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  • 1
    Electronic Resource
    Electronic Resource
    Kinetic mechanism for the ability of sulfate reducers to out-compete methanogens for acetate (1982)
    Springer
    Archives of microbiology 132 (1982), S. 285-288 
    Details
    ISSN: 1432-072X
    Keywords: Desulfobacter postgatei ; Methanosarcina barkeri ; K s values for acetate ; Methanogenesis ; Sulfate reduction ; Competition for acetate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Methanosarcina barkeri and Desulfobacter postgatei are ubiquitous anaerobic bacteria which grow on acetate or acetate plus sulfate, respectively, as sole energy sources. Their apparent K s values for acetate were determined and found to be approximately 0.2 mM for the sulfate-reducing bacterium and 3 mM for the methanogenic bacterium. In mixed cell suspensions of the two bacteria (adjusted to equal V max) the rate of acetate consumption by D. postgatei approached 15-fold the rate of M. barkeri at low acetate concentrations. The apparent inhibition of methanogenesis was of the same order as expected from the different K s value for acetate. Difference in substrate affinities can thus account for the inhibition of methanogenesis from acetate in sulfate-rich environments, where the acetate concentration is well below 1 mM.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00407967
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  • 2
    Electronic Resource
    Electronic Resource
    Carbonic anhydrase activity in acetate grown Methanosarcina barkeri (1989)
    Springer
    Archives of microbiology 151 (1989), S. 137-142 
    Details
    ISSN: 1432-072X
    Keywords: Carbonic anhydrase ; Acetate metabolism ; Carbon monoxide dehydrogenase ; Methanosarcina barkeri ; Desulfobacter postgatei ; Desulfotomaculum acetoxidans ; Peptostreptococcus productus ; Methanococcus voltae ; Escherichia coli
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Cell extracts (27000xg supernatant) of acetate grown Methanosarcina barkeri were found to have carbonic anhydrase activity (0.41 U/mg protein), which was lost upon heating or incubation with proteinase K. The activity was inhibited by Diamox (apparent K i=0.5 mM), by azide (apparent K i=1 mM), and by cyanide (apparent K i=0.02 mM). These and other properties indicate that the archaebacterium contains the enzyme carbonic anhydrase (EC 4.2.1.1). Evidence is presented that the protein is probably located in the cytoplasm. Methanol or H2/CO2 grown cells of M. barkeri showed no or only very little carbonic anhydrase activity. After transfer of these cells to acetate medium the activity was “induced” suggesting a function of this enzyme in acetate fermentation to CO2 and CH4. Interestingly, Desulfobacter postgatei and Desulfotomaculum acetoxidans, which oxidize acetate to 2 CO2 with sulfate as electron acceptor, were also found to exhibit carbonic anhydrase activity (0.2 U/mg protein).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00414428
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  • 3
    Electronic Resource
    Electronic Resource
    Methyltetrahydromethanopterin as an intermediate in methanogenesis from acetate in Methanosarcina barkeri (1989)
    Springer
    Archives of microbiology 151 (1989), S. 459-465 
    Details
    ISSN: 1432-072X
    Keywords: Methanogenesis from acetate ; Methanopterin ; Methanofuran ; Coenzyme F420 ; Coenzyme M ; 7-Mercaptoheptanoylthreonine phosphate (=component B) ; Methanosarcina barkeri
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Cell extracts (100,000×g) of acetate grown Methanosarcina barkeri (strain MS) catalyzed CH4 and CO2 formation from acetyl-CoA with specific activities of 50 nmol·min-1·mg protein-1. CH4 formation was found to be dependent on tetrahydromethanopterin (H4MPT) (apparent K M=4 μM), coenzyme M (H-S-CoM), and 7-mercaptoheptanoylthreonine phosphate (H-S-HTP=component B) rather than on methanofuran (MFR) and coenzyme F420 (F420). Methyl-H4MPT was identified as an intermediate. This compound accumulated when H-S-CoM and H-S-HTP were omitted from the assays. These and previous results indicate that methanogenesis from acetate proceeds via acetyl phosphate, acetyl-CoA, methyl-H4MPT, and CH3-S-CoM as intermediates. The disproportionation of formaldehyde to CO2 and CH4 was also studied. This reaction was shown to be dependent on H4MPT, MFR, F420, H-S-CoM, and H-S-HTP.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00416607
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  • 4
    Electronic Resource
    Electronic Resource
    Two N 5, N 10-methylenetetrahydromethanopterin dehydrogenases in the extreme thermophile Methanopyrus kandleri: characterization of the coenzyme F420-dependent enzyme (1993)
    Springer
    Archives of microbiology 160 (1993), S. 186-192 
    Details
    ISSN: 1432-072X
    Keywords: Coenzyme F420 ; Tetrahydromethanopterin ; Hydrogenase ; H2-forming methylenetrahydromethanopterin dehydrogenase ; Methanobacterium thermoautotrophicum ; Methanosarcina barkeri ; Archaeoglobus fulgidus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract It was recently reported that the extreme thermophile Methanopyrus kandleri contains only a H2-forming N 5, N 10-methylenetetrahydromethanopterin dehydrogenase which uses protons as electron acceptor. We describe here the presence in this Archaeon of a second N 5,N 10-methylenetetrahydromethanopterin dehydrogenase which is coenzyme F420-dependent. This enzyme was purified and characterized. The enzyme was colourless, had an apparent molecular mass of 300 kDa, an isoelectric point of 3.7±0.2 and was composed of only one type of subunit of apparent molecular mass of 36 kDa. The enzyme activity increased to an optimum with increasing salt concentrations. Optimal salt concentrations were e.g. 2 M (NH4)2SO4, 2 M Na2HPO4, 1.5 M K2HPO4, and 2 M NaCl. In the absence of salts the enzyme exhibited almost no activity. The salts affected mainly the V max rather than the K m of the enzyme. The catalytic mechanism of the dehydrogenase was determined to be of the ternary complex type, in agreement with the finding that the enzyme lacked a chromophoric prosthetic group. In the presence of M (NH4)2SO4 the V max was 4000 U/mg (k cat=2400 s-1) and the K m for N 5,N 10-methylenetetrahydromethanopterin and for coenzyme F420 were 80 μM and 20 μM, respectively. The enzyme was relatively heat-stable and lost no activity when incubated anaerobically in 50 mM K2HPO4 at 90°C for one hour. The N-terminal amino acid sequence was found to be similar to that of the F420-dependent N 5, N 10-methylenetetrahydromethanopterin dehydrogenase from Methanobacterium thermoautotrophicum, Methanosarcina barkeri, and Archaeoglobus fulgidus.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00249123
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  • 5
    Electronic Resource
    Electronic Resource
    Primary structure and properties of the formyltransferase from the mesophilic Methanosarcina barkeri: comparison with the enzymes from thermophilic and hyperthermophilic methanogens (1996)
    Springer
    Archives of microbiology 165 (1996), S. 97-105 
    Details
    ISSN: 1432-072X
    Keywords: Key words Formyltransferase ; Formyltetrahydrofolate ; synthase ; Hyperthermophilic enzymes ; Methanogenic ; Archaea ; Methanosarcina barkeri
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The ftr gene encoding formylmethanofuran: tetrahydromethanopterin formyltransferase (Ftr) from Methanosarcina barkeri was cloned, sequenced, and functionally expressed in Escherichia coli. The overproduced enzyme was purified eightfold to apparent homogeneity, and its catalytic properties were determined. The primary structure and the hydropathic character of the formyltransferase from Methanosarcina barkeri were compared with those of the enzymes from Methanobacterium thermoautotrophicum, Methanothermus fervidus, and Methanopyrus kandleri. The amino acid sequence of the enzyme from Methanosarcina barkeri was 64%, 61%, and 59% identical to that of the enzyme from Methanobacterium thermoautotrophicum, Methanothermus fervidus, and Methanopyrus kandleri, respectively. A negative correlation between the hydrophobicity of the enzymes and both the growth temperature optimum and the intracellular salt concentration of the four organisms was observed. The hydrophobicity of amino acid composition was +21.6 for the enzyme from Methanosarcina barkeri (growth temperature optimum 37° C, intracellular salt concentration ≈ 0.3 M), +9.9 for the enzyme from Methanobacterium thermoautotrophicum (65°C, ≈ 0.7 M), –20.8 for the enzyme from Methanothermus fervidus (83° C, ≈ 1.0 M) and –31.4 for the enzyme from Methanopyrus kandleri (98° C, 〉 1.1 M). Generally, a positive correlation between hydrophobicity and thermophilicity of enzymes and a negative correlation between hydrophobicity and halophilicity of enzymes are observed. The findings therefore indicate that the hydropathic character of the formyltransferases compared is mainly determined by the intracellular salt concentration rather than by temperature. Sequence similarities between the formyltransferases from methanogens and an open reading frame from Methylobacterium extorquens AM1 are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002030050303
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  • 6
    Electronic Resource
    Electronic Resource
    Propionate assimilation by methanogenic bacteria (1983)
    Springer
    Archives of microbiology 136 (1983), S. 106-110 
    Details
    ISSN: 1432-072X
    Keywords: Propionate assimilation ; Isoleucine biosynthesis ; Methanogenic bacteria ; Methanobacterium thermoautotrophicum ; Methanobrevibacter arboriphilus ; Methanosarcina barkeri ; 2-Methylbutyrate assimilation ; Regulation of isoleucine biosynthesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Methanobacterium thermoautotrophicum, Methanobrevibacter arboriphilus, and Methanosarcina barkeri were found to assimilate propionate when growing on media supplemented with this volatile fatty acid. [1-14C]propionate was almost exclusively incorporated into isoleucine, only C-2 of which became labelled. Assimilation of propionate by M. thermoautotrophicum was specifically inhibited by isoleucine, by 2-methylbutyrate, and by 2-oxobutyrate, whereas there was little or no effect by leucine, valine, butyrate, and acetate. This finding indicates that propionate assimilation is under regulatory control by intermediates and/or the product of isoleucine biosynthesis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00404782
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  • 7
    Electronic Resource
    Electronic Resource
    Catalysis of an isotopic exchange between CO2 and the carboxyl group of acetate by Methanosarcina barkeri grown on acetate (1984)
    Springer
    Archives of microbiology 138 (1984), S. 365-370 
    Details
    ISSN: 1432-072X
    Keywords: Methanosarcina barkeri ; Methane formation from acetate ; 14CO2/acetate exchange reaction ; Cyanide inhibition of methanogenesis ; CO inhibition of methanogenesis ; H2 inhibition of methanogenesis ; Mechanism of methane formation from acetate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Cell suspensions of Methanosarcina barkeri (strain Fusaro) grown on acetate were found to catalyze the formation of methane and CO2 from acetate (30–40 nmol/min·mg protein) and an isotopic exchange between the carboxyl group of acetate and 14CO2 (30–40 nmol/min·mg protein). An isotopic exchange between [14C]-formate and acetate was not observed. Cells grown on methanol mediated neither methane formation from acetate nor the exchange reactions. The data indicate that the isotopic exchange between CO2 and the carboxyl group of acetate is a partial reaction of methanogenesis from acetate. Both reactions were completely inhibited by low concentrations of cyanide (20 μM) or of hydrogen (0.5% in the gas phase). Methane formation from acetate was also completely inhibited by low concentrations of carbon monoxide (0.2% in the gas phase) whereas only significantly higher concentrations of CO had an effect on the exchange reaction. In the concentration range tested KCN, H2 and CO had no effect on methane formation from methanol or from H2 and CO2; however, cyanide (20 μM) also affected methane formation from CO. The results are discussed with respect to proposed mechanisms of methane and CO2 formation from acetate.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00410905
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  • 8
    Electronic Resource
    Electronic Resource
    Nickel dependence of factor F430 content in Methanobacterium thermoautotrophicum (1980)
    Springer
    Archives of microbiology 127 (1980), S. 273-277 
    Details
    ISSN: 1432-072X
    Keywords: Methanobacterium thermoautotrophicum ; Methanosarcina barkeri ; Methanobrevibacter ruminantium ; Factor F430 ; Nickel ; Iron ; Cobalt ; Molybdenum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Factor F430 is a yellow compound of unknown structure present in methanogenic bacteria. It has recently been shown to contain nickel. In this communication the influence of the nickel concentration in the growth medium on the factor F430 content of Methanobacterium thermoautotrophicum and on the nickel content of factor F430 was studied. It was found: (1) The content of factor F430 in the cells was strongly dependent on the nickel concentration of the growth medium. Cells grown on media with 2.5 μM NiCl2 contained 28 times as much factor F430 per g as those grown on media with 0.075 μM NiCl2; (2) factor F430 was synthesized in nickel deprived cells only upon the addition of nickel Nickel uptake paralleled factor F430 synthesis; (3) independent of the nickel concentration in the growth medium, the extinction coefficient at 430 nm of factor F430 per mol nickel was always near 22,500 cm-1 (mol Ni)-1. These findings indicate that nickel is an essential component of factor F430.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00427204
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  • 9
    Electronic Resource
    Electronic Resource
    Evidence for the involvement and role of a corrinoid enzyme in methane formation from acetate in Methanosarcina barkeri (1985)
    Springer
    Archives of microbiology 142 (1985), S. 175-179 
    Details
    ISSN: 1432-072X
    Keywords: Methanosarcina barkeri ; Methane formation from acetate ; Corrinoid enzyme ; Propyl iodide inhibition ; Acetolastic methanogens ; Acetate/CO2 exchange
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Methane formation from acetate in cell suspensions of Methanosarcina barkeri was inhibited by low concentrations (5 μM) of propyl iodide. Inhibition was abolished by short exposure of the suspension to light which strongly indicates that a corrinoid enzyme is involved in methanogenesis from acetate. Propyl iodide (5μM) had no effect on the exchange reaction between the carboxyl group of acetate and 14CO2, and on methane formation from methanol, from H2 and methanol, or from H2 and CO2. These findings indicate that the proposed corrinoid enzyme has a role in methyl group transfer to coenzyme M after C-C cleavage of acetate.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00447063
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  • 10
    Electronic Resource
    Electronic Resource
    Methanogenesis from acetate in cell extracts of Methanosarcina barkeri: Isotope exchange between CO2 and the carbonyl group of acetyl-CoA, and the role of H2 (1990)
    Springer
    Archives of microbiology 153 (1990), S. 156-162 
    Details
    ISSN: 1432-072X
    Keywords: Methanosarcina barkeri ; Acetate metabolism ; Methanogenesis from acetate ; H2 metabolism ; Carbon monoxide dehydrogenase ; Cyanide inhibition ; Nitrous oxide inhibition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract From our previous studies on the mechanism of methane formation from acetate it was known that cell extracts of acetate-grown Methanosarcina barkeri (100 000 × g supernatant) catalyze the conversion of acetyl-CoA plus tetrahydromethanopterin (=H4MPT) to methyl-H4MPT, CoA, CO2 and presumably H2. We report here that these extracts, in the absence of H4MPT, mediated an isotope exchange between CO2 ([S]0.5 v=0.2% in the gas phase) and the carbonyl group of acetyl-CoA at almost the same specific rate as the above conversion (10 nmol · min−1 · mg protein−1). Both the exchange and the formation of methyl-H4MPT were inhibited by N2O, suggesting that a corrinoid could be the primary methyl group acceptor in the acetyl-CoA C-C-cleavage reaction. Both activities were dependent on the presence of H2 (E0′=−414 mV). Ti(III)citrate (E0′=−480 mV) was found to substitute for H2, indicating a reductive activation of the system. In the presence of Ti(III)citrate it was shown that the formation of CO2 from the carbonyl group of acetyl-CoA is associated with a 1:1 stoichiometric generation of H2. Free CO, a possible intermediate in CO2 and H2 formation, was not detected.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00247814
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