Transformation of ortho -substituted biphenyls by Methylosinus trichosporium OB3b: substituent effects on oxidation kinetics and product formation

Lindner, Angela S.; Adriaens, Peter; Semrau, Jeremy D.

doi:10.1007/s002030000170

Cited by 20 publications

(32 citation statements)

References 23 publications

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“…The flasks were sealed with a rubber stopper threaded with glass wool–filled tubing to allow removal of headspace air, using a vacuum pump and subsequent filling with 99.99% methane (Strate Welding, Jacksonville, FL), as previously described (Lindner et al 2000). All enrichments were prepared in triplicate using 20% methane (v/v) in the headspace and incubated at 30°C with shaking at 250 rpm.…”

Section: Methodsmentioning

confidence: 99%

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Impacts of Co-Solvent Flushing on Microbial Populations Capable of Degrading Trichloroethylene

Ramakrishnan

Ogram²,

Lindner

2005

Environ Health Perspect

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With increased application of co-solvent flushing technologies for removal of nonaqueous phase liquids from groundwater aquifers, concern over the effects of the solvent on native microorganisms and their ability to degrade residual contaminant has also arisen. This study assessed the impact of ethanol flushing on the numbers and activity potentials of trichloroethylene (TCE)-degrading microbial populations present in aquifer soils taken immediately after and 2 years after ethanol flushing of a former dry cleaners site. Polymerase chain reaction analysis revealed soluble methane monooxygenase genes in methanotrophic enrichments, and 16S rRNA analysis identified Methylocystis parvus with 98% similarity, further indicating the presence of a type II methanotroph. Dissimilatory sulfite reductase genes in sulfate-reducing enrichments prepared were also observed. Ethanol flushing was simulated in columns packed with uncontaminated soils from the dry cleaners site that were dosed with TCE at concentrations observed in the field; after flushing, the columns were subjected to a continuous flow of 500 pore volumes of groundwater per week. Total acridine orange direct cell counts of the flushed and nonflushed soils decreased over the 15-week testing period, but after 5 weeks, the flushed soils maintained higher cell counts than the nonflushed soils. Inhibition of methanogenesis by sulfate reduction was observed in all column soils, as was increasing removal of total methane by soils incubated under methanotrophic conditions. These results showed that impacts of ethanol were not as severe as anticipated and imply that ethanol may mitigate the toxicity of TCE to the microorganisms.

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Section: Methodsmentioning

confidence: 99%

“…A qualitative assay was performed using naphthalene and tetrazotized ortho -dianisidine to detect activity of soluble methane monooxygenase (sMMO) in the enriched methanotrophic-mixed cultures, as previously described (Bowman et al 1993; Lindner et al 2000). …”

Section: Methodsmentioning

confidence: 99%

Impacts of Co-Solvent Flushing on Microbial Populations Capable of Degrading Trichloroethylene

Ramakrishnan

Ogram²,

Lindner

2005

Environ Health Perspect

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“…The mechanism of bioremediation of PAH involves ortho cleavage or meta cleavage type pathway, resulting in the formation of protocatechuates and catechols that are then converted to tricarboxylic acid cyclic intermediate (Kanaly and Harayama 2000). In the biodegradation of PCBs, the ability of methanotrophic bacterium Methylosinus trichosporium OB3b, expressing soluble methane monooxygenase, has been shown to oxidize a range of ortho-halogenated biphenyls (2-chloro-, 2-bromo-, and 2-iodobiphenyl) although at lower rates than the unsubstituted biphenyl (Lindner et al 2000). Hydroxylation is the dominant reaction during the degradation of the aromatic ring, followed by dehalogenation.…”

Section: Remediation Of Hazardous Organic Pollutants By Methanotrophsmentioning

confidence: 99%

“…This type of study provides a platform on how methanotrophs can be used in conjunction with anaerobic degraders for the removal of highly chlorinated biphenyls. Additional research is still needed to determine how the products of methanotrophic oxidation of ortho-substituted biphenyls are further oxidized by heterotrophic microorganisms to ensure complete mineralization (Lindner et al 2000). Some of the reports emphasize that polar regions are interesting because of the presence of POPs, transported by a complex mechanism involving successive volatilization and deposition steps from warmer areas toward cooler regions including Antarctica (Bengtson 2011).…”

Section: Remediation Of Hazardous Organic Pollutants By Methanotrophsmentioning

confidence: 99%

Methanotrophs: promising bacteria for environmental remediation

Pandey

Singh

et al. 2013

Int. J. Environ. Sci. Technol.

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Methanotrophs are unique and ubiquitous bacteria that utilize methane as a sole source of carbon and energy from the atmosphere. Besides, methanotrophs may also be targeted for bioremediation of diverse type of heavy metals and organic pollutants owing to the presence of broad-spectrum methane monooxygenases enzyme. They are highly specialized group of aerobic bacteria and have a unique capacity for oxidation of certain types of organic pollutants like alkanes, aromatics, halogenated alkenes, etc. Oxidation reactions are initiated by methane monooxygenases enzyme, which can be expressed by methanotrophs in the absence of copper. The present article describes briefly the concerns regarding the unusual reactivity and broad substrate profiles of methane monooxygenases, which indicate many potential applications in bioremediation of heavy metals and toxic organic compounds. Research is needed to develop understanding in plant-methanotrophs interactions that optimize methanotrophs utilization in the field of environmental remediation, while supporting other ecosystem services.

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“…It may be because methane is a small and unfunctionalized substrate that the hydrophobic pocket on the hydroxylase component of sMMO that has evolved to bind methane is also able to accommodate a very wide range of hydrocarbons and other molecules. Indeed, sMMO, whose known substrates number over 100, range in size from methane to naphthalene (2) and biphenyl (23), and also include carbon monoxide and ammonia (37), must surely be among the most catalytically versatile of all known enzymes.…”

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confidence: 99%

Mutagenesis of the “Leucine Gate” To Explore the Basis of Catalytic Versatility in Soluble Methane Monooxygenase

Borodina

Nichol

Dumont

et al. 2007

Appl Environ Microbiol

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Soluble methane monooxygenase (sMMO) from methane-oxidizing bacteria is a multicomponent nonheme oxygenase that naturally oxidizes methane to methanol and can also cooxidize a wide range of adventitious substrates, including mono-and diaromatic hydrocarbons. Leucine 110, at the mouth of the active site in the ␣ subunit of the hydroxylase component of sMMO, has been suggested to act as a gate to control the access of substrates to the active site. Previous crystallography of the wild-type sMMO has indicated at least two conformations of the enzyme that have the "leucine gate" open to different extents, and mutagenesis of homologous enzymes has indicated a role for this residue in the control of substrate range and regioselectivity with aromatic substrates. By further refinement of the system for homologous expression of sMMO that we developed previously, we have been able to prepare a range of site-directed mutations at position 110 in the ␣ subunit of sMMO. All the mutants (with Gly, Cys, Arg, and Tyr, respectively, at this position) showed relaxations of regioselectivity compared to the wild type with monoaromatic substrates and biphenyl, including the appearance of new products arising from hydroxylation at the 2-and 3-positions on the benzene ring. Mutants with the larger Arg and Trp residues at position 110 also showed shifts in regioselectivity during naphthalene hydroxylation from the 2-to the 1-position. No evidence that mutagenesis of Leu 110 could allow very large substrates to enter the active site was found, however, since the mutants (like the wild type) were inactive toward the triaromatic hydrocarbons anthracene and phenanthrene. Thus, our results indicate that the "leucine gate" in sMMO is more important in controlling the precision of regioselectivity than the sizes of substrates that can enter the active site.Soluble methane monooxygenase (sMMO) is one of two enzyme systems via which methane-oxidizing bacteria catalyze the oxygenation of methane to methanol, which is the particularly challenging first step in the metabolism of the kinetically unreactive methane molecule (28). sMMO is a multicomponent enzyme encoded by the six-gene operon mmoXYBZDC, in which the active binuclear iron center (8,45) that is the site of methane oxidation resides within the ␣ subunit of the hydroxylase component, encoded by mmoX (5). It may be because methane is a small and unfunctionalized substrate that the hydrophobic pocket on the hydroxylase component of sMMO that has evolved to bind methane is also able to accommodate a very wide range of hydrocarbons and other molecules. Indeed, sMMO, whose known substrates number over 100, range in size from methane to naphthalene (2) and biphenyl (23), and also include carbon monoxide and ammonia (37), must surely be among the most catalytically versatile of all known enzymes.The unusual catalytic versatility of sMMO has led to interest in its potential as a biocatalyst for bioremediation and synthetic chemistry as well as an interest in how the structure of the enzyme facil...

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Transformation of ortho -substituted biphenyls by Methylosinus trichosporium OB3b: substituent effects on oxidation kinetics and product formation

Cited by 20 publications

References 23 publications

Impacts of Co-Solvent Flushing on Microbial Populations Capable of Degrading Trichloroethylene

Impacts of Co-Solvent Flushing on Microbial Populations Capable of Degrading Trichloroethylene

Methanotrophs: promising bacteria for environmental remediation

Mutagenesis of the “Leucine Gate” To Explore the Basis of Catalytic Versatility in Soluble Methane Monooxygenase

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