The Experts below are selected from a list of 261 Experts worldwide ranked by ideXlab platform
Anaïs Cario - One of the best experts on this subject based on the ideXlab platform.
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molecular chaperone accumulation as a function of stress evidences adaptation to high hydrostatic pressure in the piezophilic archaeon thermococcus barophilus
Scientific Reports, 2016Co-Authors: Anaïs Cario, Axel Thiel, Mohamed Jebbar, Nelly Kervarec, Phil M OgerAbstract:The accumulation of mannosyl-glycerate (MG), the salinity stress response osmolyte of Thermococcales, was investigated as a function of hydrostatic pressure in Thermococcus barophilus strain MP, a hyperthermophilic, piezophilic archaeon isolated from the Snake Pit site (MAR), which grows optimally at 40 MPa. Strain MP accumulated MG primarily in response to salinity stress, but in contrast to other Thermococcales, MG was also accumulated in response to thermal stress. MG accumulation peaked for combined stresses. The accumulation of MG was drastically increased under sub-optimal hydrostatic pressure conditions, demonstrating that low pressure is perceived as a stress in this piezophile, and that the proteome of T. barophilus is low-pressure sensitive. MG accumulation was strongly reduced under supra-optimal pressure conditions clearly demonstrating the structural adaptation of this proteome to high hydrostatic pressure. The lack of MG synthesis only slightly altered the growth characteristics of two different MG synthesis deletion mutants. No shift to other osmolytes was observed. Altogether our observations suggest that the salinity stress response in T. barophilus is not essential and may be under negative selective pressure, similarly to what has been observed for its thermal stress response.
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Membrane homeoviscous adaptation in the piezo-hyperthermophilic archaeon Thermococcus barophilus
Frontiers in microbiology, 2015Co-Authors: Anaïs Cario, Vincent Grossi, Philippe Schaeffer, Philippe OgerAbstract:The archaeon Thermococcus barophilus, one of the most extreme members of hyperthermophilic Piezophiles known thus far, is able to grow at temperatures up to 103°C and pressures up to 80 MPa. We analyzed the membrane lipids of T. barophilus by high performance liquid chromatography-mass spectrometry as a function of pressure and temperature. In contrast to previous reports, we show that under optimal growth conditions (40 MPa, 85°C) the membrane spanning tetraether lipid GDGT-0 (sometimes called caldarchaeol) is a major membrane lipid of T. barophilus together with archaeol. Increasing pressure and decreasing temperature lead to an increase of the proportion of archaeol. Reversely, a higher proportion of GDGT-0 is observed under low pressure and high temperature conditions. Noticeably, pressure and temperature fluctuations also impact the level of unsaturation of apolar lipids having an irregular polyisoprenoid carbon skeleton (unsaturated lycopane derivatives), suggesting a structural role for these neutral lipids in the membrane of T. barophilus. Whether these apolar lipids insert in the membrane or not remains to be addressed. However, our results raise questions about the structure of the membrane in this archaeon and other Archaea harboring a mixture of di- and tetraether lipids.
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Membrane homeoviscous adaptation in the piezo-hyperthermophilic archaeon Thermococcus barophilus
Frontiers in Microbiology, 2015Co-Authors: Anaïs Cario, Philippe Schaeffer, Philippe M. OgerAbstract:The archaeon Thermococcus barophilus, one of the most extreme members of hyperthermophilic Piezophiles known thus far, is able to grow at temperatures up to 103°C and pressures up to 80MPa. We analyzed the membrane lipids of T. barophilus by HPLC-MS as a function of pressure and temperature. In contrast to previous reports, we show that under optimal growth conditions (40 MPa, 85°C) the membrane spanning tetraether lipid GDGT-0 (sometimes called caldarcheol) is a major membrane lipid of T. barophilus together with archaeol. Increasing pressure and decreasing temperature lead to an increase of the proportion of archaeol. Reversely, a higher proportion of GDGT-0 is observed under low pressure and high temperature conditions. Noticeably, pressure and temperature fluctuations also impact the level of unsaturation of non-polar lipids with an irregular polyisoprenoid carbon skeleton (unsaturated lycopane derivatives), suggesting a structural role for these neutral lipids in the membrane of T. barophilus. Whether these apolar lipids insert in the membrane or not remains to be addressed. However, our results raise questions about the structure of the membrane in this archaeon and other Archaea harboring a mixture of di- and tetraether lipids.
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the high pressure life of Piezophiles
Biologie Aujourd'hui, 2014Co-Authors: Philippe Oger, Anaïs CarioAbstract:The deep biosphere is composed of very different biotopes located in the depth of the oceans, the ocean crust or the lithosphere. Although very different, deep biosphere biotopes share one common feature, high hydrostatic pressure. The deep biosphere is colonized by specific organisms, called Piezophiles, that are able to grow under high hydrostatic pressure. Bacterial Piezophiles are mainly psychrophiles belonging to five genera of γ-proteobacteria, Photobacterium, Shewanella, Colwellia, Psychromonas and Moritella, while piezophilic Archaea are mostly (hyper)thermophiles from the Thermococcales. None of these genera are specific for the deep biosphere. High pressure deeply impacts the activity of cells and cellular components, and reduces the activity of numerous key processes, eventually leading to cell death of piezosensitive organisms. Biochemical and genomic studies yield a fragmented view on the adaptive mechanisms in Piezophiles. It is yet unclear whether piezophilic adaptation requires the modification of a few genes, or metabolic pathways, or a more profound reorganization of the genome, the fine tuning of gene expression to compensate the pressure-induced loss of activity of the proteins most affected by high pressure, or a stress-like physiological cell response. In contrast to what has been seen for thermophily or halophily, the adaptation to high pressure is diffuse in the genome and may concern only a small fraction of the genes.
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La vie sous pression des microorganismes piézophiles
'EDP Sciences', 2014Co-Authors: Philippe Oger, Anaïs CarioAbstract:La biosphère profonde regroupe un ensemble très disparate d’environnements localisés en profondeur dans les océans, sous le plancher océanique et dans le sous-sol. Dans la biosphère profonde, la pression hydrostatique augmente avec la profondeur pour atteindre des valeurs qui inhibent la croissance des organismes de surface. On y trouve des organismes, dits piézophiles, capables de vivre dans ces conditions extrêmes de pression. Les bactéries piézophiles connues sont principalement des γ-protéobactéries psychrophiles appartenant à cinq genres, Photobacterium, Shewanella, Colwellia, Psychromonas et Moritella, alors que les Archaea piézophiles sont toutes (hyper)thermophiles et appartiennent principalement aux Thermococcales. On ne connaît pas à ce jour de groupes microbiens limités à la biosphère profonde. La haute pression hydrostatique a un impact important sur les macromolécules biologiques et sur le cycle cellulaire, qui entraîne une baisse de fonctionnalité de nombreux composants cellulaires et éventuellement la mort cellulaire chez les organismes piézosensibles. Les différentes études physiologiques et génétiques menées à ce jour apportent une vision parcellaire des mécanismes adaptatifs possibles chez les piézophiles. Ainsi, il n’est pas clair si cette adaptation requiert la modification de seulement quelques gènes, de quelques voies métaboliques, une altération globale de nombreux gènes, et/ou une régulation compensatoire des gènes dont les produits sont les plus fortement affectés par la haute pression hydrostatique, ou une réponse compensatoire proche de la réponse au stress. L’adaptation piézophile est diffuse dans le génome, contrairement à l’adaptation thermophile ou halophile
Karine Alain - One of the best experts on this subject based on the ideXlab platform.
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pseudodesulfovibrio indicus gen nov sp nov a piezophilic sulfate reducing bacterium from the indian ocean and reclassification of four species of the genus desulfovibrio
International Journal of Systematic and Evolutionary Microbiology, 2016Co-Authors: Junwei Cao, Nicolas Gayet, Xiang Zeng, Zongze Shao, Mohamed Jebbar, Karine AlainAbstract:A novel sulfate-reducing bacterium, strain J2T, was isolated from a serpentinized peridotite sample from the Indian Ocean. Phylogenetic analysis based on 16S rRNA gene sequences showed that strain J2T clustered with the genus Desulfovibrio within the family Desulfovibrionaceae, but it showed low similarity (87.95 %) to the type species Desulfovibrio desulfuricans DSM 642T. It was most closely related to Desulfovibrio portus MSL79T (96.96 %), followed by Desulfovibrio aespoeensis Aspo-2T (96.11 %), Desulfovibrio piezophilus C1TLV30T (96.04 %) and Desulfovibrio profundus DSM 11384T (95.17 %). Other available sequences shared less than 93.33 % 16S rRNA gene sequence similarity. Cells were Gram-staining-negative, anaerobic, motile vibrios (2-6×0.4-0.6 µm). Growth was observed at salinities ranging from 0.2 to 6 % (optimum 2.5 %), from pH 5 to 8 (optimum pH 6.5-7) and at temperatures between 9 and 40 °C (optimum 30-35 °C). J2T was piezophilic, growing optimally at 10 MPa (range 0-30 MPa). J2T used lactate, malate, pyruvate, formate and hydrogen as energy sources. Sulfate, thiosulfate, sulfite, fumarate and nitrate were used as terminal electron acceptors. Lactate and pyruvate were fermented. The main fatty acids were iso-C15 : 0, anteiso-C15 : 0, summed feature 9 (iso-C17 : 1ω9c and/or C16 : 0 10-methyl) and iso-C17 : 0. The DNA G+C content of strain J2T was 63.5 mol%. The combined genotypic and phenotypic data show that strain J2T represents a novel species of a novel genus in the family Desulfovibrionaceae, for which the name Pseudodesulfovibrio indicus gen. nov., sp. nov. is proposed, with the type strain J2T (=MCCC 1A01867T = DSM 101483T). We also propose the reclassification of D. piezophilus as Pseudodesulfovibrio piezophilus comb. nov., D. profundus as Pseudodesulfovibrio profundus comb. nov., D. portus as Pseudodesulfovibrio portus comb. nov. and D. aespoeensis as Pseudodesulfovibrio aespoeensis comb. nov.
Douglas H. Bartlett - One of the best experts on this subject based on the ideXlab platform.
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corrigendum the effect of hydrostatic pressure on enrichments of hydrocarbon degrading microbes from the gulf of mexico following the deepwater horizon oil spill
Frontiers in Microbiology, 2018Co-Authors: Angeliki Marietou, Terry C Hazen, Roger Chastain, Felix Beulig, Alberto Scoma, Douglas H. BartlettAbstract:The Deepwater Horizon oil spill was one of the largest and deepest oil spills recorded. The wellhead was located at approximately 1500 m below the sea where low temperature and high pressure are key environmental characteristics. Using cells collected 4 months following the Deepwater Horizon oil spill at the Gulf of Mexico, we set up Macondo crude oil enrichments at wellhead temperature and different pressures to determine the effect of increasing depth/pressure to the in situ microbial community and their ability to degrade oil. We observed oil degradation under all pressure conditions tested [0.1, 15, and 30 megapascals (MPa)], although oil degradation profiles, cell numbers, and hydrocarbon degradation gene abundances indicated greatest activity at atmospheric pressure. Under all incubations the growth of psychrophilic bacteria was promoted. Bacteria closely related to Oleispira antarctica RB-8 dominated the communities at all pressures. At 30 MPa we observed a shift toward Photobacterium, a genus that includes Piezophiles. Alphaproteobacterial members of the Sulfitobacter, previously associated with oil-degradation, were also highly abundant at 0.1 MPa. Our results suggest that pressure acts synergistically with low temperature to slow microbial growth and thus oil degradation in deep-sea environments.
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Image_2_The Effect of Hydrostatic Pressure on Enrichments of Hydrocarbon Degrading Microbes From the Gulf of Mexico Following the Deepwater Horizon Oil Spill.TIF
2018Co-Authors: Angeliki Marietou, Terry C Hazen, Roger Chastain, Felix Beulig, Alberto Scoma, Douglas H. BartlettAbstract:The Deepwater Horizon oil spill was one of the largest and deepest oil spills recorded. The wellhead was located at approximately 1500 m below the sea where low temperature and high pressure are key environmental characteristics. Using cells collected 4 months following the Deepwater Horizon oil spill at the Gulf of Mexico, we set up Macondo crude oil enrichments at wellhead temperature and different pressures to determine the effect of increasing depth/pressure to the in situ microbial community and their ability to degrade oil. We observed oil degradation under all pressure conditions tested [0.1, 15, and 30 megapascals (MPa)], although oil degradation profiles, cell numbers, and hydrocarbon degradation gene abundances indicated greatest activity at atmospheric pressure. Under all incubations the growth of psychrophilic bacteria was promoted. Bacteria closely related to Oleispira antarctica RB-8 dominated the communities at all pressures. At 30 MPa we observed a shift toward Photobacterium, a genus that includes Piezophiles. Alphaproteobacterial members of the Sulfitobacter, previously associated with oil-degradation, were also highly abundant at 0.1 MPa. Our results suggest that pressure acts synergistically with low temperature to slow microbial growth and thus oil degradation in deep-sea environments.
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current developments in marine microbiology high pressure biotechnology and the genetic engineering of Piezophiles
Current Opinion in Biotechnology, 2015Co-Authors: Yu Zhang, Douglas H. Bartlett, Xiang XiaoAbstract:A key aspect of marine environments is elevated pressure; for example, ∼70% of the ocean is at a pressure of at least 38MPa. Many types of Bacteria and Archaea reside under these high pressures, which drive oceanic biogeochemical cycles and catalyze reactions among rocks, sediments and fluids. Most marine prokaryotes are classified as piezotolerant or as (obligate)-Piezophiles with few cultivated relatives. The biochemistry and physiology of these organisms are largely unknown. Recently, high-pressure cultivation technology has been combined with omics and DNA recombination methodologies to examine the physiology of piezophilic marine microorganisms. We are now beginning to understand the adaptive mechanisms of these organisms, along with their ecological functions and evolutionary processes. This knowledge is leading to the further development of high-pressure-based biotechnology.
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the unique 16s rrna genes of Piezophiles reflect both phylogeny and adaptation
Applied and Environmental Microbiology, 2007Co-Authors: Federico M. Lauro, Roger Chastain, Aristides A Yayanos, Lesley E Blankenship, Douglas H. BartlettAbstract:In the ocean's most extreme depths, pressures of 70 to 110 megapascals prevent the growth of all but the most hyperpiezophilic (pressure-loving) organisms. The physiological adaptations required for growth under these conditions are considered to be substantial. Efforts to determine specific adaptations permitting growth at extreme pressures have thus far focused on relatively few γ-proteobacteria, in part due to the technical difficulties of obtaining piezophilic bacteria in pure culture. Here, we present the molecular phylogenies of several new Piezophiles of widely differing geographic origins. Included are results from an analysis of the first deep-trench bacterial isolates recovered from the southern hemisphere (9.9-km depth) and of the first gram-positive piezophilic strains. These new data allowed both phylogenetic and structural 16S rRNA comparisons among deep-ocean trench Piezophiles and closely related strains not adapted to high pressure. Our results suggest that (i) the Circumpolar Deep Water acts as repository for hyperPiezophiles and drives their dissemination to deep trenches in the Pacific Ocean and (ii) the occurrence of elongated helices in the 16S rRNA genes increases with the extent of adaptation to growth at elevated pressure. These helix changes are believed to improve ribosome function under deep-sea conditions.
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The unique 16S rRNA genes of Piezophiles reflect both phylogeny and adaptation
2007Co-Authors: Federico M. Lauro, Roger Chastain, Aristides A Yayanos, Lesley E Blankenship, Douglas H. BartlettAbstract:In the ocean’s most extreme depths, pressures of 70 to 110 megapascals prevent the growth of all but the most hyperpiezophilic (pressure-loving) organisms. The physiological adaptations required for growth under these conditions are considered to be substantial. Efforts to determine specific adaptations permitting growth at extreme pressures have thus far focused on relatively few �-proteobacteria, in part due to the technical difficulties of obtaining piezophilic bacteria in pure culture. Here, we present the molecular phylogenies of several new Piezophiles of widely differing geographic origins. Included are results from an analysis of the first deep-trench bacterial isolates recovered from the southern hemisphere (9.9-km depth) and of the first grampositive piezophilic strains. These new data allowed both phylogenetic and structural 16S rRNA comparisons among deep-ocean trench Piezophiles and closely related strains not adapted to high pressure. Our results suggest that (i) the Circumpolar Deep Water acts as repository for hyperPiezophiles and drives their dissemination to deep trenches in the Pacific Ocean and (ii) the occurrence of elongated helices in the 16S rRNA genes increases with the extent of adaptation to growth at elevated pressure. These helix changes are believed to improve ribosome function under deep-sea conditions. Low temperature and high hydrostatic pressure structure deep-sea communities outside of hydrothermal vents. Tigh
Mohamed Jebbar - One of the best experts on this subject based on the ideXlab platform.
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pseudodesulfovibrio indicus gen nov sp nov a piezophilic sulfate reducing bacterium from the indian ocean and reclassification of four species of the genus desulfovibrio
International Journal of Systematic and Evolutionary Microbiology, 2016Co-Authors: Junwei Cao, Nicolas Gayet, Xiang Zeng, Zongze Shao, Mohamed Jebbar, Karine AlainAbstract:A novel sulfate-reducing bacterium, strain J2T, was isolated from a serpentinized peridotite sample from the Indian Ocean. Phylogenetic analysis based on 16S rRNA gene sequences showed that strain J2T clustered with the genus Desulfovibrio within the family Desulfovibrionaceae, but it showed low similarity (87.95 %) to the type species Desulfovibrio desulfuricans DSM 642T. It was most closely related to Desulfovibrio portus MSL79T (96.96 %), followed by Desulfovibrio aespoeensis Aspo-2T (96.11 %), Desulfovibrio piezophilus C1TLV30T (96.04 %) and Desulfovibrio profundus DSM 11384T (95.17 %). Other available sequences shared less than 93.33 % 16S rRNA gene sequence similarity. Cells were Gram-staining-negative, anaerobic, motile vibrios (2-6×0.4-0.6 µm). Growth was observed at salinities ranging from 0.2 to 6 % (optimum 2.5 %), from pH 5 to 8 (optimum pH 6.5-7) and at temperatures between 9 and 40 °C (optimum 30-35 °C). J2T was piezophilic, growing optimally at 10 MPa (range 0-30 MPa). J2T used lactate, malate, pyruvate, formate and hydrogen as energy sources. Sulfate, thiosulfate, sulfite, fumarate and nitrate were used as terminal electron acceptors. Lactate and pyruvate were fermented. The main fatty acids were iso-C15 : 0, anteiso-C15 : 0, summed feature 9 (iso-C17 : 1ω9c and/or C16 : 0 10-methyl) and iso-C17 : 0. The DNA G+C content of strain J2T was 63.5 mol%. The combined genotypic and phenotypic data show that strain J2T represents a novel species of a novel genus in the family Desulfovibrionaceae, for which the name Pseudodesulfovibrio indicus gen. nov., sp. nov. is proposed, with the type strain J2T (=MCCC 1A01867T = DSM 101483T). We also propose the reclassification of D. piezophilus as Pseudodesulfovibrio piezophilus comb. nov., D. profundus as Pseudodesulfovibrio profundus comb. nov., D. portus as Pseudodesulfovibrio portus comb. nov. and D. aespoeensis as Pseudodesulfovibrio aespoeensis comb. nov.
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molecular chaperone accumulation as a function of stress evidences adaptation to high hydrostatic pressure in the piezophilic archaeon thermococcus barophilus
Scientific Reports, 2016Co-Authors: Anaïs Cario, Axel Thiel, Mohamed Jebbar, Nelly Kervarec, Phil M OgerAbstract:The accumulation of mannosyl-glycerate (MG), the salinity stress response osmolyte of Thermococcales, was investigated as a function of hydrostatic pressure in Thermococcus barophilus strain MP, a hyperthermophilic, piezophilic archaeon isolated from the Snake Pit site (MAR), which grows optimally at 40 MPa. Strain MP accumulated MG primarily in response to salinity stress, but in contrast to other Thermococcales, MG was also accumulated in response to thermal stress. MG accumulation peaked for combined stresses. The accumulation of MG was drastically increased under sub-optimal hydrostatic pressure conditions, demonstrating that low pressure is perceived as a stress in this piezophile, and that the proteome of T. barophilus is low-pressure sensitive. MG accumulation was strongly reduced under supra-optimal pressure conditions clearly demonstrating the structural adaptation of this proteome to high hydrostatic pressure. The lack of MG synthesis only slightly altered the growth characteristics of two different MG synthesis deletion mutants. No shift to other osmolytes was observed. Altogether our observations suggest that the salinity stress response in T. barophilus is not essential and may be under negative selective pressure, similarly to what has been observed for its thermal stress response.
Philippe Oger - One of the best experts on this subject based on the ideXlab platform.
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thermococcus piezophilus sp nov a novel hyperthermophilic and piezophilic archaeon with a broad pressure range for growth isolated from a deepest hydrothermal vent at the mid cayman rise
Systematic and Applied Microbiology, 2016Co-Authors: Cecile Dalmasso, Gwendoline Selva, Damien Courtine, Philippe Oger, Stephane Lharidon, Alexandre GarlaschelliAbstract:Abstract A novel strictly anaerobic, hyperthermophilic archaeon, designated strain CDGST, was isolated from a deep-sea hydrothermal vent in the Cayman Trough at 4964 m water depth. The novel isolate is obligate anaerobe and grows chemoorganoheterotrophically with stimulation of growth by sulphur containing compounds. Its growth is optimal at 75 °C, pH 6.0 and under a pressure of 50 MPa. It possesses the broadest hydrostatic pressure range for growth that has ever been described for a microorganism. Its genomic DNA G + C content is 51.11 mol%. The novel isolate belongs to the genus Thermococcus. Phylogenetic analyses indicated that it is most closely related to Thermococcus barossii DSM17882T based on its 16S rRNA gene sequence, and to ‘Thermococcus onnurineus’ NA1 based on its whole genome sequence. The average nucleotide identity scores with these strains are 77.66% for T. barossii and 84.84% for ‘T. onnurineus’, respectively. Based on the draft whole genome sequence and phenotypic characteristics, strain CDGST is suggested to be separated into a novel species within the genus Thermococcus, with proposed name Thermococcus piezophilus (type strain CDGST = ATCC TSD-33T = UBOCC 3296T).
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Membrane homeoviscous adaptation in the piezo-hyperthermophilic archaeon Thermococcus barophilus
Frontiers in microbiology, 2015Co-Authors: Anaïs Cario, Vincent Grossi, Philippe Schaeffer, Philippe OgerAbstract:The archaeon Thermococcus barophilus, one of the most extreme members of hyperthermophilic Piezophiles known thus far, is able to grow at temperatures up to 103°C and pressures up to 80 MPa. We analyzed the membrane lipids of T. barophilus by high performance liquid chromatography-mass spectrometry as a function of pressure and temperature. In contrast to previous reports, we show that under optimal growth conditions (40 MPa, 85°C) the membrane spanning tetraether lipid GDGT-0 (sometimes called caldarchaeol) is a major membrane lipid of T. barophilus together with archaeol. Increasing pressure and decreasing temperature lead to an increase of the proportion of archaeol. Reversely, a higher proportion of GDGT-0 is observed under low pressure and high temperature conditions. Noticeably, pressure and temperature fluctuations also impact the level of unsaturation of apolar lipids having an irregular polyisoprenoid carbon skeleton (unsaturated lycopane derivatives), suggesting a structural role for these neutral lipids in the membrane of T. barophilus. Whether these apolar lipids insert in the membrane or not remains to be addressed. However, our results raise questions about the structure of the membrane in this archaeon and other Archaea harboring a mixture of di- and tetraether lipids.
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the high pressure life of Piezophiles
Biologie Aujourd'hui, 2014Co-Authors: Philippe Oger, Anaïs CarioAbstract:The deep biosphere is composed of very different biotopes located in the depth of the oceans, the ocean crust or the lithosphere. Although very different, deep biosphere biotopes share one common feature, high hydrostatic pressure. The deep biosphere is colonized by specific organisms, called Piezophiles, that are able to grow under high hydrostatic pressure. Bacterial Piezophiles are mainly psychrophiles belonging to five genera of γ-proteobacteria, Photobacterium, Shewanella, Colwellia, Psychromonas and Moritella, while piezophilic Archaea are mostly (hyper)thermophiles from the Thermococcales. None of these genera are specific for the deep biosphere. High pressure deeply impacts the activity of cells and cellular components, and reduces the activity of numerous key processes, eventually leading to cell death of piezosensitive organisms. Biochemical and genomic studies yield a fragmented view on the adaptive mechanisms in Piezophiles. It is yet unclear whether piezophilic adaptation requires the modification of a few genes, or metabolic pathways, or a more profound reorganization of the genome, the fine tuning of gene expression to compensate the pressure-induced loss of activity of the proteins most affected by high pressure, or a stress-like physiological cell response. In contrast to what has been seen for thermophily or halophily, the adaptation to high pressure is diffuse in the genome and may concern only a small fraction of the genes.
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La vie sous pression des microorganismes piézophiles
'EDP Sciences', 2014Co-Authors: Philippe Oger, Anaïs CarioAbstract:La biosphère profonde regroupe un ensemble très disparate d’environnements localisés en profondeur dans les océans, sous le plancher océanique et dans le sous-sol. Dans la biosphère profonde, la pression hydrostatique augmente avec la profondeur pour atteindre des valeurs qui inhibent la croissance des organismes de surface. On y trouve des organismes, dits piézophiles, capables de vivre dans ces conditions extrêmes de pression. Les bactéries piézophiles connues sont principalement des γ-protéobactéries psychrophiles appartenant à cinq genres, Photobacterium, Shewanella, Colwellia, Psychromonas et Moritella, alors que les Archaea piézophiles sont toutes (hyper)thermophiles et appartiennent principalement aux Thermococcales. On ne connaît pas à ce jour de groupes microbiens limités à la biosphère profonde. La haute pression hydrostatique a un impact important sur les macromolécules biologiques et sur le cycle cellulaire, qui entraîne une baisse de fonctionnalité de nombreux composants cellulaires et éventuellement la mort cellulaire chez les organismes piézosensibles. Les différentes études physiologiques et génétiques menées à ce jour apportent une vision parcellaire des mécanismes adaptatifs possibles chez les piézophiles. Ainsi, il n’est pas clair si cette adaptation requiert la modification de seulement quelques gènes, de quelques voies métaboliques, une altération globale de nombreux gènes, et/ou une régulation compensatoire des gènes dont les produits sont les plus fortement affectés par la haute pression hydrostatique, ou une réponse compensatoire proche de la réponse au stress. L’adaptation piézophile est diffuse dans le génome, contrairement à l’adaptation thermophile ou halophile