MoMiX - Modelling Mixotrophy in the extremophile alga Galdieria sulphuraria
Final Report Abstract
The thermo-acidophilic red alga Galdieria sulphuraria thrives in hot (up to 56°C) and acidic (pH values between 0 and 4) environments, such as hot volcanic springs and calderas. It displays unusual metabolic flexibility, being able to grow on more than 50 different carbon sources, such as sugars, sugar alcohols, amino acids, and polysaccharides. Due to this enormous metabolic versatility and extremophily, G. sulphuraria represents a highly interesting candidate organism for biotechnology applications. In the project MoMix we: • Showed that G. sulphuraria can simultaneously conduct photosynthesis and respiration of organic carbon sources that are present in the growth media. Under these mixotrophic conditions (autotrophy and heterotrophy running simultaneously) G. sulphuraria produces more biomass than under heterotrophic or autotrophic conditions. • Demonstrated through tracing the fate of carbon atoms from 13C-labelled glucose that the CO2 that is released from mitochondria during respiration is captured by Rubisco in the chloroplasts and integrated into biomass through photosynthesis. Thus, mitochondrial respiration serves as a “carbon concentrating mechanism”. These findings are surprising because earlier work had concluded that photosynthetic carbon assimilation does not occur in the presence of organic carbon sources. We hypothesize that this discrepancy is due to different culturing conditions. At lower than optimal cultivation temperatures, G. sulphuraria tends to lose its photosynthetic capacity in media containing an external carbon source. We further showed that approx. 1% of the genes present in Cyanidiales genomes have been acquired through horizontal gene transfers from bacteria and archaea. These findings reject earlier claims that considered eukaryotic horizontal gene transfer as artefactual and “Lamarkian”.
Publications
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Systems Biology of Cold Adaptation in the Polyextremophilic Red Alga Galdieria sulphuraria. Frontiers in Microbiology, 10.
Rossoni, Alessandro W. & Weber, Andreas P. M.
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The genomes of polyextremophilic cyanidiales contain 1% horizontally transferred genes with diverse adaptive functions. eLife, 8.
Rossoni, Alessandro W.; Price, Dana C.; Seger, Mark; Lyska, Dagmar; Lammers, Peter; Bhattacharya, Debashish & Weber, Andreas PM
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Catalytic Reactions and Energy Conservation in the Cytochrome bc1 and b6f Complexes of Energy-Transducing Membranes. Chemical Reviews, 121(4), 2020-2108.
Sarewicz, Marcin; Pintscher, Sebastian; Pietras, Rafał; Borek, Arkadiusz; Bujnowicz, Łukasz; Hanke, Guy; Cramer, William A.; Finazzi, Giovanni & Osyczka, Artur
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Mixotrophic growth of the extremophile Galdieria sulphuraria reveals the flexibility of its carbon assimilation metabolism. New Phytologist, 231(1), 326-338.
Curien, Gilles; Lyska, Dagmar; Guglielmino, Erika; Westhoff, Phillip; Janetzko, Janina; Tardif, Marianne; Hallopeau, Clément; Brugière, Sabine; Dal Bo, Davide; Decelle, Johan; Gallet, Benoit; Falconet, Denis; Carone, Michele; Remacle, Claire; Ferro, Myriam; Weber, Andreas P.M. & Finazzi, Giovanni
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Morphological bases of phytoplankton energy management and physiological responses unveiled by 3D subcellular imaging. Nature Communications, 12(1).
Uwizeye, Clarisse; Decelle, Johan; Jouneau, Pierre-Henri; Flori, Serena; Gallet, Benoit; Keck, Jean-Baptiste; Dal Bo, Davide; Moriscot, Christine; Seydoux, Claire; Chevalier, Fabien; Schieber, Nicole L.; Templin, Rachel; Allorent, Guillaume; Courtois, Florence; Curien, Gilles; Schwab, Yannick; Schoehn, Guy; Zeeman, Samuel C.; Falconet, Denis & Finazzi, Giovanni
