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The Iho670 fibers of Ignicoccus hospitalis are anchored in the cell by a spherical structure located beneath the inner membrane. J Bacteriol 2014; 196:3807-15. [PMID: 25157085 DOI: 10.1128/jb.01861-14] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
The Iho670 fibers of the hyperthermophilic crenarchaeon of Ignicoccus hospitalis were shown to contain several features that indicate them as type IV pilus-like structures. The application of different visualization methods, including electron tomography and the reconstruction of a three-dimensional model, enabled a detailed description of a hitherto undescribed anchoring structure of the cell appendages. It could be identified as a spherical structure beneath the inner membrane. Furthermore, pools of the fiber protein Iho670 could be localized in the inner as well as the outer cellular membrane of I. hospitalis cells and in the tubes/vesicles in the intermembrane compartment by immunological methods.
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Borrel G, Parisot N, Harris HMB, Peyretaillade E, Gaci N, Tottey W, Bardot O, Raymann K, Gribaldo S, Peyret P, O’Toole PW, Brugère JF. Comparative genomics highlights the unique biology of Methanomassiliicoccales, a Thermoplasmatales-related seventh order of methanogenic archaea that encodes pyrrolysine. BMC Genomics 2014; 15:679. [PMID: 25124552 PMCID: PMC4153887 DOI: 10.1186/1471-2164-15-679] [Citation(s) in RCA: 186] [Impact Index Per Article: 18.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2014] [Accepted: 07/18/2014] [Indexed: 02/08/2023] Open
Abstract
BACKGROUND A seventh order of methanogens, the Methanomassiliicoccales, has been identified in diverse anaerobic environments including the gastrointestinal tracts (GIT) of humans and other animals and may contribute significantly to methane emission and global warming. Methanomassiliicoccales are phylogenetically distant from all other orders of methanogens and belong to a large evolutionary branch composed by lineages of non-methanogenic archaea such as Thermoplasmatales, the Deep Hydrothermal Vent Euryarchaeota-2 (DHVE-2, Aciduliprofundum boonei) and the Marine Group-II (MG-II). To better understand this new order and its relationship to other archaea, we manually curated and extensively compared the genome sequences of three Methanomassiliicoccales representatives derived from human GIT microbiota, "Candidatus Methanomethylophilus alvus", "Candidatus Methanomassiliicoccus intestinalis" and Methanomassiliicoccus luminyensis. RESULTS Comparative analyses revealed atypical features, such as the scattering of the ribosomal RNA genes in the genome and the absence of eukaryotic-like histone gene otherwise present in most of Euryarchaeota genomes. Previously identified in Thermoplasmatales genomes, these features are presently extended to several completely sequenced genomes of this large evolutionary branch, including MG-II and DHVE2. The three Methanomassiliicoccales genomes share a unique composition of genes involved in energy conservation suggesting an original combination of two main energy conservation processes previously described in other methanogens. They also display substantial differences with each other, such as their codon usage, the nature and origin of their CRISPRs systems and the genes possibly involved in particular environmental adaptations. The genome of M. luminyensis encodes several features to thrive in soil and sediment conditions suggesting its larger environmental distribution than GIT. Conversely, "Ca. M. alvus" and "Ca. M. intestinalis" do not present these features and could be more restricted and specialized on GIT. Prediction of the amber codon usage, either as a termination signal of translation or coding for pyrrolysine revealed contrasted patterns among the three genomes and suggests a different handling of the Pyl-encoding capacity. CONCLUSIONS This study represents the first insights into the genomic organization and metabolic traits of the seventh order of methanogens. It suggests contrasted evolutionary history among the three analyzed Methanomassiliicoccales representatives and provides information on conserved characteristics among the overall methanogens and among Thermoplasmata.
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Affiliation(s)
- Guillaume Borrel
- />EA-4678 CIDAM, Clermont Université, Université d’Auvergne, 28 Place Henri Dunant, BP 10448, 63000 Clermont-Ferrand, France
- />School of Microbiology and Alimentary Pharmabiotic Centre, University College Cork, Cork, Ireland
| | - Nicolas Parisot
- />EA-4678 CIDAM, Clermont Université, Université d’Auvergne, 28 Place Henri Dunant, BP 10448, 63000 Clermont-Ferrand, France
- />CNRS, UMR 6023, Université Blaise Pascal, 63000 Clermont-Ferrand, France
| | - Hugh MB Harris
- />School of Microbiology and Alimentary Pharmabiotic Centre, University College Cork, Cork, Ireland
| | - Eric Peyretaillade
- />EA-4678 CIDAM, Clermont Université, Université d’Auvergne, 28 Place Henri Dunant, BP 10448, 63000 Clermont-Ferrand, France
| | - Nadia Gaci
- />EA-4678 CIDAM, Clermont Université, Université d’Auvergne, 28 Place Henri Dunant, BP 10448, 63000 Clermont-Ferrand, France
| | - William Tottey
- />EA-4678 CIDAM, Clermont Université, Université d’Auvergne, 28 Place Henri Dunant, BP 10448, 63000 Clermont-Ferrand, France
| | - Olivier Bardot
- />GReD, CNRS, UMR 6293, Inserm, UMR 1103, Clermont Université, Université d’Auvergne 28 Place Henri Dunant, BP 10448, 63000 Clermont-Ferrand, France
| | - Kasie Raymann
- />Département de Microbiologie, Unité de Biologie Moléculaire du Gène chez les Extrêmophiles, Paris Cedex 15, 75724 France
- />Cellule Pasteur UPMC, Université Pierre et Marie Curie, Paris Cedex 15, 75724 France
| | - Simonetta Gribaldo
- />Département de Microbiologie, Unité de Biologie Moléculaire du Gène chez les Extrêmophiles, Paris Cedex 15, 75724 France
- />Cellule Pasteur UPMC, Université Pierre et Marie Curie, Paris Cedex 15, 75724 France
| | - Pierre Peyret
- />EA-4678 CIDAM, Clermont Université, Université d’Auvergne, 28 Place Henri Dunant, BP 10448, 63000 Clermont-Ferrand, France
| | - Paul W O’Toole
- />School of Microbiology and Alimentary Pharmabiotic Centre, University College Cork, Cork, Ireland
| | - Jean-François Brugère
- />EA-4678 CIDAM, Clermont Université, Université d’Auvergne, 28 Place Henri Dunant, BP 10448, 63000 Clermont-Ferrand, France
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Welte C, Deppenmeier U. Bioenergetics and anaerobic respiratory chains of aceticlastic methanogens. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2013; 1837:1130-47. [PMID: 24333786 DOI: 10.1016/j.bbabio.2013.12.002] [Citation(s) in RCA: 151] [Impact Index Per Article: 13.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/28/2013] [Revised: 12/02/2013] [Accepted: 12/05/2013] [Indexed: 12/16/2022]
Abstract
Methane-forming archaea are strictly anaerobic microbes and are essential for global carbon fluxes since they perform the terminal step in breakdown of organic matter in the absence of oxygen. Major part of methane produced in nature derives from the methyl group of acetate. Only members of the genera Methanosarcina and Methanosaeta are able to use this substrate for methane formation and growth. Since the free energy change coupled to methanogenesis from acetate is only -36kJ/mol CH4, aceticlastic methanogens developed efficient energy-conserving systems to handle this thermodynamic limitation. The membrane bound electron transport system of aceticlastic methanogens is a complex branched respiratory chain that can accept electrons from hydrogen, reduced coenzyme F420 or reduced ferredoxin. The terminal electron acceptor of this anaerobic respiration is a mixed disulfide composed of coenzyme M and coenzyme B. Reduced ferredoxin has an important function under aceticlastic growth conditions and novel and well-established membrane complexes oxidizing ferredoxin will be discussed in depth. Membrane bound electron transport is connected to energy conservation by proton or sodium ion translocating enzymes (F420H2 dehydrogenase, Rnf complex, Ech hydrogenase, methanophenazine-reducing hydrogenase and heterodisulfide reductase). The resulting electrochemical ion gradient constitutes the driving force for adenosine triphosphate synthesis. Methanogenesis, electron transport, and the structure of key enzymes are discussed in this review leading to a concept of how aceticlastic methanogens make a living. This article is part of a Special Issue entitled: 18th European Bioenergetic Conference.
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Affiliation(s)
- Cornelia Welte
- Institute of Microbiology and Biotechnology, University of Bonn, Meckenheimer Allee 168, 53115 Bonn, Germany; Department of Microbiology, IWWR, Radboud University Nijmegen, Heyendaalseweg 135, 6525 AJ Nijmegen, The Netherlands.
| | - Uwe Deppenmeier
- Institute of Microbiology and Biotechnology, University of Bonn, Meckenheimer Allee 168, 53115 Bonn, Germany.
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Acetate activation in Methanosaeta thermophila: characterization of the key enzymes pyrophosphatase and acetyl-CoA synthetase. ARCHAEA-AN INTERNATIONAL MICROBIOLOGICAL JOURNAL 2012; 2012:315153. [PMID: 22927778 PMCID: PMC3426162 DOI: 10.1155/2012/315153] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/16/2012] [Accepted: 06/30/2012] [Indexed: 11/17/2022]
Abstract
The thermophilic methanogen Methanosaeta thermophila uses acetate as sole substrate for methanogenesis. It was proposed that the acetate activation reaction that is needed to feed acetate into the methanogenic pathway requires the hydrolysis of two ATP, whereas the acetate activation reaction in Methanosarcina sp. is known to require only one ATP. As these organisms live at the thermodynamic limit that sustains life, the acetate activation reaction in Mt. thermophila seems too costly and was thus reevaluated. It was found that of the putative acetate activation enzymes one gene encoding an AMP-forming acetyl-CoA synthetase was highly expressed. The corresponding enzyme was purified and characterized in detail. It catalyzed the ATP-dependent formation of acetyl-CoA, AMP, and pyrophosphate (PPi)
and was only moderately inhibited by PPi. The breakdown of PPi
was performed by a soluble pyrophosphatase. This enzyme was also purified and characterized. The pyrophosphatase hydrolyzed the major part of PPi
(KM = 0.27 ± 0.05 mM) that was produced in the acetate activation reaction. Activity was not inhibited by nucleotides or PPi. However, it cannot be excluded that other PPi-dependent enzymes take advantage of the remaining PPi
and contribute to the energy balance of the cell.
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Luoto HH, Belogurov GA, Baykov AA, Lahti R, Malinen AM. Na+-translocating membrane pyrophosphatases are widespread in the microbial world and evolutionarily precede H+-translocating pyrophosphatases. J Biol Chem 2011; 286:21633-42. [PMID: 21527638 DOI: 10.1074/jbc.m111.244483] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Membrane pyrophosphatases (PPases), divided into K(+)-dependent and K(+)-independent subfamilies, were believed to pump H(+) across cell membranes until a recent demonstration that some K(+)-dependent PPases function as Na(+) pumps. Here, we have expressed seven evolutionarily important putative PPases in Escherichia coli and estimated their hydrolytic, Na(+) transport, and H(+) transport activities as well as their K(+) and Na(+) requirements in inner membrane vesicles. Four of these enzymes (from Anaerostipes caccae, Chlorobium limicola, Clostridium tetani, and Desulfuromonas acetoxidans) were identified as K(+)-dependent Na(+) transporters. Phylogenetic analysis led to the identification of a monophyletic clade comprising characterized and predicted Na(+)-transporting PPases (Na(+)-PPases) within the K(+)-dependent subfamily. H(+)-transporting PPases (H(+)-PPases) are more heterogeneous and form at least three independent clades in both subfamilies. These results suggest that rather than being a curious rarity, Na(+)-PPases predominantly constitute the K(+)-dependent subfamily. Furthermore, Na(+)-PPases possibly preceded H(+)-PPases in evolution, and transition from Na(+) to H(+) transport may have occurred in several independent enzyme lineages. Site-directed mutagenesis studies facilitated the identification of a specific Glu residue that appears to be central in the transport mechanism. This residue is located in the cytoplasm-membrane interface of transmembrane helix 6 in Na(+)-PPases but shifted to within the membrane or helix 5 in H(+)-PPases. These results contribute to the prediction of the transport specificity and K(+) dependence for a particular membrane PPase sequence based on its position in the phylogenetic tree, identity of residues in the K(+) dependence signature, and position of the membrane-located Glu residue.
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Affiliation(s)
- Heidi H Luoto
- Department of Biochemistry and Food Chemistry, University of Turku, FIN-20014 Turku, Finland
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Williams TJ, Burg DW, Ertan H, Raftery MJ, Poljak A, Guilhaus M, Cavicchioli R. Global Proteomic Analysis of the Insoluble, Soluble, and Supernatant Fractions of the Psychrophilic Archaeon Methanococcoides burtonii Part II: The Effect of Different Methylated Growth Substrates. J Proteome Res 2009; 9:653-63. [DOI: 10.1021/pr9005102] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Timothy J. Williams
- School of Biotechnology and Biomolecular Sciences, The University of New South Wales, Sydney, 2052, NSW, Australia, Department of Molecular Biology and Genetics, Science Faculty, Istanbul University, Vezneciler, Istanbul, Turkey, Bioanalytical Mass Spectrometry Facility, The University of New South Wales, Sydney, 2052, NSW, Australia, and School of Medical Sciences, The University of New South Wales, Sydney, 2052, Australia
| | - Dominic W. Burg
- School of Biotechnology and Biomolecular Sciences, The University of New South Wales, Sydney, 2052, NSW, Australia, Department of Molecular Biology and Genetics, Science Faculty, Istanbul University, Vezneciler, Istanbul, Turkey, Bioanalytical Mass Spectrometry Facility, The University of New South Wales, Sydney, 2052, NSW, Australia, and School of Medical Sciences, The University of New South Wales, Sydney, 2052, Australia
| | - Haluk Ertan
- School of Biotechnology and Biomolecular Sciences, The University of New South Wales, Sydney, 2052, NSW, Australia, Department of Molecular Biology and Genetics, Science Faculty, Istanbul University, Vezneciler, Istanbul, Turkey, Bioanalytical Mass Spectrometry Facility, The University of New South Wales, Sydney, 2052, NSW, Australia, and School of Medical Sciences, The University of New South Wales, Sydney, 2052, Australia
| | - Mark J. Raftery
- School of Biotechnology and Biomolecular Sciences, The University of New South Wales, Sydney, 2052, NSW, Australia, Department of Molecular Biology and Genetics, Science Faculty, Istanbul University, Vezneciler, Istanbul, Turkey, Bioanalytical Mass Spectrometry Facility, The University of New South Wales, Sydney, 2052, NSW, Australia, and School of Medical Sciences, The University of New South Wales, Sydney, 2052, Australia
| | - Anne Poljak
- School of Biotechnology and Biomolecular Sciences, The University of New South Wales, Sydney, 2052, NSW, Australia, Department of Molecular Biology and Genetics, Science Faculty, Istanbul University, Vezneciler, Istanbul, Turkey, Bioanalytical Mass Spectrometry Facility, The University of New South Wales, Sydney, 2052, NSW, Australia, and School of Medical Sciences, The University of New South Wales, Sydney, 2052, Australia
| | - Michael Guilhaus
- School of Biotechnology and Biomolecular Sciences, The University of New South Wales, Sydney, 2052, NSW, Australia, Department of Molecular Biology and Genetics, Science Faculty, Istanbul University, Vezneciler, Istanbul, Turkey, Bioanalytical Mass Spectrometry Facility, The University of New South Wales, Sydney, 2052, NSW, Australia, and School of Medical Sciences, The University of New South Wales, Sydney, 2052, Australia
| | - Ricardo Cavicchioli
- School of Biotechnology and Biomolecular Sciences, The University of New South Wales, Sydney, 2052, NSW, Australia, Department of Molecular Biology and Genetics, Science Faculty, Istanbul University, Vezneciler, Istanbul, Turkey, Bioanalytical Mass Spectrometry Facility, The University of New South Wales, Sydney, 2052, NSW, Australia, and School of Medical Sciences, The University of New South Wales, Sydney, 2052, Australia
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Hydrogen is a preferred intermediate in the energy-conserving electron transport chain of Methanosarcina barkeri. Proc Natl Acad Sci U S A 2009; 106:15915-20. [PMID: 19805232 DOI: 10.1073/pnas.0905914106] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Methanogens use an unusual energy-conserving electron transport chain that involves reduction of a limited number of electron acceptors to methane gas. Previous biochemical studies suggested that the proton-pumping F(420)H(2) dehydrogenase (Fpo) plays a crucial role in this process during growth on methanol. However, Methanosarcina barkeri Delta fpo mutants constructed in this study display no measurable phenotype on this substrate, indicating that Fpo plays a minor role, if any. In contrast, Delta frh mutants lacking the cytoplasmic F(420)-reducing hydrogenase (Frh) are severely affected in their ability to grow and make methane from methanol, and double Delta fpo/Delta frh mutants are completely unable to use this substrate. These data suggest that the preferred electron transport chain involves production of hydrogen gas in the cytoplasm, which then diffuses out of the cell, where it is reoxidized with transfer of electrons into the energy-conserving electron transport chain. This hydrogen-cycling metabolism leads directly to production of a proton motive force that can be used by the cell for ATP synthesis. Nevertheless, M. barkeri does have the flexibility to use the Fpo-dependent electron transport chain when needed, as shown by the poor growth of the Delta frh mutant. Our data suggest that the rapid enzymatic turnover of hydrogenases may allow a competitive advantage via faster growth rates in this freshwater organism. The mutant analysis also confirms the proposed role of Frh in growth on hydrogen/carbon dioxide and suggests that either Frh or Fpo is needed for aceticlastic growth of M. barkeri.
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8
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Malinen AM, Belogurov GA, Baykov AA, Lahti R. Na+-Pyrophosphatase: A Novel Primary Sodium Pump. Biochemistry 2007; 46:8872-8. [PMID: 17605473 DOI: 10.1021/bi700564b] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Membrane-bound pyrophosphatase (PPase) is commonly believed to couple pyrophosphate (PPi) hydrolysis to H+ transport across the membrane. Here, we demonstrate that two newly isolated bacterial membrane PPases from the mesophile Methanosarcina mazei (Mm-PPase) and the moderate thermophile Moorella thermoacetica and a previously described PPase from the hyperthermophilic bacterium Thermotoga maritima catalyze Na+ rather than H+ transport into Escherichia coli inner membrane vesicles (IMV). When assayed in uncoupled IMV, the three PPases exhibit an absolute requirement for Na+ but display the highest hydrolyzing activity in the presence of both Na+ and K+. Steady-state kinetic analysis of PPi hydrolysis by Mm-PPase revealed two Na+ binding sites. One of these sites can also bind K+, resulting in a 10-fold increase in the affinity of the other site for Na+ and a 2-fold increase in maximal velocity. PPi-driven 22Na+ transport into IMV containing Mm-PPase was unaffected by the protonophore carbonyl cyanide m-chlorophenylhydrazone, inhibited by the Na+ ionophore monensin, and activated by the K+ ionophore valinomycin. The Na+ transport was accompanied by the generation of a positive inside membrane potential as reported by Oxonol VI. These findings define Na+-dependent PPases as electrogenic Na+ pumps. Phylogenetic analysis suggests that ancient gene duplication preceded the split of Na+- and H+-PPases.
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Affiliation(s)
- Anssi M Malinen
- Department of Biochemistry and Food Chemistry, University of Turku, FIN-20014 Turku, Finland
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Erkel C, Kube M, Reinhardt R, Liesack W. Genome of Rice Cluster I Archaea--the Key Methane Producers in the Rice Rhizosphere. Science 2006; 313:370-2. [PMID: 16857943 DOI: 10.1126/science.1127062] [Citation(s) in RCA: 110] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Rice fields are a global source of the greenhouse gas methane, which is produced by methanogenic archaea, and by methanogens of Rice Cluster I (RC-I) in particular. RC-I methanogens are not yet available in pure culture, and the mechanistic reasons for their prevalence in rice fields are unknown. We reconstructed a complete RC-I genome (3.18 megabases) using a metagenomic approach. Sequence analysis demonstrated an aerotolerant, H2/CO2-dependent lifestyle and enzymatic capacities for carbohydrate metabolism and assimilatory sulfate reduction, hitherto unknown among methanogens. These capacities and a unique set of antioxidant enzymes and DNA repair mechanisms as well as oxygen-insensitive enzymes provide RC-I with a selective advantage over other methanogens in its habitats, thereby explaining the prevalence of RC-I methanogens in the rice rhizosphere.
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Affiliation(s)
- Christoph Erkel
- Max-Planck-Institute for Terrestrial Microbiology, Karl-von-Frisch-Strasse, 35043 Marburg, Germany
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10
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Au KM, Barabote RD, Hu KY, Saier MH. Evolutionary appearance of H+-translocating pyrophosphatases. Microbiology (Reading) 2006; 152:1243-1247. [PMID: 16622041 DOI: 10.1099/mic.0.28581-0] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Affiliation(s)
- Ka M Au
- Division of Biological Sciences, University of California at San Diego, La Jolla, CA 92093-0116, USA
| | - Ravi D Barabote
- Division of Biological Sciences, University of California at San Diego, La Jolla, CA 92093-0116, USA
| | - Kuang Yu Hu
- Division of Biological Sciences, University of California at San Diego, La Jolla, CA 92093-0116, USA
| | - Milton H Saier
- Division of Biological Sciences, University of California at San Diego, La Jolla, CA 92093-0116, USA
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López-Marqués RL, Pérez-Castiñeira JR, Losada M, Serrano A. Differential regulation of soluble and membrane-bound inorganic pyrophosphatases in the photosynthetic bacterium Rhodospirillum rubrum provides insights into pyrophosphate-based stress bioenergetics. J Bacteriol 2004; 186:5418-26. [PMID: 15292143 PMCID: PMC490873 DOI: 10.1128/jb.186.16.5418-5426.2004] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Soluble and membrane-bound inorganic pyrophosphatases (sPPase and H(+)-PPase, respectively) of the purple nonsulfur bacterium Rhodospirillum rubrum are differentially regulated by environmental growth conditions. Both proteins and their transcripts were found in cells of anaerobic phototrophic batch cultures along all growth phases, although they displayed different time patterns. However, in aerobic cells that grow in the dark, which exhibited the highest growth rates, Northern and Western blot analyses as well as activity assays demonstrated high sPPase levels but no H(+)-PPase. It is noteworthy that H(+)-PPase is highly expressed in aerobic cells under acute salt stress (1 M NaCl). H(+)-PPase was also present in anaerobic cells growing at reduced rates in the dark under either fermentative or anaerobic respiratory conditions. Since H(+)-PPase was detected not only under all anaerobic growth conditions but also under salt stress in aerobiosis, the corresponding gene is not invariably repressed by oxygen. Primer extension analyses showed that, under all anaerobic conditions tested, the R. rubrum H(+)-PPase gene utilizes two activator-dependent tandem promoters, one with an FNR-like sequence motif and the other with a RegA motif, whereas in aerobiosis under salt stress, the H(+)-PPase gene is transcribed from two further tandem promoters involving other transcription factors. These results demonstrate a tight transcriptional regulation of the H(+)-PPase gene, which appears to be induced in response to a variety of environmental conditions, all of which constrain cell energetics.
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MESH Headings
- Adaptation, Physiological
- Aerobiosis
- Anaerobiosis
- Bacterial Proteins/biosynthesis
- Bacterial Proteins/metabolism
- Base Sequence
- Blotting, Northern
- Blotting, Western
- DNA, Bacterial/chemistry
- DNA, Bacterial/isolation & purification
- Diphosphates/metabolism
- Energy Metabolism
- Gene Expression Regulation, Bacterial
- Inorganic Pyrophosphatase/biosynthesis
- Inorganic Pyrophosphatase/genetics
- Inorganic Pyrophosphatase/metabolism
- Light
- Membrane Proteins/biosynthesis
- Membrane Proteins/metabolism
- Molecular Sequence Data
- Osmotic Pressure
- Promoter Regions, Genetic
- RNA, Bacterial/analysis
- RNA, Bacterial/biosynthesis
- RNA, Messenger/analysis
- RNA, Messenger/biosynthesis
- Rhodospirillum rubrum/genetics
- Rhodospirillum rubrum/growth & development
- Rhodospirillum rubrum/metabolism
- Sequence Analysis, DNA
- Transcription Initiation Site
- Transcription, Genetic
- Transcriptional Activation
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Affiliation(s)
- Rosa L López-Marqués
- Instituto de Bioquímica Vegetal y Fotosíntesis, Universidad de Sevilla-CSIC, 41092 Seville, Spain
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