PSII-dependent and Nda2-dependent pathways for H2 photoproduction were investigated in the green microalga Chlamydomonas reinhardtii after suphur-deprivation. For this purpose, H2 gas production was compared for wild-type and Nda2-deficient cells with or without DCMU (a PSII-inhibitor) in the same experimental conditions. Nda2-deficiency caused a 30 % decrease of the maximal H2 photoevolution rate observed shortly after the establishment of anoxia, and an acceleration of the decline of H2 photoevolution rate with time. DCMU addition to Nda2-deficient cells completely inhibited H2 photoproduction, showing that the PSII-independent H2 photoproduction relies on the presence of Nda2, which feeds the photosynthetic electron transport chain with electrons derived from oxidative catabolism. Nda2-protein abundance increased as a result of sulphur deprivation and further during the H2 photoproduction process, resulting in high rates of non-photochemical plastoquinone reduction in control cells. Nda2-deficiency had no significant effect on photosynthetic and respiratory capacities in sulphur-deprived cells, but caused changes in the cell energetic status (ATP and NADPH/NADP+ ratio). The rapid decline of H2 photoevolution rate with time in Nda2-deficient cells revealed a more pronounced inhibition of H2 photoproduction by accumulated H2 in the absence of non-photochemical plastoquinone reduction. Nda2 is therefore important for linking H2 photoproduction with catabolism of storage carbon compounds, and seems also involved in regulating the redox poise of the photosynthetic electron transport chain during H2 photoproduction. [less ▲]

Detailed reference viewed: 48 (13 ULg)
Full Text
Peer Reviewed
See detailInterplay between non-photochemical plastoquinone reduction and re-oxidation in pre-illuminated Chlamydomonas reinhardtii: a chlorophyll fluorescence study
Houyoux, Pierre-Alain; Ghysels, Bart ULg; Lecler, Renaud ULg et al

in Photosynthesis Research (2011), 110

In photosynthetic eukaryotes, the redox state of the plastoquinone (PQ) pool is an important sensor for mechanisms that regulate the photosynthetic electron transport. In higher plants, a multimeric ... [more ▼]

In photosynthetic eukaryotes, the redox state of the plastoquinone (PQ) pool is an important sensor for mechanisms that regulate the photosynthetic electron transport. In higher plants, a multimeric nicotinamide adenine dinucleotide (phosphate) (NAD(P))H dehydroge- nase (NDH) complex and a plastid terminal oxidase (PTOX) are involved in PQ redox homeostasis in the dark. We recently demonstrated that in the microalgae Chla- mydomonas reinhardtii, which lacks the multimeric NDH complex of higher plants, non-photochemical PQ reduction is mediated by a monomeric type-II NDH (Nda2). In this study, we further explore the nature and the importance of non-photochemical PQ reduction and oxidation in relation to redox homeostasis in this alga by recording the ‘dark’ chlorophyll fluorescence transients of pre-illuminated algal samples. From the observation that this fluorescence tran- sient is modified by addition of propyl gallate, a known inhibitor of PTOX, and in a Nda2-deficient strain we conclude that it reflects post-illumination changes in the redox state of PQ resulting from simultaneous PTOX and Nda2 activity. We show that the post-illumination fluo- rescence transient can be used to monitor changes in the relative rates of the non-photochemical PQ reduction and reoxidation in response to different physiological situa- tions. We study this fluorescence transient in algae acclimated to high light and in a mutant deficient in mitochondrial respiration. Some of our observations indi- cate that the chlororespiratory pathway participates in redox homeostasis in C. reinhardtii. [less ▲]

Detailed reference viewed: 32 (15 ULg)
Full Text
See detailInsertional mutagenesis to select mutants for modified hydrogen photoproduction in Chlamydomonas reinhardtii
Godaux, Damien ULg; Emonds-alt, Barbara; Cardol, Pierre ULg et al

Poster (2011, September 18)

The unicellular green alga Chlamydomonas reinhardtii has evolved the ability to redirect electrons from the photosynthetic chain to drive hydrogen production via chloroplast oxygen-sensitive hydrogenases ... [more ▼]

The unicellular green alga Chlamydomonas reinhardtii has evolved the ability to redirect electrons from the photosynthetic chain to drive hydrogen production via chloroplast oxygen-sensitive hydrogenases. This process occurs under anaerobic conditions and provides a biological basis for solar-driven hydrogen production. Nevertheless, the yield is a major limitation for an economic viability and fundamental knowledge is still needed in order to have a better understanding of the process. In 2000, Melis and co-worker defined a protocol allowing a sustainable hydrogen production in sulfur deprivation condition. By adjustment of an existent protocol called the Winkler test, we are trying to isolate mutants with an attenuated photosynthesis to respiration capacity ratio (P/R ratio). This kind of mutants could be able to reach anoxia needed for hydrogenases activity without the stressful impact of sulfur deprivation. An insertional mutagenesis of Chlamydomonas has been carried out with an hygromycin resistance cassette and about 2500 transformants have generated and screened by the adapted Winkler test. We have isolated several oxygen-consuming mutants and the most promising one is subject to functional, molecular and genetic characterization. [less ▲]

Detailed reference viewed: 46 (11 ULg)
Full Text
See detailInsertional mutagenesis to select mutants for modified hydrogen photoproduction in Chlamydomonas reinhardtii
Godaux, Damien ULg; Emonds-Alt, Barbara ULg; Cardol, Pierre ULg et al

Poster (2011, May 17)

The unicellular green alga Chlamydomonas reinhardtii has evolved the ability to redirect electrons from the photosynthetic chain to drive hydrogen production via chloroplast oxygen-sensitive hydrogenases ... [more ▼]

The unicellular green alga Chlamydomonas reinhardtii has evolved the ability to redirect electrons from the photosynthetic chain to drive hydrogen production via chloroplast oxygen-sensitive hydrogenases. This process occurs under anaerobic conditions and provides a biological basis for solar-driven hydrogen production. Nevertheless, the yield is a major limitation for an economic viability and fundamental knowledge is still needed in order to have a better understanding of the process. In 2000, Melis and co-worker defined a protocol allowing a sustainable hydrogen production in sulfur deprivation condition. By adjustment of an existent protocol called the Winkler test, we are trying to isolate mutants with an attenuated photosynthesis to respiration capacity ratio (P/R ratio). This kind of mutants could be able to reach anoxia needed for hydrogenases activity without the stressful impact of sulfur deprivation. An insertional mutagenesis of Chlamydomonas has been carried out with an hygromycin resistance cassette and about 2500 transformants have generated and screened by the adapted Winkler test. We have isolated several oxygen-consuming mutants and the most promising one is subject to functional, molecular and genetic characterization. To discover new genes involved in hydrogenases activity, we are also planning to screen the same insertional library for mutants with attenuated levels of hydrogen photoproduction, using sensitive chemochromic sensor films which turn in blue in presence of hydrogen. We are currently making the chemochromic sensor WO3 films by dip-coating which is on the brink of being useable. [less ▲]

Detailed reference viewed: 95 (24 ULg)
Peer Reviewed
See detailA Chlamydomonas mutant locked in anaerobiosis
Ghysels, Bart ULg; Matagne, René-Fernand ULg; Franck, Fabrice ULg

Conference (2011, May)

The soil dwelling microalga Chlamydomonas reinhardtii most likely encounters transient periods of anaerobiosis in its natural environment, for instance at night time or when photosynthesis is turned down ... [more ▼]

The soil dwelling microalga Chlamydomonas reinhardtii most likely encounters transient periods of anaerobiosis in its natural environment, for instance at night time or when photosynthesis is turned down in response to macronutrient limitation. Anoxic conditions trigger state I to state II transition in C.r. and the induction of a chloroplast hydrogenase., which ability to accept electrons from reduced Fd results in a transient light driven H2 evolution. We present evidence that hydrogenase induction and state transitions are required for the induction of photosynthesis in anaerobiosis and therefore critical for this alga in order to survive transient anaerobic periods in the dark. In an anaerobic metabolic context the induction of photosynthesis is severely slowed down. The highly reduced state of the NAD(P) pools and the absence of O2 as electron sink hamper light driven reoxydation of the intersystem electron carriers while CO2 assimilation by the Calvin cycle is inhibited by ATP deficiency. We have seen that gradual increase of hydrogenase activity during anaerobiosis restores a PSI acceptor pool and leads to a reduction of the induction lag of oxygenic photosynthesis. A mutant HydEF devoid of hydrogenase maturation genes typically shows 3 to 4 times longer lag phases that the WT. State transitions provide another mechanism by which photosynthetic electron transport can be unlocked in anaerobic conditions. A state II conformation is known to stimulate photo-phosphorylation, and may therefore restore Calvin cycle activity in an ATP depleted metabolic context. We observed that an anaerobically adapted stt7 mutant locked in state I is only able to induce oxygenic photosynthesis upon hydrogenase expression. We therefore constructed a double mutant Stt7HydEF impaired of state transition ability and hydrogenase activity and found it to have lost the capacity of inducing photosynthesis in anaerobic conditions. [less ▲]

Detailed reference viewed: 70 (6 ULg)