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  • 1
    Digitale Medien
    Digitale Medien
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 186 (2000), S. 0 
    ISSN: 1574-6968
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Biologie
    Notizen: The rate and products of trichloroethylene (TCE) oxidation by Methylomicrobium album BG8 expressing membrane-associated methane monooxygenase (pMMO) were determined using 14C radiotracer techniques. [14C]TCE was degraded at a rate of 1.24 nmol (min mg protein)−1 with the initial production of glyoxylate and then formate. Radiolabeled CO2 was also found after incubating M. album BG8 for 5 h with [14C]TCE. Experiments with purified pMMO from Methylococcus capsulatus Bath showed that TCE could be mineralized to CO2 by pMMO. Oxygen uptake studies verified that M. album BG8 could oxidize glyoxylate and that pMMO was responsible for the oxidation based on acetylene inactivation studies. Here we propose a pathway of TCE oxidation by pMMO-expressing cells in which TCE is first converted to TCE-epoxide. The epoxide then spontaneously undergoes HCl elimination to form glyoxylate which can be further oxidized by pMMO to formate and CO2.
    Materialart: Digitale Medien
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  • 2
    Digitale Medien
    Digitale Medien
    Springer
    Archives of microbiology 133 (1982), S. 28-32 
    ISSN: 1432-072X
    Schlagwort(e): Uranium oxidation ; Iron oxidation ; Thiobacillus ferrooxidans ; Carbon dioxide fixation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The stoichiometric oxidation of uranous-to uranyl-uranium byThiobacllus ferrooxidans is demonstrated. Fixation of14CO2 and the effect of inhibitors demonstrate that energy is conserved during the oxidation and used for energy-dependent “reverse electron flow” and carbon dioxide fixation.
    Materialart: Digitale Medien
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  • 3
    Digitale Medien
    Digitale Medien
    Springer
    Archives of microbiology 154 (1990), S. 453-458 
    ISSN: 1432-072X
    Schlagwort(e): Flavocytochrome c-554 ; Cytochrome c-553 ; Cytochrome c′ ; CO-binding ; Cytochromes ; Beggiatoa alba ; Sulfide oxidation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Three c-type cytochromes were purified from the filamentous sulfur-oxidizing bacterium, Beggiatoa alba strain B18LD, by ammonium sulfate fractionation, flat bed isoelectric focusing and gel filtration. Two of the cytochromes; flavocytochrome c-554 and cytochrome c′, were similar to cytochromes found in anoxygenic photosynthetic bacteria. Flavocytochrome c-554 had an apparent molecular weight of 21,000, an isoelectric focusing point at pH 4.4, contained FMN as the flavin component and had absorption maxima at 410, 450 and 470 nm in the oxidized form and at 417, 523 and 554 nm in the dithionite-reduced from. Cytochrome c′ was also an acidic protein with a pI of 4.8 and an apparent molecular weight of 18,000. The absorption spectra maxima were at 400, 490 and 635 nm in the oxidized form, at 424 and 550 nm in the dithione-reduced form and at 415 and 555 nm in the dithionite-reduced plus CO form. The third cytochrome characterized, cytochrome c-553 had an apparent molecular weight of 13,000, an isoelectric point at pH 4.4 and showed absorption maxima at 411 nm in the oxidized form and at 418, 523 and 553 nm in the dithionite-reduced form. Cytochrome c-553 was also isolated as a complex with a non-heme protein with a molecular weight of 16,000. The non-heme protein altered the absorption spectra and isoelectric point of cytochrome c-553.
    Materialart: Digitale Medien
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  • 4
    Digitale Medien
    Digitale Medien
    Springer
    Archives of microbiology 161 (1994), S. 258-265 
    ISSN: 1432-072X
    Schlagwort(e): Methanotrophs ; Methylotrophy ; Cytochrome oxidase ; Cytochrome aa 3 ; Cytochrome c ; Methylococcus capsulatus (Bath)
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract A cytochrome aa 3-type oxidase was isolated with and without a c-type cytochrome (cytochrome c-557) from Methylococcus capsulatus Bath by ion-exchange and hydrophobic chromatography in the presence of Triton X-100. Although cytochrome c-557 was not a constitutive component of the terminal oxidase, the cytochrome c ascorbate-TMPD oxidase activity of the enzyme decreased dramatically when the ratio of cytochrome c-557 to heme a dropped below 1:3. On denaturing gels, the purified enzyme dissociated into three subunits with molecular weights of 46,000, 28,000 and 20,000. The enzyme contains two heme groups (a and a 3), absorption maximum at 422 nm in the resting state, at 445 and 601 nm in the dithionite reduced form and at 434 and 598 nm in the dithionite reduced plus CO form. Denaturing gels of the cytochrome aa 3-cytochrome c-557 complex showed the polypeptides associated with cytochrome aa 3 plus a heme c-staining subunit with a molecular weight of 37,000. The complex contains approximately two heme a, one heme c, absorption maximum at 420 nm in the resting state and at 421, 445, 522, 557 and 601 nm in the dithionite reduced form. The specific activity of the purified enzyme was 130 mol O2/min · mol heme a compared to 753 mol O2/min · mol heme a when isolated with cytochrome c-557.
    Materialart: Digitale Medien
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  • 5
    Digitale Medien
    Digitale Medien
    Springer
    Archives of microbiology 161 (1994), S. 258-265 
    ISSN: 1432-072X
    Schlagwort(e): Key words: Methanotrophs – Methylotrophy – Cytochrome oxidase – Cytochrome aa3– Cytochrome c–Methylococcus capsulatus (Bath)
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract. A cytochrome aa 3-type oxidase was isolated with and without a c-type cytochrome (cytochrome c-557) from Methylococcus capsulatus Bath by ion-exchange and hydrophobic chromatography in the presence of Triton X-100. Although cytochrome c-557 was not a constitutive component of the terminal oxidase, the cytochrome c ascorbate-TMPD oxidase activity of the enzyme decreased dramatically when the ratio of cytochrome c-557 to heme a dropped below 1:3. On denaturing gels, the purified enzyme dissociated into three subunits with molecular weights of 46,000, 28,000 and 20,000. The enzyme contains two heme groups (a and a 3), absorption maximum at 422 nm in the resting state, at 445 and 601 nm in the dithionite reduced form and at 434 and 598 nm in the dithionite reduced plus CO form. Denaturing gels of the cytochrome aa 3-cytochrome c-557 complex showed the polypeptides associated with cytochrome aa 3 plus a heme c-staining subunit with a molecular weight of 37,000. The complex contains approximately two heme a, one heme c, absorption maximum at 420 nm in the resting state and at 421, 445, 522, 557 and 601 nm in the dithionite reduced form. The specific activity of the purified enzyme was 130 mol O2/min⋅mol heme a compared to 753 mol O2/min⋅mol heme a when isolated with cytochrome c-557.
    Materialart: Digitale Medien
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  • 6
    Digitale Medien
    Digitale Medien
    Springer
    Archives of microbiology 133 (1982), S. 33-37 
    ISSN: 1432-072X
    Schlagwort(e): Uranium oxidation ; Iron oxidation ; Oxygen uptake ; Carbon dioxide fixation ; Uranium toxicity ; Thorium toxicity ; Thiobacillus ferrooxidans
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Kinetic constants for the oxidation of uranous and ferrous ions byThiobacillus ferrooxidans were estimated. The kinetics indicate a direct biological mechanism for uranium oxidation. The complex interrelations of ferric, uranyl and uranous ion inhibition are considered.
    Materialart: Digitale Medien
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  • 7
    ISSN: 1432-072X
    Schlagwort(e): Ubiquinone ; Isoprenoid quinone ; Quinone composition ; Thiobacillus ferrooxidans ; Mass spectrometry ; High performance liquid chromatography ; Thin layer chromatography
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract A method was developed for the isolation of bacterial isoprenoid quinones. This method gave good yields and was superior to two standard methods that were also tested, because the cell membrane isolation and methanol extraction steps could be eliminated. The ubiquinone composition of Thiobacillus ferrooxidans was analyzed; only ubiquinone-8 was detected and its identification was resolved by thin layer chromatography, high performance liquid chromatography, and mass spectrometry.
    Materialart: Digitale Medien
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  • 8
    Digitale Medien
    Digitale Medien
    Springer
    Archives of microbiology 135 (1983), S. 250-253 
    ISSN: 1432-072X
    Schlagwort(e): Uranium ; Thiobacilli ; Cell fractionation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The uptake and cellular distribution of UO 2 2+ were investigated in washed cell suspensions of Thiobacillus ferrooxidans. The uptake was dependent on external concentration of uranium (0.01–10.0 mM) and was influenced by the pH of the reaction mixture, but not by 1 mM transition metals ions or by the previous growth history of the cells. Cells inactivated by either ultraviolet radiation or potassium cyanide accumulated about 40% more uranium than did viable cells especially at a high, toxic UO 2 2+ concentration. Most of the uranium was associated with the cell wall and membrane fractions and relatively little uranium was detected in the cytoplasmic, lipopolysaccaride and periplasmic space material fractions. Cells poisoned with potassium cyanide were found to have an 8 to 11-fold increase in the cytoplasmic concentration of uranium.
    Materialart: Digitale Medien
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  • 9
    ISSN: 1432-072X
    Schlagwort(e): Key words Particulate methane monooxygenase ; Trichloroethylene ; Dichloromethane ; Inhibition
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Whole-cell assays were used to measure the effect of dichloromethane and trichloroethylene on methane oxidation by Methylosinus trichosporium OB3b synthesizing the membrane-associated or particulate methane monooxygenase (pMMO). For M. trichosporium OB3b grown with 20 μM copper, no inhibition of methane oxidation was observed in the presence of either dichloromethane or trichloroethylene. If 20 mM formate was added to the reaction vials, however, methane oxidation rates increased and inhibition of methane oxidation was observed in the presence of dichloromethane and trichloroethylene. In the presence of formate, dichloromethane acted as a competitive inhibitor, while trichloroethylene acted as a noncompetitive inhibitor. The finding of noncompetitive inhibition by trichloroethylene was further examined by measuring the inhibition constants K iE and K iES. These constants suggest that trichloroethylene competes with methane at some sites, although it can bind to others if methane is already bound. Whole-cell oxygen uptake experiments for active and acetylene-treated cells also showed that provision of formate could stimulate both methane and trichloroethylene oxidation and that trichloroethylene did not affect formate dehydrogenase activity. The finding that different chlorinated hydrocarbons caused different inhibition patterns can be explained by either multiple substrate binding sites existing in pMMO or multiple forms of pMMO with different activities. The whole-cell analysis performed here cannot distinguish between these models, and further work should be done on obtaining active preparations of the purified pMMO.
    Materialart: Digitale Medien
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  • 10
    ISSN: 1572-9729
    Schlagwort(e): methanotrophs ; membrane associated methane monooxygenase ; trichloroethylene oxidation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Energietechnik , Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract Trichloroethylene (TCE) oxidation was examined in 9 different methanotrophs grown under conditions favoring expression of the membrane associated methane monooxygenase. Depending on the strain, TCE oxidation rates varied from 1 to 677 pmol/min/mg cell protein. Levels of TCE in the reaction mixture were reduced to below 40 nmolar in some strains. Cells incubated in the presence of acetylene, a selective methane monooxygenase inhibitor, did not oxidize TCE. Cultures actively oxidizing TCE were monitored for the presence of the soluble methane monooxygenase (sMMO) and membrane associated enzyme (pMMO). Transmission electron micrographs revealed the cultures always contained the internal membrane systems characteristic of cells expressing the pMMO. Naphthalene oxidation by whole cells, or by the cell free, soluble or membrane fractions was never observed. SDS denaturing gels of the membrane fraction showed the polypeptides associated with the pMMO. Cells exposed to 14C-acetylene showed one labeled band at 26 kDa, and this protein was observed in the membrane fraction. In the one strain examined by EPR spectroscopy, the membrane fraction of TCE oxidizing cells showed the copper complexes characteristic of the pMMO. Lastly, most of the strains tested showed no hybridization to sMMO gene probes. These findings show that the pMMO is capable of TCE oxidation; although the rates are lower than those observed for the sMMO.
    Materialart: Digitale Medien
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