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  • Comprar Psychrophiles: From Biodiversity to Biotechnolgy | Margesin, Rosa | 9783540743347 | Springer
    2020
    Co-Authors: Rosa Margesin, Franz Schinner, Jeanclaude Marx, Charles Gerday
    Abstract:

    Tienda online donde Comprar Psychrophiles: From Biodiversity to Biotechnolgy al precio 206,10 € de Margesin, Rosa | Schinner, Franz | Marx, Jean-Claude | Gerday, Charles, tienda de Libros de Medicina, Libros de Biologia - Zoologia

  • enzyme catalysis in Psychrophiles
    2017
    Co-Authors: Tony Collins, Charles Gerday
    Abstract:

    Cold-active enzymes are produced by organisms, known as Psychrophiles, adapted to permanently cold habitats. Low temperatures have an exponential deleterious effct on reaction rates, and thus psychrophilic enzymes have to be adapted to secure appropriate reaction rates in their environment. These enzymes have a high specific activity at low temperatures, in any case higher than that of their mesophilic and thermophilic counterparts, and display a shift of the apparent optimum temperature for activity towards low temperatures as well as a reduced thermal stability and increased flexibility. The increased flexibility may be global, involving the overall edifice, or local, involving only those zones crucial for activity, be they near or distant from the active site. The reduced thermodynamic stability of cold-adapted enzymes is illustrated by a significantly lower stabilisation energy as compared to that of their mesophilic and thermophilic counterparts, yet maximum stability occurs at similar temperatures in all cases. The comparison of their three-dimensional structures with higher temperature-adapted homologues, in conjunction with various mutagenesis studies, has shown that their high activity results from rather discrete molecular changes that tend to decrease the stability of the molecular edifice. Each cold-adapted enzyme however adopts a specific strategy. There is apparently a continuum in the adaptation, with some enzymes showing extremely acute cold adaptation, as illustrated by a severe shift of the activity towards low temperatures, whereas others appear to cover a broader range of temperatures. This probably depends on the specific evolutionary history of the organisms which produce them.

  • comprar Psychrophiles from biodiversity to biotechnolgy margesin rosa 9783540743347 springer
    2008
    Co-Authors: Rosa Margesin, Franz Schinner, Jeanclaude Marx, Charles Gerday
    Abstract:

    Tienda online donde Comprar Psychrophiles: From Biodiversity to Biotechnolgy al precio 206,10 € de Margesin, Rosa | Schinner, Franz | Marx, Jean-Claude | Gerday, Charles, tienda de Libros de Medicina, Libros de Biologia - Zoologia

  • crystallization and preliminary x ray diffraction studies of alpha amylase from the antarctic psychrophile alteromonas haloplanctis a23
    Protein Science, 1996
    Co-Authors: Nushin Aghajari, Georges Feller, Charles Gerday, Richard Haser
    Abstract:

    A cold-active alpha-amylase was purified from culture supernatants of the antarctic psychrophile Alteromonas haloplanctis A23 grown at 4 degrees C. In order to contribute to the understanding of the molecular basis of cold adaptations, crystallographic studies of this cold-adapted enzyme have been initiated because a three-dimensional structure of a mesophilic counterpart, pig pancreatic alpha-amylase, already exists. alpha-Amylase from A. haloplanctis, which shares 53% sequence identity with pig pancreatic alpha-amylase, has been crystallized and data to 1.85 A have been collected. The space group is found to be C222(1) with a = 71.40 A, b = 138.88 A, and c = 115.66 A. Until now, a three-dimensional structure of a psychrophilic enzyme is lacking.

  • Crystallization and preliminary X-ray diffraction studies of a-amylase from the antarctic psychrophile
    1996
    Co-Authors: Nushin Aghajari, Georges Feller, Charles Gerday, Richard Haser, I Chemin, Joseph Aiguier
    Abstract:

    A cold-active a-amylase was purified from culture su- pernatants of the antarctic psychrophile Alteromonas haloplanctis A23 grown at 4 "C. In order to contribute to the understanding of the molecular basis of cold adaptations, crystallographic studies of this cold-adapted enzyme have been initiated because a three- dimensional structure of a mesophilic counterpart, pig pancreatic a-amylase, already exists. a-Amylase from A. haloplanctis, which shares 53% sequence identity with pig pancreatic a-amylase, has been crystallized and data to 1.85 A have been collected. The space group is found to be C222, with a = 71.40 A, b = 138.88 A, and c = 115.66 A. Until now, a three-dimensional structure of a psy- chrophilic enzyme is lacking.

Stefan Falk - One of the best experts on this subject based on the ideXlab platform.

Georges Feller - One of the best experts on this subject based on the ideXlab platform.

  • cryosphere and Psychrophiles insights into a cold origin of life
    Life, 2017
    Co-Authors: Georges Feller
    Abstract:

    Psychrophiles thrive permanently in the various cold environments on Earth. Their unsuspected ability to remain metabolically active in the most extreme low temperature conditions provides insights into a possible cold step in the origin of life. More specifically, metabolically active psychrophilic bacteria have been observed at −20 °C in the ice eutectic phase (i.e., the liquid veins between sea ice crystals). In the context of the RNA world hypothesis, this ice eutectic phase would have provided stability to the RNA molecules and confinement of the molecules in order to react and replicate. This aspect has been convincingly tested by laboratory experiments.

  • Is there a cold shock response in the Antarctic psychrophile Pseudoalteromonas haloplanktis
    Extremophiles, 2012
    Co-Authors: Florence Piette, Pierre Leprince, Georges Feller
    Abstract:

    The growth behavior and the proteomic response after a cold shock were investigated in the psychrophilic Antarctic bacterium Pseudoalteromonas haloplanktis. Remarkably, no cold-induced proteins were observed in the proteome, whereas some key proteins were repressed. This suggests noticeable differences in the cold shock response between a true psychrophile and mesophiles.

  • The protein folding challenge in Psychrophiles: Facts and current issues
    Environmental Microbiology, 2011
    Co-Authors: Florence Piette, Caroline Struvay, Georges Feller
    Abstract:

    The protein folding process in Psychrophiles is impaired by low temperature, which exerts several physicochemical constraints, such as a decrease in the folding rate, reduced molecular diffusion rates and increased solvent viscosity, which interfere with conformational sampling. Furthermore, folding assistance is required at various folding steps according to the protein size. Recent studies in the field have provided contrasting and sometimes contradictory results, although protein folding generally appears as a rate-limiting step for the growth of Psychrophiles. It is proposed here that these discrepancies reflect the diverse adaptive strategies adopted by Psychrophiles in order to allow efficient protein folding at low temperature. Cold adaptations apparently superimpose on pre-existing cellular organization, resulting in different adaptive strategies. In addition, microbial lifestyle further modulates the properties of the chaperone machinery, which possibly explains the occurrence of cold-adapted and non-cold-adapted protein chaperones in Psychrophiles.

  • Biotechnological applications of Psychrophiles
    Environmental Technology, 2010
    Co-Authors: Rosa Margesin, Georges Feller
    Abstract:

    Low temperature environments are numerous on Earth and have been successfully colonized by cold-loving organisms termed Psychrophiles. Cold-adapted microorganisms can be used as cell factories for the production of unstable compounds as well as for bioremediation of polluted cold soils and wastewaters. Furthermore, their biomolecules, mainly proteins and enzymes characterized by a high catalytic activity and pronounced heat-lability, have already found useful applications in various domains such as molecular biology, medical research, industrial food or feed technologies, detergents or cosmetics.

  • Life at low temperatures: is disorder the driving force?
    Extremophiles, 2007
    Co-Authors: Georges Feller
    Abstract:

    The thermodynamic characterization of various biological systems from Psychrophiles points to a larger entropic contribution when compared to the corresponding mesophilic or (hyper) thermophilic counterparts, either at the level of the macromolecules (thermodynamic and kinetic stabilities) or of their function (ligand binding, catalytic activity). It is suggested here that in an environment characterized by a low heat content (enthalpy) and at temperatures that strongly slowdown molecular motions, the cold-adapted biological systems rely on a larger disorder to maintain macromolecular dynamics and function. Such pre-eminent involvement of entropy is observed in the experimental results and, from a macroscopic point of view, is also reflected for instance by the steric hindrances introduced by cis -unsaturated and branched lipids to maintain membrane fluidity, by the loose conformation of psychrophilic proteins or by the local destabilization of tRNA by dihydrouridine in psychrophilic bacteria.

Tessa Pocock - One of the best experts on this subject based on the ideXlab platform.

Norman P. A. Huner - One of the best experts on this subject based on the ideXlab platform.

  • Changes in salinity impacts growth, photochemistry and photoinhibition in the Antarctic psychrophile Chlamydomonas raudensis UWO 241.
    2008
    Co-Authors: Tessa Pocock, Norman P. A. Huner, Adrien Vetterli, Stefan Falk
    Abstract:

    Changes in salinity impacts growth, photochemistry and photoinhibition in the Antarctic psychrophile Chlamydomonas raudensis UWO 241.

  • The small domain of cytochrome f from the psychrophile Chlamydomonas raudensis UWO 241 modulates the apparent molecular mass and decreases the accumulation of cytochrome f in the mesophile Chlamydomonas reinhardtii.
    Biochemistry and Cell Biology, 2007
    Co-Authors: Loreta Gudynaite-savitch, Christelle Loiselay, Leonid V. Savitch, John Simmondsj. Simmonds, Susanne E. Kohalmi, Yves Choquety. Choquet, Norman P. A. Huner
    Abstract:

    Cytochrome f from the psychrophile Chlamydomonas raudensis UWO 241 has a lower thermostability of its c- type heme and an apparent molecular mass that is 7 kDa lower than that of the model mesophilic green alga Chlamydomo- nas reinhardtii. We combined chloroplast transformation, site-directed mutagensis, and the creation of chimeric fusion constructs to assess the contribution of specific domains and (or) amino acids residues to the structure, stability, and accu- mulation of cytochrome f, as well as its function in photosynthetic intersystem electron transport. We demonstrate that dif- ferences in the amino acid sequence of the small domain and specific charged amino acids in the large domain of cytochrome f alter the physical properties of this protein but do not affect either the thermostability of the c-type heme, the apparent half-life of cytochrome f in the presence of the chloroplastic protein synthesis inhibitor chloramphenicol, or the capacity for photosynthetic intersystem electron transport, measured as e - /P700. However, pulse-labeling with ( 14 C)ace- tate, combined with immunoblotting, indicated that the negative autoregulation of cytochrome f accumulation observed in mesophilic C. reinhardtii transformed with chimeric constructs from the psychrophile was likely the result of the defective association of the chimeric forms of cytochrome f with the other subunits of the cytochrome b6/f complex native to the C. reinhardtii wild type. These results are discussed in terms of the unique fatty acid composition of the thylakoid membranes of C. raudensis UWO 241 adapted to cold environments.

  • The Antarctic psychrophile, Chlamydomonas raudensis Ettl (UWO241) (Chlorophyceae, Chlorophyta), exhibits a limited capacity to photoacclimate to red light
    Journal of Phycology, 2005
    Co-Authors: Rachael M. Morgan-kiss, Loreta Gudynaite-savitch, Tessa Pocock, Alexander G. Ivanov, Marianna Krol, Norman P. A. Huner
    Abstract:

    The psychrophilic Antarctic alga, Chlamydomonas raudensis Ettl (UWO241), grows under an extreme environment of low temperature and low irradiance of a limited spectral quality (blue-green). We investigated the ability of C. raudensis to acclimate to long-term imbalances in excitation caused by light quality through adjustments in photosystem stoichiometry. Log-phase cultures of C. raudensis and C. reinhardtii grown under white light were shifted to either blue or red light for 12 h. Previously, we reported that C. raudensis lacks the ability to redistribute light energy via the short-term mechanism of state transitions. However, similar to the model of mesophilic alga, C. reinhardtii, the psychrophile retained the capacity for long-term adjustment in energy distribution between PSI and PSII by modulating the levels of PSI reaction center polypeptides, PsaA/PsaB, with minimal changes in the content of the PSII polypeptide, D1, in response to changes in light quality. The functional consequences of the modulation in PSI/PSII stoichiometry in the psychrophile were distinct from those observed in C. reinhardtii. Exposure of C. raudensis to red light caused 1) an inhibition of growth and photosynthetic rates, 2) an increased reduction state of the intersystem plastoquinone pool with concomitant increases in nonphotochemical quenching, 3) an uncoupling of the major light-harvesting complex from the PSII core, and 4) differential thylakoid protein phosphorylation profiles compared with C. reinhardtii. We conclude that the characteristic low levels of PSI relative to PSII set the limit in the capacity of C. raudensis to photoacclimate to an environment enriched in red light.

  • The Antarctic psychrophile, Chlamydomonas subcaudata, is deficient in state I-state II transitions
    Planta, 2001
    Co-Authors: Rachael M. Morgan-kiss, Alexander G. Ivanov, Norman P. A. Huner
    Abstract:

    State I–State II transitions were monitored in vivo and in vitro in the Antarctic, psychrophillic, green alga, Chlamydomonas subcaudata, as changes in the low-temperature (77 K) chlorophyll fluorescence emission maxima at 722 nm (F722) relative to 699 nm (F699). As expected, the control mesophillic species, Chlamydomonas reinhardtii, was able to modulate the light energy distribution between photosystem II and photosystem I in response to exposure to four different conditions: (i) dark/anaerobic conditions, (ii) a change in Mg2+ concentration, (iii) red light, and (iv) increased incubation temperature. This was correlated with the ability to phosphorylate both of its major light-harvesting polypeptides. In contrast, exposure of C. subcaudata to the same four conditions induced minimum alterations in the 77 K fluorescence emission spectra, which was correlated with the ability to phosphorylate only one of its major light-harvesting polypeptides. Thus, C. subcaudata appears to be deficient in the ability to undergo a State I–State II transition. Functionally, this is associated with alterations in the apparent redox status of the intersystem electron transport chain and with higher rates of photosystem I cyclic electron transport in the psychrophile than in the mesophile, based on in vivo P700 measurements. Structurally, this deficiency is associated with reduced levels of Psa A/B relative to D1, the absence of specific photosystem I light-harvesting polypeptides [R.M. Morgan et al. (1998) Photosynth Res 56:303–314] and a cytochrome b6/f complex that exhibits a form of cytochrome f that is approximately 7 kDa smaller than that observed in C. reinhardtii. We conclude that the Antarctic psychrophile, C. subcaudata, is an example of a natural variant deficient in State I–State II transitions.