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  • 1
    Electronic Resource
    Electronic Resource
    Immunocytochemical localization of methyl-coenzyme M reductase in Methanobacterium thermoautotrophicum (1987)
    Springer
    Archives of microbiology 147 (1987), S. 190-194 
    Details
    ISSN: 1432-072X
    Keywords: Methanobacterium thermoautotrophicum ; Methyl-CoM reductase ; Immunocytochemistry ; Colloidal gold ; Energy conservation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Cells of Methanobacterium thermoautotrophicum were fixed with glutaraldehyde, sectioned and labeled with antibodies against the β subunit of component C (=methyl-CoM reductase) of methyl-CoM reductase system and with colloidal gold-labeled protein A. It was found that the gold particles were located predominantly in the vicinity of the cytoplasmic membrane, when the cells were grown under conditions where methyl-CoM reductase was not overproduced. This finding confirms the recent data obtained with Methanococcus voltae showing via the same immunocytochemical localization technique that in this organism methyl-CoM reductase is membrane associated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00415283
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  • 2
    Electronic Resource
    Electronic Resource
    ATP formation coupled to caffeate reduction by H2 in Acetobacterium woodii NZva16 (1988)
    Springer
    Archives of microbiology 150 (1988), S. 447-451 
    Details
    ISSN: 1432-072X
    Keywords: Acetobacterium woodii ; Caffeate reduction ; ATP formation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We have addressed the question, whether the reduction of caffeate in Acetobacterium woodii strain NZva16 is coupled to ATP synthesis by electron transport phosphorylation. The following results were obtained: 1. Cultures of A. woodii with H2 and CO2, grew to greater cell densities, when caffeate was also present. Caffeate was reduced to give hydrocaffeate and less acetate was formed. The cell yield based on the amount of caffeate reduced was approximately 1 g dry cells/mol. 2. Non-growing bacterial suspensions catalyzed the reduction of caffeate by H2. The specific activity (0.2–1.0 μmol · min−1 · mg−1 bacterial protein) was as high as expected for a catabolic reaction. 3. The ATP content of bacteria incubated, with H2 increased from 〈 1 to about 7 μmol per g cellular protein on the addition of caffeate. The ATP yield was calculated as 0.06 mol ATP · mol−1 caffeate from the initial velocity of ATP formation and the activity of caffeate reduction. Valinomycin together with nigericin inhibited ATP formation and caused a 2–3-fold increase of the activity of caffeate reduction. Protonophores were without, effect. 4. Caffeate in the presence of H2 caused the uptake of tetraphenylphosphonium cation by the bacteria. The uptake was abolished by valinomycin plus nigericin, and was considerably enhanced by monensin. Protonophores were without effect, even in the presence of monensin. It is concluded that caffeate reduction by H2 is coupled to ATP formation by electron transport phosphorylation. However, the failure of protonophores to prevent phosphorylation and TPP uptake cannot be explained.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00422285
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  • 3
    Electronic Resource
    Electronic Resource
    Pyruvate – a novel substrate for growth and methane formation in Methanosarcina barkeri (1994)
    Springer
    Archives of microbiology 161 (1994), S. 33-46 
    Details
    ISSN: 1432-072X
    Keywords: Key words:Methanosarcina barkeri– Pyruvate-utilizing mutant – Methanogenesis – Archaea – Pyruvate fermentation – Acetate fermentation – Growth yields (YCH4) – Ferredoxin – Pyruvate: ferredoxin oxidoreductase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract. Methanosarcina barkeri strain Fusaro was found to grow on pyruvate as sole carbon and energy source after an incubation period of 10 – 12 weeks in the presence of high pyruvate concentrations (100 mM). Growth studies, cell suspension experiments and enzymatic investigations were performed with pyruvate-utilizing M. barkeri. For comparison acetate-adapted cells of M. barkeri were analyzed. 1. Pyruvate-utilizing M. barkeri grew on pyruvate (100 mM) with an initial doubling time of about 25 h (37 °C, pH 6.5) up to cell densities of about 0.8 g cell dry weight/l. The specific growth rate was linearily dependent on the pyruvate concentration up to 100 mM indicating that pyruvate was taken up by passive diffusion. Only CO2 and CH4 were detected as fermentation products. As calculated from fermentation balances pyruvate was converted to CH4 and CO2 according to following equation: Pyruvate−+H++0.5 H2O→1.25 CH4+1.75 CO2. The molar growth yield (YCH4) was about 14 g dry weight cells/mol CH4. In contrast the growth yield (YCH4) of M. barkeri during growth on acetate (Acetate−+H+→CH4+CO2) was about 3 g/mol CH4. 2. Cell suspensions of pyruvate-grown M. barkeri catalyzed the conversion of pyruvate to CH4, CO2 and H2 (5 – 15 nmol pyruvate consumed/min×mg protein). At low cell concentrations (0.5 mg protein/ml) 1 mol pyruvate was converted to 1 mol CH4, 2 mol CO2 and 1 mol H2. At higher cell concentration less H2 and CO2 and more CH4 were formed due to CH4 formation from H2/CO2. The rate of pyruvate conversion was linearily dependent on the pyruvate concentration up to about 30 mM. Cell suspensions of acetate-grown M. barkeri also catalyzed the conversion of 1 mol pyruvate to 1 mol CH4, 2 mol CO2 and 1 mol H2 at similar rates and with similar affinity for pyruvate as pyruvate-grown cells. 3. Cell extracts of both pyruvate-grown and acetate-grown M. barkeri contained pyruvate: ferredoxin oxidoreductase. The specific activity in pyruvate-grown cells (0.8 U/mg) was 8-fold higher than in acetate-grown cells (0.1 U/mg). Coenzyme F420 was excluded as primary electron acceptor of pyruvate oxidoreductase. Cell extracts of pyruvate-grown M. barkeri contained carbon monoxide dehydrogenase activity and hydrogenase activity catalyzing the reduction by carbon monoxide and hydrogen of both methylviologen and ferredoxin (from Clostridium). This is the first report on growth of a methanogen on pyruvate as sole carbon and energy source, i.e. on a substrate more complex than acetate.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00248891
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  • 4
    Electronic Resource
    Electronic Resource
    Glucose fermentation of acetate, CO2 and H2 in the anaerobic hyperthermophilic eubacterium Thermotoga maritima: involvement of the Embden-Meyerhof pathway (1994)
    Springer
    Archives of microbiology 161 (1994), S. 460-470 
    Details
    ISSN: 1432-072X
    Keywords: Key words:Thermotoga maritima– Hyperthermophiles – (Eu)Bacteria – Glucose fermentation – Acetate formation – Embden-Meyerhof pathway – Hexokinase – Phosphofructokinase – Acetate kinase – Sulfur reduction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract. The hyperthermophilic anaerobic eubacterium Thermotoga maritima was grown on glucose as carbon and energy source. During growth 1 mol glucose was fermented to 2 mol acetate, 2 mol CO2 and 4 mol H2. The molar growth yield on glucose (Yglucose) was about 45 g cell dry mass/mol glucose. In the presence of elemental sulfur growing cultures of T. maritima converted 1 mol glucose to 2 mol acetate, 2 mol CO2 about 0.5 mol H2 and about 3.5 mol H2S. Yglucose was about 45 g/mol. Cell extracts contained all enzymes of the Embden-Meyerhof pathway: hexokinase (0.29 U/mg, 50 °C), glucose-6-phosphate isomerase (0.56 U/mg, 50 °C), phosphofructokinase (0.19 U/mg, 50 °C), fructose-1,6-bisphosphate aldolase (0.033 U/mg, 50 °C), triosephosphate isomerase (6.3 U/mg, 50 °C), glyceraldehyde-3-phosphate dehydrogenase (NAD+ reducing: 0.63 U/mg, 50 °C), phosphoglycerate kinase (3.7 U/mg, 50 °C), phosphoglycerate mutase (0.4 U/mg, 50 °C); enolase (4 U/mg, 80 °C), pyruvate kinase (0.05 U/mg, 50 °C). Furthermore, cell extracts contained pyruvate: ferredoxin oxidoreductase (0.43 U/mg, 60 °C); NADH: ferredoxin oxidoreductase (benzylviologen reduction: 0.46 U/mg, 80 °C); hydrogenase (benzylviologen reduction: 15 U/mg, 80 °C), phosphate acetyltransferase (0.13 U/mg, 80 °C), acetate kinase (1.2 U/mg, 55 °C), lactate dehydrogenase (0.16 U/mg, 80 °C) and pyruvate carboxylase (0.02 U/mg, 50 °C). The findings indicate that the hyperthermophilic eubacterium T. maritima ferments sugars (glucose) to acetate, CO2 and H2 involving the Embden-Meyerhof pathway, phosphate acetyltransferase and acetate kinase. Thus, the organism differs from the hyperthermophilic archaeon Pyrococcus furiosus which ferments sugars to acetate, CO2 and H2 involving a modified non-phosphorylated Entner-Doudoroff pathway and acetyl-CoA synthetase (ADP forming).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00307766
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  • 5
    Electronic Resource
    Electronic Resource
    Testing the “methanochondrion concept”: are nucleotides transported across internal membranes in Methanobacterium thermoautotrophicum? (1987)
    Springer
    Archives of microbiology 146 (1987), S. 370-376 
    Details
    ISSN: 1432-072X
    Keywords: Methanobacterium thermoautotrophicum ; Nucleotide transport ; Nucleotide binding ; Protoplasts ; Membrane vesicles ; Methanochondrion concept
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In order to test the “Methanochondrion concept”, uptake of adenine nucleotides in various membrane preparations of Methanobacterium thermoautotrophicum was studied. The uptake showed properties which are in general interpreted as indicative of a transport mechanism: (i) kinetics in the time range of minutes, (ii) temperature dependence, (iii) substrate specificity and (iv) failure to remove the substrate by extensive washing. However, nucleotide transport as an interpretation of this “uptake” can definitely be excluded. Not only an exchange mechanism of the mitochondrial type, but also a general exchange or an uniport mechanism was ruled out. In contrast, the “nucleotide uptake” was shown to be actually a tight and specific binding of ADP and ATP to binding sites at the interior side of the cell membrane. This was conclusively demonstrated in protoplasts obtained from M. thermoautotrophicum cells. In these protoplasts which do not contain internal membranes also nucleotide binding was observed, but only after disruption of the plasma membrane by osmotic lysis, which leads to the exposure of binding sites.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00410938
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  • 6
    Electronic Resource
    Electronic Resource
    Monensin and gramicidin stimulate CH4 formation from H2 and CO2 in Methanobacterium thermoautotrophicum at low external Na+ concentration (1986)
    Springer
    Archives of microbiology 146 (1986), S. 181-185 
    Details
    ISSN: 1432-072X
    Keywords: Methanobacterium thermoautotrophicum ; Na+ dependent methanogenesis ; Na+/H+ antiporter ; Monensin ; Gramicidin ; Uncoupler
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Methane formation from H2 and CO2 in methanogenic bacteria is a Na+-dependent process. In this communication the effects of Na+ ionophores, of uncouplers, and of Na+/H+ antiporter inhibitors on methane formation from H2 and CO2 were studied with Methanobacterium thermoautotrophicum. 1. Na+ ionophores (the Na+/H+ antiporters monensin and lasalocid and the Na+ uniporter gramicidin) stimulated methanogenesis at lwo external Na+ concentrations when the K+ concentration was high. The ionophores had no effect at high external Na+ concentrations and were inhibitory at low external K+ concentrations. 2. Uncouplers (protonophores and valinomycin plus K+) inhibited methanogenesis at low external Na+ concentration at both low and high external K+ concentrations. Inhibition by uncouplers was relieved by the addition of either Na+ or Na+ ionophores. 3. Na+/H+ antiporter inhibitors (harmaline, amiloride, and NH 4 + ) inhibited methanogenesis at low external Na+ concentration. Inhibition was relieved by the addition of either Na+ or of the Na+ ionophores. The results are discussed with respect to the role of Na transport across the cytoplasmic membrane in methanogenesis from H2 and CO2.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00402348
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  • 7
    Electronic Resource
    Electronic Resource
    Oxidation of organic compounds to CO2 with sulfur or thiosulfate as electron acceptor in the anaerobic hyperthermophilic archaea Thermoproteus tenax and Pyrobaculum islandicum proceeds via the citric acid cycle (1994)
    Springer
    Archives of microbiology 162 (1994), S. 286-294 
    Details
    ISSN: 1432-072X
    Keywords: Key words     Thermoproteus tenax ; Pyrobaculum ; islandicum ; Hyperthermophiles ; Archaea ; Acetyl-CoA oxidation ; Citric acid cycle ; Sulfur respiration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract      The oxidation of organic compounds with elemental sulfur or thiosulfate as electron acceptor was studied in the anaerobic hyperthermophilic archaea Thermoproteus tenax and Pyrobaculum islandicum. T. tenax was grown on either glucose or casamino acids and sulfur; P. islandicum on peptone and either elemental sulfur or thiosulfate as electron acceptor. During exponential growth only CO 2 and H2S rather than acetate, alanine, lactate, and succinate were detected as fermentation products of both organisms; the ratio of CO2/H2S formed was 1 : 2 with elemental sulfur and 1 : 1 with thiosulfate as electron acceptor. Cell extracts of T. tenax and P. islandicum contained all enzymes of the citric acid cycle in catabolic activities: citrate synthase, aconitase, isocitrate dehydrogenase (NADP+ -reducing), oxoglutarate : benzylviologen oxidoreductase, succinyl-CoA synthetase, succinate dehydrogenase, fumarase and malate dehydrogenase (NAD+-reducing). Carbon monoxide dehydrogenase activity was not detected. We conclude that in T. tenax and P. islandicum organic compounds are completely oxidized to CO2 with sulfur or thiosulfate as electron acceptor and that acetyl-CoA oxidation to CO2 proceeds via the citric acid cycle.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00301853
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  • 8
    Electronic Resource
    Electronic Resource
    Why do sulfate-reducing bacteria outcompete methanogenic bacteria for substrates? (1983)
    Springer
    Oecologia 60 (1983), S. 264-266 
    Details
    ISSN: 1432-1939
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The apparent Ks values for H2 of several phylogenetically distant strains of both methanogenic bacteria and sulfate-reducing bacteria were measured. The sulfate reducers had Ks values of about 2 μM whereas the Ks values of the methanogens were 6–20 μM. This indicates that probably all sulfate-reducing bacteria have a higher substrate affinity for H2 than the methanogenic bacteria. Difference in substrate affinity can thus account for the inhibition of methanogenesis from H2 and CO2 in sulfate-rich ecosystems (mainly saltwater marshes), where the H2 concentration is well below 5 μM. Possible explanations for this general phenomenon are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00379530
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  • 9
    Electronic Resource
    Electronic Resource
    Metabolism of hyperthermophiles (1995)
    Springer
    World journal of microbiology and biotechnology 11 (1995), S. 26-57 
    Details
    ISSN: 1573-0972
    Keywords: Acetate formation ; acetyl-CoA oxidation ; Archaea ; Bacteria ; chemolithoautotroph ; chemoorganoheterotroph ; glycolytic pathway ; hyperthermophiles ; metabolic pathways ; peptide metabolism ; sugar metabolism
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Hyperthermophiles are characterized by a temperature optimum for growth between 80 and 110°C. They are considered to represent the most ancient phenotype of living organisms and thus their metabolic design might reflect the situation at an early stage of evolution. Their modes of metabolism are diverse and include chemolithoautotrophic and chemoorganoheterotrophic. No extant phototrophic hyperthermophiles are known. Lithotrophic energy metabolism is mostly anaerobic or microaerophilic and based on the oxidation of H2 or S coupled to the reduction of S, SO inf4 sup2- , CO2 and NO inf3 sup- but rarely to O2. the substrates are derived from volcanic activities in hyperthermophilic habitats. The lithotrophic energy metabolism of hyperthermophiles appears to be similar to that of mesophiles. Autotrophic CO2 fixation proceeds via the reductive citric acid cycle, considered to be one of the first metabolic cycles, and via the reductive acetyl-CoA/carbon monoxide dehydrogenase pathway. The Calvin cycle has not been found in hyperthermophiles (or any Archaea). Organotrophic metabolism mainly involves peptides and sugars as substrates, which are either oxidized to CO2 by external electron acceptors or fermented to acetate and other products. Sugar catabolism in hyperthermophiles involves non-phosphorylated versions of the Entner-Doudoroff pathway and modified versions of the Embden-Meyerhof pathway. The ‘classical’ Embden-Meyerhof pathway is present in hyperthermophilic Bacteria (Thermotoga) but not in Archaea. All hyperthermophiles (and Archaea) tested so far utilize pyruvate:ferredoxin oxidoreductase for acetyl-CoA formation from pyruvate. Acetyl-CoA oxidation in anaerobic sulphur-reducing and aerobic hyperthermophiles proceeds via the citric acid cycle; in the hyperthermophilic sulphate-reducer Archaeoglobus an oxidative acetyl-CoA/carbon monoxide dehydrogenase pathway is operative. Acetate formation from acetyl-CoA in Archaea, including hyperthermophiles, is catalysed by acetyl-CoA synthetase (ADP-forming), a novel prokarvotic enzyme involved in energy conservation. In Bacteria, including the hyperthermophile Thermotoga, acetyl-CoA conversion to acetate involves two enzymes, phosphate acetyltransferase and acetate kinase.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00339135
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