The Experts below are selected from a list of 270 Experts worldwide ranked by ideXlab platform
Jeremy D Semrau - One of the best experts on this subject based on the ideXlab platform.
-
methanobactin from Methylosinus trichosporium ob3b inhibits n2o reduction in denitrifiers
The ISME Journal, 2018Co-Authors: Jin Chang, Jeremy D Semrau, Alan A Dispirito, Wenyu Gu, Doyoung Park, Sukhwan YoonAbstract:Methanotrophs synthesize methanobactin, a secondary metabolite that binds copper with an unprecedentedly high affinity. Such a strategy may provide methanotrophs a “copper monopoly” that can inhibit the activity of copper-containing enzymes of other microbes, e.g., copper-dependent N2O reductases. Here, we show that methanobactin from Methylosinus trichosporium OB3b inhibited N2O reduction in denitrifiers. When Pseudomonas stutzeri DCP-Ps1 was incubated in cocultures with M. trichosporium OB3b or with purified methanobactin from M. trichosporium OB3b, stoichiometric N2O production was observed from NO3− reduction, whereas no significant N2O accumulation was observed in cocultures with a mutant defective in methanobactin production. Copper uptake by P. stutzeri DCP-Ps1 was inhibited by the presence of purified methanobactin, leading to a significant downregulation of nosZ transcription. Similar findings were observed with three other denitrifier strains. These results suggest that in situ stimulation of methanotrophs can inadvertently increase N2O emissions, with the potential for increasing net greenhouse gas emissions.
-
copper and cerium regulated gene expression in Methylosinus trichosporium ob3b
Applied Microbiology and Biotechnology, 2017Co-Authors: Wenyu Gu, Jeremy D SemrauAbstract:In aerobic methanotrophs, copper and cerium control the expression and activity of different forms of methane monooxygenase and methanol dehydrogenase, respectively. To exploit methanotrophy for the valorization of methane, it is crucial to determine if these metals exert more global control on gene expression in methanotrophs. Using RNA-Seq analysis we compared the transcriptome of Methylosinus trichosporium OB3b grown in the presence of varying amounts of copper and cerium. When copper was added in the absence of cerium, expression of genes encoding for both soluble and particulate methane monooxygenases varied as expected. Genes encoding for copper uptake, storage, and efflux also increased, indicating that methanotrophs must carefully control copper homeostasis. When cerium was added in the absence of copper, expression of genes encoding for alternative methanol dehydrogenases varied as expected, but few other genes were found to have differential expression. When cerium concentrations were varied in the presence of copper, few genes were found to be either up- or downregulated, indicating that copper over rules any regulation by cerium. When copper was increased in the presence of cerium, however, many genes were upregulated, most notably multiple steps of the central methane oxidation pathway, the serine cycle, and the ethylmalonyl-CoA pathway. Many genes were also downregulated, including those encoding for nitrogenase and hydrogenase. Collectively, these data suggest that copper plays a larger role in regulating gene expression in methanotrophs, but that significant changes occur when both copper and cerium are present.
-
carbon source regulation of gene expression in Methylosinus trichosporium ob3b
Applied Microbiology and Biotechnology, 2017Co-Authors: Muhammad Farhan Ul Haque, Alan A Dispirito, Bipin S Baral, Wenyu Gu, Jeremy D SemrauAbstract:Gene expression in methanotrophs has been shown to be affected by the availability of a variety of metals, most notably copper regulating expression of alternative forms of methane monooxygenase. Here, we show that growth substrate also affects expression of genes encoding for enzymes responsible for the oxidation of methane to formaldehyde and the assimilation of carbon. Specifically, in Methylosinus trichosporium OB3b, expression of genes involved in the conversion of methane to methanol (pmoA and mmoX) and methanol to formaldehyde (mxaF, xoxF1, and xoxF2) as well as in carbon assimilation (fae1, fae2, metF, and sga) decreased when this strain was grown on methanol vs. methane, indicating that methanotrophs manipulate gene expression in response to growth substrate as well as the availability of copper. Interestingly, growth of M. trichosporium OB3b on methane vs. methanol was similar despite such large changes in gene expression. Finally, methanol-grown cultures of M. trichosporium OB3b also exhibited the “copper-switch.” That is, expression of pmoA increased and mmoX decreased in the presence of copper, indicating that copper still controlled the expression of alternative forms of methane monooxygenase in M. trichosporium OB3b even though methane was not provided. Such findings indicate that methanotrophs can sense and respond to multiple environmental parameters simultaneously.
-
cerium regulates expression of alternative methanol dehydrogenases in Methylosinus trichosporium ob3b
Applied and Environmental Microbiology, 2015Co-Authors: Muhammad Farhan Ul Haque, Bhagyalakshmi Kalidass, Alan A Dispirito, Nathan L Bandow, Erick A Turpin, Jeremy D SemrauAbstract:Methanotrophs have multiple methane monooxygenases that are well known to be regulated by copper, i.e., a “copper switch.” At low copper/biomass ratios the soluble methane monooxygenase (sMMO) is expressed while expression and activity of the particulate methane monooxygenase (pMMO) increases with increasing availability of copper. In many methanotrophs there are also multiple methanol dehydrogenases (MeDHs), one based on Mxa and another based on Xox. Mxa-MeDH is known to have calcium in its active site, while Xox-MeDHs have been shown to have rare earth elements in their active site. We show here that the expression levels of Mxa-MeDH and Xox-MeDH in Methylosinus trichosporium OB3b significantly decreased and increased, respectively, when grown in the presence of cerium but the absence of copper compared to the absence of both metals. Expression of sMMO and pMMO was not affected. In the presence of copper, the effect of cerium on gene expression was less significant, i.e., expression of Mxa-MeDH in the presence of copper and cerium was slightly lower than in the presence of copper alone, but Xox-MeDH was again found to increase significantly. As expected, the addition of copper caused sMMO and pMMO expression levels to significantly decrease and increase, respectively, but the simultaneous addition of cerium had no discernible effect on MMO expression. As a result, it appears Mxa-MeDH can be uncoupled from methane oxidation by sMMO in M. trichosporium OB3b but not from pMMO.
-
methanobactin from methylocystis sp strain sb2 affects gene expression and methane monooxygenase activity in Methylosinus trichosporium ob3b
Applied and Environmental Microbiology, 2015Co-Authors: Muhammad Farhan Ulhaque, Bhagyalakshmi Kalidass, Alexey Vorobev, Bipin S Baral, Alan A Dispirito, Jeremy D SemrauAbstract:Methanotrophs can express a cytoplasmic (soluble) methane monooxygenase (sMMO) or membrane-bound (particulate) methane monooxygenase (pMMO). Expression of these MMOs is strongly regulated by the availability of copper. Many methanotrophs have been found to synthesize a novel compound, methanobactin (Mb), that is responsible for the uptake of copper, and methanobactin produced by Methylosinus trichosporium OB3b plays a key role in controlling expression of MMO genes in this strain. As all known forms of methanobactin are structurally similar, it was hypothesized that methanobactin from one methanotroph may alter gene expression in another. When Methylosinus trichosporium OB3b was grown in the presence of 1 μM CuCl2, expression of mmoX, encoding a subunit of the hydroxylase component of sMMO, was very low. mmoX expression increased, however, when methanobactin from Methylocystis sp. strain SB2 (SB2-Mb) was added, as did whole-cell sMMO activity, but there was no significant change in the amount of copper associated with M. trichosporium OB3b. If M. trichosporium OB3b was grown in the absence of CuCl2, the mmoX expression level was high but decreased by several orders of magnitude if copper prebound to SB2-Mb (Cu-SB2-Mb) was added, and biomass-associated copper was increased. Exposure of Methylosinus trichosporium OB3b to SB2-Mb had no effect on expression of mbnA, encoding the polypeptide precursor of methanobactin in either the presence or absence of CuCl2. mbnA expression, however, was reduced when Cu-SB2-Mb was added in both the absence and presence of CuCl2. These data suggest that methanobactin acts as a general signaling molecule in methanotrophs and that methanobactin “piracy” may be commonplace.
Ichiro Okura - One of the best experts on this subject based on the ideXlab platform.
-
improvement of the purification method for retaining the activity of the particulate methane monooxygenase from Methylosinus trichosporium ob3b
Biotechnology Letters, 2002Co-Authors: Akimitsu Miyaji, Toshiaki Kamachi, Ichiro OkuraAbstract:The purification method of particulate methane monooxygenase (pMMO) from Methylosinus trichosporium OB3b was improved, and purified pMMO retained its activity with duroquinol as a reductant. n-Dodecyl-β,d-maltoside was used for the solubilization of pMMO and Brij 58 was used for the purification for anion exchange chromatography. Compared to the original pMMO activity in the membrane fraction, 88% of the activity was now retained in the purified material. The purified pMMO monomer (94 kDa) contained only two copper atoms and did not contain iron. Both copper ions showed only a typical type II copper EPR signal with a superhyperfine structure at the g⊥ region, indicating that the type II copper ions play an important role as the active site of methane hydroxylation in pMMO.
-
role of iron and copper in particulate methane monooxygenase of Methylosinus trichosporium ob3b
Catalysis Surveys From Japan, 2000Co-Authors: Masayuki Takeguchi, Ichiro OkuraAbstract:The role of iron and copper in particulate methane monooxygenase (pMMO) of Methylosinus trichosporium OB3b is described, and an overview of the enzyme's properties is presented. The pMMO from M. trichosporium OB3b was solubilized in the detergent n-dodecyl-β-D-maltoside and purified by chromatographic techniques. The enzyme consists of 0.9 iron atoms and 12.8 copper atoms per molecule. The iron site in pMMO may be mononuclear non-heme iron. Copper exists as either copper ion coupled to four nitrogen atoms and/or trinuclear copper cluster wherein copper ions are ferromagnetically coupled.
-
Effect of bovine serum albumin on particulate methane monooxygenase from Methylosinus trichosporium OB3b
Journal of Molecular Catalysis A-chemical, 1999Co-Authors: Masayuki Takeguchi, Ichiro OkuraAbstract:The effect of some additives on the membrane bound particulate methane monooxygenase (pMMO) from Methylosinus trichosporium OB3b was studied. The pMMO activity was stimulated by exogenously supplied bovine serum albumin (BSA), but was inhibited by ovalbumin and excess copper (II) ion. When the membrane was treated with BSA, the amount of copper (II) ion in the membrane decreased, but the specific activity increased about 1.8 times compared with the as-isolated membrane. BSA may remove excess copper (II) ions in the membrane, inhibiting the pMMO activity. When the excess copper is removed by BSA, pMMO activity is stimulated.
-
semicontinuous methanol biosynthesis by Methylosinus trichosporium ob3b
Journal of Molecular Catalysis A-chemical, 1999Co-Authors: Takako Furuto, Masayuki Takeguchi, Ichiro OkuraAbstract:Abstract Methylosinus trichosporium OB3b is a methanotrophic bacterium containing methane monooxygenase, catalyzing hydroxylation of methane to methanol. When methane is oxidized, the product is subsequently oxidized by methanol dehydrogenase contained in the same bacterium. To prevent further oxidation of methanol, the cell suspension was treated by cyclopropanol, an irreversible inhibitor for methanol dehydrogenase, leading to extracellular methanol accumulation. However, the batch type of methanol synthesis by M. trichosporium OB3b was terminated at ca. 6 mM of methanol, for MMO is inhibited by increasing methanol concentration. For prolonged methanol accumulation, a semicontinuous process was carried out. In this process, the reaction was repeated several times and the produced methanol was 36.1 μmol for 6 h.
-
Electron Spin-Echo Envelope Modulation Studies on Copper Site of Particulate Methane Monooxygenase from Methylosinus trichosporium OB3b.
Chemistry Letters, 1999Co-Authors: Masayuki Takeguchi, Kouichi Fukui, Hiroaki Ohya, Ichiro OkuraAbstract:The electron spin-echo envelope modulation (ESEEM) effect was studied on the type II copper site in the particulate methane monooxygenase (pMMO) from Methylosinus trichosporium OB3b. From comparing the ESEEM spectra of the membranes treated with ethylenediaminetetraacetic acid and some model compounds, it was clarified that there were at least two imidazole ligands bound copper (II) in pMMO.
Masayuki Takeguchi - One of the best experts on this subject based on the ideXlab platform.
-
role of iron and copper in particulate methane monooxygenase of Methylosinus trichosporium ob3b
Catalysis Surveys From Japan, 2000Co-Authors: Masayuki Takeguchi, Ichiro OkuraAbstract:The role of iron and copper in particulate methane monooxygenase (pMMO) of Methylosinus trichosporium OB3b is described, and an overview of the enzyme's properties is presented. The pMMO from M. trichosporium OB3b was solubilized in the detergent n-dodecyl-β-D-maltoside and purified by chromatographic techniques. The enzyme consists of 0.9 iron atoms and 12.8 copper atoms per molecule. The iron site in pMMO may be mononuclear non-heme iron. Copper exists as either copper ion coupled to four nitrogen atoms and/or trinuclear copper cluster wherein copper ions are ferromagnetically coupled.
-
Effect of bovine serum albumin on particulate methane monooxygenase from Methylosinus trichosporium OB3b
Journal of Molecular Catalysis A-chemical, 1999Co-Authors: Masayuki Takeguchi, Ichiro OkuraAbstract:The effect of some additives on the membrane bound particulate methane monooxygenase (pMMO) from Methylosinus trichosporium OB3b was studied. The pMMO activity was stimulated by exogenously supplied bovine serum albumin (BSA), but was inhibited by ovalbumin and excess copper (II) ion. When the membrane was treated with BSA, the amount of copper (II) ion in the membrane decreased, but the specific activity increased about 1.8 times compared with the as-isolated membrane. BSA may remove excess copper (II) ions in the membrane, inhibiting the pMMO activity. When the excess copper is removed by BSA, pMMO activity is stimulated.
-
semicontinuous methanol biosynthesis by Methylosinus trichosporium ob3b
Journal of Molecular Catalysis A-chemical, 1999Co-Authors: Takako Furuto, Masayuki Takeguchi, Ichiro OkuraAbstract:Abstract Methylosinus trichosporium OB3b is a methanotrophic bacterium containing methane monooxygenase, catalyzing hydroxylation of methane to methanol. When methane is oxidized, the product is subsequently oxidized by methanol dehydrogenase contained in the same bacterium. To prevent further oxidation of methanol, the cell suspension was treated by cyclopropanol, an irreversible inhibitor for methanol dehydrogenase, leading to extracellular methanol accumulation. However, the batch type of methanol synthesis by M. trichosporium OB3b was terminated at ca. 6 mM of methanol, for MMO is inhibited by increasing methanol concentration. For prolonged methanol accumulation, a semicontinuous process was carried out. In this process, the reaction was repeated several times and the produced methanol was 36.1 μmol for 6 h.
-
Electron Spin-Echo Envelope Modulation Studies on Copper Site of Particulate Methane Monooxygenase from Methylosinus trichosporium OB3b.
Chemistry Letters, 1999Co-Authors: Masayuki Takeguchi, Kouichi Fukui, Hiroaki Ohya, Ichiro OkuraAbstract:The electron spin-echo envelope modulation (ESEEM) effect was studied on the type II copper site in the particulate methane monooxygenase (pMMO) from Methylosinus trichosporium OB3b. From comparing the ESEEM spectra of the membranes treated with ethylenediaminetetraacetic acid and some model compounds, it was clarified that there were at least two imidazole ligands bound copper (II) in pMMO.
-
Role of iron in particulate methane monooxygenase from Methylosinus trichosporium OB3b
Biometals, 1999Co-Authors: Masayuki Takeguchi, Masataka Ohashi, Ichiro Okura*Abstract:The effect of iron ions on particulate methane monooxygenase was studied by using the EDTA-treated membranes from Methylosinus trichosporium OB3b. When the membrane was treated with EDTA the activity remained 82% of the as-isolated membranes, and the activity of the EDTA-treated membranes was strongly influenced by the addition of metal ions. Among the metal ions, ferric, ferrous and cupric ions stimulated the activity, indicating those ions were needed for the activity. When propargylamine was added, pMMO activity decreased and also the iron ESR signal decreased. As the ESR signal involves the ferrous nitrosyl complex in EDTA-treated membranes, the active site of pMMO may contain a mononuclear non-heme iron.
Peter Adriaens - One of the best experts on this subject based on the ideXlab platform.
-
quantitative structure biodegradation relationships for ortho substituted biphenyl compounds oxidized by Methylosinus trichosporium ob3b
Environmental Toxicology and Chemistry, 2003Co-Authors: Angela S Lindner, Jeremy D Semrau, Callie Whitfield, Ning Chen, Peter AdriaensAbstract:: Methanotrophs, bacteria that thrive in the presence of stable methane and oxygen concentrations, can cometabolically oxidize ortho-substituted biphenyls to yield a variety of hydroxylated products. Despite awareness of the susceptibility of ortho-substituted biphenyls and other aromatic compounds to methanotrophic oxidation, the molecular properties relevant for predicting rates of methanotrophic oxidation are unknown. To this end, we have developed quantitative structure-biodegradation relationships using oxygen uptake activity by the type 2 methanotroph. Methylosinus trichosporium OB3b, expressing the soluble form of methane monooxygenase and in the presence of nine ortho-substituted biphenyls. Multivariate analysis yielded the strongest correlations using the initial slope of the oxygen uptake rate versus substrate concentration curve as the dependent variable. Quantum mechanical descriptors, including the sum of carbon charges on the substituted ring, the charge on the substituted carbon, and the width of compound calculated using computationally derived bond lengths and dihedral angles, correlated more strongly with oxygen uptake activity than did empirically derived electronic descriptors. The resulting models suggest a significant influence of substituent electronic nature and size and the involvement of the substituted carbon site in the oxidation of these compounds by M. trichosporium OB3b.
-
transformation of ortho substituted biphenyls by Methylosinus trichosporium ob3b substituent effects on oxidation kinetics and product formation
Archives of Microbiology, 2000Co-Authors: Angela S Lindner, Peter Adriaens, Jeremy D SemrauAbstract:The ability of Methylosinus trichosporium OB3b, expressing soluble methane monooxygenase, to oxidize a range of ortho-substituted biphenyls was examined to better understand how substituents affect both the rate and products of oxidation in comparison to biphenyl. Inhibition of oxidation was observed over the tested substrate range for both biphenyl and ortho-halogenated biphenyls (2-chloro-, 2-bromo-, and 2-iodobiphenyl). No inhibition was observed during the oxidation of 2-hydroxybiphenyl and 2-methylbiphenyl. Analysis of the products of oxidation showed that, depending on the substituent, ring hydroxylation, substituent oxidation, and elimination pathways could occur. The type and abundance of products formed along with the relatively high kinetic isotope effect observed for deuterated vs. nondeuterated biphenyl (k h/k d = 3.4±0.02) are consistent with mechanisms that include both hydrogen abstraction and NIH-shift pathways. Knowledge of these substituent-dependent reaction rates and mechanisms enhances our understanding of the methanotrophic aryl transformation potential and allows for better prediction of the formation of oxidized intermediates by methanotrophic bacteria.
Angela S Lindner - One of the best experts on this subject based on the ideXlab platform.
-
quantitative structure biodegradation relationships for ortho substituted biphenyl compounds oxidized by Methylosinus trichosporium ob3b
Environmental Toxicology and Chemistry, 2003Co-Authors: Angela S Lindner, Jeremy D Semrau, Callie Whitfield, Ning Chen, Peter AdriaensAbstract:: Methanotrophs, bacteria that thrive in the presence of stable methane and oxygen concentrations, can cometabolically oxidize ortho-substituted biphenyls to yield a variety of hydroxylated products. Despite awareness of the susceptibility of ortho-substituted biphenyls and other aromatic compounds to methanotrophic oxidation, the molecular properties relevant for predicting rates of methanotrophic oxidation are unknown. To this end, we have developed quantitative structure-biodegradation relationships using oxygen uptake activity by the type 2 methanotroph. Methylosinus trichosporium OB3b, expressing the soluble form of methane monooxygenase and in the presence of nine ortho-substituted biphenyls. Multivariate analysis yielded the strongest correlations using the initial slope of the oxygen uptake rate versus substrate concentration curve as the dependent variable. Quantum mechanical descriptors, including the sum of carbon charges on the substituted ring, the charge on the substituted carbon, and the width of compound calculated using computationally derived bond lengths and dihedral angles, correlated more strongly with oxygen uptake activity than did empirically derived electronic descriptors. The resulting models suggest a significant influence of substituent electronic nature and size and the involvement of the substituted carbon site in the oxidation of these compounds by M. trichosporium OB3b.
-
transformation of ortho substituted biphenyls by Methylosinus trichosporium ob3b substituent effects on oxidation kinetics and product formation
Archives of Microbiology, 2000Co-Authors: Angela S Lindner, Peter Adriaens, Jeremy D SemrauAbstract:The ability of Methylosinus trichosporium OB3b, expressing soluble methane monooxygenase, to oxidize a range of ortho-substituted biphenyls was examined to better understand how substituents affect both the rate and products of oxidation in comparison to biphenyl. Inhibition of oxidation was observed over the tested substrate range for both biphenyl and ortho-halogenated biphenyls (2-chloro-, 2-bromo-, and 2-iodobiphenyl). No inhibition was observed during the oxidation of 2-hydroxybiphenyl and 2-methylbiphenyl. Analysis of the products of oxidation showed that, depending on the substituent, ring hydroxylation, substituent oxidation, and elimination pathways could occur. The type and abundance of products formed along with the relatively high kinetic isotope effect observed for deuterated vs. nondeuterated biphenyl (k h/k d = 3.4±0.02) are consistent with mechanisms that include both hydrogen abstraction and NIH-shift pathways. Knowledge of these substituent-dependent reaction rates and mechanisms enhances our understanding of the methanotrophic aryl transformation potential and allows for better prediction of the formation of oxidized intermediates by methanotrophic bacteria.