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Tamby A, Sinninghe Damsté JS, Villanueva L. Microbial membrane lipid adaptations to high hydrostatic pressure in the marine environment. Front Mol Biosci 2023; 9:1058381. [PMID: 36685280 PMCID: PMC9853057 DOI: 10.3389/fmolb.2022.1058381] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2022] [Accepted: 11/29/2022] [Indexed: 01/09/2023] Open
Abstract
The deep-sea is characterized by extreme conditions, such as high hydrostatic pressure (HHP) and near-freezing temperature. Piezophiles, microorganisms adapted to high pressure, have developed key strategies to maintain the integrity of their lipid membrane at these conditions. The abundance of specific membrane lipids, such as those containing unsaturated and branched-chain fatty acids, rises with increasing HHP. Nevertheless, this strategy is not universal among piezophiles, highlighting the need to further understand the effects of HHP on microbial lipid membranes. Challenges in the study of lipid membrane adaptations by piezophiles also involve methodological developments, cross-adaptation studies, and insight into slow-growing piezophiles. Moreover, the effects of HHP on piezophiles are often difficult to disentangle from effects caused by low temperature that are often characteristic of the deep sea. Here, we review the knowledge of membrane lipid adaptation strategies of piezophiles, and put it into the perspective of marine systems, highlighting the future challenges of research studying the effects of HHP on the microbial lipid composition.
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Affiliation(s)
- Anandi Tamby
- Department of Marine Microbiology and Biogeochemistry (MMB), NIOZ Royal Netherlands Institute for Sea Research, Den Burg, Netherlands,*Correspondence: Anandi Tamby,
| | - Jaap S. Sinninghe Damsté
- Department of Marine Microbiology and Biogeochemistry (MMB), NIOZ Royal Netherlands Institute for Sea Research, Den Burg, Netherlands,Department of Earth Sciences, Faculty of Geosciences, Utrecht University, Utrecht, Netherlands
| | - Laura Villanueva
- Department of Marine Microbiology and Biogeochemistry (MMB), NIOZ Royal Netherlands Institute for Sea Research, Den Burg, Netherlands,Department of Earth Sciences, Faculty of Geosciences, Utrecht University, Utrecht, Netherlands
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Roumagnac M, Pradel N, Bartoli M, Garel M, Jones AA, Armougom F, Fenouil R, Tamburini C, Ollivier B, Summers ZM, Dolla A. Responses to the Hydrostatic Pressure of Surface and Subsurface Strains of Pseudothermotoga elfii Revealing the Piezophilic Nature of the Strain Originating From an Oil-Producing Well. Front Microbiol 2020; 11:588771. [PMID: 33343528 PMCID: PMC7746679 DOI: 10.3389/fmicb.2020.588771] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2020] [Accepted: 11/16/2020] [Indexed: 11/13/2022] Open
Abstract
Microorganisms living in deep-oil reservoirs face extreme conditions of elevated temperature and hydrostatic pressure. Within these microbial communities, members of the order Thermotogales are predominant. Among them, the genus Pseudothermotoga is widespread in oilfield-produced waters. The growth and cell phenotypes under hydrostatic pressures ranging from 0.1 to 50 MPa of two strains from the same species originating from subsurface, Pseudothermotoga elfii DSM9442 isolated from a deep African oil-producing well, and surface, P. elfii subsp. lettingae isolated from a thermophilic sulfate-reducing bioreactor, environments are reported for the first time. The data support evidence for the piezophilic nature of P. elfii DSM9442, with an optimal hydrostatic pressure for growth of 20 MPa and an upper limit of 40 MPa, and the piezotolerance of P. elfii subsp. lettingae with growth occurring up to 20 MPa only. Under the experimental conditions, both strains produce mostly acetate and propionate as volatile fatty acids with slight variations with respect to the hydrostatic pressure for P. elfii DSM9442. The data show that the metabolism of P. elfii DSM9442 is optimized when grown at 20 MPa, in agreement with its piezophilic nature. Both Pseudothermotoga strains form chained cells when the hydrostatic pressure increases, especially P. elfii DSM9442 for which 44% of cells is chained when grown at 40 MPa. The viability of the chained cells increases with the increase in the hydrostatic pressure, indicating that chain formation is a protective mechanism for P. elfii DSM9442.
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Affiliation(s)
- Marie Roumagnac
- Aix Marseille Univ., Université de Toulon, CNRS, IRD, MIO, Marseille, France
| | - Nathalie Pradel
- Aix Marseille Univ., Université de Toulon, CNRS, IRD, MIO, Marseille, France
| | - Manon Bartoli
- Aix Marseille Univ., Université de Toulon, CNRS, IRD, MIO, Marseille, France
| | - Marc Garel
- Aix Marseille Univ., Université de Toulon, CNRS, IRD, MIO, Marseille, France
| | - Aaron A Jones
- ExxonMobil Research and Engineering Company, Annandale, NJ, United States
| | - Fabrice Armougom
- Aix Marseille Univ., Université de Toulon, CNRS, IRD, MIO, Marseille, France
| | - Romain Fenouil
- Aix Marseille Univ., Université de Toulon, CNRS, IRD, MIO, Marseille, France
| | - Christian Tamburini
- Aix Marseille Univ., Université de Toulon, CNRS, IRD, MIO, Marseille, France
| | - Bernard Ollivier
- Aix Marseille Univ., Université de Toulon, CNRS, IRD, MIO, Marseille, France
| | - Zarath M Summers
- ExxonMobil Research and Engineering Company, Annandale, NJ, United States
| | - Alain Dolla
- Aix Marseille Univ., Université de Toulon, CNRS, IRD, MIO, Marseille, France
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Li XG, Zhang WJ, Xiao X, Jian HH, Jiang T, Tang HZ, Qi XQ, Wu LF. Pressure-Regulated Gene Expression and Enzymatic Activity of the Two Periplasmic Nitrate Reductases in the Deep-Sea Bacterium Shewanella piezotolerans WP3. Front Microbiol 2018; 9:3173. [PMID: 30622525 PMCID: PMC6308320 DOI: 10.3389/fmicb.2018.03173] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2018] [Accepted: 12/07/2018] [Indexed: 01/06/2023] Open
Abstract
Shewanella species are widely distributed in marine environments, from the shallow coasts to the deepest sea bottom. Most Shewanella species possess two isoforms of periplasmic nitrate reductases (NAP-α and NAP-β) and are able to generate energy through nitrate reduction. However, the contributions of the two NAP systems to bacterial deep-sea adaptation remain unclear. In this study, we found that the deep-sea denitrifier Shewanella piezotolerans WP3 was capable of performing nitrate respiration under high hydrostatic pressure (HHP) conditions. In the wild-type strain, NAP-β played a dominant role and was induced by both the substrate and an elevated pressure, whereas NAP-α was constitutively expressed at a relatively lower level. Genetic studies showed that each NAP system alone was sufficient to fully sustain nitrate-dependent growth and that both NAP systems exhibited substrate and pressure inducible expression patterns when the other set was absent. Biochemical assays further demonstrated that NAP-α had a higher tolerance to elevated pressure. Collectively, we report for the first time the distinct properties and contributions of the two NAP systems to nitrate reduction under different pressure conditions. The results will shed light on the mechanisms of bacterial HHP adaptation and nitrogen cycling in the deep-sea environment.
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Affiliation(s)
- Xue-Gong Li
- Laboratory of Deep Sea Microbial Cell Biology, Institute of Deep-Sea Science and Engineering, Chinese Academy of Sciences, Sanya, China.,International Associated Laboratory of Evolution and Development of Magnetotactic Multicellular Organisms, CNRS-Marseille/CAS, Sanya, China
| | - Wei-Jia Zhang
- Laboratory of Deep Sea Microbial Cell Biology, Institute of Deep-Sea Science and Engineering, Chinese Academy of Sciences, Sanya, China.,International Associated Laboratory of Evolution and Development of Magnetotactic Multicellular Organisms, CNRS-Marseille/CAS, Sanya, China
| | - Xiang Xiao
- State Key Laboratory of Microbial Metabolism, School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, Shanghai, China.,State Key Laboratory of Ocean Engineering, School of Naval Architecture, Ocean and Civil Engineering, Shanghai Jiao Tong University, Shanghai, China
| | - Hua-Hua Jian
- State Key Laboratory of Microbial Metabolism, School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, Shanghai, China
| | - Ting Jiang
- Laboratory of Deep Sea Microbial Cell Biology, Institute of Deep-Sea Science and Engineering, Chinese Academy of Sciences, Sanya, China.,University of Chinese Academy of Sciences, Beijing, China
| | - Hong-Zhi Tang
- Laboratory of Deep Sea Microbial Cell Biology, Institute of Deep-Sea Science and Engineering, Chinese Academy of Sciences, Sanya, China.,University of Chinese Academy of Sciences, Beijing, China
| | - Xiao-Qing Qi
- Laboratory of Deep Sea Microbial Cell Biology, Institute of Deep-Sea Science and Engineering, Chinese Academy of Sciences, Sanya, China.,International Associated Laboratory of Evolution and Development of Magnetotactic Multicellular Organisms, CNRS-Marseille/CAS, Sanya, China
| | - Long-Fei Wu
- International Associated Laboratory of Evolution and Development of Magnetotactic Multicellular Organisms, CNRS-Marseille/CAS, Sanya, China.,Aix Marseille Université, CNRS, LCB, Marseille, France
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Xiong L, Jian H, Zhang Y, Xiao X. The Two Sets of DMSO Respiratory Systems of Shewanella piezotolerans WP3 Are Involved in Deep Sea Environmental Adaptation. Front Microbiol 2016; 7:1418. [PMID: 27656177 PMCID: PMC5013071 DOI: 10.3389/fmicb.2016.01418] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2016] [Accepted: 08/26/2016] [Indexed: 12/04/2022] Open
Abstract
Dimethyl sulfoxide (DMSO) is an abundant methylated sulfur compound in deep sea ecosystems. However, the mechanism underlying DMSO-induced reduction in benthic microorganisms is unknown. Shewanella piezotolerans WP3, which was isolated from a west Pacific deep sea sediment, can utilize DMSO as the terminal electron acceptor. In this study, two putative dms gene clusters [type I (dmsEFA1B1G1H1) and type II (dmsA2B2G2H2)] were identified in the WP3 genome. Genetic and physiological analyses demonstrated that both dms gene clusters were functional and the transcription of both gene clusters was affected by changes in pressure and temperature. Notably, the type I system is essential for WP3 to thrive under in situ conditions (4°C/20 MPa), whereas the type II system is more important under high pressure or low temperature conditions (20°C/20 MPa, 4°C/0.1 MPa). Additionally, DMSO-dependent growth conferred by the presence of both dms gene clusters was higher than growth conferred by either of the dms gene clusters alone. These data collectively suggest that the possession of two sets of DMSO respiratory systems is an adaptive strategy for WP3 survival in deep sea environments. We propose, for the first time, that deep sea microorganisms might be involved in global DMSO/DMS cycling.
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Affiliation(s)
- Lei Xiong
- State Key Laboratory of Microbial Metabolism, School of Life Sciences and Biotechnology, Shanghai Jiao Tong University Shanghai, China
| | - Huahua Jian
- State Key Laboratory of Microbial Metabolism, School of Life Sciences and Biotechnology, Shanghai Jiao Tong University Shanghai, China
| | - Yuxia Zhang
- State Key Laboratory of Microbial Metabolism, School of Life Sciences and Biotechnology, Shanghai Jiao Tong University Shanghai, China
| | - Xiang Xiao
- State Key Laboratory of Microbial Metabolism, School of Life Sciences and Biotechnology, Shanghai Jiao Tong UniversityShanghai, China; State Key Laboratory of Ocean Engineering, School of Naval Architecture, Ocean and Civil Engineering, Shanghai Jiao Tong UniversityShanghai, China
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Oikawa Y, Sinmura Y, Ishizaka H, Midorikawa R, Kawamoto J, Kurihara T, Kato C, Horikoshi K, Tamegai H. Nar is the dominant dissimilatory nitrate reductase under high pressure conditions in the deep-sea denitrifier Pseudomonas sp. MT-1. J GEN APPL MICROBIOL 2015; 61:10-4. [PMID: 25833675 DOI: 10.2323/jgam.61.10] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
The deep-sea denitrifier Pseudomonas sp. MT-1 has two gene clusters encoding dissimilatory nitrate reductases, periplasmic nitrate reductase (Nap) and membrane-bound nitrate reductase (Nar). In order to investigate the physiological role of these enzymes, we constructed the disrupted mutants of napA, narG, and narK (encoding the catalytic subunits of Nap and Nar, as well as the nitrate transporter, respectively). The napA mutant showed almost the same growth rate as the wild-type under both atmospheric and high pressure of 30 MPa. On the other hand, the narG and narK mutants showed growth deficiencies under atmospheric pressure which were more pronounced at a pressure of 30 MPa. Thus, Nar was shown to be the dominant dissimilatory nitrate reductase in MT-1, especially under high pressure, whereas Nap can support the growth with denitrification to some extent. Further, nitrate reductase activity of the soluble and membrane fractions of MT-1 was measured under high pressure. Both activities were highly piezotolerant even under a pressure of 150 MPa. Therefore, the stability of nitrate reductases under high pressure is not a limiting step for the growth of MT-1 under these conditions. Although the reason why Nar rather than Nap is dominant and the physiological role of Nap in MT-1 are still unclear, we have demonstrated the mechanisms of the denitrification system in the environment of the deep-sea.
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Affiliation(s)
- Yuji Oikawa
- Department of Correlative Study in Physics and Chemistry, Graduate School of Integrated Basic Sciences, Nihon University
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Wu WF, Wang FP, Li JH, Yang XW, Xiao X, Pan YX. Iron reduction and mineralization of deep-sea iron reducing bacterium Shewanella piezotolerans WP3 at elevated hydrostatic pressures. GEOBIOLOGY 2013; 11:593-601. [PMID: 24102974 DOI: 10.1111/gbi.12061] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/29/2013] [Accepted: 08/20/2013] [Indexed: 06/02/2023]
Abstract
In this study, iron reduction and concomitant biomineralization of a deep-sea iron reducing bacterium (IRB), Shewanella piezotolerans WP3, were systematically examined at different hydrostatic pressures (0.1, 5, 20, and 50 MPa). Our results indicate that bacterial iron reduction and induced biomineralization are influenced by hydrostatic pressure. Specifically, the iron reduction rate and extent consistently decreases with the increase in hydrostatic pressure. By extrapolation, the iron reduction rate should drop to zero by ~68 MPa, which suggests a possible shut-off of enzymatic iron reduction of WP3 at this pressure. Nano-sized superparamagnetic magnetite minerals are formed under all the experimental pressures; nevertheless, even as magnetite production decreases, the crystallinity and grain size of magnetite minerals increase at higher pressure. These results imply that IRB may play an important role in iron reduction, biomineralization, and biogeochemical cycling in deep-sea environments.
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Affiliation(s)
- W F Wu
- Biogeomagnetism Group, Paleomagnetism and Geochronology Lab, Key Laboratory of the Earth's Deep Interior, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing, China; France-China Bio-Mineralization and Nano-Structures Laboratory, Chinese Academy of Sciences, Beijing, China
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Regulation of cytochrome c- and quinol oxidases, and piezotolerance of their activities in the deep-sea piezophile Shewanella violacea DSS12 in response to growth conditions. Biosci Biotechnol Biochem 2013; 77:1522-8. [PMID: 23832349 DOI: 10.1271/bbb.130197] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The facultative piezophile Shewanella violacea DSS12 is known to have respiratory components that alter under the influence of hydrostatic pressure during growth, suggesting that its respiratory system is adapted to high pressure. We analyzed the expression of the genes encoding terminal oxidases and some respiratory components of DSS12 under various growth conditions. The expression of some of the genes during growth was regulated by both the O2 concentration and hydrostatic pressure. Additionally, the activities of cytochrome c oxidase and quinol oxidase of the membrane fraction of DSS12 grown under various conditions were measured under high pressure. The piezotolerance of cytochrome c oxidase activity was dependent on the O2 concentration during growth, while that of quinol oxidase was influenced by pressure during growth. The activity of quinol oxidase was more piezotolerant than that of cytochrome c oxidase under all growth conditions. Even in the membranes of the non-piezophile Shewanella amazonensis, quinol oxidase was more piezotolerant than cytochrome c oxidase, although both were highly piezosensitive as compared to the activities in DSS12. By phylogenetic analysis, piezophile-specific cytochrome c oxidase, which is also found in the genome of DSS12, was identified in piezophilic Shewanella and related genera. Our observations suggest that DSS12 constitutively expresses piezotolerant respiratory terminal oxidases, and that lower O2 concentrations and higher hydrostatic pressures induce higher piezotolerance in both types of terminal oxidases. Quinol oxidase might be the dominant terminal oxidase in high-pressure environments, while cytochrome c oxidase might also contribute. These features should contribute to adaptation of DSS12 in deep-sea environments.
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Le Bihan T, Rayner J, Roy MM, Spagnolo L. Photobacterium profundum under pressure: a MS-based label-free quantitative proteomics study. PLoS One 2013; 8:e60897. [PMID: 23741291 PMCID: PMC3669370 DOI: 10.1371/journal.pone.0060897] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2012] [Accepted: 03/04/2013] [Indexed: 11/19/2022] Open
Abstract
Photobacterium profundum SS9 is a Gram-negative bacterium, originally collected from the Sulu Sea. Its genome consists of two chromosomes and a 80 kb plasmid. Although it can grow under a wide range of pressures, P. profundum grows optimally at 28 MPa and 15°C. Its ability to grow at atmospheric pressure allows for both easy genetic manipulation and culture, making it a model organism to study piezophily. Here, we report a shotgun proteomic analysis of P. profundum grown at atmospheric compared to high pressure using label-free quantitation and mass spectrometry analysis. We have identified differentially expressed proteins involved in high pressure adaptation, which have been previously reported using other methods. Proteins involved in key metabolic pathways were also identified as being differentially expressed. Proteins involved in the glycolysis/gluconeogenesis pathway were up-regulated at high pressure. Conversely, several proteins involved in the oxidative phosphorylation pathway were up-regulated at atmospheric pressure. Some of the proteins that were differentially identified are regulated directly in response to the physical impact of pressure. The expression of some proteins involved in nutrient transport or assimilation, are likely to be directly regulated by pressure. In a natural environment, different hydrostatic pressures represent distinct ecosystems with their own particular nutrient limitations and abundances. However, the only variable considered in this study was atmospheric pressure.
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Affiliation(s)
- Thierry Le Bihan
- SynthSys, The University of Edinburgh, Edinburgh, United Kingdom
- Institute of Structural and Molecular Biology, University of Edinburgh, Edinburgh, United Kingdom
- * E-mail: (TLB); (LS)
| | - Joe Rayner
- SynthSys, The University of Edinburgh, Edinburgh, United Kingdom
- Centre for Science at Extreme Conditions, University of Edinburgh, Edinburgh, United Kingdom
| | - Marcia M. Roy
- Wellcome Trust Centre for Cell Biology, School of Biological Sciences, University of Edinburgh, Edinburgh, United Kingdom
| | - Laura Spagnolo
- Institute of Structural and Molecular Biology, University of Edinburgh, Edinburgh, United Kingdom
- Centre for Science at Extreme Conditions, University of Edinburgh, Edinburgh, United Kingdom
- * E-mail: (TLB); (LS)
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The respiratory system of the piezophile Photobacterium profundum SS9 grown under various pressures. Biosci Biotechnol Biochem 2012; 76:1506-10. [PMID: 22878211 DOI: 10.1271/bbb.120237] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
It is known that the facultative piezophile Shewanella violacea DSS12 alters its respiratory components under the influence of hydrostatic pressure during growth. This can be considered one of the mechanisms of bacterial adaptation to high pressure. In this study, we investigated the respiratory system of another well-studied piezophile, Photobacterium profundum SS9. We analyzed cytochrome contents, the expression of genes encoding respiratory components in P. profundum SS9 grown under various conditions, and the pressure dependency of the terminal oxidase activities. Activity was more tolerant of relatively high pressures, such as 125 MPa when the cells were grown under high pressure as compared with cells grown under atmospheric pressure. Such properties observed are similar to the case of S. violacea. However, the contents of the cytochromes and expression of the respiratory genes were not influenced by growth pressure in P. profundum SS9, inconsistent with the case of S. violacea. We suggest that the mechanism of the piezoadaptation of the respiratory system of P. profundum SS9 differs from that of S. violacea, as described above, and that each strain chooses its own strategy.
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Eicosapentaenoic acid plays a role in stabilizing dynamic membrane structure in the deep-sea piezophile Shewanella violacea: a study employing high-pressure time-resolved fluorescence anisotropy measurement. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2011; 1818:574-83. [PMID: 22037146 DOI: 10.1016/j.bbamem.2011.10.010] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/19/2011] [Revised: 09/29/2011] [Accepted: 10/10/2011] [Indexed: 11/24/2022]
Abstract
Shewanella violacea DSS12 is a psychrophilic piezophile that optimally grows at 30MPa. It contains a substantial amount of eicosapentaenoic acid (EPA) in the membrane. Despite evidence linking increased fatty acid unsaturation and bacterial growth under high pressure, little is known of how the physicochemical properties of the membrane are modulated by unsaturated fatty acids in vivo. By means of the newly developed system performing time-resolved fluorescence anisotropy measurement under high pressure (HP-TRFAM), we demonstrate that the membrane of S. violacea is highly ordered at 0.1MPa and 10°C with the order parameter S of 0.9, and the rotational diffusion coefficient D(w) of 5.4μs(-1) for 1-[4-(trimethylamino)pheny]-6-phenyl-1,3,5-hexatriene in the membrane. Deletion of pfaA encoding the omega-3 polyunsaturated fatty acid synthase caused disorder of the membrane and enhanced the rotational motion of acyl chains, in concert with a 2-fold increase in the palmitoleic acid level. While the wild-type membrane was unperturbed over a wide range of pressures with respect to relatively small effects of pressure on S and D(w), the ΔpfaA membrane was disturbed judging from the degree of increased S and decreased D(w). These results suggest that EPA prevents the membrane from becoming hyperfluid and maintains membrane stability against significant changes in pressure. Our results counter the generally accepted concept that greater fluidity is a membrane characteristic of microorganisms that inhabit cold, high-pressure environments. We suggest that retaining a certain level of membrane physical properties under high pressure is more important than conferring membrane fluidity alone.
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