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  • 1
    ISSN: 1432-072X
    Keywords: Hydrogen bacteria ; Hydrogenase ; Localization ; Membrane bound enzymes ; NAD reduction ; Stability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Alcaligenes eutrophus strains H 16, B 19, G 27 and N9A contained two different hydrogenases. One enzyme catalyzed the reduction of NAD by hydrogen and was strictly localized in the soluble cell fraction, while the second enzyme was found to be particulate and unable to react with NAD. All other tested strains, Alcaligenes paradoxus SA 29, Pseudomonas facilis, P. palleronii RH 2, Pseudomonas sp. strain GA 3, Paracoccus denitrificans, Aquaspirillum autotrophicum SA 32, and Corynebacterium autotrophicum 14g and 7C contained only a single enzyme exclusively bound to membranes. This was established using fractional centrifugation, indicator enzyme systems, gentle methods of cell disintegration and discontinuous sucrose density gradient centrifugation. In cell-free extracts obtained by rough disruption (sonication) of cells, hydrogenase was associated to particles of different size and sedimentation velocity. A partial solubilization of hydrogenase caused by sonication was observed with P. facilis. Without exception, the particulate hydrogenases were found (1) to be unable to reduce pyridine nucleotides, and (2) to reduce methylene blue at an extremely high activity. The eminent reaction rate of 34 μmoles H2 oxidized per min and mg protein has been determined in particle suspensions of Pseudomonas sp. strain GA 3. All hydrogenases were stable during storage under hydrogen atmosphere, except the soluble enzyme from A. eutrophus H 16 which was shown to be more stable under aerobic conditions.
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Archives of microbiology 116 (1978), S. 125-132 
    ISSN: 1432-072X
    Keywords: Heterocyst ; Blue-green algae ; Anabaena ; Nitrogenase ; Hydrogenase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Isolated heterocysts of Anabaena 7120 evolve H2 in an ATP-dependent nitrogenase-catalyzed process that is inhibited by N2 and C2H2. Heterocysts have an active uptake hydrogenase that only requires an electron acceptor of positive redox potential, e.g., methylene blue, dichlorophenolindophenol or potassium ferricyanide. O2 supplied at low partial pressures is a very effective physiological oxidant for H2 uptake. High concentrations of O2 are inhibitory to H2 uptake. The oxyhydrogen reaction in heterocysts appears to be mediated by a cytochrome-cytochrome oxidase system, and it supports ATP synthesis via oxidative phosphorylation. Attempts to demonstrate acetylene reduction in isolated heterocysts employing H2 as an electron donor were unsuccessful. It is suggested that the uptake hydrogenase functions to conserve reductant that otherwise would be dissipated via nitrogenase-catalyzed H2 evolution.
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  • 3
    ISSN: 1432-072X
    Keywords: Cyanobacteria ; Knallgas reaction ; Hydrogenase ; Hydrogen utilization ; Nitrogenase ; Nitrogen fixation ; Isolated heterocysts ; Anabaena cylindrica ; Nostoc muscorum ; Anabaena variabilis ; Anacystis nidulans ; Cyanophora paradoxa
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Several blue-green algae were surveyed for the occurrence of the hydrogenase which was assayed by the oxyhydrogen or Knallgas reaction in the intact organisms. In aerobically grown cultures, the reaction was detectable in Anabaena cylindrica, Nostoc muscorum and in two Anabaena variabilis species, whereas virtually no activity was observed in Anacystis nidulans and Cyanophora paradoxa. In these latter two algae, the reaction was, however, found after growth under molecular hydrogen for several days, which drastically increased the activity levels with all the algae tested. In the nitrogen fixing species, the activity of the Knallgas reaction was enhanced when all combined nitrogen was omitted from the media. H2 and hydrogenase could not significantly support the CO2-fixation in photoreduction experiments with all blue-green algae investigated here. Hydrogenase was assayed by the dithionite and methyl viologen dependent evolution of hydrogen and was found to be present with essentially the same specific activity levels in preparations of both heterocysts and vegetative cells from Anabaena cylindrica. Na2S2O4 as well as H2 supported the C2H2-reduction of the isolated heterocysts. The H2-dependent C2H2-reduction did not require the presence of oxygen but was strictly light-dependent where H2 served as an electron donor to photosystem I of these cells. It is concluded that hydrogen can be utilized by two different pathways in blue-green algae.
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  • 4
    ISSN: 1432-072X
    Keywords: Clostridium sp. La 1 ; Carbon sources ; Clostridium kluyveri ; Hydrogenase ; Enoate reductase ; Relationship of enoate reductase and hydrogenase ; Iron ; Sulfur
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The enzyme activities of Clostridium La 1 and Clostridium kluyveri involved in the stereospecific hydrogenation of α,β-unsaturated carbonyl compounds with hydrogen gas were measured. In C. La 1 the specific activities of hydrogenase and enoate reductase depended heavily on the growth phase and the composition of the medium. During growth in batch cultures on 70 mM crotonate the specific activity of hydrogenase increased and then dropped to about 10% of its maximum value, whereas the activity of enoate reductase reached its maximum in cells of the stationary phase. Under certain conditions during growth the activity ratio hydrogenase: enoate reductase changed from 120 to 1. Thus, the rate limiting enzyme for the hydrogenation can be either the hydrogenase or the enoate reductase, depending on the growth conditions of the cells. The specific activities of ferredoxin-NAD reductase and butyryl-CoA dehydrogenase increased 3-4-fold during growth on crotonate. By turbidostatic experiments it was shown that at constant input of high crotonate concentrations (200 mM) the enoate reductase activity was almost completely suppressed; it increased steadily with decreasing crotonate down to an input concentration of 35 mM. Glucose as carbon source led to high hydrogenase and negligible enoate reductase activities. The latter could be induced by changing the carbon source of the medium from glucose to crotonate. Tetracycline inhibited the formation of enoate reductase. A series of other carbon sources was tested. They can be divided into ones which result in high hydrogenase and rather low enoate reductase activities and others which cause the reverse effect. When the Fe2+ concentration in crotonate medium was growth limiting, cells with relatively high hydrogenase activity and very low enoate reductase activity in the stationary phase were obtained. At Fe2+ concentrations above 3·10-7 M enoate reductase increased and hydrogenase activity reached its minimum. The ratio of activities changes by a factor of about 200. In a similar way the dependence of enzyme activities on the concentration of sulfate was studied. In batch cultures of Clostridium kluyveri a similar opposite time course of enoate reductase and hydrogenase was found. The possible physiological significance of this behavior is discussed.
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  • 5
    ISSN: 1432-072X
    Keywords: Rhizobium japonicum ; Chemolithotrophic growth ; Hydrogenase ; Electron transport ; Cytochromes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The addition of H2 to suspensions of chemolithotrophically grown Rhizobium japonicum strikingly increased the rates of reduction of cytochromes of the b and c-types. There was no effect of H2, however, on the cytochrome reduction rates of suspensions of heterotrophically cultured cells which do not show hydrogenase activity. An additional component whose difference spectrum appears to be similar to that of b-type cytochromes was found in chemolithotrophically grown R. japonicum. The behavior of this additional component in the presence and absence of H2 and KCN was investigated and it is concluded that it is involved in H2 metabolism.
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Archives of microbiology 139 (1984), S. 361-365 
    ISSN: 1432-072X
    Keywords: Acetobacterium woodii ; Acetogenic bacteria ; Hydrogenase ; Carbon monoxide dehydrogenase ; Ferredoxin ; Flavodoxin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Hydrogenase from fructose-grown cells of Acetobacterium woodii has been purified 70-fold to a specific activity of 3,500 μmol hydrogen oxidized per min per mg of protein measured at 35°C and pH 7.6 with methyl viologen as electron acceptor. At the same conditions with reduced methyl viologen as electron donor the enzyme catalyzes the evolvement of 440 μmol of H2 per min per mg of protein. The enzyme was found in the soluble portion of the cell, indicating that it is either not membrane-bound or is loosely associated with the membrane. The purified enzyme, which does not contain nickel, exhibits spectroscopic properties similar to the iron-sulfur hydrogenase of Clostridium pasteurianum. The enzyme is strongly inhibited by carbon monoxide, with 50% inhibition occurring at approximately 7 nM CO. Ferredoxin, flavodoxin, and carbon monoxide dehydrogenase are reduced in hydrogen-dependent reaction by the A. woodi hydrogenase.
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  • 7
    ISSN: 1432-072X
    Keywords: Bacillus tusciae ; New species ; Taxonomy ; Ecology ; Chemolithoautotrophy ; Hydrogen oxidation ; Hydrogenase ; Thermophily ; Geothermal manifestation ; Solfatara
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A thermophilic, chemolithoautotrophic, hydrogen-oxidizing sporeformer has been isolated from ponds in a solfatara in the geothermal area of Tuscany (Italy). Some physicochemical parameters of the habitat were determined. The habitat was characterized by the presence of molecular hydrogen in the escaping gases, a very low content of phosphate and organic matter. Temperature and water level in the ponds varied widely. The organism formed oval, subterminal spores, which swelled distinctly the sporangium. Optimal growth occured between pH 4.2 and 4.8 at 55°C. It grew best under autotrophic conditions, but organic substrates including short chain fatty acids, amino acids and alcohols could also support heterotrophic growth. Sugars were not metabolized. The hydrogenase was soluble but did not reduce pyridine nucleotides. Based on its morphological and biochemical features, the organism belongs to the genus Bacillus, but differs from all the previously described species. It is therefore proposed as constituting a new species, Bacillus tusciae.
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  • 8
    ISSN: 1432-072X
    Keywords: Nitrogenase ; Hydrogenase ; Rhizobium japonicum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The conditions necessary for coordinate derepression of nitrogenase and O2-dependent hydrogenase activities in free-living cultures of Rhizobium japonicum were studied. Carbon sources were screened for their ability to support nitrogenase, and then hydrogenase activities. There was a positive correlation between the level of nitrogenase and corresponding hydrogenase activities among the various carbon substrates. The carbon substrate α-ketoglutarate was able to support the highest levels of both nitrogenase and hydrogenase activities. When cells were incubated in α-ketoglutarate-containing medium, without added H2 but in the presence of acetylene (to block H2 evolution from nitrogenase) significant hydrogenase activity was still observed. Complete inhibition of nitrogenase-dependent H2 evolution by acetylene was verified by the use of a Hup- mutant. Hydrogen is therefore not required to induce hydrogenase. The presence of 10% acetylene inhibited derepression of hydrogenase. Constitutive (Hupc) mutants were isolated which contained up to 9 times the level of hydrogenase acitivity than the wild type in nitrogenase induction medium. These mutants did not have greater nitrogenase activities than the wild type.
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  • 9
    ISSN: 1432-072X
    Keywords: Rhizobium ; Nitrogenase ; Hydrogenase ; H2/N2 ratio ; Chemostat ; Growth yields ; Cyanide assimilation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract When cyanide is gradually added to a nitrogenfixing culture, Rhizobium ORS 571 is capable of assimilating large amounts of cyanide using its nitrogenase. Under these conditions the molar growth yield on succinate (Y succ) increases from 27 at the start of cyanide addition to 38 at the end. The respiratory chain of cells grown at a concentration of 7 mM cyanide is still very sensitive to cyanide. The increase in growth yield is explained by a decrease in hydrogen production by nitrogenase as soon as cyanide is assimilated. This is confirmed by calculating the influence of hydrogen production on Y succ. Hydrogen production by nitrogenase has a greater influence on growth yields than the presence or absence of hydrogenase activity. At the end of cyanide addition when all cell nitrogen is synthesized from cyanide and no nitrogen fixation occurs, nitrogenase will be in a very oxidized state.
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  • 10
    ISSN: 1432-072X
    Keywords: Coryneform Hydrogen Bacterium ; Autotrophic Growth ; Entner-Doudoroff Pathway ; Hydrogenase ; Slime Formation ; Corynebacterium autotrophicum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract 1. Corynebacterium autotrophicum strain 7 C was isolated from an enrichment culture designed for propane oxidizing bacteria. The cells are Grampositive, immotile, short, irregularly formed rods. The colonies are yellow-pigmented and slimy. The yellow pigmentation is due to carotenoids. 2. Growth occurs either autotrophically in mineral medium under an atmosphere of 70% H2+20% O2+10% CO2 or heterotrophically with fructose or many organic acids as substrates. 3. The hexoses and gluconate are degraded via the Entner-Doudoroff pathway. 6-Phosphogluconate dehydrogenase is not detectable. 4. A NAD reducing hydrogenase has not been detected; the hydrogenase is localized in the particle fraction of the crude extract and reduces methylene blue. The specific activity of hydrogenase in the crude extract of autotrophically grown cells is 2400 μl H2/mg protein · hr. During growth on fructose the enzyme is constitutively formed (1200 μl H2/mg protein · hr). 5. The utilization of fructose was suppressed by hydrogen. The inhibitory effect was significant, when either fully adapted or autotrophically grown cells were exposed to a hydrogen containing atmosphere.
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