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Volker Muller - One of the best experts on this subject based on the ideXlab platform.
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chloride and organic osmolytes a hybrid strategy to cope with elevated salinities by the moderately halophilic chloride dependent bacterium halobacillus halophilus
Environmental Microbiology, 2013Co-Authors: Stephan H Saum, Peter Palm, Markus Rampp, Friedhelm Pfeiffer, Volker Muller, Stephan C Schuster, Dieter OesterheltAbstract:Summary Salt acclimation in moderately halophilic bacteria is the result of action of a grand interplay orchestrated by signals perceived from the environment. To elucidate the cellular players involved in sensing and responding to changing salinities we have determined the genome sequence of Halobacillus halophilus, a Gram-positive moderate halophilic bacterium that has a strict requirement for the anion chloride. Halobacillus halophilus synthesizes a multitude of different compatible solutes and switches its osmolyte strategy with the external salinity and growth phase. Based on the emerging genome sequence, the compatible solutes glutamate, glutamine, proline and ectoine have already been experimentally studied. The biosynthetic routes for acetyl ornithine and acetyl lysine are also delineated from the genome sequence. Halobacillus halophilus is nutritionally very versatile and most compatible solutes cannot only be produced but also used as carbon and energy sources. The genome sequence unravelled isogenes for many pathways indicating a fine regulation of metabolism. Halobacillus halophilus is unique in integrating the concept of compatible solutes with the second fundamental principle to cope with salt stress, the accumulation of molar concentrations of salt (Cl-) in the cytoplasm. Extremely halophilic bacteria/archaea, which exclusively rely on the salt-in strategy, have a high percentage of acidic proteins compared with non-Halophiles with a low percentage. Halobacillus halophilus has an intermediate position which is consistent with its ability to integrate both principles.
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the nature and function of carotenoids in the moderately halophilic bacterium halobacillus halophilus
2011Co-Authors: Saskia Kocher, Volker MullerAbstract:Carotenoids are widely distributed in extremophiles. Among these organisms especially C30 and C50 carotenoids are found. Here, we describe the structure and function of carotenoids in Halophiles with focus on the moderately halophilic bacterium Halobacillus halophilus. H. halophilus produces an unusual C30 carotenoid. The structure was solved by HR-MS and NMR analyses as methyl glucosyl-3,4-dehydro-apo-8 -lycopenoate. Six genes could be identified that are involved in the biosynthesis of carotenoids. Together with the structural analyses of intermediates of methyl glucosyl-3,4-dehydro-apo-8 -lycopenoate produced by a pigment mutant a putative and unique biosynthesis pathway could be postulated. The isolated carotenoid and its intermediates showed a high antioxidative activity and also the protective function of these pigments could be demonstrated for H. halophilus.
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synthesis of glycine betaine from choline in the moderate halophile halobacillus halophilus co regulation of two divergent polycistronic operons
Environmental Microbiology Reports, 2009Co-Authors: Janin Burkhardt, Bettina Bauer, Xaver Sewald, Stephan H Saum, Volker MullerAbstract:Summary The moderately halophilic bacterium Halobacillus halophilus can synthesize glycine betaine from choline. Oxidation of choline is induced by salinity and repressed by exogenous glycine betaine. The genes encoding the choline dehydrogenase (gbsB) and the glycine betaine aldehyde dehydrogenase (gbsA) were identified and shown to constitute an operon. Divergent to this operon is another operon containing gbsR and gbsU that encode proteins with similarities to a transcriptional regulator and a glycine betaine-binding protein respectively. Synthesis of the four Gbs proteins was strictly dependent on the choline concentration of the medium. Salinity was essential for the production of GbsB and increased the production of GbsA, GbsR and GbsU. Glycine betaine repressed the production of all four Gbs proteins with half maximal inhibition at 0.1 mM glycine betaine.
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regulation of osmoadaptation in the moderate halophile halobacillus halophilus chloride glutamate and switching osmolyte strategies
Saline Systems, 2008Co-Authors: Stephan H Saum, Volker MullerAbstract:The moderate halophile Halobacillus halophilus is the paradigm for chloride dependent growth in prokaryotes. Recent experiments shed light on the molecular basis of the chloride dependence that is reviewed here. In the presence of moderate salinities Halobacillus halophilus mainly accumulates glutamine and glutamate to adjust turgor. The transcription of glnA2 (encoding a glutamine synthetase) as well as the glutamine synthetase activity were identified as chloride dependent steps. Halobacillus halophilus switches its osmolyte strategy and produces proline as the main compatible solute at high salinities. Furthermore, Halobacillus halophilus also shifts its osmolyte strategy at the transition from the exponential to the stationary phase where proline is exchanged by ectoine. Glutamate was found as a “second messenger” essential for proline production. This observation leads to a new model of sensing salinity by sensing the physico-chemical properties of different anions.
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growth phase dependent switch in osmolyte strategy in a moderate halophile ectoine is a minor osmolyte but major stationary phase solute in halobacillus halophilus
Environmental Microbiology, 2008Co-Authors: Stephan H Saum, Volker MullerAbstract:Summary The moderately halophilic, chloride-dependent bacterium Halobacillus halophilus switches its osmolyte strategy with the salinity in its environment by the production of different compatible solutes. Ectoine is produced predominantly at very high salinities, along with proline. Interestingly, ectoine production is growth phase dependent which led to a more than 1000-fold change in the ectoine : proline ratio from 0.04 in exponential to 27.4 in late stationary phase cultures. The genes encoding the ectoine biosynthesis pathway were identified on the chromosome in the order ectABC. They form an operon that is expressed in a salinity-dependent manner with low-level expression below 1.5 M NaCl but 10-fold and 23-fold increased expression at 2.5 and 3.0 M NaCl respectively. The temporal expression of genes involved in osmoresponse is different with gdh/gln and pro genes being first, followed by ect genes. Chloride had no effect on expression of ect genes, but stimulated cellular EctC synthesis as well as ectoine production. These data demonstrate, for the first time, a growth-phase dependent switch in osmolyte strategy in a moderate halophile and, additionally, represent another piece of the chloride regulon of H. halophilus.
Stephan H Saum - One of the best experts on this subject based on the ideXlab platform.
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chloride and organic osmolytes a hybrid strategy to cope with elevated salinities by the moderately halophilic chloride dependent bacterium halobacillus halophilus
Environmental Microbiology, 2013Co-Authors: Stephan H Saum, Peter Palm, Markus Rampp, Friedhelm Pfeiffer, Volker Muller, Stephan C Schuster, Dieter OesterheltAbstract:Summary Salt acclimation in moderately halophilic bacteria is the result of action of a grand interplay orchestrated by signals perceived from the environment. To elucidate the cellular players involved in sensing and responding to changing salinities we have determined the genome sequence of Halobacillus halophilus, a Gram-positive moderate halophilic bacterium that has a strict requirement for the anion chloride. Halobacillus halophilus synthesizes a multitude of different compatible solutes and switches its osmolyte strategy with the external salinity and growth phase. Based on the emerging genome sequence, the compatible solutes glutamate, glutamine, proline and ectoine have already been experimentally studied. The biosynthetic routes for acetyl ornithine and acetyl lysine are also delineated from the genome sequence. Halobacillus halophilus is nutritionally very versatile and most compatible solutes cannot only be produced but also used as carbon and energy sources. The genome sequence unravelled isogenes for many pathways indicating a fine regulation of metabolism. Halobacillus halophilus is unique in integrating the concept of compatible solutes with the second fundamental principle to cope with salt stress, the accumulation of molar concentrations of salt (Cl-) in the cytoplasm. Extremely halophilic bacteria/archaea, which exclusively rely on the salt-in strategy, have a high percentage of acidic proteins compared with non-Halophiles with a low percentage. Halobacillus halophilus has an intermediate position which is consistent with its ability to integrate both principles.
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synthesis of glycine betaine from choline in the moderate halophile halobacillus halophilus co regulation of two divergent polycistronic operons
Environmental Microbiology Reports, 2009Co-Authors: Janin Burkhardt, Bettina Bauer, Xaver Sewald, Stephan H Saum, Volker MullerAbstract:Summary The moderately halophilic bacterium Halobacillus halophilus can synthesize glycine betaine from choline. Oxidation of choline is induced by salinity and repressed by exogenous glycine betaine. The genes encoding the choline dehydrogenase (gbsB) and the glycine betaine aldehyde dehydrogenase (gbsA) were identified and shown to constitute an operon. Divergent to this operon is another operon containing gbsR and gbsU that encode proteins with similarities to a transcriptional regulator and a glycine betaine-binding protein respectively. Synthesis of the four Gbs proteins was strictly dependent on the choline concentration of the medium. Salinity was essential for the production of GbsB and increased the production of GbsA, GbsR and GbsU. Glycine betaine repressed the production of all four Gbs proteins with half maximal inhibition at 0.1 mM glycine betaine.
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regulation of osmoadaptation in the moderate halophile halobacillus halophilus chloride glutamate and switching osmolyte strategies
Saline Systems, 2008Co-Authors: Stephan H Saum, Volker MullerAbstract:The moderate halophile Halobacillus halophilus is the paradigm for chloride dependent growth in prokaryotes. Recent experiments shed light on the molecular basis of the chloride dependence that is reviewed here. In the presence of moderate salinities Halobacillus halophilus mainly accumulates glutamine and glutamate to adjust turgor. The transcription of glnA2 (encoding a glutamine synthetase) as well as the glutamine synthetase activity were identified as chloride dependent steps. Halobacillus halophilus switches its osmolyte strategy and produces proline as the main compatible solute at high salinities. Furthermore, Halobacillus halophilus also shifts its osmolyte strategy at the transition from the exponential to the stationary phase where proline is exchanged by ectoine. Glutamate was found as a “second messenger” essential for proline production. This observation leads to a new model of sensing salinity by sensing the physico-chemical properties of different anions.
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growth phase dependent switch in osmolyte strategy in a moderate halophile ectoine is a minor osmolyte but major stationary phase solute in halobacillus halophilus
Environmental Microbiology, 2008Co-Authors: Stephan H Saum, Volker MullerAbstract:Summary The moderately halophilic, chloride-dependent bacterium Halobacillus halophilus switches its osmolyte strategy with the salinity in its environment by the production of different compatible solutes. Ectoine is produced predominantly at very high salinities, along with proline. Interestingly, ectoine production is growth phase dependent which led to a more than 1000-fold change in the ectoine : proline ratio from 0.04 in exponential to 27.4 in late stationary phase cultures. The genes encoding the ectoine biosynthesis pathway were identified on the chromosome in the order ectABC. They form an operon that is expressed in a salinity-dependent manner with low-level expression below 1.5 M NaCl but 10-fold and 23-fold increased expression at 2.5 and 3.0 M NaCl respectively. The temporal expression of genes involved in osmoresponse is different with gdh/gln and pro genes being first, followed by ect genes. Chloride had no effect on expression of ect genes, but stimulated cellular EctC synthesis as well as ectoine production. These data demonstrate, for the first time, a growth-phase dependent switch in osmolyte strategy in a moderate halophile and, additionally, represent another piece of the chloride regulon of H. halophilus.
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glutamate restores growth but not motility in the absence of chloride in the moderate halophile halobacillus halophilus
Extremophiles, 2007Co-Authors: Stephan H Saum, Markus Roesler, Christiane Koller, Jasmin F Sydow, Volker MullerAbstract:Halobacillus halophilus is a strictly chloride-dependent, moderately halophilic bacterium that synthesizes glutamate and glutamine as the major compatible solutes at intermediate NaCl concentrations. The key enzyme in production of the compatible solutes glutamine and glutamate, glutamine synthetase, is dependent on chloride on a transcriptional and activity level. This led us to ask whether exogenous supply of glutamate may relief the chloride dependence of growth of H. halophilus. Growth of H. halophilus in minimal medium at 1 M NaCl was stimulated by exogenous glutamate and transport experiments revealed a chloride-independent glutamate uptake by whole cells. Growth was largely impaired in the absence of chloride and, at the same time, glutamate and glutamine pools were reduced by 90%. Exogenous glutamate fully restored growth, and cellular glutamate and glutamine pools were refilled. Although glutamate could restore growth in the absence of chloride, another chloride-dependent process, flagellum synthesis and motility, was not restored by glutamate. The differential effect of glutamate on the two chloride-dependent processes, growth and motility, indicates that glutamate can not substitute chloride in general but apparently bypasses one function of the chloride regulon, the adjustment of pool sizes of compatible solutes.
Vincent Marty - One of the best experts on this subject based on the ideXlab platform.
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Molecular adaptation and salt stress response of Halobacterium salinarum cells revealed by neutron spectroscopy.
Extremophiles, 2015Co-Authors: Pierre Vauclare, Vincent Marty, Elisa Fabiani, Nicolas Martinez, Marion Jasnin, Frank Gabel, Judith Peters, Giuseppe Zaccai, Bruno FranzettiAbstract:Halobacterium salinarum is an extreme halophile archaeon with an absolute requirement for a multimolar salt environment. It accumulates molar concentrations of KCl in the cytosol to counterbalance the external osmotic pressure imposed by the molar NaCl. As a consequence, cytosolic proteins are permanently exposed to low water activity and highly ionic conditions. In non-adapted systems, such conditions would promote protein aggregation, precipitation, and denaturation. In contrast, in vitro studies showed that proteins from extreme halophilic cells are themselves obligate Halophiles. In this paper, adaptation via dynamics to low-salt stress in H. salinarum cells was measured by neutron scattering experiments coupled with microbiological characterization. The molecular dynamic properties of a proteome represent a good indicator for environmental adaptation and the neutron/microbiology approach has been shown to be well tailored to characterize these modifications. In their natural setting, halophilic organisms often have to face important variations in environmental salt concentration. The results showed deleterious effects already occur in the H. salinarum proteome, even when the external salt concentration is still relatively high, suggesting the onset of survival mechanisms quite early when the environmental salt concentration decreases.
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Adaptation de l'Archaea halophile halobacterium salinarum aux stress environnementaux : mécanismes de survie et rôle de la protéolyse intracellulaire
2011Co-Authors: Vincent MartyAbstract:Les systemes moleculaires decrits chez les Archaea mettent en evidence un caractere primitif et une simplicite, comparativement a leurs homologues eucaryotes. Par ailleurs, leur caractere extremophile a pour consequence une hyper-robustesse qui rend leur manipulation in vitro et les etudes structurales beaucoup plus aisees. Ainsi les Archaea representent de bons modeles pour comprendre les fonctions cellulaires complexes, particulierement celles qui mettent en jeu de grandes machineries moleculaires, comme celles impliquees dans la proteolyse. Mon travail de these a consiste a comprendre les mecanismes de resistance et l'importance des systemes de proteolyse dans l'adaptation des Archaea Halophiles aux stress environnementaux. Les Archaea Halophiles accumulent des concentrations multi-molaires de KCl/NaCl dans leur cytosol (3.4M KCl / 1.1M NaCl chez Halobacterium salinarum). Ainsi, les proteines de ces organismes sont elles-memes Halophiles et ne sont solubles et repliees que dans des conditions de salinite extremes (de 2 a 5M).Nous avons etudie la reponse de l'Archaea halophile stricte H. salinarum a des stress, dont les stress a basse salinite, en se focalisant en particulier sur les modifications de la dynamique moleculaire du proteome in vivo (diffusion neutronique). Au cours de ce travail, il a ete mis en evidence un phenomene de survie a la basse salinite associe a des modifications morphologiques.Un autre objectif de ma these a ete de contribuer a la comprehension du role dans la proteolyse intracellulaire du complexe aminopeptidasique TET, dans les conditions de stress mises en place dans les etudes precedentes.
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Adaptation de l'Archaea halophile halobacterium salinarum aux stress environnementaux : mécanismes de survie et rôle de la protéolyse intracellulaire
2011Co-Authors: Vincent MartyAbstract:Les systèmes moléculaires décrits chez les Archaea mettent en évidence un caractère primitif et une simplicité, comparativement à leurs homologues eucaryotes. Par ailleurs, leur caractère extrêmophile a pour conséquence une hyper-robustesse qui rend leur manipulation in vitro et les études structurales beaucoup plus aisées. Ainsi les Archaea représentent de bons modèles pour comprendre les fonctions cellulaires complexes, particulièrement celles qui mettent en jeu de grandes machineries moléculaires, comme celles impliquées dans la protéolyse. Mon travail de thèse a consisté à comprendre les mécanismes de résistance et l'importance des systèmes de protéolyse dans l'adaptation des Archaea Halophiles aux stress environnementaux. Les Archaea Halophiles accumulent des concentrations multi-molaires de KCl/NaCl dans leur cytosol (3.4M KCl / 1.1M NaCl chez Halobacterium salinarum). Ainsi, les protéines de ces organismes sont elles-mêmes Halophiles et ne sont solubles et repliées que dans des conditions de salinité extrêmes (de 2 à 5M).Nous avons étudié la réponse de l'Archaea halophile stricte H. salinarum à des stress, dont les stress à basse salinité, en se focalisant en particulier sur les modifications de la dynamique moléculaire du protéome in vivo (diffusion neutronique). Au cours de ce travail, il a été mis en évidence un phénomène de survie à la basse salinité associé à des modifications morphologiques.Un autre objectif de ma thèse a été de contribuer à la compréhension du rôle dans la protéolyse intracellulaire du complexe aminopeptidasique TET, dans les conditions de stress mises en place dans les études précédentes.
Markus Roesler - One of the best experts on this subject based on the ideXlab platform.
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glutamate restores growth but not motility in the absence of chloride in the moderate halophile halobacillus halophilus
Extremophiles, 2007Co-Authors: Stephan H Saum, Markus Roesler, Christiane Koller, Jasmin F Sydow, Volker MullerAbstract:Halobacillus halophilus is a strictly chloride-dependent, moderately halophilic bacterium that synthesizes glutamate and glutamine as the major compatible solutes at intermediate NaCl concentrations. The key enzyme in production of the compatible solutes glutamine and glutamate, glutamine synthetase, is dependent on chloride on a transcriptional and activity level. This led us to ask whether exogenous supply of glutamate may relief the chloride dependence of growth of H. halophilus. Growth of H. halophilus in minimal medium at 1 M NaCl was stimulated by exogenous glutamate and transport experiments revealed a chloride-independent glutamate uptake by whole cells. Growth was largely impaired in the absence of chloride and, at the same time, glutamate and glutamine pools were reduced by 90%. Exogenous glutamate fully restored growth, and cellular glutamate and glutamine pools were refilled. Although glutamate could restore growth in the absence of chloride, another chloride-dependent process, flagellum synthesis and motility, was not restored by glutamate. The differential effect of glutamate on the two chloride-dependent processes, growth and motility, indicates that glutamate can not substitute chloride in general but apparently bypasses one function of the chloride regulon, the adjustment of pool sizes of compatible solutes.
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motility and flagellum synthesis in halobacillus halophilus are chloride dependent
Journal of Bacteriology, 2000Co-Authors: Markus Roesler, Gerhard Wanner, Volker MullerAbstract:The motility of Halobacillus halophilus as observed on swarm agar plates was strictly dependent on the chloride concentration. Cl− was apparently not used as the coupling ion for flagellar rotation. Cells grown in the absence of chloride were devoid of flagella, but flagellation was restored upon the addition of chloride. These experiments indicate that chloride is involved in synthesis of flagella in H. halophilus.
Dieter Oesterhelt - One of the best experts on this subject based on the ideXlab platform.
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chloride and organic osmolytes a hybrid strategy to cope with elevated salinities by the moderately halophilic chloride dependent bacterium halobacillus halophilus
Environmental Microbiology, 2013Co-Authors: Stephan H Saum, Peter Palm, Markus Rampp, Friedhelm Pfeiffer, Volker Muller, Stephan C Schuster, Dieter OesterheltAbstract:Summary Salt acclimation in moderately halophilic bacteria is the result of action of a grand interplay orchestrated by signals perceived from the environment. To elucidate the cellular players involved in sensing and responding to changing salinities we have determined the genome sequence of Halobacillus halophilus, a Gram-positive moderate halophilic bacterium that has a strict requirement for the anion chloride. Halobacillus halophilus synthesizes a multitude of different compatible solutes and switches its osmolyte strategy with the external salinity and growth phase. Based on the emerging genome sequence, the compatible solutes glutamate, glutamine, proline and ectoine have already been experimentally studied. The biosynthetic routes for acetyl ornithine and acetyl lysine are also delineated from the genome sequence. Halobacillus halophilus is nutritionally very versatile and most compatible solutes cannot only be produced but also used as carbon and energy sources. The genome sequence unravelled isogenes for many pathways indicating a fine regulation of metabolism. Halobacillus halophilus is unique in integrating the concept of compatible solutes with the second fundamental principle to cope with salt stress, the accumulation of molar concentrations of salt (Cl-) in the cytoplasm. Extremely halophilic bacteria/archaea, which exclusively rely on the salt-in strategy, have a high percentage of acidic proteins compared with non-Halophiles with a low percentage. Halobacillus halophilus has an intermediate position which is consistent with its ability to integrate both principles.
