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Norman P A Huner - One of the best experts on this subject based on the ideXlab platform.
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Adaptation to Low Temperature in a Photoautotrophic Antarctic Psychrophile, Chlamydomonas sp. UWO 241
Photosynthesis: Structures Mechanisms and Applications, 2017Co-Authors: Beth Szyszka, Alexander G. Ivanov, Norman P A HunerAbstract:Permanent cold environments account for a large portion of the Earth. These environments are inhabited by various micro-organisms that have often adapted to unique combinations of selection pressures. Therefore, there is considerable interest in understanding survival strategies utilized by extremophiles to exist in such harsh environments. This chapter summarizes common adaptive mechanisms of psychrophilic organisms with focus on the unique photosynthetic characteristics of a unicellular green microalga, Chlamydomonas sp. UWO241. Chlamydomonas sp. UWO 241 was isolated from perennially, ice-covered Lake Bonney, Antarctica where it has adapted to constant low temperatures and high salinity. A unique characteristic of this algal strain is its inability to undergo state transitions combined with its high rates of photosystem I cyclic electron transport. Consequently, in contrast to mesophilic green algal species such as Chlamydomonas reinhardtii which undergo state transitions, Chlamydomonas sp. UWO241 does not phosphorylate LHCII polypeptides. Rather, the Antarctic Psychrophile exhibits a unique, light-dependent, thylakoid polypeptide phosphorylation profile associated with a photosystem I supercomplex which also contains the cytochrome b6/f complex. The stability of this photosystem I supercomplex in Chlamydomonas sp. UWO 241 is sensitive to its phosphorylation status as well as high salt concentrations. The role of the photosystem I supercomplex and its phosphorylation status in the regulation of photosystem I cyclic electron transport is discussed. We suggest that Chlamydomonas sp. UWO 241 should be considered a model system to study psychrophily and adaptation to low temperature in eukaryotic photoautrophs.
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Changes in salinity impact growth, photochemistry and photoinhibition in the Antarctic Psychrophile C. Raudensis
2008Co-Authors: Tessa Pocock, Adrien Vetterli, Norman P A Huner, Stefan FalkAbstract:Changes in salinity impact growth, photochemistry and photoinhibition in the Antarctic Psychrophile C. Raudensis
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Changes in salinity impacts growth, photochemistry and photoinhibition in the Antarctic Psychrophile Chlamydomonas raudensis UWO 241.
2008Co-Authors: Tessa Pocock, Adrien Vetterli, Norman P A Huner, Stefan FalkAbstract:Changes in salinity impacts growth, photochemistry and photoinhibition in the Antarctic Psychrophile Chlamydomonas raudensis UWO 241.
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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, 2007Co-Authors: Loreta Gudynaite-savitch, Christelle Loiselay, John Simmondsj. Simmonds, Susanne E. Kohalmi, Yves Choquety. Choquet, Leonid V Savitch, Norman P A HunerAbstract: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.
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The Antarctic Psychrophile, Chlamydomonas raudensis Ettl (UWO241) (Chlorophyceae, Chlorophyta), exhibits a limited capacity to photoacclimate to red light
Journal of Phycology, 2005Co-Authors: Rachael M. Morgan-kiss, Loreta Gudynaite-savitch, Tessa Pocock, Marianna Krol, Alexander G. Ivanov, Norman P A HunerAbstract: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.
Tessa Pocock - One of the best experts on this subject based on the ideXlab platform.
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Changes in salinity impact growth, photochemistry and photoinhibition in the Antarctic Psychrophile C. Raudensis
2008Co-Authors: Tessa Pocock, Adrien Vetterli, Norman P A Huner, Stefan FalkAbstract:Changes in salinity impact growth, photochemistry and photoinhibition in the Antarctic Psychrophile C. Raudensis
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Changes in salinity impacts growth, photochemistry and photoinhibition in the Antarctic Psychrophile Chlamydomonas raudensis UWO 241.
2008Co-Authors: Tessa Pocock, Adrien Vetterli, Norman P A Huner, Stefan FalkAbstract:Changes in salinity impacts growth, photochemistry and photoinhibition in the Antarctic Psychrophile Chlamydomonas raudensis UWO 241.
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The Antarctic Psychrophile, Chlamydomonas raudensis Ettl (UWO241) (Chlorophyceae, Chlorophyta), exhibits a limited capacity to photoacclimate to red light
Journal of Phycology, 2005Co-Authors: Rachael M. Morgan-kiss, Loreta Gudynaite-savitch, Tessa Pocock, Marianna Krol, Alexander G. Ivanov, Norman P A HunerAbstract: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.
Georges Feller - One of the best experts on this subject based on the ideXlab platform.
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Energetics of Protein Stability at Extreme Environmental Temperatures in Bacterial Trigger Factors
2013Co-Authors: Caroline Struvay, Sonia Negro, André Matagne, Georges FellerAbstract:Trigger factor is the first molecular chaperone interacting cotranslationally with virtually all nascent polypeptides synthesized by the ribosome in bacteria. The stability of this primary folding assistant was investigated using trigger factors from the Antarctic Psychrophile Pseudoalteromonas haloplanktis, the mesophile Escherichia coli, and the hyperthermophile Thermotoga maritima. This series covers nearly all temperatures encountered by living organisms. We show that proteins adapt their stability over the whole range of biological temperatures via adjustments of the same fundamental mechanisms, involving increases in enthalpic stabilization and decreases in unfolding rates, in parallel with the environmental temperature. Enthalpic stabilization in trigger factors is characterized by large increases in the melting temperature, Tm, ranging from 33 to 96.6 °C, associated with similarly large increases in unfolding enthalpy as revealed by differential scanning calorimetry. Stopped-flow spectroscopy shows that the folding rate constants for the three investigated proteins are similar, whereas the unfolding rate constants differ by several orders of magnitude, revealing that kinetic resistance to unfolding drives adjustments of protein stability. While the unusual stability of hyperthermophilic proteins has attracted much attention, this study indicates that they are an extreme case of a more general continuum, the other extreme being represented by natively unstable proteins from Psychrophiles
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Is there a cold shock response in the Antarctic Psychrophile Pseudoalteromonas haloplanktis
Extremophiles, 2012Co-Authors: Florence Piette, Pierre Leprince, Georges FellerAbstract: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.
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life in the cold proteomics of the antarctic bacterium pseudoalteromonas haloplanktis
2012Co-Authors: Florence Piette, Caroline Struvay, Amandine Godin, Alexandre Cipolla, Georges FellerAbstract:It is frequently overlooked that the majority (>80%) of the Earth’s biosphere is cold and permanently exposed to temperatures below 5 °C (Rodrigues & Tiedje, 2008). Such low mean temperatures mainly arise from the fact that ~70% of the Earth’s surface is covered by oceans that have a constant temperature of 4°C below 1000 m depth, irrespective of the latitude. The polar regions account for another 15%, to which the glacier and alpine regions must be added, as well as the permafrost representing more than 20% of terrestrial soils. All these low temperature biotopes have been successfully colonized by cold-adapted microorganisms, termed Psychrophiles (Margesin et al., 2008). These organisms do not merely endure such low and extremely inhospitable conditions but are irreversibly adapted to these environments as most Psychrophiles are unable to grow at mild (or mesophilic) temperatures. Extreme Psychrophiles have been traditionally sampled from Antarctic and Arctic sites, assuming that low temperatures persisting over a geological time-scale have promoted deep and efficient adaptations to freezing conditions. In addition to ice caps and sea ice, polar regions also possess unusual microbiotopes such as porous rocks in Antarctic dry valleys hosting microbial communities surviving at -60 °C (Cary et al., 2010), the liquid brine veins between sea ice crystals harboring metabolically-active microorganisms at -20 °C (Deming, 2002) or permafrost cryopegs, i.e. salty water pockets that have remained liquid at -10 °C for about 100 000 years (Gilichinsky et al., 2005). Psychrophiles and their biomolecules also possess an interesting biotechnological potential, which has already found several applications (Margesin & Feller, 2010). Cold exerts severe physicochemical constraints on living organisms including increased water viscosity, decreased molecular diffusion rates, reduced biochemical reaction rates, perturbation of weak interactions driving molecular recognition and interaction, strengthening of hydrogen bonds that, for instance, stabilize inhibitory nucleic acid structures, increased solubility of gases and stability of toxic metabolites as well as reduced fluidity of cellular membranes (D'Amico et al., 2006; Gerday & Glansdorff, 2007; Margesin et al., 2008; Rodrigues & Tiedje, 2008). Previous biochemical studies have revealed various adaptations at the molecular level such as the synthesis of cold-active enzymes by Psychrophiles or the incorporation of membrane lipids promoting homeoviscosity in cold conditions. It was shown that the high level of specific activity at low temperatures of coldadapted enzymes is a key adaptation to compensate for the exponential decrease in
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crystallization and preliminary x ray diffraction studies of alpha amylase from the antarctic Psychrophile alteromonas haloplanctis a23
Protein Science, 1996Co-Authors: Nushin Aghajari, Georges Feller, Charles Gerday, Richard HaserAbstract: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.
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The beta-lactamase secreted by the antarctic Psychrophile Psychrobacter immobilis A8.
Applied and Environmental Microbiology, 1995Co-Authors: Georges Feller, Pascal Sonnet, Charles GerdayAbstract:A class C beta-lactamase has been purified from the culture supernatant of the antarctic Psychrophile Psychrobacter immobilis A8. This psychrophilic beta-lactamase displays a low level of thermal stability and a low optimal temperature of activity. In contrast to other cold-adapted enzymes, its level of specific activity is not higher than that of mesophilic class C beta-lactamases.
Rachael M Morgankiss - One of the best experts on this subject based on the ideXlab platform.
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the antarctic Psychrophiles chlamydomonas spp uwo241 and ice mdv exhibit differential restructuring of photosystem i in response to iron
Photosynthesis Research, 2019Co-Authors: Greg Cook, Amber Grace Teufel, John C. Priscu, Wei Li, Isha Kalra, Xin Wang, Rachael M MorgankissAbstract:Chlamydomonas sp. UWO241 is a psychrophilic alga isolated from the deep photic zone of a perennially ice-covered Antarctic lake (east lobe Lake Bonney, ELB). Past studies have shown that C. sp. UWO241 exhibits constitutive downregulation of photosystem I (PSI) and high rates of PSI-associated cyclic electron flow (CEF). Iron levels in ELB are in the nanomolar range leading us to hypothesize that the unusual PSI phenotype of C. sp. UWO241 could be a response to chronic Fe-deficiency. We studied the impact of Fe availability in C. sp. UWO241, a mesophile, C. reinhardtii SAG11-32c, as well as a Psychrophile isolated from the shallow photic zone of ELB, Chlamydomonas sp. ICE-MDV. Under Fe-deficiency, PsaA abundance and levels of photooxidizable P700 (ΔA820/A820) were reduced in both Psychrophiles relative to the mesophile. Upon increasing Fe, C. sp. ICE-MDV and C. reinhardtii exhibited restoration of PSI function, while C. sp. UWO241 exhibited only moderate changes in PSI activity and lacked almost all LHCI proteins. Relative to Fe-excess conditions (200 µM Fe2+), C. sp. UWO241 grown in 18 µM Fe2+ exhibited downregulation of light harvesting and photosystem core proteins, as well as upregulation of a bestrophin-like anion channel protein and two CEF-associated proteins (NdsS, PGL1). Key enzymes of starch synthesis and shikimate biosynthesis were also upregulated. We conclude that in response to variable Fe availability, the Psychrophile C. sp. UWO241 exhibits physiological plasticity which includes restructuring of the photochemical apparatus, increased PSI-associated CEF, and shifts in downstream carbon metabolism toward storage carbon and secondary stress metabolites.
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the antarctic Psychrophiles chlamydomonas spp uwo241 and ice mdv exhibit differential restructuring of photosystem i in response to iron
Photosynthesis Research, 2019Co-Authors: Greg Cook, Amber Grace Teufel, John C. Priscu, Wei Li, Isha Kalra, Xin Wang, Rachael M MorgankissAbstract:Chlamydomonas sp. UWO241 is a psychrophilic alga isolated from the deep photic zone of a perennially ice-covered Antarctic lake (east lobe Lake Bonney, ELB). Past studies have shown that C. sp. UWO241 exhibits constitutive downregulation of photosystem I (PSI) and high rates of PSI-associated cyclic electron flow (CEF). Iron levels in ELB are in the nanomolar range leading us to hypothesize that the unusual PSI phenotype of C. sp. UWO241 could be a response to chronic Fe-deficiency. We studied the impact of Fe availability in C. sp. UWO241, a mesophile, C. reinhardtii SAG11-32c, as well as a Psychrophile isolated from the shallow photic zone of ELB, Chlamydomonas sp. ICE-MDV. Under Fe-deficiency, PsaA abundance and levels of photooxidizable P700 (ΔA820/A820) were reduced in both Psychrophiles relative to the mesophile. Upon increasing Fe, C. sp. ICE-MDV and C. reinhardtii exhibited restoration of PSI function, while C. sp. UWO241 exhibited only moderate changes in PSI activity and lacked almost all LHCI proteins. Relative to Fe-excess conditions (200 µM Fe2+), C. sp. UWO241 grown in 18 µM Fe2+ exhibited downregulation of light harvesting and photosystem core proteins, as well as upregulation of a bestrophin-like anion channel protein and two CEF-associated proteins (NdsS, PGL1). Key enzymes of starch synthesis and shikimate biosynthesis were also upregulated. We conclude that in response to variable Fe availability, the Psychrophile C. sp. UWO241 exhibits physiological plasticity which includes restructuring of the photochemical apparatus, increased PSI-associated CEF, and shifts in downstream carbon metabolism toward storage carbon and secondary stress metabolites.
Stefan Falk - One of the best experts on this subject based on the ideXlab platform.
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Changes in salinity impact growth, photochemistry and photoinhibition in the Antarctic Psychrophile C. Raudensis
2008Co-Authors: Tessa Pocock, Adrien Vetterli, Norman P A Huner, Stefan FalkAbstract:Changes in salinity impact growth, photochemistry and photoinhibition in the Antarctic Psychrophile C. Raudensis
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Changes in salinity impacts growth, photochemistry and photoinhibition in the Antarctic Psychrophile Chlamydomonas raudensis UWO 241.
2008Co-Authors: Tessa Pocock, Adrien Vetterli, Norman P A Huner, Stefan FalkAbstract:Changes in salinity impacts growth, photochemistry and photoinhibition in the Antarctic Psychrophile Chlamydomonas raudensis UWO 241.
