201
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Wilkins PC, Dalton H, Podmore ID, Deighton N, Symons MC. Biological methane activation involves the intermediacy of carbon-centered radicals. EUROPEAN JOURNAL OF BIOCHEMISTRY 1992; 210:67-72. [PMID: 1332869 DOI: 10.1111/j.1432-1033.1992.tb17391.x] [Citation(s) in RCA: 25] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
The spin-trapping technique has demonstrated that carbon-centered radicals are produced during soluble-methane-monooxygenase catalysis of the hydroxylation of several different types of substrate. The resulting spin-adducts were identified from the hyperfine splitting constants in their EPR spectra. Isotopic labelling showed unequivocally that the trapped radicals were derived from substrate. The carbon-centered substrate radicals are believed to result from hydrogen-atom abstraction by a ferryl species in a cytochrome-P-450-like mechanism. No hydroxy radical nor an oxygen-based radical of any kind was detected in any of the spin-trapping experiments.
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Affiliation(s)
- P C Wilkins
- Department of Biological Sciences, University of Warwick, Coventry, England
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202
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Rosenzweig AC, Frederick CA, Lippard SJ. Crystallization and preliminary X-ray analysis of the methane monooxygenase hydroxylase protein from Methylococcus capsulatus (Bath). J Mol Biol 1992; 227:583-5. [PMID: 1404375 DOI: 10.1016/0022-2836(92)90913-5] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Methane monooxygenase is a multicomponent enzyme system that catalyzes the conversion of methane to methanol in methanotrophic bacteria. Catalysis occurs at non-heme dinuclear iron centers contained in the hydroxylase component of the system, a dimer of composition alpha 2 beta 2 gamma 2. The hydroxylase protein from Methylococcus capsulatus (Bath) has been crystallized from aqueous solutions containing polyethylene glycol, lithium sulfate, and ammonium acetate. The crystals are orthorhombic, space group P2(1)2(1)2(1), with one dimer of relative molecular mass M(r) = 252,000 in the asymmetric unit. The unit cell dimensions are a = 62.6 A, b = 110.1 A, c = 333.5 A. The crystals diffract uniformly beyond 2.5 A resolution. Crystals of the related hydroxylase from Methylosinus trichosporium OB3b have also been obtained.
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Affiliation(s)
- A C Rosenzweig
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge 02139
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203
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Uchiyama H, Nakajima T, Yagi O, Nakahara T. Role of heterotrophic bacteria in complete mineralization of trichloroethylene by Methylocystis sp. strain M. Appl Environ Microbiol 1992; 58:3067-71. [PMID: 1444420 PMCID: PMC183049 DOI: 10.1128/aem.58.9.3067-3071.1992] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
Biodegradation experiments with radioactively labeled trichloroethylene showed that 32% of the radioactive carbon was converted to glyoxylic acid, dichloroacetic acid and trichloroacetic acid and that the same percentage was converted to CO2 and CO after 140 h of incubation by a pure culture of a type II methane-utilizing bacterium, Methylocystis sp. strain M, isolated from a mixed culture, MU-81, in our laboratory. In contrast, these water-soluble (14C)trichloroethylene degradation products were completely or partially degraded further and converted to CO2 by the MU-81 mixed culture. This phenomenon was attributed to the presence of a heterotrophic bacterium (strain DA4), which was identified as Xanthobacter autotrophicus, in the MU-81 culture. The results indicate that the heterotrophic bacteria play an important role in complete trichloroethylene degradation by methanotrophs.
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Affiliation(s)
- H Uchiyama
- National Institute for Environmental Studies, Onogawa, Japan
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204
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Oremland RS, Culbertson CW. Evaluation of Methyl Fluoride and Dimethyl Ether as Inhibitors of Aerobic Methane Oxidation. Appl Environ Microbiol 1992; 58:2983-92. [PMID: 16348771 PMCID: PMC183037 DOI: 10.1128/aem.58.9.2983-2992.1992] [Citation(s) in RCA: 73] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Methyl fluoride (MF) and dimethyl ether (DME) were effective inhibitors of aerobic methanotrophy in a variety of soils. MF and DME blocked consumption of CH
4
as well as the oxidation of
14
CH
4
to
14
CO
2
, but neither MF nor DME affected the oxidation of [
14
C]methanol or [
14
C]formate to
14
CO
2
. Cooxidation of ethane and propane by methane-oxidizing soils was also inhibited by MF. Nitrification (ammonia oxidation) in soils was inhibited by both MF and DME. Production of N
2
O via nitrification was inhibited by MF; however, MF did not affect N
2
O production associated with denitrification. Methanogenesis was partially inhibited by MF but not by DME. Methane oxidation was ∼100-fold more sensitive to MF than was methanogenesis, indicating that an optimum concentration could be employed to selectively block methanotrophy. MF inhibited methane oxidation by cell suspensions of
Methylococcus capsulatus
; however, DME was a much less effective inhibitor.
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Affiliation(s)
- R S Oremland
- U.S. Geological Survey, ms 465, 345 Middlefield Road, Menlo Park, California 94025
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205
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Ensign SA, Hyman MR, Arp DJ. Cometabolic degradation of chlorinated alkenes by alkene monooxygenase in a propylene-grown Xanthobacter strain. Appl Environ Microbiol 1992; 58:3038-46. [PMID: 1444418 PMCID: PMC183045 DOI: 10.1128/aem.58.9.3038-3046.1992] [Citation(s) in RCA: 76] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
Propylene-grown Xanthobacter cells (strain Py2) degraded several chlorinated alkenes of environmental concern, including trichloroethylene, 1-chloroethylene (vinyl chloride), cis- and trans-1,2-dichloroethylene, 1,3-dichloropropylene, and 2,3-dichloropropylene. 1,1-Dichloroethylene was not degraded efficiently, while tetrachloroethylene was not degraded. The role of alkene monooxygenase in catalyzing chlorinated alkene degradations was established by demonstrating that glucose-grown cells which lack alkene monooxygenase and propylene-grown cells in which alkene monooxygenase was selectively inactivated by propyne were unable to degrade the compounds. C2 and C3 chlorinated alkanes were not oxidized by alkene monooxygenase, but a number of these compounds were inhibitors of propylene and ethylene oxidation, suggesting that they compete for binding to the enzyme. A number of metabolites enhanced the rate of degradation of chlorinated alkenes, including propylene oxide, propionaldehyde, and glucose. Propylene stimulated chlorinated alkene oxidation slightly when present at a low concentration but became inhibitory at higher concentrations. Toxic effects associated with chlorinated alkene oxidations were determined by measuring the propylene oxidation and propylene oxide-dependent O2 uptake rates of cells previously incubated with chlorinated alkenes. Compounds which were substrates for alkene monooxygenase exhibited various levels of toxicity, with 1,1-dichloroethylene and trichloroethylene being the most potent inactivators of propylene oxidation and 1,3- and 2,3-dichloropropylene being the most potent inactivators of propylene oxide-dependent O2 uptake. No toxic effects were seen when cells were incubated with chlorinated alkenes anaerobically, indicating that the product(s) of chlorinated alkene oxidation mediates toxicity.
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Affiliation(s)
- S A Ensign
- Laboratory for Nitrogen Fixation Research, Oregon State Univrsity, Corvallis 97331-2902
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206
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Froland W, Andersson K, Lee S, Liu Y, Lipscomb J. Methane monooxygenase component B and reductase alter the regioselectivity of the hydroxylase component-catalyzed reactions. A novel role for protein-protein interactions in an oxygenase mechanism. J Biol Chem 1992. [DOI: 10.1016/s0021-9258(19)37083-8] [Citation(s) in RCA: 78] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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207
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Graham DW, Korich DG, LeBlanc RP, Sinclair NA, Arnold RG. Applications of a colorimetric plate assay for soluble methane monooxygenase activity. Appl Environ Microbiol 1992; 58:2231-6. [PMID: 1637160 PMCID: PMC195760 DOI: 10.1128/aem.58.7.2231-2236.1992] [Citation(s) in RCA: 74] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
A straightforward method is described for screening methanotrophic colonies for soluble methane monooxygenase (sMMO) activity on solid media. Such activity results in the development of a colored complex between 1-naphthol, which is formed when sMMO reacts with naphthalene, and o-dianisidine (tetrazotized). Methanotrophic colonies expressing sMMO turned deep purple when exposed successively to naphthalene and o-dianisidine. The method was evaluated within the contexts of two potential applications. The first was for the enumeration of Methylosinus trichosporium OB3b in a methane-amended, unsaturated soil column dedicated to vinyl chloride treatment. The second application was for the isolation and enumeration of sMMO-bearing methanotrophs from sanitary landfill soils. The technique was effective in both applications.
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Affiliation(s)
- D W Graham
- Department of Civil Engineering and Engineering Mechanics, University of Arizona, Tucson 85721
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208
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Alvarez-Cohen L, McCarty PL, Boulygina E, Hanson RS, Brusseau GA, Tsien HC. Characterization of a methane-utilizing bacterium from a bacterial consortium that rapidly degrades trichloroethylene and chloroform. Appl Environ Microbiol 1992; 58:1886-93. [PMID: 1377902 PMCID: PMC195700 DOI: 10.1128/aem.58.6.1886-1893.1992] [Citation(s) in RCA: 46] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
A mixed culture of bacteria grown in a bioreactor with methane as a carbon and energy source rapidly oxidized trichloroethylene and chloroform. The most abundant organism was a crescent-shaped bacterium that bound the fluorescent oligonucleotide signature probes that specifically hybridize to serine pathway methylotrophs. The 5S rRNA from this bacterium was found to be 93.5% homologous to the Methylosinus trichosporium OB3b 5S RNA sequence. A type II methanotrophic bacterium, isolated in pure culture from the bioreactor, synthesized soluble methane monooxygenase during growth in a copper-limited medium and was also capable of rapid trichloroethylene oxidation. The bacterium contained the gene that encodes the soluble methane monooxygenase B component on an AseI restriction fragment identical in size to a restriction fragment present in AseI digests of DNA from bacteria in the mixed culture. The sequence of the 16S rRNA from the pure culture was found to be 92 and 94% homologous to the 16S rRNAs of M. trichosporium OB3b and M. sporium, respectively. Both the pure and mixed cultures oxidized naphthalene to naphthol, indicating the presence of soluble methane monooxygenase. The mixed culture also synthesized soluble methane monooxygenase, as evidenced by the presence of proteins that cross-reacted with antibodies prepared against purified soluble methane monooxygenase components from M. trichosporium OB3b on Western blots (immunoblots). It was concluded that a type II methanotrophic bacterium phylogenetically related to Methylosinus species synthesizes soluble methane monooxygenase and is responsible for trichloroethylene oxidation in the bioreactor.
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Affiliation(s)
- L Alvarez-Cohen
- Department of Civil Engineering, University of California, Berkeley 94720
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209
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Abstract
Trichloroethylene was oxidized by purified toluene dioxygenase obtained from recombinant E. coli strains. The major oxidation products were formic acid and glyoxylic acid. Other potential products, dichloroacetic acid, chloral, phosgene, carbon monoxide, and carbon dioxide, were not detected. [14C]trichloroethylene became covalently attached to protein components and NADPH suggesting non-specific alkylation by reactive products. Oxidation of deuterated trichloroethylene yielded 50.2% deuterated formate. Oxidation of trichloroethylene in D2O yielded 43.7% deuterated formate. These data indicate that both carbon atoms are giving rise to formic acid. The results are consistent with a mechanism of TCE oxygenation not involving epoxide, dioxetane, or dihydroxy intermediates and indicate significant differences from those previously proposed for cytochrome P-450 (Miller, R.E. & Guengerich, F.P. (1982) Biochemistry 21, 1090-1097) or methane monooxygenase (Fox, B.G., Borneman, B.G., Wackett, L.P., & Lipscomb, J.D. (1990) Biochemistry 29, 6419-6227).
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Affiliation(s)
- S Li
- Department of Biochemistry, University of Minnesota, Navarre, MN 55392
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210
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Modulation of the epidermal growth factor mitogenic response by metabolites of linoleic and arachidonic acid in Syrian hamster embryo fibroblasts. Differential effects in tumor suppressor gene (+) and (-) phenotypes. J Biol Chem 1992. [DOI: 10.1016/s0021-9258(19)50085-0] [Citation(s) in RCA: 107] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
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211
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Ormö M, deMaré F, Regnström K, Aberg A, Sahlin M, Ling J, Loehr T, Sanders-Loehr J, Sjöberg B. Engineering of the iron site in ribonucleotide reductase to a self-hydroxylating monooxygenase. J Biol Chem 1992. [DOI: 10.1016/s0021-9258(19)50335-0] [Citation(s) in RCA: 55] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
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212
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Abstract
Mycobacterium aurum L1, capable of growth on vinyl chloride as a sole carbon and energy source, was previously isolated from soil contaminated with vinyl chloride (S. Hartmans et al., Biotechnol. Lett. 7:383-388, 1985). The initial step in vinyl chloride metabolism in strain L1 is catalyzed by alkene monooxygenase, transforming vinyl chloride into the reactive epoxide chlorooxirane. The enzyme responsible for chlorooxirane degradation appeared to be very unstable and thus hampered the characterization of the second step in vinyl chloride metabolism. Dichloroethenes are also oxidized by vinyl chloride-grown cells of strain L1, but they are not utilized as growth substrates. Three additional bacterial strains which utilize vinyl chloride as a sole carbon and energy source were isolated from environments with no known vinyl chloride contamination. The three new isolates were similar to strain L1 and were also identified as Mycobacterium aurum.
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Affiliation(s)
- S Hartmans
- Division of Industrial Microbiology, Department of Food Science, Wageningen Agricultural University, The Netherlands
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213
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14C2H2- and 14CO2-labeling studies of the de novo synthesis of polypeptides by Nitrosomonas europaea during recovery from acetylene and light inactivation of ammonia monooxygenase. J Biol Chem 1992. [DOI: 10.1016/s0021-9258(18)45979-0] [Citation(s) in RCA: 152] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
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214
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King GM. Ecological Aspects of Methane Oxidation, a Key Determinant of Global Methane Dynamics. ADVANCES IN MICROBIAL ECOLOGY 1992. [DOI: 10.1007/978-1-4684-7609-5_9] [Citation(s) in RCA: 154] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
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215
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Trichloroethylene oxidation by the membrane-associated methane monooxygenase in type I, type II and type X methanotrophs. Biodegradation 1992. [DOI: 10.1007/bf00124489] [Citation(s) in RCA: 52] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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216
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Jacobs MH, Van den Wijngaard AJ, Pentenga M, Janssen DB. Characterization of the epoxide hydrolase from an epichlorohydrin-degrading Pseudomonas sp. EUROPEAN JOURNAL OF BIOCHEMISTRY 1991; 202:1217-22. [PMID: 1662605 DOI: 10.1111/j.1432-1033.1991.tb16493.x] [Citation(s) in RCA: 58] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
An epoxide hydrolase was purified to homogeneity from the epichlorohydrin-utilizing bacterium Pseudomonas sp. strain AD1. The enzyme was found to be a monomeric protein with a molecular mass of 35 kDa. With epichlorohydrin as the substrate, the enzyme followed Michaelis-Menten kinetics with a Km value of 0.3 mM and a Vmax of 34 mumol.min-1.mg protein-1. The epoxide hydrolase catalyzed the hydrolysis of several epoxides, including epichlorohydrin, epibromohydrin, epoxyoctane and styrene epoxide. With all chiral compounds tested, both stereoisomers were converted. Amino acid sequencing of cyanogen bromide-generated peptides did not yield sequences with similarities to other known proteins.
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Affiliation(s)
- M H Jacobs
- Department of Biochemistry, University of Groningen, The Netherlands
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217
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218
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Rataj M, Kauth J, Donnelly M. Oxidation of deuterated compounds by high specific activity methane monooxygenase from Methylosinus trichosporium. Mechanistic implications. J Biol Chem 1991. [DOI: 10.1016/s0021-9258(18)55117-6] [Citation(s) in RCA: 56] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
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219
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Rasche ME, Hyman MR, Arp DJ. Factors Limiting Aliphatic Chlorocarbon Degradation by
Nitrosomonas europaea
: Cometabolic Inactivation of Ammonia Monooxygenase and Substrate Specificity. Appl Environ Microbiol 1991; 57:2986-94. [PMID: 16348568 PMCID: PMC183909 DOI: 10.1128/aem.57.10.2986-2994.1991] [Citation(s) in RCA: 104] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The soil nitrifying bacterium
Nitrosomonas europaea
is capable of degrading trichloroethylene (TCE) and other halogenated hydrocarbons. TCE cometabolism by
N. europaea
resulted in an irreversible loss of TCE biodegradative capacity, ammonia-oxidizing activity, and ammonia-dependent O
2
uptake by the cells. Inactivation was not observed in the presence of allylthiourea, a specific inhibitor of the enzyme ammonia monooxygenase, or under anaerobic conditions, indicating that the TCE-mediated inactivation required ammonia monooxygenase activity. When
N. europaea
cells were incubated with [
14
C]TCE under conditions which allowed turnover of ammonia monooxygenase, a number of cellular proteins were covalently labeled with
14
C. Treatment of cells with allylthiourea or acetylene prior to incubation with [
14
C]TCE prevented incorporation of
14
C into proteins. The ammonia-oxidizing activity of cells inactivated in the presence of TCE could be recovered through a process requiring de novo protein synthesis. In addition to TCE, a series of chlorinated methanes, ethanes, and other ethylenes were screened as substrates for ammonia monooxygenase and for their ability to inactivate the ammonia-oxidizing system of
N. europaea
. The chlorocarbons could be divided into three classes depending on their biodegradability and inactivating potential: (i) compounds which were not biodegradable by
N. europaea
and which had no toxic effect on the cells; (ii) compounds which were cooxidized by
N. europaea
and had little or no toxic effect on the cells; and (iii) compounds which were cooxidized and produced a turnover-dependent inactivation of ammonia oxidation by
N. europaea
.
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Affiliation(s)
- M E Rasche
- Laboratory for Nitrogen Fixation Research, Department of Botany and Plant Pathology, 2082 Cordley Hall, Oregon State University, Corvallis, Oregon 97331-2902
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220
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Newman LM, Wackett LP. Fate of 2,2,2-trichloroacetaldehyde (chloral hydrate) produced during trichloroethylene oxidation by methanotrophs. Appl Environ Microbiol 1991; 57:2399-402. [PMID: 1768109 PMCID: PMC183583 DOI: 10.1128/aem.57.8.2399-2402.1991] [Citation(s) in RCA: 31] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
Four different methanotrophs expressing soluble methane monooxygenase produced 2,2,2-trichloroacetaldehyde, or chloral hydrate, a controlled substance, during the oxidation of trichloroethylene. Chloral hydrate concentrations decreased in these cultures between 1 h and 24 h of incubation. Chloral hydrate was shown to be biologically transformed to trichloroethanol and trichloroacetic acid by Methylosinus trichosporium OB3b. At elevated pH and temperature, chloral hydrate readily decomposed and chloroform and formic acid were detected as products.
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Affiliation(s)
- L M Newman
- Gray Freshwater Biological Institute, University of Minnesota, Navarre 55392
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221
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Liu K, Lippard S. Redox properties of the hydroxylase component of methane monooxygenase from Methylococcus capsulatus (Bath). Effects of protein B, reductase, and substrate. J Biol Chem 1991. [DOI: 10.1016/s0021-9258(18)98768-5] [Citation(s) in RCA: 29] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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222
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Shields MS, Montgomery SO, Cuskey SM, Chapman PJ, Pritchard PH. Mutants of Pseudomonas cepacia G4 defective in catabolism of aromatic compounds and trichloroethylene. Appl Environ Microbiol 1991; 57:1935-41. [PMID: 1892384 PMCID: PMC183502 DOI: 10.1128/aem.57.7.1935-1941.1991] [Citation(s) in RCA: 71] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Pseudomonas cepacia G4 possesses a novel pathway of toluene catabolism that is shown to be responsible for the degradation of trichloroethylene (TCE). This pathway involves conversion of toluene via o-cresol to 3-methylcatechol. In order to determine the enzyme of toluene degradation that is responsible for TCE degradation, chemically induced mutants, blocked in the toluene ortho-monooxygenase (TOM) pathway of G4, were examined. Mutants of the phenotypic class designated TOM A- were all defective in their ability to oxidize toluene, o-cresol, m-cresol, and phenol, suggesting that a single enzyme is responsible for conversion of these compounds to their hydroxylated products (3-methylcatechol from toluene, o-cresol, and m-cresol and catechol from phenol) in the wild type. Mutants of this class did not degrade TCE. Two other mutant classes which were blocked in toluene catabolism, TOM B-, which lacked catechol-2,3-dioxygenase, and TOM C-, which lacked 2-hydroxy-6-oxoheptadienoic acid hydrolase activity, were fully capable of TCE degradation. Therefore, TCE degradation is directly associated with the monooxygenation capability responsible for toluene, cresol, and phenol hydroxylation.
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Affiliation(s)
- M S Shields
- Technical Resources Inc., Gulf Breeze, Florida
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223
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Henry SM, Grbić-Galić D. Inhibition of trichloroethylene oxidation by the transformation intermediate carbon monoxide. Appl Environ Microbiol 1991; 57:1770-6. [PMID: 1908211 PMCID: PMC183466 DOI: 10.1128/aem.57.6.1770-1776.1991] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Inhibition of trichloroethylene (TCE) oxidation by the transformation intermediate carbon monoxide (CO) was evaluated with the aquifer methanotroph Methylomonas sp. strain MM2. CO was a TCE transformation intermediate. During TCE oxidation, approximately 9 mol% of the TCE was transformed to CO. CO was oxidized by Methylomonas sp. strain MM2, and when formate was provided as an electron donor, the CO oxidation rate doubled. The rate of CO oxidation without formate was 4.6 liter mg (dry weight)-1 day-1, and the rate with formate was 10.2 liter mg (dry weight)-1 day-1. CO inhibited TCE oxidation, both by exerting a demand for reductant and through competitive inhibition. The Ki for CO inhibition of TCE oxidation, 4.2 microM, was much less than the Ki for methane inhibition of TCE oxidation, 116 microM. CO also inhibited methane oxidation, and the degree of inhibition increased with increasing CO concentration. When CO was present, formate amendment was necessary for methane oxidation to occur and both substrates were simultaneously oxidized. CO at a concentration greater than that used in the inhibition studies was not toxic to Methylomonas sp. strain MM2.
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Affiliation(s)
- S M Henry
- Department of Civil Engineering, Stanford University, California 94305-4020
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224
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Alvarez-Cohen L, McCarty PL. Product toxicity and cometabolic competitive inhibition modeling of chloroform and trichloroethylene transformation by methanotrophic resting cells. Appl Environ Microbiol 1991; 57:1031-7. [PMID: 1905516 PMCID: PMC182841 DOI: 10.1128/aem.57.4.1031-1037.1991] [Citation(s) in RCA: 155] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
The rate and capacity for chloroform (CF) and trichloroethylene (TCE) transformation by a mixed methanotrophic culture of resting cells (no exogenous energy source) and formate-fed cells were measured. As reported previously for TCE, formate addition resulted in an increased CF transformation rate (0.35 day-1 for resting cells and 1.5 day-1 for formate-fed cells) and transformation capacity (0.0065 mg of CF per mg of cells for resting cells and 0.015 mg of CF per mg of cells for formate-fed cells), suggesting that depletion of energy stores affects transformation behavior. The observed finite transformation capacity, even with an exogenous energy source, suggests that toxicity was also a factor. CF transformation capacity was significantly lower than that for TCE, suggesting a greater toxicity from CF transformation. The toxicity of CF, TCE, and their transformation products to whole cells was evaluated by comparing the formate oxidation activity of acetylene-treated cells to that of non-acetylene-treated cells with and without prior exposure to CF or TCE. Acetylene arrests the activity of methane monooxygenase in CF and TCE oxidation without halting cell activity toward formate. Significantly diminished formate oxidation by cells exposed to either CR or TCE without acetylene compared with that with acetylene suggests that the solvents themselves were not toxic under the experimental conditions but their transformation products were. The concurrent transformation of CF and TCE by resting cells was measured, and results were compared with predictions from a competitive-inhibition cometabolic transformation model. The reasonable fit between model predictions and experimental observations was supportive of model assumptions.
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Affiliation(s)
- L Alvarez-Cohen
- Department of Civil Engineering, University of California, Berkeley 94720
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225
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Oldenhuis R, Oedzes JY, van der Waarde JJ, Janssen DB. Kinetics of chlorinated hydrocarbon degradation by Methylosinus trichosporium OB3b and toxicity of trichloroethylene. Appl Environ Microbiol 1991; 57:7-14. [PMID: 2036023 PMCID: PMC182657 DOI: 10.1128/aem.57.1.7-14.1991] [Citation(s) in RCA: 166] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
The kinetics of the degradation of trichloroethylene (TCE) and seven other chlorinated aliphatic hydrocarbons by Methylosinus trichosporium OB3b were studied. All experiments were performed with cells grown under copper stress and thus expressing soluble methane monooxygenase. Compounds that were readily degraded included chloroform, trans-1,2-dichloroethylene, and TCE, with Vmax values of 550, 330, and 290 nmol min-1 mg of cells-1, respectively. 1,1-Dichloroethylene was a very poor substrate. TCE was found to be toxic for the cells, and this phenomenon was studied in detail. Addition of activated carbon decreased the acute toxicity of high levels of TCE by adsorption, and slow desorption enabled the cells to partially degrade TCE. TCE was also toxic by inactivating the cells during its conversion. The degree of inactivation was proportional to the amount of TCE degraded; maximum degradation occurred at a concentration of 2 mumol of TCE mg of cells-1. During conversion of [14C]TCE, various proteins became radiolabeled, including the alpha-subunit of the hydroxylase component of soluble methane monooxygenase. This indicated that TCE-mediated inactivation of cells was caused by nonspecific covalent binding of degradation products to cellular proteins.
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Affiliation(s)
- R Oldenhuis
- Department of Biochemistry, University of Groningen, The Netherlands
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226
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Fox BG, Liu Y, Dege JE, Lipscomb JD. Complex formation between the protein components of methane monooxygenase from Methylosinus trichosporium OB3b. Identification of sites of component interaction. J Biol Chem 1991. [DOI: 10.1016/s0021-9258(18)52470-4] [Citation(s) in RCA: 127] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
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227
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Duine JA, van Dijken JP. Enzymes of industrial potential from methylotrophs. BIOTECHNOLOGY (READING, MASS.) 1991; 18:233-52. [PMID: 1909915 DOI: 10.1016/b978-0-7506-9188-8.50017-6] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
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228
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Brusseau GA, Tsien HC, Hanson RS, Wackett LP. Optimization of trichloroethylene oxidation by methanotrophs and the use of a colorimetric assay to detect soluble methane monooxygenase activity. Biodegradation 1990; 1:19-29. [PMID: 1368139 DOI: 10.1007/bf00117048] [Citation(s) in RCA: 172] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Methylosinus trichosporium OB3b biosynthesizes a broad specificity soluble methane monooxygenase that rapidly oxidizes trichloroethylene (TCE). The selective expression of the soluble methane monooxygenase was followed in vivo by a rapid colorimetric assay. Naphthalene was oxidized by purified soluble methane monooxygenase or by cells grown in copper-deficient media to a mixture of 1-naphthol and 2-naphthol. The naphthols were detected by reaction with tetrazotized o-dianisidine to form purple diazo dyes with large molar absorptivities. The rate of color formation with the rapid assay correlated with the velocity of TCE oxidation that was determined by gas chromatography. Both assays were used to optimize conditions for TCE oxidation by M. trichosporium OB3b and to test several methanotrophic bacteria for the ability to oxidize TCE and naphthalene.
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Affiliation(s)
- G A Brusseau
- Gray Freshwater Biological Institute, University of Minnesota, Navarre 55392
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