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  • 1
    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: Methanosarcina barkeri ; Pyruvate-utilizing mutant ; Methanogenesis ; Archaea ; Pyruvate fermentation ; Acetate fermentation ; Growth yields (Y ch4 ) ; 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 (Ych 4) was about 14 g dry weight cells/mol CH4. In contrast the growth yield (Ych 4) of M. barkeri during growth on acctate (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 x 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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  • 2
    Electronic Resource
    Electronic Resource
    Pyruvate metabolism of the hyperthermophilic archaebacterium Pyrococcus furiosus (1991)
    Springer
    Archives of microbiology 155 (1991), S. 366-377 
    Details
    ISSN: 1432-072X
    Keywords: Pyrococcus furiosus ; Hyperthermophilic archabacteria ; Pyruvate fermentation ; Growth yields ; Hydrogen inhibition ; Sulfur stimulation ; Pyruvate:ferredoxin oxidoreductase ; Acetyl-CoA synthetase (ADP forming) ; Adenylate kinase ; ATPase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The hyperthermophilic anaerobe Pyrococcus furiosus was found to grow on pyruvate as energy and carbon source. Growth was dependent on yeast extract (0.1%). The organism grew with doublings times of about 1 h up to cell densities of 1–2×108 cells/ml. During growth 0.6–0.8 mol acetate and 1.2–1.5 mol CO2 and 0.8 mol H2 were formed per mol of pyruvate consumed. The molar growth yield was 10–11 g cells(dry weight)/mol pyruvate. Cell suspensions catalyzed the conversion of 1 mol of pyruvate to 0.6–0.8 mol acetate, 1.2–1.5 mol CO2, 1.2 mol H2 and 0.03 mol acetoin. After fermentation of [3-14C]pyruvate the specific radioactivities of pyruvate, CO2 and acetate were equal to 1:0.01:1. Cellfree extracts contained the following enzymatic activities: pyruvate: ferredoxin (methyl viologen) oxidoreductase (0.2 U mg-1, T=60°C, with Clostridium pasteurianum ferredoxin as electron acceptor; 1.4 U mg-1 at 90°C, with methyl viologen as electron acceptor); acetyl-CoA synthetase (ADP forming) [acetyl-CoA+ADP+Pi⇆acetate+ATP+CoA] (0.34 U mg-1, T=90°C), and hydrogen: methyl viologen oxidoreductase (1.75 U mg-1). Phosphate acetyl-transferase activity, acetate kinase activity, and carbon monoxide:methyl viologen oxidoreductase activity could not be detected. These findings indicate that the archaebacterium P. furiosus ferments pyruvate to acetate, CO2 and H2 involving only three enzymes, a pyruvate:ferredoxin oxidoreductase, a hydrogenase and an acetyl-CoA synthetase (ADP forming).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00243457
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    Paper (German National Licenses)
    Fulltext
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