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degradation of halogenated aliphatic compounds by xanthobacter autotrophicus gj10.a bacterium that is able to utilize a number of halogenated short-chain hydrocarbons and halogenated carboxylic acids as sole carbon source for growth was identified as a strain of xanthobacter autotrophicus. the organism constitutively produces two different dehalogenases. one enzyme is specific for halogenated alkanes, whereas the other, which is more heat stable and has a higher ph optimum, is specific for halogenated carboxylic acids. haloalkanes were hydrolyzed in cell extracts to produce a ...19853994371
degradation of 1,2-dichloroethane by ancylobacter aquaticus and other facultative methylotrophs.cultures of the newly isolated bacterial strains ad20, ad25, and ad27, identified as strains of ancylobacter aquaticus, were capable of growth on 1,2-dichloroethane (dce) as the sole carbon and energy source. these strains, as well as two other new dce utilizers, were facultative methylotrophs and were also able to grow on 2-chloroethanol, chloroacetate, and 2-chloropropionate. in all strains tested, dce was degraded by initial hydrolytic dehalogenation to 2-chloroethanol, followed by oxidation ...19921575500
propachlor degradation by a soil bacterial community.soil from a pesticide disposal site was used to enrich for microorganisms that degraded the acylanilide herbicide propachlor (2-chloro-n-isopropylacetanilide). after seven transfers of the enrichment, the culture contained about six strains. the highest yield of microbial biomass occurred if just two of these isolates, strains dak3 and mab2, were inoculated into a mineral salts medium containing propachlor. when only strain dak3 was grown on propachlor, a metabolite (2-chloro-n-isopropylacetamid ...19911768085
involvement of a large plasmid in the degradation of 1,2-dichloroethane by xanthobacter autotrophicus.xanthobacter autotrophicus gj10 is a bacterium that can degrade short-chain halogenated aliphatic compounds such as 1,2-dichloroethane. a 200-kb plasmid, pxau1, was isolated from this strain and shown to contain the dhla gene, which codes for haloalkane dehalogenase, the first enzyme in the degradation pathway of 1,2-dichloroethane by gj10. loss of pxau1 resulted in loss of haloalkane dehalogenase activity, significantly decreased chloroacetaldehyde dehydrogenase activity, and loss of resistance ...19911872615
isolation and characterization of the facultative methylotroph mycobacterium id-y.a facultatively methylotrophic mycobacterium was isolated from cleveland harbor, ohio, usa. the isolate, designated id-y, used a wide range of carbon and energy sources including methane and several other hydrocarbons. it displayed a growth cycle from rod-shaped exponential-phase cells, with many cell pairs exhibiting v-formation, to cocco-bacillary stationary-phase cells. a fixation technique involving glutaraldehyde/alcian blue resulted in the observation of a three-layered cell wall. isolate ...19873655742
isolation, complementation and partial characterization of mutants of the methanol autotroph xanthobacter h4-14 defective in methanol dissimilation.seven mutants of xanthobacter h4-14, unable to grow on methanol but capable of growth on formate, were isolated and complemented with a chromosomal clone bank constructed in the broad-host-range cosmid pvk100. one mutant could not be complemented but the others fell into four distinct complementation groups that involved three different recombinant clones. all of the complementing regions were separated by at least 10 kbp. the five complementation classes had different phenotypic characteristics ...19873312480
degradation of 3-chloro-2-methylpropionic acid by xanthobacter sp. cimw 99.both stereoisomers of 3-chloro-2-methylpropionic acid (cmpa) and its methyl esters (mecmpa) serve as growth substrates for a bacterial isolate (xanthobacter sp. cimw 99) when supplied as sole source of carbon and energy. biodegradation of dl-cmpa and dl-mecmpa was shown to be via a common pathway; an initial, constitutive, esterase converted the methyl ester to the corresponding carboxylic acid. further metabolism required the activation of cmpa involving a coa-, atp-, mg(2+)-dependent chloroacy ...19911368112
cloning of 1,2-dichloroethane degradation genes of xanthobacter autotrophicus gj10 and expression and sequencing of the dhla gene.a gene bank from the chlorinated hydrocarbon-degrading bacterium xanthobacter autotrophicus gj10 was prepared in the broad-host-range cosmid vector plafr1. by using mutants impaired in dichloroethane utilization and strains lacking dehalogenase activities, several genes involved in 1,2-dichloroethane metabolism were isolated. the haloalkane dehalogenase gene dhla was subcloned, and it was efficiently expressed from its own constitutive promoter in strains of a pseudomonas sp., escherichia coli, ...19892687254
organization of genes necessary for growth of the hydrogen-methanol autotroph xanthobacter sp. strain h4-14 on hydrogen and carbon dioxide.mutants unable to grow on h2 and co2 were isolated in the hydrogen-methanol autotroph xanthobacter sp. strain h4-14 and complemented with a clone bank constructed in a broad-host-range cosmid vector. the mutants fell into two classes. class i mutants (cfx-) cannot grow on hydrogen or methanol and are deficient in one or more of the key enzymes of the calvin cycle. class ii mutants (hox-) can grow on methanol but not on hydrogen and lack hydrogenase activity. restriction maps of the complementing ...19852987188
characterization of an fmn-containing cyclohexanone monooxygenase from a cyclohexane-grown xanthobacter sp.a soluble cyclohexanone monooxygenase was purified 16.1-fold to homogeneity from a xanthobacter sp. grown upon cyclohexane as sole source of carbon and energy. the native enzyme is a 50-kda single polypeptide chain associated with fmn rather than fad as flavin prosthetic group in a 1:1 stoichiometric relationship. the monooxygenase catalyses the transformation of cyclohexanone to the lactone 1-oxa-2-oxocycloheptane in an oxygen ring insertion reaction. only related cycloalkanone substrates are a ...19892540966
uniform designation for genes of the calvin-benson-bassham reductive pentose phosphate pathway of bacteria.structural and regulatory genes encoding enzymes and proteins of the reductive pentose phosphate pathway have been isolated from a number of bacteria recently. in the phototroph rhodobacter sphaeroides, and in two chemoautotrophic bacteria, alcaligenes eutrophus and xanthobacter flavus, these genes have been found in distinct operons. however, in these three organisms and in other bacteria where certain of these genes have been discovered, a uniform nomenclature to designate these genes has been ...19921490592
lack of homology between two haloacetate dehalogenase genes encoded on a plasmid from moraxella sp. strain b.two genes encoding haloacetate dehalogenases, h-1 and h-2, are closely linked on a plasmid from moraxella sp. strain b. h-1 predominantly acts on fluoroacetate, but h-2 does not. to elucidate the molecular relationship between the two enzymes, we compared their structural genes. two restriction fragments of the plasmid dna were subcloned on m13 phages and their nucleotide sequences were determined. the sequence of each fragment contained an open reading frame that was identified as the structura ...19921512562
nucleotide sequences of the genes encoding fructosebisphosphatase and phosphoribulokinase from xanthobacter flavus h4-14.the genes encoding fructosebisphosphatase and phosphoribulokinase present on a 2.5 kb sali fragment from xanthobacter flavus h4-14 were sequenced. two large open reading frames (orfs) were identified, preceded by plausible ribosome-binding sites. the orfs were transcribed in the same direction and were separated by 39 base pairs. they encoded proteins of 364 and 291 amino acids, with molecular masses of 38739 and 33409 da, respectively. the orfs were identified as the genes encoding fbpase and p ...19901964170
cometabolic degradation of chlorinated alkenes by alkene monooxygenase in a propylene-grown xanthobacter strain.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 ...19921444418
role of heterotrophic bacteria in complete mineralization of trichloroethylene by methylocystis sp. strain m.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 wer ...19921444420
purification and characterization of hydrolytic haloalkane dehalogenase from xanthobacter autotrophicus gj10.a new enzyme, haloalkane dehalogenase, was isolated from the 1,2-dichloroethane-utilizing bacterium xanthobacter autotrophicus gj10. the purified enzyme catalyzed the hydrolytic dehalogenation of n-halogenated c1 to c4 alkanes, including chlorinated, brominated, and iodinated compounds. the highest activity was found with 1,2-dichloroethane, 1,3-dichloropropane, and 1,2-dibromoethane. the enzyme followed michaelis-menten kinetics, and the km for 1,2-dichloroethane was 1.1 mm. maximum activity wa ...19854019411
sequence analysis of the upstream region of dhlb, the gene encoding haloalkanoic acid dehalogenase of xanthobacter autotrophicus gj10.the dna sequence upstream of the dhlb gene encoding the haloalkanoic acid dehalogenase of xanthobacter autotrophicus gj10 was determined and contained an open reading frame, designated dhlc, which encoded a protein with a significant similarity with the family of na(+)-dependent symport proteins. the dhlc gene was subcloned under control of a t7 promoter, and found to encode a polypeptide of 45 kda on sds-page. upstream of dhlc, a -24/-12 promoter sequence was found. further upstream, in the opp ...19957580000
the membrane-bound hydrogenase of alcaligenes eutrophus: ii. localization and immunological comparison with other hydrogenase systems.immunological comparison of the soluble and the membrane-bound hydrogenase of alcaligenes eutrophus revealed no common antigenic determinants shared by the native proteins, however, a small amount of cross-reacting material was detected after freezing and thawing. immune precipitation assays supported previous observations indicating the membrane-bound hydrogenase to be localized in the outer surface of the cytoplasmic membrane. the membrane-bound hydrogenases of a. eutrophus and pseudomonas pse ...19806156647
degradation of 4-hydroxyphenylacetate by xanthobacter 124x. physiological resemblance with other gram-negative bacteria.xanthobacter 124x when grom on 4-hydroxyphenylacetate was able to hydroxylate this compound yielding homogenisate. ring fission of this latter compound gave maleylacetoacetate which was isomerized to fumarylacetoacetate. the isomerase involved resembled maleylacetoacetate isomerases in gram-negative bacteria in that glutathione was required for activity. fumarate and acetoacetate were both detected as products of the hydrolysis of fumarylacetoacetate.19863767351
crystallization of haloalkane dehalogenase from xanthobacter autotrophicus gj10.haloalkane dehalogenases are enzymes that release chloride or bromide from n-halogenated alkanes. x-ray quality crystals of haloalkane dehalogenase from the 1,2-dichloroethane-degrading bacterium xanthobacter autotrophicus gj10 have been grown at room temperature from 64% saturated ammonium sulfate solutions (ph 6.2 to 6.4). the crystals diffract in the x-ray beam to at least 2.4 a resolution (1 a = 0.1 nm). their space group is p2(1)2(1)2, with cell dimensions a = 94.1 a, b = 72.8 a, c = 41.4 a ...19883398051
fructosebisphosphatase isoenzymes of the chemoautotroph xanthobacter flavus.xanthobacter flavus employs two fructosebisphosphatase (fbpase)-sedoheptulosebisphosphatase (sbpase) enzymes. one of these is constitutively expressed and has a high fbpase-to-sbpase ratio. the alternative enzyme, which is encoded by cbbf, is induced during autotrophic growth. the cbbf gene was expressed in escherichia coli, and the fbpase was purified to homogeneity. the purified enzyme has a specific fbpase activity of 114 mumol/min/mg of protein, a michaelis constant for fructosebisphosphate ...19957592335
characterization of the haloacid dehalogenase from xanthobacter autotrophicus gj10 and sequencing of the dhlb gene.the haloacid dehalogenase of the 1,2-dichloroethane-utilizing bacterium xanthobacter autotrophicus gj10 was purified from a mutant with an eightfold increase in expression of the enzyme. the mutant was obtained by selecting for enhanced resistance to monobromoacetate. the enzyme was purified through (nh4)2so4 fractionation, deae-cellulose chromatography, and hydroxylapatite chromatography. the molecular mass of the protein was 28 kda as determined with sodium dodecyl sulfate-polyacrylamide gel e ...19911744048
emendation of xanthobacter flavus as a motile species.xanthobacter flavus 301t (t = type strain) and other strains, including h4-14, both of which were previously described as nonmotile, were reproducibly motile and peritrichously flagellated during the log phase when they were cultured in medium lacking tricarboxylic acid cycle intermediates. therefore, the species description is emended to include motility and flagellation. similarly, xanthobacter autotrophicus was found to be flagellated and motile, but this finding was not consistently reproduc ...19921581192
carbon dioxide fixation in the metabolism of propylene and propylene oxide by xanthobacter strain py2.evidence for a requirement for co2 in the productive metabolism of aliphatic alkenes and epoxides by the propylene-oxidizing bacterium xanthobacter strain py2 is presented. in the absence of co2, whole-cell suspensions of propylene-grown cells catalyzed the isomerization of propylene oxide (epoxypropane) to acetone. in the presence of co2, no acetone was produced. acetone was not metabolized by suspensions of propylene-grown cells, in either the absence or presence of co2. the degradation of pro ...19957592382
characterization of xanthobacter strains h4-14 and 25a and enzyme profiles after growth under autotrophic and heterotrophic conditions.all xanthobacter strains studied are versatile autotrophic bacteria, able to grow on methanol and other substrates. strain 25a, a yellow-pigmented, pleomorphic, gram-negative bacterium, capable of autotrophic growth on methanol, formate, thiosulfate, and molecular hydrogen, was isolated from an enrichment culture inoculated with soil from a subtropical greenhouse. subsequent studies showed that the organism also grows on a wide range of multicarbon substrates. ammonia, nitrate and molecular nitr ...19902337378
the role of spontaneous cap domain mutations in haloalkane dehalogenase specificity and evolution.the first step in the utilization of the xenobiotic chlorinated hydrocarbon 1,2-dichloroethane by xanthobacter autotrophicus is catalyzed by haloalkane dehalogenase (dh1a). the enzyme hydrolyses 1-haloalkanes to the corresponding alcohols. this allows the organism to grow also on short-chain (c2-c4) 1-chloro-n-alkanes. we have expressed dh1a in a strain of pseudomonas that grows on long-chain alcohols and have selected 12 independent mutants that utilize 1-chlorohexane. six different mutant enzy ...19948021255
crystal structure of haloalkane dehalogenase: an enzyme to detoxify halogenated alkanes.haloalkane dehalogenase from xanthobacter autotrophicus gj10 converts 1-haloalkanes to the corresponding alcohols and halide ions with water as the sole cosubstrate and without any need for oxygen or cofactors. the three-dimensional structure has been determined by multiple isomorphous replacement techniques using three heavy atom derivatives. the structure has been refined at 2.4 a resolution to an r-factor of 17.9%. the monomeric enzyme is a spherical molecule and is composed to two domains: d ...19912026135
oxygen tolerance of strictly aerobic hydrogen-oxidizing bacteria.growth of various bacteria, especially aerobic hydrogen-oxidizing bacteria, in the presence of 2 to 100% (v/v) oxygen in the gas atmosphere was evaluated. the bacterial strains included alcaligenes eutrophus, a. paradoxus, aquaspirillum autotrophicum, arthrobacter spec. strain 11 x, escherichia coli, arthrobacter globiformis, nocardia opaca, n. autotrophica, paracoccus denitrificans, pseudomonas facilis, p. putida, and xanthobacter autotrophicus. under heterotrophic conditions with fructose or g ...19827049081
structural analysis of an acidic polysaccharide secreted by xanthobacter sp. (atcc 53272).the structure of an acidic polysaccharide secreted by a xanthobacter sp. has been investigated by glycosyl-residue and glycosyl-linkage composition analyses, and the characterization of oligoglycosyl fragments of the polysaccharide has been carried out by chemical analyses, 1h-n.m.r. spectroscopy, fast-atom bombardment mass spectrometry, and electron-impact mass spectrometry. the polysaccharide, which contains o-acetyl groups (approximately 5%) that have not been located, has the tetraglycosyl r ...19902073637
methanol dissimilation in xanthobacter h4-14: activities, induction and comparison to pseudomonas am1 and paracoccus denitrificans.methanol dissimilatory enzymes detected in the methanol autotroph xanthobacter h4-14 were a typical phenazine methosulphate-linked methanol dehydrogenase, a nad+-linked formate dehydrogenase, and a dye-linked formaldehyde dehydrogenase that could be assayed only by activity stains of polyacrylamide gels. this same methanol dehydrogenase activity was found in ethanol-grown cells and was apparently utilized for ethanol oxidation. formaldehyde dehydrogenase activities were investigated in paracoccu ...19852933486
influence of organic nutrients and cocultures on the competitive behavior of 1,2-dichloroethane-degrading bacteria.the effects of organic nutrients and cocultures on substrate removal by and competitive behavior of 1,2-dichloroethane-degrading bacteria were investigated. xanthobacter autotrophicus gj10 needed biotin for optimal growth on 1,2-dichloroethane. in continuous culture, dilution of biotin to a concentration below 0.2 nm resulted in washout. growth could be restored by inoculation with the 2-chloroethanol utilizer pseudomonas sp. strain gj1, leading to a new steady state in which about 1% of the mix ...19938250561
identification and organization of carbon dioxide fixation genes in xanthobacter flavus h4-14.the genes encoding the large (cfxl) and small (cfxs) subunits of ribulose-1,5-bisphosphate carboxylase (rubisc/o) from xanthobacter flavus h4-14 were identified and characterized. the rubisc/o genes are separated by 11 bp and cotranscribed in escherichia coli from the lac promoter in the order cfxls. primer extension and r-loop experiments with rna isolated from autotrophically grown x. flavus h4-14 showed that transcription of cfxl and cfxs initiated 22 bp upstream from cfxl and resulted in a m ...19911900916
the molybdenum nitrogenase from wild-type xanthobacter autotrophicus exhibits properties reminiscent of alternative nitrogenases.in the presence of molybdate (1 microm) 2-3.5% oxygen and with sucrose as carbon source, xanthobacter autotrophicus gz29, a microaerophilic nitrogen-fixing hydrogen-oxidizing bacterium, grew diazotrophically with a minimal doubling time of 2.5 h and a calculated absorbance of up to 52 (546 nm). the maximal specific activity obtained was 145 nmol ethylene reduced . min-1 . mg protein-1 (crude extract). the mo nitrogenase was derepressed to a comparable level with methionine as nitrogen source. va ...19957607241
cloning and sequence analysis of a plasmid-encoded 2-haloacid dehalogenase gene from pseudomonas putida no. 109.the 2-haloacid dehalogenase of pseudomonas putida no. 109 was mediated by a 74-kb conjugative plasmid, which was transferred by mating into pseudomonas and escherichia coli and there expressed the dehalogenase. a 2.8-kb ecori-fragment generated from the plasmid was cloned and sequenced. the dehalogenase gene (dehh109) was identified by comparison with the n-terminal amino acid sequence and the molecular weight of the enzyme protein. the gene dehh109 coded for a 224-amino acid protein of m(r) 25, ...19947764511
continuous degradation of trichloroethylene by xanthobacter sp. strain py2 during growth on propene.propene-grown xanthobacter sp. strain py2 cells can degrade trichloroethylene (tce), but the transformation capacity of such cells was limited and depended on both the tce concentration and the biomass concentration. toxic metabolites presumably accumulated extracellularly, because the fermentation of glucose by yeast cells was inhibited by tce degradation products formed by strain py2. the affinity of the propene monooxygenase for tce was low, and this allowed strain py2 to grow on propene in t ...19957487026
demonstration of a molybdenum- and vanadium-independent nitrogenase in a nifhdk-deletion mutant of rhodobacter capsulatus.in rhodobacter capsulatus there exists, in addition to a conventional mo-containing nitrogenase, a second, mo-indendent nitrogenase which was demonstrated in wild-type cells as well as in cells of a nifhdk- mutant. to construct this r. capsulatus mutant, a 4-kb bglii-hindiii fragment encompassing nifk, nifd and most of the nifh coding region was substituted by an interposon coding for kanamycin resistance. the alternative nitrogenase is repressed by molybdenum. mo concentration greater than 1 pp ...19911999188
crystallographic and fluorescence studies of the interaction of haloalkane dehalogenase with halide ions. studies with halide compounds reveal a halide binding site in the active site.haloalkane dehalogenase from xanthobacter autotrophicus gj10 catalyzes the conversion of 1,2-dichloroethane to 2-chloroethanol and chloride without use of oxygen or cofactors. the active site is situated in an internal cavity, which is accessible from the solvent, even in the crystal. crystal structures of the dehalogenase enzyme complexed with iodoacetamide, chloroacetamide, iodide, and chloride at ph 6.2 and 8.2 revealed a halide binding site between the ring nh's of two tryptophan residues, t ...19938369276
dna hybridization analysis of the nif region of two methylotrophs and molecular cloning of nif-specific dna.dna isolated from two diazotrophic methylotrophs, the obligate methanotroph methylosinus sp. strain 6 and the methanol autotroph xanthobacter sp. h4-14, hybridized to dna fragments encoding nitrogen fixation (nif) genes from klebsiella pneumoniae. this interspecific nif homology was limited to dna fragments encoding the nitrogenase structural proteins (nifh, nifd, and nifk) and specific methylotroph dna sequences. the hybridization patterns obtained with the two methylotrophs were dissimilar, in ...19846321444
comparative studies of genes encoding thermostable l-2-halo acid dehalogenase from pseudomonas sp. strain yl, other dehalogenases, and two related hypothetical proteins from escherichia coli.we have determined the nucleotide sequence of the gene encoding thermostable l-2-halo acid dehalogenase (l-dex) from the 2-chloroacrylate-utilizable bacterium pseudomonas sp. strain yl. the open reading frame consists of 696 nucleotides corresponding to 232 amino acid residues. the protein molecular weight was estimated to be 26,179, which was in good agreement with the subunit molecular weight of the enzyme. the gene was efficiently expressed in the recombinant escherichia coli cells: the amoun ...19947944368
complementation of xanthobacter py2 mutants defective in epoxyalkane degradation, and expression and nucleotide sequence of the complementing dna fragment.three xanthobacter py2 mutants (m3, m8 and m10) lacking epoxyalkane-degrading activity were isolated and characterized. all mutants were able to grow on acetone, the degradation product of 1,2-epoxypropane conversions. furthermore, they contained the unidentified 'low molecular mass fraction' (lmf) necessary for epoxyalkane-degrading activity. three cosmids from a gene bank complemented the mutation in m10 and m8 but not in mutant m3. epoxyalkane-degrading activity in crude extracts of 1,2-epoxy ...19957704278
crystallization and preliminary x-ray analysis of l-2-haloacid dehalogenase from xanthobacter autotrophicus gj10.haloacid dehalogenases are enzymes that cleave carbon-chlorine or carbon-bromine bonds of 2-haloalkanoates. x-ray-quality crystals of l-2-haloacid dehalogenase from the 1,2-dichloroethane-degrading bacterium xanthobacter autotrophicus gj10 have been grown at room temperature from 20% peg 8000, 200 mm sodium formate at ph 6.8-7.0, using macroseeding techniques. the crystals, which diffract in the x-ray beam up to 2.0 a resolution, belong to the spacegroup c2221. cell parameters are a = 58.8 a, b ...19958580854
refined x-ray structures of haloalkane dehalogenase at ph 6.2 and ph 8.2 and implications for the reaction mechanism.the crystal structure of haloalkane dehalogenase from xanthobacter autotrophicus gj10 has been refined at 1.9 a resolution at two different ph values, the ph of crystallization (ph 6.2) and the ph of optimal activity (ph 8.2), to final r-factors of 16.8% and 16.4%, respectively. both models show good stereochemical quality. two non-glycine residues have main-chain torsion angles that are located outside the "allowed" regions in a ramachandran plot. one of them is the nucleophilic residue asp124, ...19938355275
degradation of 1,4-dichlorobenzene by xanthobacter flavus 14p1.xanthobacter flavus 14p1 was isolated from sludge of the river mulde by selective enrichment with 1,4-dichlorobenzene as the sole source of carbon and energy. the bacterium did not use other aromatic or chloroaromatic compounds as growth substrates. during growth on 1,4-dichlorobenzene, stoichiometric amounts of chloride ions were released. degradation products of 1,4-dichlorobenzene were identified by gas chromatography-mass spectrometry analysis. 3,6-dichloro-cis-1,2-dihydroxycyclohexa-3,5-die ...19958526500
histidine 289 is essential for hydrolysis of the alkyl-enzyme intermediate of haloalkane dehalogenase.haloalkane dehalogenase (dhla) from xanthobacter autotrophicus gj10 catalyzes the hydrolytic cleavage of carbon-halogen bonds in a broad range of halogenated aliphatic compounds. previous work has shown that asp124, which is located close to the internal substrate-binding cavity, carries out a nucleophilic attack on the c-alpha of the alkylhalide, displacing the halogen. the resulting alkyl-enzyme intermediate is subsequently hydrolyzed. in order to study the role of his289 in the hydrolysis of ...19957737973
the calvin cycle enzyme phosphoglycerate kinase of xanthobacter flavus required for autotrophic co2 fixation is not encoded by the cbb operon.during autotrophic growth of xanthobacter flavus, energy derived from the oxidation of hydrogen methanol or formate is used to drive the assimilation of co2 via the calvin cycle. the genes encoding the calvin cycle enzymes are organized in the cbb operon, which is expressed only during autotrophic growth. although it has been established that the transcriptional activator cbbr is required for the expression of the cbb operon, it is unclear whether cbbr is the only factor contributing to the regu ...19947928974
bacterial degradation of glycol ethers.assimilation of ethyleneglycol (eg) ethers by polyethyleneglycol-utilizing bacteria was examined. ethyleneglycol ether-utilizing bacteria were also isolated from soil and activated sludge samples by enrichment-culture techniques. three strains (4-5-3, ec 1-2-1 and mc 2-2-1) were selected and characterized as pseudomonas sp. 4-5-3, xanthobacter autotrophicus, and an unidentified gram-negative, non-spore-forming rod respectively. their growth characteristics were examined: pseudomonas sp. 4-5-3 as ...19958597556
carboxylation of epoxides to beta-keto acids in cell extracts of xanthobacter strain py2.a novel enzymatic reaction involved in the metabolism of aliphatic epoxides by xanthobacter strain py2 is described. cell extracts catalyzed the co2-dependent carboxylation of propylene oxide (epoxypropane) to form acetoacetate and beta-hydroxybutyrate. the time courses of acetoacetate and beta-hydroxybutyrate formaton indicate that acetoacetate is the primary product of propylene oxide carboxylation and that beta-hydroxybutyrate is a secondary product formed by the reduction of acetoacetate. an ...19968631727
purification and characterization of chlorobenzene cis-dihydrodiol dehydrogenase from xanthobacter flavus 14p1.chlorobenzene cis-dihydrodiol dehydrogenase was purified to homogeneity from xanthobacter flavus 14p1, which used 1,4-dichlorobenzene as the sole source of carbon and energy. the enzyme converted a number of halogenated substrates with high specific activity. the pi of the native chlorobenzene cis-dihydrodiol dehydrogenase was 5.4, and the molecular mass was approximately 100 kda, as determined by gel filtration. the enzyme was composed of four apparently identical subunits with a molecular mass ...19968599538
xanthobacter tagetidis sp. nov., an organism associated with tagetes species and able to grow on substituted thiophenes.members of the marigold genus of flowering plants (the genus tagetes), which synthesize and accumulate thiophene compounds in their roots, were investigated as potential sources of bacteria able to degrade substituted thiophenes. batch and continuous enrichment cultures inoculated with compost from root balls of tagetes patula and tagetes erecta reproducibly produced the same predominant type of bacterium when they were supplied with thiophene-2-carboxylate (t2c) or thiophene-2-acetate (t2a) as ...19979103627
structure of a myristoyl-acp-specific thioesterase from vibrio harveyi.the crystal structure of a myristoyl acyl carrier protein specific thioesterase (c14acp-te) from a bioluminescent bacterium, vibrio harveyi, was solved by multiple isomorphous replacement methods and refined to an r factor of 22% at 2.1-a resolution. this is the first elucidation of a three-dimensional structure of a thioesterase. the overall tertiary architecture of the enzyme resembles closely the consensus fold of the rapidly expanding superfamily of alpha/beta hydrolases, although there is n ...19948068614
oxidative metabolism of inorganic sulfur compounds by bacteria.the history of the elucidation of the microbiology and biochemistry of the oxidation of inorganic sulfur compounds in chemolithotrophic bacteria is briefly reviewed, and the contribution of martinus beijerinck to the study of sulfur-oxidizing bacteria highlighted. recent developments in the biochemistry, enzymology and molecular biology of sulfur oxidation in obligately and facultatively lithotrophic bacteria are summarized, and the existence of at least two major pathways of thiosulfate (sulfur ...19979049021
construction of an expression and site-directed mutagenesis system of haloalkane dehalogenase in escherichia coli.haloalkane dehalogenase from xanthobacter autotrophicus was efficiently expressed in escherichia coli bl21 (de3) and e. coli jm101. after introduction of restriction sites by pcr the haloalkane dehalogenase gene (dhla) was translationally fused behind the t7 (phi 10), trc, and tac promoters. this resulted in expression at 30 degrees c up to 38 and 18% of the total soluble cellular protein with the t7 and trc promoters, respectively. dehalogenase expression under control of the tac promoter was b ...19938251760
the plasmid-located haloalkane dehalogenase gene from rhodococcus rhodochrous ncimb 13064.the haloalkane dehalogenase (dhaa) gene from rhodococcus rhodochrous ncimb 13064 was cloned and sequenced. its comparison with the previously studied dhla gene from xanthobacter autotrophicus gj10 did not show homology. however, the amino acid sequences of the products of these genes showed approximately 30% identity and several of the catalytic amino acid residues were conserved in the ncimb 13,064 dehalogenase. a high level of dhaa expression was demonstrated in escherichia coli cells and this ...19979025284
primary structure and phylogeny of the calvin cycle enzymes transketolase and fructosebisphosphate aldolase of xanthobacter flavus.xanthobacter flavus, a gram-negative facultatively autotrophic bacterium, employs the calvin cycle for the fixation of carbon dioxide. cells grown under autotrophic growth conditions possess an fe(2+)-dependent fructosebisphosphate (fbp) aldolase (class ii) in addition to a class i fbp aldolase. by nucleotide sequencing and heterologous expression in escherichia coli, genes encoding transketolase (ec 2.2.1.1.; cbbt) and class ii fbp aldolase (ec 4.1.2.13; cbba) were identified. a partial open re ...19968550527
induction of the gap-pgk operon encoding glyceraldehyde-3-phosphate dehydrogenase and 3-phosphoglycerate kinase of xanthobacter flavus requires the lysr-type transcriptional activator cbbr.in a previous study, a gene (pgk) encoding phosphoglycerate kinase was isolated from a genomic library of xanthobacter flavus. although this gene is essential for autotrophic growth, it is not located within the cbb operon encoding other calvin cycle enzymes. an analysis of the nucleotide sequence upstream from pgk showed the presence of a gene encoding glyceraldehyde-3-phosphate dehydrogenase and the 3' end of an open reading frame encoding a protein which is 50% identical to transketolase enco ...19968550526
non-covalent binding of the heavy atom compound [au(cn)2]- at the halide binding site of haloalkane dehalogenase from xanthobacter autotrophicus gj10.the na[au(cn)2] heavy atom derivative contributed considerably to the successful elucidation of the crystal structure of haloalkane dehalogenase isolated from xanthobacter autotrophicus gj10. the gold cyanide was located in an internal cavity of the enzyme, which also contains the catalytic residues. refinement of the dehalogenase-gold cyanide complex at 0.25 nm to an r-factor of 16.7% demonstrates that the heavy atom molecule binds non-covalently between two tryptophan residues pointing into th ...19938500621
a novel type of pyridine nucleotide-disulfide oxidoreductase is essential for nad+- and nadph-dependent degradation of epoxyalkanes by xanthobacter strain py2.epoxide degradation in cell extracts of xanthobacter strain py2 has been reported to be dependent on nad+ and dithiols. this multicomponent system has now been fractionated. a key protein encoded by a dna fragment complementing a xanthobacter strain py2 mutant unable to degrade epoxides was purified and analyzed. this nadp-dependent protein, a novel type of pyridine nucleotide-disulfide oxidoreductase, is essential for epoxide degradation. nadph, acting as the physiological cofactor, replaced th ...19968932325
expression and regulation of bradyrhizobium japonicum and xanthobacter flavus co2 fixation genes in a photosynthetic bacterial host.calvin cycle carbon dioxide fixation genes encoded on dna fragments from two nonphotosynthetic, chemolithoautotrophic bacteria, bradyrhizobium japonicum and xanthobacter flavus, were found to complement and support photosynthetic growth of a ribulose 1,5-bisphosphate carboxylase-oxygenase (rubisco) deletion mutant of the purple nonsulfur bacterium rhodobacter sphaeroides. the regulation of rubisco expression was analyzed in the complemented r. sphaeroides rubisco deletion mutant. distinct differ ...19938423157
aliphatic and chlorinated alkenes and epoxides as inducers of alkene monooxygenase and epoxidase activities in xanthobacter strain py2.the inducible nature of the alkene oxidation system of xanthobacter strain py2 has been investigated. cultures grown with glucose as the carbon source did not contain detectable levels of alkene monooxygenase or epoxidase, two key enzymes of alkene and epoxide metabolism. upon addition of propylene to glucose-grown cultures, alkene monooxygenase and epoxidase activities increased and after an 11-h induction period reached levels of specific activity comparable to those in propylene-grown cells. ...19968572713
identification of functional residues in a 2-hydroxymuconic semialdehyde hydrolase. a new member of the alpha/beta hydrolase-fold family of enzymes which cleaves carbon-carbon bonds.the 2-hydroxymuconic semialdehyde hydrolase, xylf, of the pseudomonas putida tol plasmid-encoded pathway for the catabolism of toluene and xylenes, catalyzes one of the rarest types of enzyme reaction (ec 3.7.1.9), the hydrolysis of a carbon-carbon bond in its substrate, the ring-fission product of 3-alkyl-substituted catechols. in this study, amino acid sequence comparisons between xylf and other hydrolases, and analysis of the similarity between the predicted secondary structure of xylf and th ...19957890778
genes encoding rubisco in pseudomonas hydrogenothermophila are followed by a novel cbbq gene similar to nirq of the denitrification gene cluster from pseudomonas species.the cbbl and cbbs genes, encoding ribulose 1,5-bisphosphate carboxylase/oxygenase (rubisco), were cloned and sequenced from a thermophilic hydrogen-oxidizing bacterium, pseudomonas hydrogenothermophila strain th-1. the cbbl gene encoded a 474-amino-acid (aa) protein (53,285 da); cbbs encoded a 124-aa protein (14,656 da). an orf found downstream from the cbbls genes encoded a 267-aa protein (29,565 da) which had no similarity to cbbx located downstream from cbbls from alcaligenes eutrophus and xa ...19957883189
primary structure and catalytic mechanism of the epoxide hydrolase from agrobacterium radiobacter ad1.the epoxide hydrolase gene from agrobacterium radiobacter ad1, a bacterium that is able to grow on epichlorohydrin as the sole carbon source, was cloned by means of the polymerase chain reaction with two degenerate primers based on the n-terminal and c-terminal sequences of the enzyme. the epoxide hydrolase gene coded for a protein of 294 amino acids with a molecular mass of 34 kda. an identical epoxide hydrolase gene was cloned from chromosomal dna of the closely related strain a. radiobacter c ...19979169427
enzymology of the degradation of (di)chlorobenzenes by xanthobacter flavus 14p1.xanthobacter flavus 14p1 used 1,4-dichlorobenzene as the sole source of carbon and energy but did not grow on other (chloro)aromatic compounds. 1,4-dichlorobenzene was attacked by a chlorobenzene dioxygenase, and the intermediate chlorocatechol was metabolized by the modified ortho pathway. all enzymes necessary to convert 1, 4-dichlorobenzene to 3-oxoadipate showed a low substrate specificity and also accepted the respective intermediates of chlorobenzene or 1, 3-dichlorobenzene degradation. of ...19979148781
involvement of an atp-dependent carboxylase in a co2-dependent pathway of acetone metabolism by xanthobacter strain py2.the metabolism of acetone by the aerobic bacterium xanthobacter strain py2 was investigated. cell suspensions of xanthobacter strain py2 grown with propylene or glucose as carbon sources were unable to metabolize acetone. the addition of acetone to cultures grown with propylene or glucose resulted in a time-dependent increase in acetone-degrading activity. the degradation of acetone by these cultures was prevented by the addition of rifampin and chloramphenicol, demonstrating that new protein sy ...19968763926
purification and characterization of two components of epoxypropane isomerase/carboxylase from xanthobacter py2.epoxypropane isomerase from xanthobacter py2 has been resolved into at least two components (a and b) by ion-exchange chromatography. both components were required for the degradation of epoxypropane and were purified further. component a was apparently homohexameric with a subunit m(r) of about 44,000, and possessed nad(+)-dependent dihydrolipoamide dehydrogenase activity and lipoamide reductase activity. it was sensitive to inhibition by o-phenanthroline and the thiol-specific reagents n-ethyl ...19968912687
evolving enzyme technology for pharmaceutical applications: case studies.the case studies focus on two types of enzyme applications for pharmaceutical development. demethylmacrocin o-methyltransferase, macrocin o-methyltransferase (both putatively rate-limiting) and tylosin reductase were purified from streptomyces fradiae, characterized and the genes manipulated for increasing tylosin biosynthesis in s. fradiae. the rate-limiting enzyme, deacetoxycephalosporin c (daoc) synthase/hydroxylase (expandase/ hydroxylase), was purified from cephalosporium acremonium, its ge ...19979451830
cbbr, a lysr-type transcriptional activator, is required for expression of the autotrophic co2 fixation enzymes of xanthobacter flavus.xanthobacter flavus is able to grow autotrophically with the enzymes of the calvin cycle for the fixation of co2, which are specified by the cbblsxfp gene cluster. previously, the 5' end of an open reading frame (cbbr), displaying a high sequence similarity to the lysr family of regulatory proteins and transcribed divergently from cbblsxfp, was identified (w. g. meijer, a. c. arnberg, h. g. enequist, p. terpstra, m. e. lidstrom, and l. dijkhuizen, mol. gen. genet. 225:320-330, 1991). this paper ...19938407781
characterization of three protein components required for functional reconstitution of the epoxide carboxylase multienzyme complex from xanthobacter strain py2.epoxide carboxylase from xanthobacter strain py2 catalyzes the reductant- and nad+-dependent carboxylation of aliphatic epoxides to beta-keto acids. epoxide carboxylase from xanthobacter strain py2 has been resolved from cell extracts by anion-exchange chromatography into three protein components, designated i, ii, and iii, that are obligately required for functional reconstitution of epoxide carboxylase activity. component ii has been purified to homogeneity on the basis of its ability to compl ...19979150202
genetic adaptation of bacteria to halogenated aliphatic compounds.the bacterial degradation and detoxification of chlorinated xenobiotic compounds requires the production of enzymes that are capable of recognizing and converting compounds which do not occur at significant concentrations in nature. we have studied the catabolic route of 1,2-dichloroethane as an example of a pathway for the conversion of such a synthetic compound. in strains of xanthobacter and ancylobacter that have been isolated on 1,2-dichloroethane, the first catabolic step is catalyzed by a ...19958565904
cloning and sequence analysis of a novel insertion element from plasmids harbored by the carbofuran-degrading bacterium, sphingomonas sp. cfo6.sphingomonas sp. cfo6 (a member of the alpha group of proteobacteria) was isolated from a washington soil by enrichment on the insecticide carbofuran as a sole source of carbon and energy. this strain has been shown to harbor five plasmids, at least some of which are required for catabolism of carbofuran. rearrangements, deletions, and loss of individual plasmids resulting in the loss of the carbofuran-degrading phenotype were observed following treatment with heat or introduction of tn5. severa ...19979200220
adaptation of xanthobacter autotrophicus gj10 to bromoacetate due to activation and mobilization of the haloacetate dehalogenase gene by insertion element is1247.monobromoacetate (mba) is toxic for the 1,2-dichloroethane-degrading bacterium xanthobacter autotrophicus gj10 at concentrations higher than 5 mm. mutants which are able to grow on higher concentrations of mba were isolated and found to overexpress haloacid dehalogenase, which is encoded by the dhlb gene. in mutant gj10m50, a dna fragment (designated is1247) had copied itself from a position on the chromosome that was not linked to the dhlb region to a site immediately upstream of dhlb, resultin ...19957868610
proton nuclear magnetic resonance investigation of the [2fe-2s](1-)-containing "rieske-type" protein from xanthobacter strain py2.proton nmr spectra of the rieske-type ferredoxin from xanthobacter strain py2 were recorded in both h2o and d2o buffered solutions at ph 7.2. several well-resolved hyperfine-shifted 1h nmr signals were observed in the 90 to -20 ppm chemical shift range. comparison of spectra recorded in h2o and d2o buffered solutions indicated that the signals at -11.4 (l) and -15.5 (m) ppm were solvent-exchangeable and thus were assigned to the two histidine n epsilon 2h protons. the remaining observed signals ...19979398188
purification to homogeneity and reconstitution of the individual components of the epoxide carboxylase multiprotein enzyme complex from xanthobacter strain py2.epoxide metabolism in the aerobic bacterium xanthobacter strain py2 proceeds by an nadph- and nad+-dependent carboxylation reaction that forms beta-keto acids as products. epoxide carboxylase, the enzyme catalyzing this reaction, was resolved from the soluble fraction of cell-free extracts into four protein components that are obligately required for functional reconstitution of epoxide carboxylase activity. one of these components, component ii, has previously been purified and characterized as ...19979405410
three-dimensional structure of l-2-haloacid dehalogenase from xanthobacter autotrophicus gj10 complexed with the substrate-analogue formate.the l-2-haloacid dehalogenase from the 1,2-dichloroethane degrading bacterium xanthobacter autotrophicus gj10 catalyzes the hydrolytic dehalogenation of small l-2-haloalkanoic acids to yield the corresponding d-2-hydroxyalkanoic acids. its crystal structure was solved by the method of multiple isomorphous replacement with incorporation of anomalous scattering information and solvent flattening, and was refined at 1.95-a resolution to an r factor of 21.3%. the three-dimensional structure is simil ...19979407083
xanthobacter flavus employs a single triosephosphate isomerase for heterotrophic and autotrophic metabolism.the expression of the cbb and gap-pgk operons of xanthobacter flavus encoding enzymes of the calvin cycle is regulated by the transcriptional regulator cbbr. in order to identify other genes involved in the regulation of these operons, a mutant was isolated with a lowered activity of a fusion between the promoter of the cbb operon and the reporter gene lacz. this mutant was unable to grow autotrophically and had a reduced growth rate on medium supplemented with gluconate or succinate. the regula ...19979202469
the alkene monooxygenase from xanthobacter py2 is a binuclear non-haem iron protein closely related to toluene 4-monooxygenase.the genes encoding the six polypeptide components of the alkene monooxygenase from xanthobacter py2 have been sequenced. the predicted amino acid sequence of the first orf shows homology with the iron binding subunits of binuclear non-haem iron containing monooxygenases including benzene monooxygenase, toluene 4-monooxygenase (> 60% sequence similarity) and methane monooxygenase (> 40% sequence similarity) and that the necessary sequence motifs associated with iron co-ordination are also present ...19989688534
closely related form i ribulose bisphosphate carboxylase/oxygenase molecules that possess different co2/o2 substrate specificities.the deduced primary sequence (cbbl and cbbs) of form i ribulose 1, 5-bisphosphate carboxylase/oxygenase (rubisco) from bradyrhizobium japonicum places this enzyme within the type ic subgroup of red-like rubisco enzymes. in addition, b. japonicum appears to organize most of the structural genes of the calvin-benson-bassham (cbb) pathway in at least one major operon. functional expression and characterization of the b. japonicum and xanthobacter flavus enzymes from this group revealed that these m ...19999882445
computational site-directed mutagenesis of haloalkane dehalogenase in position 172.the application of molecular modelling and quantum-chemistry calculations for the 'computational site-directed mutagenesis' of haloalkane dehalogenase is described here. the exhaustive set of single point mutants of haloalkane dehalogenase in position 172 was constructed by homology modelling. the ability of substituting residues to stabilize the halide ion formed during the dehalogenation reaction in the enzyme active site was probed by quantum-chemical calculations. a simplified modelling proc ...19989862209
molecular analysis of bacterial isolates and total community dna from kraft pulp mill effluent treatment systems.chloroaliphatics are major components of bleached kraft mill effluents. gene probes and oligonucleotide primers were developed to monitor kraft pulp mill effluent treatment systems for the presence of key genes (dehalogenases) responsible for the dehalogenation of chloroaliphatic organics. the primers were used for polymerase chain reaction (pcr) analysis of genomic dna extracted from dehalogenating bacterial isolates and from total community dna extracted from water and sediments of mill efflue ...19989734304
non-enzymatic and enzymatic hydrolysis of alkyl halides: a haloalkane dehalogenation enzyme evolved to stabilize the gas-phase transition state of an sn2 displacement reaction.the semiempirical pm3 method, calibrated against ab initio hf/6-31+g(d) theory, has been used to elucidate the reaction of 1, 2-dichloroethane (dce) with the carboxylate of asp-124 at the active site of haloalkane dehalogenase of xanthobacter autothropicus. asp-124 and 13 other amino acid side chains that make up the active site cavity (glu-56, trp-125, phe-128, phe-172, trp-175, leu-179, val-219, phe-222, pro-223, val-226, leu-262, leu-263, and his-289) were included in the calculations. the th ...19979237991
purification and characterization of acetone carboxylase from xanthobacter strain py2.acetone metabolism in the aerobic bacterium xanthobacter strain py2 proceeds by a carboxylation reaction forming acetoacetate as the first detectable product. in this study, acetone carboxylase, the enzyme catalyzing this reaction, has been purified to homogeneity and characterized. acetone carboxylase was comprised of three polypeptides with molecular weights of 85,300, 78,300, and 19,600 arranged in an alpha2beta2gamma2 quaternary structure. the carboxylation of acetone was coupled to the hydr ...19979237998
toxic effects of modified fenton reactions on xanthobacter flavus fb71the toxic effects of modified fenton reactions on xanthobacter flavus fb71, measured as microbial survival rates, were determined as part of an investigation of simultaneous abiotic and biotic oxidations of xenobiotic chemicals. a central composite, rotatable experimental design was developed to study the survival rates of x. flavus under various concentrations of hydrogen peroxide and iron(ii) and at different initial cell populations. a model based on the experimental results, relating microor ...19989758796
alkene monooxygenase from xanthobacter strain py2. purification and characterization of a four-component system central to the bacterial metabolism of aliphatic alkenes.alkene monooxygenase from xanthobacter strain py2 is an inducible enzyme that catalyzes the o2- and nadh-dependent epoxidation of short chain (c2 to c6) alkenes to their corresponding epoxides as the initial step in the utilization of aliphatic alkenes as carbon and energy sources. in the present study, alkene monooxygenase has been resolved from the soluble fraction of cell-free extracts into four components, each of which has been purified to homogeneity, that are obligately required for alken ...19979312093
identification and characterization of epoxide carboxylase activity in cell extracts of nocardia corallina b276.the metabolism of aliphatic epoxides (epoxyalkanes) by the alkene-utilizing actinomycete nocardia corallina b276 was investigated. suspensions of n. corallina cells grown with propylene as the carbon source readily degraded propylene and epoxypropane, while suspensions of glucose-grown cells did not. the addition of propylene and epoxypropane to glucose-grown cells resulted in a time-dependent increase in propylene- and epoxypropane-degrading activities that was prevented by the addition of rifa ...19989555888
cloning, sequence and expression of a linear plasmid-based and a chromosomal homolog of chloroacetaldehyde dehydrogenase-encoding genes in xanthobacter autotrophicus gj10.the degradation of 1,2-dichloroethane (dce) by xanthobacter autotrophicus gj10 proceeds via chloroacetaldehyde (caa), a toxic intermediate in the cells if it is not metabolized further by the nad(+)-dependent caa dehydrogenases. here, we describe the cloning, sequence and expression in escherichia coli of alda, a plasmid-located caa dehydrogenase-encoding gene of gj10 as well as a chromosomal homolog, designated aldb. the dna-predicted amino acid (aa) sequences of the two proteins (505 aa in ald ...19989511738
alteration of the substrate range of haloalkane dehalogenase by site-directed mutagenesis.we attempted to expand the range of chlorinated solvents degraded by xanthobacter autotrophicus gj10 to include trichloroethylene by the rational modification of the enzyme haloalkane dehalogenase. the amino acids phe164, asp170, phe172 and trp175 were individually replaced with alanine by site-directed mutagenesis. all substitutions produced enzymes with lower than wild type activity with 1,2-dichloroethane. the phe164ala and asp170ala mutants were 3 and 2 times more active than was the wild ty ...199810099367
determination of pollutant diffusion coefficients in naturally formed biofilms using a single tube extractive membrane bioreactor.a novel technique has been used to determine the effective diffusion coefficients for 1,1,2-trichloroethane (tce), a nonreacting tracer, in biofilms growing on the external surface of a silicone rubber membrane tube during degradation of 1,2-dichloroethane (dce) by xanthobacter autotrophicus gj10 and monochlorobenzene (mcb) by pseudomonas js150. experiments were carried out in a single tube extractive membrane bioreactor (stemb), whose configuration makes it possible to measure the transmembrane ...199810099317
sulfur oxidation in rice field soil: activity, enumeration, isolation and characterization of thiosulfate-oxidizing bacteria.in rice paddy fields the bulk soil is anoxic, but oxygenated zones occur in the surrounding of the rice roots to where oxygen is transported via the aerenchyma system of the rice plants. in the anaerobic soil compartments sulfate is consumed by sulfate-reducing bacteria. in the rhizosphere the reduced sulfur compounds can be reoxidized by sulfur-oxidizing bacteria. measurements of the potential activity of thiosulfate-oxidizing bacteria in soil slurries derived from planted rice soil microcosms ...19989924825
bacterial 2,4-dioxygenases: new members of the alpha/beta hydrolase-fold superfamily of enzymes functionally related to serine hydrolases.1h-3-hydroxy-4-oxoquinoline 2,4-dioxygenase (qdo) from pseudomonas putida 33/1 and 1h-3-hydroxy-4-oxoquinaldine 2,4-dioxygenase (hod) from arthrobacter ilicis rü61a catalyze an n-heterocyclic-ring cleavage reaction, generating n-formylanthranilate and n-acetylanthranilate, respectively, and carbon monoxide. amino acid sequence comparisons between qdo, hod, and a number of proteins belonging to the alpha/beta hydrolase-fold superfamily of enzymes and analysis of the similarity between the predict ...199910482514
distribution of tetrahydromethanopterin-dependent enzymes in methylotrophic bacteria and phylogeny of methenyl tetrahydromethanopterin cyclohydrolases.the methylotrophic proteobacterium methylobacterium extorquens am1 possesses tetrahydromethanopterin (h(4)mpt)-dependent enzymes, which are otherwise specific to methanogenic and sulfate-reducing archaea and which have been suggested to be involved in formaldehyde oxidation to co(2) in m. extorquens am1. the distribution of h(4)mpt-dependent enzyme activities in cell extracts of methylotrophic bacteria from 13 different genera are reported. h(4)mpt-dependent activities were detected in all of th ...199910482517
identification of the catalytic triad in the haloalkane dehalogenase from sphingomonas paucimobilis ut26.the haloalkane dehalogenase from sphingomonas paucimobilis ut26 (linb) is the enzyme involved in the gamma-hexachlorocyclohexane degradation. this enzyme hydrolyses a broad range of halogenated aliphatic compounds via an alkyl-enzyme intermediate. linb is believed to belong to the family of alpha/beta-hydrolases which employ a catalytic triad, i.e. nucleophile-histidine-acid, during the catalytic reaction. the position of the catalytic triad within the sequence of linb was probed by a site-direc ...199910100638
purification and characterization of a flavoprotein involved in the degradation of epoxyalkanes by xanthobacter py2.recently a newly discovered pyridine nucleotide-disulfide oxidoreductase was reported to be essential for the degradation of epoxyalkanes by the xanthobacter py2 [swaving, j., de bont, j. a. m., westphal, a. & de kok, a. (1996) j. bacteriol. 178, 6644-6646]. the disulfide oxidoreductase has now been purified from propene-grown xanthobacter py2. this enzyme (component ii) is a nadph-dependent fad-containing homodimeric protein. the physiological substrate for this enzyme is unknown. the enzyme wa ...19989799115
oxygen activating nonheme iron enzymes.the past year has witnessed significant advances in the study of oxygen-activating nonheme iron enzymes. thirteen crystal structures of substrate and substrate analog complexes of protocatechuate 3, 4-dioxygenase have revealed intimate details about changes at the enzyme active site during catalysis. crystallographic data have established a 2-his-1-carboxylate facial triad as a structural motif common to a number of mononuclear nonheme iron enzymes, including isopenicillin n synthase, tyrosine h ...19989667935
haloalkane dehalogenases: steady-state kinetics and halide inhibition.the substrate specificities and product inhibition patterns of haloalkane dehalogenases from xanthobacter autotrophicus gj10 (xadhl) and rhodococcus rhodochrous (rrdhl) have been compared using a ph-indicator dye assay. in contrast to xadhl, rrdhl is efficient toward secondary alkyl halides. using steady-state kinetics, we have shown that halides are uncompetitive inhibitors of xadhl with 1, 2-dichloroethane as the varied substrate at ph 8.2 (cl-, kii = 19 +/- 0.91; br-, kii = 2.5 +/- 0.19 mm; i ...199910231528
new roles for co2 in the microbial metabolism of aliphatic epoxides and ketones.short-chain aliphatic epoxides and ketones are two classes of toxic organic compounds formed biogenically and anthropogenically. in spite of their toxicity, these compounds are utilized as primary carbon and energy sources or are generated as intermediate metabolites in the metabolism of other compounds (e.g., alkenes, alkanes, and secondary alcohols) by a number of diverse bacteria. one bacterium capable of using both classes of compounds is the gram-negative aerobe xanthobacter strain py2. stu ...19989477250
chemolithoautotrophy and mixotrophy in the thiophene-2-carboxylic acid-utilizing xanthobacter tagetidisxanthobacter tagetidis grew as a chemolithotrophic autotroph on thiosulfate and other inorganic sulfur compounds, as a heterotroph on thiophene-2-carboxylic acid, acetic acid and alpha-ketoglutaric acid, and as a mixotroph on thiosulfate in combination with thiophene-2-carboxylic acid and/or acetic acid. autotrophic growth on one-carbon organosulfur compounds, and intermediates in their oxidation are also reported. thiosulfate enhanced the growth yields in mixotrophic cultures, presumably by act ...19989477260
optimization of simultaneous chemical and biological mineralization of perchloroethylene.optimization of the simultaneous chemical and biological mineralization of perchloroethylene (pce) by modified fenton's reagent and xanthobacter flavus was investigated by using a central composite rotatable experimental design. concentrations of pce, hydrogen peroxide, and ferrous iron and the microbial cell number were set as variables. percent mineralization of pce to co2 was investigated as a response. a second-order, quadratic response surface model was generated and fit the data adequately ...199910347081
detection and classification of hyperfine-shifted 1h, 2h, and 15n resonances of the rieske ferredoxin component of toluene 4-monooxygenase.t4moc is a 12.3 kda soluble rieske ferredoxin that is obligately required for electron transfer between the oxidoreductase and diiron hydroxylase components of toluene 4-monooxygenase from pseudomonas mendocina kr1. our preliminary 1h nmr studies of oxidized and reduced t4moc [markley, j. l., xia, b., chae, y. k., cheng, h., westler, w. m., pikus, j. d., and fox, b. g. (1996) in protein structure function relationships (zaidi, z., and smith, d., eds.) pp 135-146, plenum press, london] revealed t ...19999888813
the alkene monooxygenase from xanthobacter strain py2 is closely related to aromatic monooxygenases and catalyzes aromatic monohydroxylation of benzene, toluene, and phenol.the genes encoding the six polypeptide components of the alkene monooxygenase from xanthobacter strain py2 (xamo) have been located on a 4.9-kb fragment of chromosomal dna previously cloned in cosmid pny2. sequencing and analysis of the predicted amino acid sequences indicate that the components of xamo are homologous to those of the aromatic monooxygenases, toluene 2-, 3-, and 4-monooxygenase and benzene monooxygenase, and that the gene order is identical. the genes and predicted polypeptides a ...199910103255
the lysr-type transcriptional regulator cbbr controlling autotrophic co2 fixation by xanthobacter flavus is an nadph sensor.autotrophic growth of xanthobacter flavus is dependent on the fixation of carbon dioxide via the calvin cycle and on the oxidation of simple organic and inorganic compounds to provide the cell with energy. maximal induction of the cbb and gap-pgk operons encoding enzymes of the calvin cycle occurs in the absence of multicarbon substrates and the presence of methanol, formate, hydrogen, or thiosulfate. the lysr-type transcriptional regulator cbbr regulates the expression of the cbb and gap-pgk op ...19989515907
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