Mass spectrometric measurements of methane and oxygen utilization by methanotrophic bacteria

Abstract A mass spectrometer with membrane inlet was used to measure methane and oxygen utilization rates at various methane concentrations in Methylosinus trichosporium and a locally isolated strain of a methane-oxidizing coccus (OU-4-1). The apparent K _m for methane was found to be 2 μM for M. trichosporium and 0.8 μM for strain OU-4-1. These K _m-values are 10–30 times lower than most previously reported values. The ratio of oxygen to methane utilization rates was 1.7 for M. trichosporium and 1.5 for strain OU-4-1 corresponding to a growth yield of 0.38 and 0.63 g dry weight/g methane, respectively.     

Stimulation by interferon of induction of differentiation of human promyelocytic leukemia cells

F₁-ATPase was isolated from yeast $\text{S.}\text{cerevisiae}$. The constituent subunits 1 and 2 were purified by gel permeation chromatography, and their amino acid compositions determined. Both subunits have a similar composition except for $\text{1}\text{2}$ cystine, methionine, leucine, histidine, and tryptophan. When F₁ is treated for three hours with 5′-p-[³H]fluorosulfonylbenzoyl adenosine in dimethylsulfoxide, 90% of the activity is lost. Disc gel electrophoresis of the modified complex showed that over 90% of the label was associated with subunit 2. A labelled peptide from a $\text{S.}\text{aureus}$ digest of subunit 2 was isolated and sequenced. It had the following amino acid sequence: His-Try¹-Asp-Val-Ala-Ser-Lys-Val-Gln-Glu, whereby Tyr¹ is the modified amino acid residue. This sequence shows homology to other sequences obtained from maize, beef heart, and $\text{E.}\text{coli}$ F₁-ATPases.     

Unsaturated fatty acid-dependent oxidation of epinephrine in homogenates of the gorgonian, Pseudoplexaura porosa

A novel epinephrine oxidation system in homogenates of the gorgonian Pseudoplexaura porosa was discovered. The enzymatic reaction required an unsaturated fatty acid and molecular oxygen or hydrogen peroxide. Diphenylisobenzofuran was also oxidized by Ps. porosa homogenates in the presence of an unsaturated fatty acid. Hydroxyl radical and superoxide anion did not appear to be involved in either of these oxidative reactions. The production of lipid hydroperoxides was not necessary for epinephrine oxidation and, with the exception of arachidonic acid, lipid hydroperoxide production did not occur. Evidence is presented for the involvement of singlet oxygen or a similar activated oxygen intermediate in the reactions, and a possible mechanism was proposed. The use of arachidonate-dependent epinephrine oxidation as a measure of prostaglandin synthetase activity is criticized.     

Relative contributions of biological and chemical reactions to the overall rate of pyrite oxidation at temperatures between 30 degrees C and 70 degrees C

The stoichiometry and kinetics of the spontaneous, chemical reaction between pyrite and ferric iron was studied at 30, 45, and 70 degrees C in shake flasks at pH 1.5 by monitoring the ferrous iron, total iron, elemental sulfur, and sulfate concentration profiles in time. It was found that the sulfur moiety of pyrite was oxidized completely to sulfate. Elemental sulfur was not produced in detectable amounts. The iron moiety of pyrite was released as ferrous iron. All observed initial reaction rates could be fitted into an empirical equation. This equation includes the concentrations of ferric iron and pyrite, and a constant which is dependent on the temperature and the nature of the main anion present. It was observed that ferrous iron formed during the reaction slowed down the oxidation of pyrite by ferric iron. The extent of this effect decreased with increasing temperature. With the aid of the empirical equation, the contribution of the chemical oxidation of pyrite by ferric iron to the overall oxidation in a hypothetical plug-flow reactor, in which biologically mediated oxdidation of pyrite and ferrous iron by oxygen also takes place, can be assessed. At 30, 45, and 70 degrees C, respectively, 2, 8-17, and 43% of the pyrite was oxidized chemically by ferric iron. Therefore, it is expected that only in reactors operating at high temperatures with extremely thermophilic bacteria, will chemical oxidation cause a significant deviation from the apparent first order overall kinetics of biological pyrite oxidation.     

Expression of streptomycete cholesterol oxidase inEscherichia coli

Summary A streptomycete gene coding for extracellular cholesterol oxidase (choA) was subcloned and expressed inEscherichia coli. The pUCO series recombinants were obtained by inserting thechoA gene into the uniqueKpnI site of pUC19 vector. Expression was observed with pUCO192A and pUCO193 constructs in which the cloned gene(s) were aligned with the upstreamlacZ promoter. Isopropyl -d-thioglucopyranoside (IPTG) enhanced this expression up to 2.5-fold. Specific Cho activity in the cell extracts of the stable pUCO193 transformant were 0.004 U and 0.007 U per mg protein without and with IPTG induction, respectively. Cho activity was detected in the spent medium of this culture, suggesting possible secretion of the enzyme.     

Sulfate reduction and S-oxidation in a moorland pool sediment

In an oligotrophic moorland pool in The Netherlands, S cycling near the sediment/water boundary was investigated by measuring (1) SO₄ ^2– reduction rates in the sediment, (2) depletion of SO₄ ^2– in the overlying water column and (3) release of³⁵S from the sediment into the water column. Two locations differing in sediment type (highly organic and sandy) were compared, with respect to reduction rates and depletion of SO₄ ^2– in the overlying water.Sulfate reduction rates in sediments of an oligotrophic moorland pool were estimated by diagenetic modelling and whole core³⁵SO₄ ^2– injection. Rates of SO₄ ^2– consumption in the overlying water were estimated by changes in SO₄ ^2– concentration over time in in situ enclosures. Reduction rates ranged from 0.27–11.2 mmol m^–2 d^–1. Rates of SO₄ ^2– uptake from the enclosed water column varied from –0.5, –0.3 mmol m^–2 d^–1 (November) to 0.43–1.81 mmol m^–2 d^–1 (July, August and April). Maximum rates of oxidation to SO₄ ^2– in July 1990 estimated by combination of SO₄ ^2– reduction rates and rates of in situ SO₄ ^2– uptake in the enclosed water column were 10.3 and 10.5 mmol m^–2 d^–1 at an organic rich and at a sandy site respectively.Experiments with³⁵S^2– and³⁵SO₄ ^2– tracer suggested (1) a rapid formation of organically bound S from dissimilatory reduced SO₄ ^2– and (2) the presence of mainly non SO₄ ^2–-S derived from reduced S transported from the sediment into the overlying water. A³⁵S^2– tracer experiment showed that about 7% of³⁵S^2– injected at 1 cm depth in a sediment core was recovered in the overlying water column.Sulfate reduction rates in sediments with higher volumetric mass fraction of organic matter did not significantly differ from those in sediments with a lower mass fraction of organic matter.Corresponding author     

Oxidation of methane in boreal forest soils: a comparison of seven measures

Methane oxidation rates were measured in boreal forest soils using seven techniques that provide a range of information on soil CH₄ oxidation. These include: (a) short-term static chamber experiments with a free-air (1.7 ppm CH₄) headspace, (b) estimating CH₄ oxidation rates from soil CH₄ distributions and (c)²²²Rn-calibrated flux measurements, (d) day-long static chamber experiments with free-air and amended (+20 to 2000 PPM CH₄) headspaces, (e) jar experiments on soil core sections using free-air and (f) amended (+500 ppm CH₄) headspaces, and (g) jar experiments on core sections involving tracer additions of¹⁴CH₄. Short-term unamended chamber measurements,²²²Rn-calibrated flux measurements, and soil CH₄ distributions show independently that the soils are capable of oxidizing atmospheric CH₄ at rates ranging to < 2 mg m^–2 d^–1. Jar experiments with free-air headspaces and soil CH₄ profiles show that CH₄ oxidation occurs to a soil depth of 60 cm and is maximum in the 10 to 20 cm zone. Jar experiments and chamber measurements with free-air headspaces show that CH₄ oxidation occurs at low (< 0.9 ppm) thresholds. The¹⁴CH₄-amended jar experiments show the distribution of end products of CH₄ oxidation; 60% is transformed to CO₂ and the remainder is incorporated in biomass. Chamber and jar experiments under amended atmospheres show that these soils have a high capacity for CH₄ oxidation and indicate potential CH₄ oxidation rates as high as 867 mg m^–2 d^–1. Methane oxidation in moist soils modulates CH₄ emission and can serve as a negative feedback on atmospheric CH₄ increases.     

Electrocatalytic properties of polypyrrole in amperometric electrodes

The electrocatalytic oxidation of NADH, ascorbate, urate, xanthine and H₂O₂ at different polypyrrole electrodes has been investigated. The conducting polymer was grown on platinum, glassy carbon, or graphite electrodes and modified by means of enclosed redox-active anions or other redox-active compounds covalently bound to either the N- or the β-position of the pyrrole. Copolymers of pyrrole and N-substituted pyrrole derivatives of chloranil or 2,3-dicholoro-1,4-naphthoquinone showed outstanding electrocatalytic properties for the oxidation of NADH. The application of these electrodes in amperometric steady-state measurements or flow-injection systems in combination with dehydrogenase reactions has been possible.     

Effect of Different Isomers of Dihydroxybenzoic Acids (DBA) on the Rate of DL-DOPA Oxidation by Mushroom Tyrosinase

Dihydroxybenzoic acids (DBA), such as 3,4-DRA, 3,5-DBA, and 2,4-DBA—at all concentrations tested—inhibited the rate of DL-DOPA oxidation to dopachrome (λmax = 475 nm) by mushroom tyrosinase. 2,3-DBA and 2,5-DBA at relatively low concentration had a synergistic effect on the reaction, whereas at relatively high concentrations they inhibited the rate of DL-DOPA oxidation. The synergistic effect of 0.6-13.3 mM 2,3-DRA on the rate of DL-DOPA oxidation to dopachrome (λmax = 475 nm) was found to be due to the ability of 2,3-DBA-o-quinone (formed by the oxidation of 2,3-DBA by mushroom tyrosinase or by sodium periodate) to oxidize DL-DOPA to dopachrome (via dopaquinone) non-enzymatically. A similar explanation is likely to be valid for the synergism exerted by 2,5-DBA on the rate of DL-DOPA oxidation by mushroom tyrosinase.     

Uranous ion oxidation and carbon dioxide fixation byThiobacillus ferrooxidans

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.Abbreviations HOQNO 2-heptyl-4-hydroxyquinoline-N-oxide - 8-HQ 8-hydroxyquinoline - TTFA thenoyltrifluoroacetone