| the terminal reductases for selenate and nitrate respiration in thauera selenatis are two distinct enzymes. | a number of approaches have been used to show that a recently isolated selenate-respiring bacterium, thauera selenatis, is able to synthesize both a selenate reductase (sr) and a nitrate reductase (nr). (i) the ph optimum of the sr was found to be 6.0; that of the nr was 7.0. (ii) the presence of nitrate did not inhibit selenate reduction in selenate-grown cells. (iii) in cell extracts, the highest sr or nr activity was observed in cells grown with the respective electron acceptor. (iv) mutants ... | 1992 | 1429454 |
| taxonomic position of aromatic-degrading denitrifying pseudomonad strains k 172 and kb 740 and their description as new members of the genera thauera, as thauera aromatica sp. nov., and azoarcus, as azoarcus evansii sp. nov., respectively, members of the beta subclass of the proteobacteria. | in the past workers have isolated several pseudomonad strains which have been used for studies of anaerobic aromatic metabolism. the best studied of these strains are strains kb 740t (t = type strain) and k 172t. the taxonomic positions of these two organisms were determined by classical methods, including experiments to determine substrate spectrum, quinone type, and total fatty acid composition. our results clearly excluded these strains from the authentic genus pseudomonas, which belongs to t ... | 1995 | 7537067 |
| purification and properties of benzyl alcohol dehydrogenase from a denitrifying thauera sp. | toluene and related aromatic compounds are anaerobically degraded by the denitrifying bacterium thauera sp. strain k172 via oxidation to benzoyl-coa. the postulated initial step is methylhydroxylation of toluene to benzyl alcohol, which is either a free or enzyme-bound intermediate. cells grown with toluene or benzyl alcohol contained benzyl alcohol dehydrogenase, which is possibly the second enzyme in the proposed pathway. the enzyme was purified from benzyl-alcohol-grown cells and characterize ... | 1995 | 7575097 |
| anaerobic degradation of ethylbenzene and other aromatic hydrocarbons by new denitrifying bacteria. | anaerobic degradation of alkylbenzenes with side chains longer than that of toluene was studied in freshwater mud samples in the presence of nitrate. two new denitrifying strains, ebn1 and pbn1, were isolated on ethylbenzene and n-propylbenzene, respectively. for comparison, two further denitrifying strains, ton1 and mxyn1, were isolated from the same mud with toluene and m-xylene, respectively. sequencing of 16srdna revealed a close relationship of the new isolates to thauera selenatis. the str ... | 1995 | 7710331 |
| identification of grass-associated and toluene-degrading diazotrophs, azoarcus spp., by analyses of partial 16s ribosomal dna sequences. | the genus azoarcus includes nitrogen-fixing, grass-associated strains as well as denitrying toluene degraders. in order to identify and group members of the genus azoarcus, phylogenetic analysis based on partial sequences of 16s rrna genes (16s rdnas) is proposed. 16s rrna-targeted pcr using specific primers to exclude amplification in the majority of other members of the beta subclass of the class proteobacteria was combined with direct sequencing of the pcr products. tree inference from compar ... | 1995 | 7793946 |
| thauera selenatis gen. nov., sp. nov., a member of the beta subclass of proteobacteria with a novel type of anaerobic respiration. | a recently isolated, selenate-respiring microorganism (strain axt [t = type strain]) was classified by using a polyphasic approach in which both genotypic and phenotypic characteristics were determined. strain axt is a motile, gram-negative, rod-shaped organism with a single polar flagellum. on the basis of phenotypic characteristics, this organism can be classified as a pseudomonas sp. however, a comparison of the 16s rrna sequence of strain axt with the sequences of other organisms indicated t ... | 1993 | 8427805 |
| benzoyl-coenzyme a reductase (dearomatizing), a key enzyme of anaerobic aromatic metabolism. atp dependence of the reaction, purification and some properties of the enzyme from thauera aromatica strain k172. | anoxic metabolism of many aromatic compounds proceeds via the common intermediate benzoyl-coa. benzoyl-coa is dearomatized by benzoyl-coa reductase (dearomatizing) in a two-electron reduction step, possibly yielding cyclohex-1,5-diene-1-carboxyl-coa. this process has to overcome a high activation energy and is considered a biological birch reduction. the central, aromatic-ring-reducing enzyme was investigated for the first time in the denitrifying bacterium thauera aromatica strain k172. a spect ... | 1995 | 8575453 |
| evidence that anaerobic oxidation of toluene in the denitrifying bacterium thauera aromatica is initiated by formation of benzylsuccinate from toluene and fumarate. | toluene is degraded anoxically to co2 by the denitrifying bacterium thauera aromatica. toluene first becomes oxidized to benzoyl-coa by o2-independent reactions. benzoyl-coa is then reduced to non-aromatic products by benzoyl-coa reductase. we set out to study the reactions employed for the initial activation of toluene and its oxidation to the level of benzoate. evidence is provided for a novel way of toluene degradation based on experiments with cell-free extracts and with whole toluene-grown ... | 1996 | 8706665 |
| 4-hydroxybenzoyl coenzyme a reductase (dehydroxylating) is required for anaerobic degradation of 4-hydroxybenzoate by rhodopseudomonas palustris and shares features with molybdenum-containing hydroxylases. | the anaerobic degradation of 4-hydroxybenzoate is initiated by the formation of 4-hydroxybenzoyl coenzyme a, with the next step proposed to be a dehydroxylation to benzoyl coenzyme a, the starting compound for a central pathway of aromatic compound ring reduction and cleavage. three open reading frames, divergently transcribed from the 4-hydroxybenzoate coenzyme a ligase gene, hbaa, were identified and sequenced from the phototrophic bacterium rhodopseudomonas palustris. these genes, named hbabc ... | 1997 | 9006014 |
| identification and sequence analysis of two regulatory genes involved in anaerobic toluene metabolism by strain t1. | t1 is a denitrifying bacterium isolated for its ability to grow with toluene serving as the sole carbon source. mutants of this strain that have defects in the toluene utilization pathway have been isolated and have been separated into classes based on growth phenotypes. a cosmid clone has been isolated by complementing the tutb16 (for toluene utilization) mutation. the complementing gene has been localized to a 3.3-kb dna fragment. an additional open reading frame upstream of the tutb gene has ... | 1997 | 9023943 |
| anaerobic mineralization of cholesterol by a novel type of denitrifying bacterium | a novel denitrifying bacterium, strain 72chol, was enriched and isolated under strictly anoxic conditions on cholesterol as sole electron donor and carbon source. strain 72chol grew on cholesterol with oxygen or nitrate as electron acceptor. strictly anaerobic growth in the absence of oxygen was demonstrated using chemically reduced culture media. during anaerobic growth, nitrate was initially reduced to nitrite. at low nitrate concentrations, nitrite was further reduced to nitrogen gas. ammonia ... | 1997 | 9094222 |
| purification and characterization of the selenate reductase from thauera selenatis. | thauera selenatis is one of two isolated bacterial species that can obtain energy by respiring anaerobically with selenate as the terminal electron acceptor. the reduction of selenate to selenite is catalyzed by a selenate reductase, previously shown to be located in the periplasmic space of the cell. this study describes the purification of the enzyme from t. selenatis grown anaerobically with selenate. the enzyme is a trimeric alphabetagamma complex with an apparent mr of 180,000. the alpha, b ... | 1997 | 9295321 |
| anaerobic metabolism of l-phenylalanine via benzoyl-coa in the denitrifying bacterium thauera aromatica. | the anaerobic metabolism of phenylalanine was studied in the denitrifying bacterium thauera aromatica, a member of the beta-subclass of the proteobacteria. phenylalanine was completely oxidized and served as the sole source of cell carbon. evidence is presented that degradation proceeds via benzoyl-coa as the central aromatic intermediate; the aromatic ring-reducing enzyme benzoyl-coa reductase was present in cells grown on phenylalanine. intermediates in phenylalanine oxidation to benzoyl-coa w ... | 1997 | 9297469 |
| 4-hydroxybenzoyl-coa reductase (dehydroxylating) from the denitrifying bacterium thauera aromatica--prosthetic groups, electron donor, and genes of a member of the molybdenum-flavin-iron-sulfur proteins. | 4-hydroxybenzoyl-coa reductase catalyzes an important reaction in the anaerobic metabolism of phenolic compounds, i.e. the reductive removal of an aromatic hydroxyl group. the prosthetic groups and the natural electron donor of the enzyme were investigated and the genes were cloned and sequenced. the enzyme is a molybdenum-flavin-iron-sulfur protein of subunit composition of alpha2beta2gamma2. it contains approximately 1.3 flavin nucleotide, probably fad, 1.9 mo, 15 fe, and 12.5 acid-labile sulf ... | 1998 | 9490068 |
| identification and characterization of the natural electron donor ferredoxin and of fad as a possible prosthetic group of benzoyl-coa reductase (dearomatizing), a key enzyme of anaerobic aromatic metabolism. | under anoxic conditions most aromatic compounds are metabolized via benzoyl-coa which becomes reduced by benzoyl-coa reductase (dearomatizing); this enzyme was recently described in the bacterium thauera aromatica [boll, m. & fuchs, g. (1995) eur. j. biochem. 234, 921-933]. it catalyzes the reaction benzoyl-coa + 2 e- + 2 h+ + 2 mgatp + 2 h2o --> cyclohexa-1,5-diene-1-carboxyl-coa + 2 mgadp + 2 pi. the iron-sulfur protein has a native molecular mass of 160-170 kda and consists of four different ... | 1998 | 9490071 |
| anaerobic degradation of alpha-resorcylate by thauera aromatica strain ar-1 proceeds via oxidation and decarboxylation to hydroxyhydroquinone. | anaerobic degradation of alpha-resorcylate (3,5-dihydroxybenzoate) was studied with the denitrifying strain ar-1, which was assigned to the described species thauera aromatica. alpha-resorcylate degradation does not proceed via the benzoyl-coa, the resorcinol, or the phloroglucinol pathway. instead, alpha-resorcylate is converted to hydroxyhydroquinone (1,2,4-trihydroxybenzene) by dehydrogenative oxidation and decarboxylation. nitrate, k3[fe(cn)6], dichlorophenol indophenol, and the nad+ analogu ... | 1998 | 9531634 |
| phenylacetyl-coa:acceptor oxidoreductase, a new alpha-oxidizing enzyme that produces phenylglyoxylate. assay, membrane localization, and differential production in thauera aromatica. | anaerobic oxidation of phenylalanine and phenylacetate proceeds via alpha-oxidation of phenylacetyl-coa to phenylglyoxylate. this four-electron oxidation system was studied in the denitrifying bacterium thauera aromatica. it is membrane-bound and was solubilized with triton x-100. the system used dichlorophenolindophenol as an artificial electron acceptor; a spectrophotometric assay was developed. no other products besides phenylglyoxylate and coenzyme a were observed. the enzyme was quite oxyge ... | 1998 | 9575237 |
| biochemical and genetic characterization of benzylsuccinate synthase from thauera aromatica: a new glycyl radical enzyme catalysing the first step in anaerobic toluene metabolism. | toluene is anoxically degraded to co2 by the denitrifying bacterium thauera aromatica. the initial reaction in this pathway is the addition of fumarate to the methyl group of toluene, yielding benzylsuccinate as the first intermediate. we purified the enzyme catalysing this reaction, benzylsuccinate synthase (ec 4.1.99-), and studied its properties. the enzyme was highly oxygen sensitive and contained a redox-active flavin cofactor, but no iron centres. the native molecular mass was 220 kda; fou ... | 1998 | 9632263 |
| differential induction of enzymes involved in anaerobic metabolism of aromatic compounds in the denitrifying bacterium thauera aromatica. | differential induction of enzymes involved in anaerobic metabolism of aromatic substrates was studied in the denitrifying bacterium thauera aromatica. this metabolism is divided into (1) peripheral reactions transforming the aromatic growth substrates to the common intermediate benzoyl-coa, (2) the central benzoyl-coa pathway comprising ring-reduction of benzoyl-coa and subsequent beta-oxidation to 3-hydroxypimelyl-coa, and (3) the pathway of beta-oxidation of 3-hydroxypimelyl-coa to three acety ... | 1998 | 9683649 |
| identification of denitrifier strain t1 as thauera aromatica and proposal for emendation of the genus thauera definition. | bacterial strain, t1, originally isolated by p.j. evans on the basis of its capacity for toluene degradation under denitrifying conditions, has been classified as thauera aromatica. in a comprehensive study of strains of this species, it was found that the cells have a different type of flagellar insertion from that of cells of the type species of the genus, thauera selenatis, suggesting the convenience of an emendation of the description of the genus thauera. further studies on a larger collect ... | 1998 | 9734042 |
| cyclohexa-1,5-diene-1-carbonyl-coa hydratase [corrected], an enzyme involved in anaerobic metabolism of benzoyl-coa in the denitrifying bacterium thauera aromatica. | many aromatic compounds can be metabolized by bacteria under anoxic conditions via benzoyl-coa as the common intermediate. the central pathway of benzoyl-coa metabolism is initiated by an atp-driven reduction of the aromatic ring producing cyclohexa-1,5-diene-1-carbonyl-coa. the 1,5-dienoyl-coa intermediate is thought to be transformed to 6-hydroxycyclohex-1-ene-1-carbonyl-coa by a specific dienoyl-coa hydratase catalyzing the formal addition of water to one of the double bonds. this dienoyl-coa ... | 1998 | 9738901 |
| a two-component system involved in regulation of anaerobic toluene metabolism in thauera aromatica. | the genes for a two-component regulatory system of the denitrifying toluene-degrading bacterium thauera aromatica were identified immediately upstream of the genes for benzylsuccinate synthase (bssdcab), the first enzyme involved in anaerobic toluene metabolism. the genes apparently encode the regulators of toluene catabolic enzymes and were therefore termed tdisr (for toluene degradation including sensor and regulator). the tdir gene product was overproduced in escherichia coli and assayed for ... | 1998 | 9741082 |
| genes coding for the benzoyl-coa pathway of anaerobic aromatic metabolism in the bacterium thauera aromatica. | many aromatic compounds are anaerobically oxidized to co2 via benzoyl-coa as the common aromatic intermediate. in thauera aromatica, the central benzoyl-coa pathway comprises the atp-driven two-electron reduction of the benzene ring; this reaction uses a ferredoxin as electron donor and is catalyzed by benzoyl-coa reductase. the first intermediate, cyclohex-1,5-diene-1-carboxyl-coa, is subsequently hydrated by dienoyl-coa hydratase to 6-hydroxycyclohex-1-ene-1-carboxyl-coa. formation of the main ... | 1998 | 9746358 |
| thauera linaloolentis sp. nov. and thauera terpenica sp. nov., isolated on oxygen-containing monoterpenes (linalool, menthol, and eucalyptol) nitrate. | the monoterpenes menthol, linalool, and eucalyptol were recently used as sole electron donor and carbon source for the isolation of three denitrifying bacterial strains 21mol, 47lol, and 58eu. the motile, mesophilic, gram-negative rods had a strictly respiratory metabolism. monoterpenes were completely mineralised to carbon dioxide, nitrate was reduced to dinitrogen. strain 47lol utilised aliphatic monoterpenes, strain 21mol oxygenated monocyclic monoterpenes, and strain 58eu the bicyclic eucaly ... | 1998 | 9841126 |
| biotransformation of monoterpenes, bile acids, and other isoprenoids in anaerobic ecosystems. | isoprenoic compounds play a major part in the global carbon cycle. biosynthesis and mineralization by aerobic bacteria have been intensively studied. this review describes our knowledge on the anaerobic metabolism of isoprenoids, mainly by denitrifying and fermentative bacteria. nitrate-reducing beta-proteobacteria were isolated on monoterpenes as sole carbon source and electron donor. thauera spp. were obtained on the oxygen-containing monoterpenes linalool, menthol, and eucalyptol. several str ... | 1998 | 9990726 |
| phenylacetyl-coa:acceptor oxidoreductase, a membrane-bound molybdenum-iron-sulfur enzyme involved in anaerobic metabolism of phenylalanine in the denitrifying bacterium thauera aromatica. | phenylacetic acids are common intermediates in the microbial metabolism of various aromatic substrates including phenylalanine. in the denitrifying bacterium thauera aromatica phenylacetate is oxidized, under anoxic conditions, to the common intermediate benzoyl-coa via the intermediates phenylacetyl-coa and phenylglyoxylate (benzoylformate). the enzyme that catalyzes the four-electron oxidation of phenylacetyl-coa has been purified from this bacterium and studied. the enzyme preparation catalyz ... | 1999 | 10336636 |
| fermented whey--an inexpensive feed source for a laboratory-scale selenium-bioremediation reactor system inoculated with thauera selenatis. | it is critical that an inexpensive electrondonor/carbon-source be found for selenium bioremediation using the selenate-respiring bacterium, thauera selenatis. since acetate is a preferred substrate for growth of this organism, a method was developed for fermenting the lactose in whey to large amounts of acetate. indigenous whey microorganisms fermented the whey lactose in this manner when grown in continuous culture at a very slow dilution rate (d = 0.05 h-1). the successful use of the fermented ... | 1999 | 10390824 |
| 6-hydroxycyclohex-1-ene-1-carbonyl-coa dehydrogenase and 6-oxocyclohex-1-ene-1-carbonyl-coa hydrolase, enzymes of the benzoyl-coa pathway of anaerobic aromatic metabolism in the denitrifying bacterium thauera aromatica. | benzoyl-coa is a common intermediate in the anaerobic bacterial metabolism of many aromatic substrates. two enzymes and ferredoxin of the central benzoyl-coa pathway in thauera aromatica have been purified so far. benzoyl-coa reductase reduces the aromatic ring with reduced ferredoxin yielding cyclohexa-1,5-diene-1-carbonyl-coa [boll, m. & fuchs, g. (1995) eur. j. biochem. 234, 921-933]. dienoyl-coa hydratase subsequently adds one molecule of water and thereby produces 6-hydroxycyclohex-1-ene-1- ... | 1999 | 10406950 |
| thauera mechernichensis sp. nov., an aerobic denitrifier from a leachate treatment plant. | a heterotrophic bacterial strain tl1t capable of aerobic denitrification was previously enriched in continuous culture from a landfill leachate treatment plant and isolated as a pure culture. the taxonomic position of this isolate within the beta-subclass of the proteobacteria was determined by 16s rdna sequence analysis and by conventional taxonomy including substrate spectrum, quinone type (ubiquinone q-8) and cellular fatty acid composition. detection of the specific polyamine 2-hydroxyputres ... | 1999 | 10425762 |
| 2-hydroxyglutaryl-coa dehydratase from clostridium symbiosum. | component d (hgdab) of 2-hydroxyglutaryl-coa dehydratase from clostridium symbiosum was purified to homogeneity. it is able to use component a from acidaminococcus fermentans (hgdc) to initiate catalysis together with atp, mg2+ and a strong reducing agent such as ti(iii)citrate. component d from c. symbiosum has a 6 x higher specific activity compared with that from a. fermentans and contains a second [4fe-4s] cluster but the same amount of riboflavin 5'-phosphate (1.0 per heterodimeric enzyme, ... | 1999 | 10491198 |
| anaerobic oxidation of the aromatic plant hydrocarbon p-cymene by newly isolated denitrifying bacteria. | the capability of nitrate-reducing bacteria to degrade alkyltoluenes in the absence of molecular oxygen was investigated with the three isomers of xylene, ethyltoluene, and isopropyltoluene (cymene) in enrichment cultures inoculated with freshwater mud. denitrifying enrichment cultures developed most readily (within 4 weeks) with p-cymene, a natural aromatic hydrocarbon occurring in plants, and with m-xylene (within 6 weeks). enrichment of denitrifiers that utilized m-ethyltoluene and p-ethyltol ... | 1999 | 10550472 |
| anaerobic toluene-catabolic pathway in denitrifying thauera aromatica: activation and beta-oxidation of the first intermediate, (r)-(+)-benzylsuccinate. | anaerobic catabolism of toluene is initiated by addition of the methyl group of toluene to the double bond of a fumarate cosubstrate to yield the first intermediate, benzylsuccinate. this reaction is catalysed by the glycyl-radical enzyme benzylsuccinate synthase, as shown for the denitrifying bacterium thauera aromatica. benzylsuccinate is further oxidized to benzoyl-coa, the central intermediate of anaerobic degradation of aromatic compounds. the authors show here by experiments with cell extr ... | 1999 | 10589736 |
| anaerobic toluene catabolism of thauera aromatica: the bbs operon codes for enzymes of beta oxidation of the intermediate benzylsuccinate. | the pathway of anaerobic toluene oxidation to benzoyl coenzyme a (benzoyl-coa) consists of an initial reaction catalyzed by benzylsuccinate synthase, a glycyl radical enzyme adding the methyl group of toluene to the double bond of a fumarate cosubstrate, and a subsequent beta-oxidation pathway of benzylsuccinate. benzylsuccinate synthase has been studied in some detail, whereas the enzymes participating in beta oxidation of benzylsuccinate are unknown. we have investigated these enzymes by analy ... | 2000 | 10629170 |
| transcriptional analysis of the tute tutfdgh gene cluster from thauera aromatica strain t1. | the denitrifying strain t1, identified as thauera aromatica, is able to grow with toluene serving as its sole carbon source. previous work identified two genes, tutd and tute, that are involved in toluene metabolism. two small open reading frames, tutf and tutg, which may also play a role in toluene metabolism, were also identified. the present work examines the transcriptional organization and regulation of these toluene utilization genes. northern analysis indicates that the four genes are org ... | 2000 | 10698784 |
| description of strain 3cb-1, a genomovar of thauera aromatica, capable of degrading 3-chlorobenzoate coupled to nitrate reduction. | a gram-negative bacterium, strain 3cb-1, isolated from a 3-chlorobenzoate enrichment culture inoculated with a sediment sample is capable of degrading various aromatic compounds and halogenated derivatives with nitrate as electron acceptor. compounds capable of serving as carbon and energy sources include 3-chlorobenzoate, 3-bromobenzoate, 2-fluorobenzoate, 4-fluorobenzoate, benzoate, 3-hydroxybenzoate, 4-hydroxybenzoate, 3-aminobenzoate, protocatechuate, m-cresol and p-cresol. oxygen, nitrate a ... | 2000 | 10758860 |
| reassessment of the taxonomic structure of the diazotrophic genus azoarcus sensu lato and description of three new genera and new species, azovibrio restrictus gen. nov., sp. nov., azospira oryzae gen. nov., sp. nov. and azonexus fungiphilus gen. nov., sp. nov. | the taxonomic structure of members of the genus azoarcus sensu lato was reassessed in a polyphasic approach. two species, azoarcus communis and azoarcus indigens, three unnamed species containing diazotrophs associated with kallar grass roots (groups c, d) and a group of strains (e) isolated from fungi were analysed. they were compared by page analyses of cellular proteins, genomic fingerprints, morphological and nutritional features to new isolates from rice roots. all strains within groups c, ... | 2000 | 10758872 |
| nonaromatic products from anoxic conversion of benzoyl-coa with benzoyl-coa reductase and cyclohexa-1,5-diene-1-carbonyl-coa hydratase. | the enzymes benzoyl-coa reductase and cyclohex-1, 5-diene-1-carbonyl-coa hydratase catalyzing the first steps of benzoyl-coa conversion under anoxic conditions were purified from the denitrifying bacterium, thauera aromatica. reaction products obtained with [ring-(13)c(6)]benzoyl-coa and [ring-(14)c]benzoyl-coa as substrates were analyzed by high pressure liquid chromatography and by nmr spectroscopy. the main product obtained with titanium(iii) citrate or with reduced [8fe-8s]-ferredoxin from t ... | 2000 | 10766750 |
| unusual spectroscopic and electrochemical properties of the 2[4fe-4s] ferredoxin of thauera aromatica. | a reduced ferredoxin serves as the natural electron donor for key enzymes of the anaerobic aromatic metabolism in the denitrifying bacterium thauera aromatica. it contains two [4fe-4s] clusters and belongs to the chromatium vinosum type of ferredoxins (cvfd) which differ from the "clostridial" type by a six-amino acid insertion between two successive cysteines and a c-terminal alpha-helical amino acid extension. the electrochemical and electron paramagnetic resonance (epr) spectroscopic properti ... | 2000 | 10769152 |
| 2-hydroxycyclohexanecarboxyl coenzyme a dehydrogenase, an enzyme characteristic of the anaerobic benzoate degradation pathway used by rhodopseudomonas palustris. | a gene, badh, whose predicted product is a member of the short-chain dehydrogenase/reductase family of enzymes, was recently discovered during studies of anaerobic benzoate degradation by the photoheterotrophic bacterium rhodopseudomonas palustris. purified histidine-tagged badh protein catalyzed the oxidation of 2-hydroxycyclohexanecarboxyl coenzyme a (2-hydroxychc-coa) to 2-ketocyclohexanecarboxyl-coa. these compounds are proposed intermediates of a series of three reactions that are shared by ... | 2000 | 10781543 |
| two distinct pathways for anaerobic degradation of aromatic compounds in the denitrifying bacterium thauera aromatica strain ar-1. | denitrifying bacteria degrade many different aromatic compounds anaerobically via the well-described benzoyl-coa pathway. we have shown recently that the denitrifiers azoarcus anaerobius and thauera aromatica strain ar-1 use a different pathway for anaerobic degradation of resorcinol (1,3-dihydroxybenzene) and 3,5-dihydroxybenzoate, respectively. both substrates are converted to hydroxyhydroquinone (1,2,4-trihydroxybenzene). in the membrane fraction of t. aromatica strain ar-1 cells grown with 3 ... | 2000 | 10795679 |
| cloning and sequencing of the genes encoding the periplasmic-cytochrome b-containing selenate reductase of thauera selenatis. | the periplasmic selenate reductase (ser) of thauera selennatis is a component of the electron transport chain catalyzing selenate reduction with acetate as the electron donor (i.e., selenate respiration). the purified enzyme consists of three subunits (sera, serb and serc). using transposon (i.e., tn5) mutagenesis selenate reductase mutants were isolated. junction fragments of dna adjacent to the integrated tn5 were used, together with oligonucleotides derived from the n-termini of sera and serb ... | 2000 | 10826693 |
| epr and mössbauer studies of benzoyl-coa reductase. | benzoyl-coa reductase catalyzes the two-electron transfer from a reduced ferredoxin to the aromatic ring of benzoyl-coa; this reaction is coupled to stoichiometrical atp hydrolysis. a very low reduction potential (less than -1 v) is required for the first electron transfer to the aromatic ring. in this work the nature of the redox centers of purified benzoyl-coa reductase from thauera aromatica was studied by epr and mössbauer spectroscopy. the results obtained indicated the presence of three [4 ... | 2000 | 10903310 |
| isolation and characterization of diverse halobenzoate-degrading denitrifying bacteria from soils and sediments. | denitrifying bacteria capable of degrading halobenzoates were isolated from various geographical and ecological sites. the strains were isolated after initial enrichment on one of the monofluoro-, monochloro-, or monobromo-benzoate isomers with nitrate as an electron acceptor, yielding a total of 33 strains isolated from the different halobenzoate-utilizing enrichment cultures. each isolate could grow on the selected halobenzoate with nitrate as the terminal electron acceptor. the isolates obtai ... | 2000 | 10919805 |
| genes involved in anaerobic metabolism of phenol in the bacterium thauera aromatica. | genes involved in the anaerobic metabolism of phenol in the denitrifying bacterium thauera aromatica have been studied. the first two committed steps in this metabolism appear to be phosphorylation of phenol to phenylphosphate by an unknown phosphoryl donor ("phenylphosphate synthase") and subsequent carboxylation of phenylphosphate to 4-hydroxybenzoate under release of phosphate ("phenylphosphate carboxylase"). both enzyme activities are strictly phenol induced. two-dimensional gel electrophore ... | 2000 | 11004186 |
| anaerobic utilization of essential oils by denitrifying bacteria. | plant volatile organic compounds are a major carbon source in nature. we studied the degradability of these substances by anaerobic microorganisms in enrichment cultures with representative essential oils as organic substrates and nitrate as electron acceptor. lemon and pine needle oil supported microbial growth in the presence of pure oil, whereas parsley seed, camphor, sage, fennel, and mint oil supported growth only when the essential oils were dissolved in an overlying phase of 2,2,4,4,6,8,8 ... | 2000 | 11194974 |
| anaerobic utilization of alkylbenzenes and n-alkanes from crude oil in an enrichment culture of denitrifying bacteria affiliating with the beta-subclass of proteobacteria. | denitrifying bacteria were enriched from freshwater sediment with added nitrate as electron acceptor and crude oil as the only source of organic substrates. the enrichment cultures were used as laboratory model systems for studying the degradative potential of denitrifying bacteria with respect to crude oil constituents, and the phylogenetic affiliation of denitrifiers that are selectively enriched with crude oil. the enrichment culture exhibited two distinct growth phases. during the first phas ... | 1999 | 11207730 |
| 13c/12c isotope fractionation of aromatic hydrocarbons during microbial degradation. | the influence of microbial degradation on the 13c/12c isotope composition of aromatic hydrocarbons is presented using toluene as a model compound. four different toluene-degrading bacterial strains grown in batch culture with oxygen, nitrate, ferric iron or sulphate as electron acceptors were studied as representatives of different environmental redox conditions potentially prevailing in contaminated aquifers. the biological degradation induced isotope shifts in the residual, non-degraded toluen ... | 1999 | 11207760 |
| anaerobic metabolism of 3-hydroxybenzoate by the denitrifying bacterium thauera aromatica. | the anaerobic metabolism of 3-hydroxybenzoate was studied in the denitrifying bacterium thauera aromatica. cells grown with this substrate were adapted to grow with benzoate but not with 4-hydroxybenzoate. vice versa, 4-hydroxybenzoate-grown cells did not utilize 3-hydroxybenzoate. the first step in 3-hydroxybenzoate metabolism is a coenzyme a (coa) thioester formation, which is catalyzed by an inducible 3-hydroxybenzoate-coa ligase. the enzyme was purified and characterized. further metabolism ... | 2001 | 11208796 |
| metabolism of benzoate, cyclohex-1-ene carboxylate, and cyclohexane carboxylate by "syntrophus aciditrophicus" strain sb in syntrophic association with h(2)-using microorganisms. | the metabolism of benzoate, cyclohex-1-ene carboxylate, and cyclohexane carboxylate by "syntrophus aciditrophicus" in cocultures with hydrogen-using microorganisms was studied. cyclohexane carboxylate, cyclohex-1-ene carboxylate, pimelate, and glutarate (or their coenzyme a [coa] derivatives) transiently accumulated during growth with benzoate. identification was based on comparison of retention times and mass spectra of trimethylsilyl derivatives to the retention times and mass spectra of authe ... | 2001 | 11282627 |
| ethylbenzene dehydrogenase, a novel hydrocarbon-oxidizing molybdenum/iron-sulfur/heme enzyme. | the initial enzyme of ethylbenzene metabolism in denitrifying azoarcus strain ebn1, ethylbenzene dehydrogenase, was purified and characterized. the soluble periplasmic enzyme is the first known enzyme oxidizing a nonactivated hydrocarbon without molecular oxygen as cosubstrate. it is a novel molybdenum/iron-sulfur/heme protein of 155 kda, which consists of three subunits (96, 43, and 23 kda) in an alphabetagamma structure. the n-terminal amino acid sequence of the alpha subunit is similar to tha ... | 2001 | 11294876 |
| evaluation of the denitrifying microbiota of anoxic reactors. | removal of inorganic nitrogen compounds from wastewaters can be accomplished by a combination of the biological processes of nitrification and denitrification. the information on the microbiota present in denitrifying reactors is still scarce. in the present work the evaluation of the denitrifying microbiota of different reactor sludges was performed by specific activity measurements and mpn count of denitrifiers. we also present the isolation and physiological and phylogenetic characterisation ... | 2001 | 11311436 |
| characterization of halobenzoate-degrading, denitrifying azoarcus and thauera isolates and description of thauera chlorobenzoica sp. nov. | the taxonomic relationships of azoarcus and thauera isolates in the beta-subclass of the proteobacteria capable of degrading fluoro-, chloro- or bromobenzoate under denitrifying conditions were analysed. a detailed classification of these strains was performed using a polyphasic approach, which included studies on morphology, phenotypic characterization, fatty acid analysis, 16s rrna gene sequence analysis, 16s rrna gene mapping (ribotyping) and dna-dna hybridization. the analyses of fatty acids ... | 2001 | 11321105 |
| single turnover epr studies of benzoyl-coa reductase. | benzoyl-coa reductase (bcr) catalyzes the atp-driven transport of two electrons from a reduced 2[4fe-4s] ferredoxin to the aromatic ring of benzoyl-coa. a mechanism involving radical species and very low potential electrons similar to the birch reduction of aromatics has been suggested for this reaction. the redox centers of bcr have previously been identified, by epr- and mössbauer spectroscopy, to be three cysteine-ligated [4fe-4s] clusters [boll et al. (2000) j. biol. chem. 275, 31857-31868] ... | 2001 | 11412115 |
| succinyl-coa:(r)-benzylsuccinate coa-transferase: an enzyme of the anaerobic toluene catabolic pathway in denitrifying bacteria. | anaerobic microbial toluene catabolism is initiated by addition of fumarate to the methyl group of toluene, yielding (r)-benzylsuccinate as first intermediate, which is further metabolized via beta-oxidation to benzoyl-coenzyme a (coa) and succinyl-coa. a specific succinyl-coa:(r)-benzylsuccinate coa-transferase activating (r)-benzylsuccinate to the coa-thioester was purified and characterized from thauera aromatica. the enzyme is fully reversible and forms exclusively the 2-(r)-benzylsuccinyl-c ... | 2001 | 11418570 |
| involvement of coenzyme a esters and two new enzymes, an enoyl-coa hydratase and a coa-transferase, in the hydration of crotonobetaine to l-carnitine by escherichia coli. | two proteins (caib and caid) were found to catalyze the reversible biotransformation of crotonobetaine to l-carnitine in escherichia coli in the presence of a cosubstrate (e.g., gamma-butyrobetainyl-coa or crotonobetainyl-coa). caib (45 kda) and caid (27 kda) were purified in two steps to electrophoretic homogeneity from overexpression strains. caib was identified as crotonobetainyl-coa:carnitine coa-transferase by maldi-tof mass spectrometry and enzymatic assays. the enzyme exhibits high cosubs ... | 2001 | 11551212 |
| stable hydrogen and carbon isotope fractionation during microbial toluene degradation: mechanistic and environmental aspects. | primary features of hydrogen and carbon isotope fractionation during toluene degradation were studied to evaluate if analysis of isotope signatures can be used as a tool to monitor biodegradation in contaminated aquifers. d/h hydrogen isotope fractionation during microbial degradation of toluene was measured by gas chromatography. per-deuterated toluene-d(8) and nonlabeled toluene were supplied in equal amounts as growth substrates, and kinetic isotope fractionation was calculated from the shift ... | 2001 | 11571192 |
| benzylsuccinate synthase of azoarcus sp. strain t: cloning, sequencing, transcriptional organization, and its role in anaerobic toluene and m-xylene mineralization. | biochemical studies in azoarcus sp. strain t have demonstrated that anaerobic oxidation of both toluene and m-xylene is initiated by addition of the aromatic hydrocarbon to fumarate, forming benzylsuccinate and 3-methyl benzylsuccinate, respectively. partially purified benzylsuccinate synthase was previously shown to catalyze both of these addition reactions. in this study, we identified and sequenced the genes encoding benzylsuccinate synthase from azoarcus sp. strain t and examined the role of ... | 2001 | 11698363 |
| mechanism of atp-driven electron transfer catalyzed by the benzene ring-reducing enzyme benzoyl-coa reductase. | benzoyl-coa reductase (bcr) from the bacterium thauera aromatica catalyzes the two-electron reduction of benzoyl-coa (bcoa) to a nonaromatic cyclic diene. in a process analogous to enzymatic nitrogen reduction, bcr couples the electron transfer to the aromatic ring to a stoichiometric hydrolysis of 2 atp/2e(-). reduced but not oxidized bcr hydrolyzes atp to adp. in this work, purified bcr was shown to catalyze an isotope exchange from [(14)c]adp to [(14)c]atp, which was approximately 15% of the ... | 2001 | 11698658 |
| influence of electrochemical properties in determining the sensitivity of [4fe-4s] clusters in proteins to oxidative damage. | interconversion between [4fe-4s] cubane and [3fe-4s] cuboidal states represents one of the simplest structural changes an iron-sulphur cluster can undertake. this reaction is implicated in oxidative damage and in modulation of the activity and regulation of certain enzymes, and it is therefore important to understand the factors governing cluster stability and the processes that activate cluster conversion. in the present study, protein film voltammetry has been used to induce and monitor the ox ... | 2001 | 11736664 |
| operon structure and expression of the genes for benzylsuccinate synthase in thauera aromatica strain k172. | the first step in anaerobic toluene degradation is the addition of a fumarate cosubstrate to the methyl group of toluene, as catalyzed by the glycyl radical enzyme benzylsuccinate synthase. the bssdcab genes code for the subunits of benzylsuccinate synthase (bssa, b and c) and an additional enzyme implicated in activating the enzyme by introducing the glycyl radical (bssd). quantitation of the amounts of benzylsuccinate synthase and activating enzyme showed that both proteins are only synthesize ... | 2002 | 11807562 |
| a birch-like mechanism in enzymatic benzoyl-coa reduction: a kinetic study of substrate analogues combined with an ab initio model. | benzoyl-coa reductase from the anaerobic bacterium thauera aromatica catalyzes the atp-driven two-electron reduction of the aromatic moiety of benzoyl-coa. a birch mechanism involving alternate one-electron and one-proton transfer steps to the aromatic ring was previously proposed for benzoyl-coa reductase. due to the high redox barrier, the first electron transfer step yielding a radical anion is considered the rate-limiting step in this reaction. focusing on the mechanism of substrate reductio ... | 2002 | 11827519 |
| crystallization and preliminary x-ray analysis of the selenate reductase from thauera selenatis. | selenate reductase from thauera selenatis was crystallized using ammonium sulfate as a precipitant. crystals of selenate reductase belong to the space group c2, with unit-cell parameters a = 116.9, b = 67.5, c = 186.7 a, beta = 90 degrees. native data to 2.1 a resolution have been collected and a heavy-atom derivative has been identified following soaking of the crystals in a solution of trimethyl lead acetate. | 2002 | 11914503 |
| methylation of inorganic and organic selenium by the bacterial thiopurine methyltransferase. | escherichia coli cells expressing the tpm gene encoding the bacterial thiopurine methyltransferase (btpmt) are shown to methylate selenite and (methyl)selenocysteine into dimethylselenide (dmse) and dimethyldiselenide (dmdse). e. coli cells expressing tpm from a gene library cosmid clone (harboring a pseudomonas syringae insert of about 20 kb) also methylated selenate into dmse and dmdse. btpmt is the first methyltransferase shown to be involved in the methylation of these selenium derivatives. | 2002 | 12003960 |
| phylogenetic and metabolic diversity of bacteria degrading aromatic compounds under denitrifying conditions, and description of thauera phenylacetica sp. nov., thauera aminoaromaticasp. nov., and azoarcus buckelii sp. nov. | six strains of denitrifying bacteria isolated from various oxic and anoxic habitats on different monocyclic aromatic substrates were characterized by sequencing 16s rrna genes, determining physiological and morphological traits, and dna-dna hybridization. according to these criteria, strains s100, sp and lg356 were identified as members of thauera aromatica. strains b5-1 and b5-2 were tentatively affiliated to the species azoarcus tolulyticus. strains b4p and s2 were only distantly related to ea ... | 2002 | 12070766 |
| anaerobic degradation of protocatechuate (3,4-dihydroxybenzoate) by thauera aromatica strain ar-1. | the denitrifying bacterium thauera aromatica strain ar-1 grows anaerobically with protocatechuate (3,4-dihydroxybenzoate (dhb)) as sole energy and carbon source. this bacterium harbors two distinct pathways for degradation of aromatic compounds, the benzoyl-coenzyme a (coa) pathway for benzoate degradation and the hydroxyhydroquinone (hhq) pathway for degradation of 3,5-dhb. in order to elucidate whether protocatechuate is degraded via the benzoyl-coa or the hhq pathway, induction experiments we ... | 2002 | 12076800 |
| properties of 2-oxoglutarate:ferredoxin oxidoreductase from thauera aromatica and its role in enzymatic reduction of the aromatic ring. | benzoyl coenzyme a (benzoyl-coa) reductase is a key enzyme in the anaerobic metabolism of aromatic compounds catalyzing the atp-driven reductive dearomatization of benzoyl-coa. the enzyme from thauera aromatica uses a reduced 2[4fe-4s] ferredoxin as electron donor. in this work, we identified 2-oxoglutarate:ferredoxin oxidoreductase (kgor) as the ferredoxin reducing enzyme. kgor activity was increased 10- to 50-fold in t. aromatica cells grown under denitrifying conditions on an aromatic substra ... | 2002 | 12081970 |
| characterization of bacterial consortia capable of degrading 4-chlorobenzoate and 4-bromobenzoate under denitrifying conditions. | 4-chlorobenzoate and 4-bromobenzoate were readily degraded in denitrifying enrichment cultures established with river sediment, estuarine sediment or agricultural soil as inoculum. stable denitrifying consortia were obtained and maintained by serial dilution and repeated feeding of substrates. microbial community analyses were performed to characterize the 4-chlorobenzoate and 4-bromobenzoate degrading consortia with terminal restriction fragment length polymorphism (t-rflp) and cloning of 16s r ... | 2002 | 12167535 |
| microbial aspects of anaerobic btex degradation. | combined with conventional methods, developments in both geochemical (delineation of redox processes) and molecular microbial methods (analysis of 16s rdna genes and functional genes) have allowed us to study in details microorganisms and genes involved in the anaerobic degradation of benzene, toluene, ethylbenzene and xylene (btex) under specific redox conditions. this review summarizes recent research in this field. the potential for anaerobic btex degradation is widely spread. specific groups ... | 2002 | 12244754 |
| a real-time polymerase chain reaction method for monitoring anaerobic, hydrocarbon-degrading bacteria based on a catabolic gene. | we have developed a real-time polymerase chain reaction (pcr) method that can quantify hydrocarbon-degrading bacteria in sediment samples based on a catabolic gene associated with the first step of anaerobic toluene and xylene degradation. the target gene, bssa, codes for the alpha-subunit of benzylsuccinate synthase. the primer-probe set for real-time pcr was based on consensus regions of bssa from four denitrifying bacterial strains; bssa sequences for two of these strains were determined duri ... | 2002 | 12269751 |
| rna stable isotope probing, a novel means of linking microbial community function to phylogeny. | identifying microorganisms responsible for recognized environmental processes remains a great challenge in contemporary microbial ecology. only in the last few years have methodological innovations provided access to the relationship between the function of a microbial community and the phylogeny of the organisms accountable for it. in this study stable-isotope-labeled [13c]phenol was fed into a phenol-degrading community from an aerobic industrial bioreactor, and the 13c-labeled rna produced wa ... | 2002 | 12406726 |
| (r)-benzylsuccinyl-coa dehydrogenase of thauera aromatica, an enzyme of the anaerobic toluene catabolic pathway. | the first intermediate of anaerobic toluene catabolism, (r)-benzylsuccinate, is formed by enzymic addition of the methyl group of toluene to a fumarate cosubstrate and is subsequently activated to (r)-2-benzylsuccinyl-coa. this compound is then oxidised to benzoyl-coa and succinyl-coa by a specific beta-oxidation pathway. the enzyme catalysing the first oxidation step of this pathway, (r)-benzylsuccinyl-coa dehydrogenase, is encoded by the bbsg gene in thauera aromatica. it was functionally over ... | 2002 | 12420174 |
| construction and characterization of insertion/deletion mutations of the tutf, tutd, and tutg genes of thauera aromatica strain t1. | thauera aromatica t1 was isolated for its ability to use toluene as a sole carbon source under denitrifying conditions. a genetic approach was used to examine the roles of the tutf, tutd, and tutg gene products (part of a single operon) in the metabolism of toluene. the genes were individually deleted from the chromosome and each resulting mutant strain was unable to metabolize toluene. plasmids carrying individual in-frame gene deletions failed to complement the corresponding chromosomal deleti ... | 2002 | 12445643 |
| anaerobic mineralization of quaternary carbon atoms: isolation of denitrifying bacteria on pivalic acid (2,2-dimethylpropionic acid). | the degradability of pivalic acid was established by the isolation of several facultative denitrifying strains belonging to zoogloea resiniphila, to thauera and herbaspirillum, and to comamonadaceae, related to [aquaspirillum] and acidovorax, and of a nitrate-reducing bacterium affiliated with moraxella osloensis. pivalic acid was completely mineralized to carbon dioxide. the catabolic pathways may involve an oxidation to dimethylmalonate or a carbon skeleton rearrangement, a putative 2,2-dimeth ... | 2003 | 12620885 |
| use of a green fluorescent protein-based reporter fusion for detection of nitric oxide produced by denitrifiers. | to determine if green fluorescent protein could be used as a reporter for detecting nitric oxide production, gfp was fused to nnrs from rhodobacter sphaeroides 2.4.3. nnrs was chosen because its expression requires nitric oxide. the presence of the fusion in r. sphaeroides 2.4.3 resulted in a significant increase in fluorescent intensity of the cells, but only when nitrite reductase was active. cells lacking nitrite reductase activity and consequently the ability to generate nitric oxide were on ... | 2003 | 12839764 |
| sterolibacterium denitrificans gen. nov., sp. nov., a novel cholesterol-oxidizing, denitrifying member of the beta-proteobacteria. | a bacterial strain (chol-1s(t)) that is able to oxidize cholesterol to co2 and reduce nitrate to dinitrogen was enriched and isolated from an upflow sludge bed (usb) anoxic reactor that treats sanitary landfill leachate from the city of montevideo, uruguay. cells of strain chol-1s(t) were gram-negative, rod-shaped to slightly curved, measured 0.5-0.6 x 1.0-1.3 microm and were motile by a single polar flagellum. strain chol-1s(t) grew optimally at 30-32 degrees c and ph 7.0, with a doubling time ... | 2003 | 12892131 |
| benzoate-coenzyme a ligase from thauera aromatica: an enzyme acting in anaerobic and aerobic pathways. | in the denitrifying member of the beta-proteobacteria thauera aromatica, the anaerobic metabolism of aromatic acids such as benzoate or 2-aminobenzoate is initiated by the formation of the coenzyme a (coa) thioester, benzoyl-coa and 2-aminobenzoyl-coa, respectively. both aromatic substrates were transformed to the acyl-coa intermediate by a single coa ligase (amp forming) that preferentially acted on benzoate. this benzoate-coa ligase was purified and characterized as a 57-kda monomeric protein. ... | 2003 | 12897012 |
| tepidiphilus margaritifer gen. nov., sp. nov., isolated from a thermophilic aerobic digester. | a moderately thermophilic bacterium is described, strain n2-214(t), that was isolated from an enrichment culture, growing on caprolactone, obtained from a sample from a water-treatment sludge aerobic digester operating at temperatures around 60 degrees c. the organism was aerobic, gram-negative, oxidase- and catalase-positive, with a polar flagellum, and capable of growth at temperatures as high as 61 degrees c. the major fatty acids of strain n2-214(t) were c(16 : 0), c(18 : 1) and cyclo-c(19 : ... | 2003 | 13130025 |
| molecular analysis of microbial communities in nitrification and denitrification reactors treating high ammonia leachate. | molecular analysis of microbial populations in two bench-scale nitrification and denitrification reactors fed with high ammonia landfill leachate was conducted in this study by using dgge, cloning, and fish techniques in addition to classical efficiency control parameters. nitrification tank was operated with a computer-controlled alkalinity dosing system to supply the alkalinity intermittently as consumed on the basis of on-line ph monitoring. by keeping the ph at 7.0 with this system, 99% nitr ... | 2003 | 14524656 |
| evolution of the bacterial community during granules formation in denitrifying reactors followed by molecular, culture-independent techniques. | the microbial community in two acetate-fed denitrifying reactors, inoculated with methanogenic sludge, was monitored by 16s rdna-based methods (sscp and fish). both reactors converged to similar, stable communities. the predominant organisms belonged to the genera thauera, paracoccus and denitrobacter, detected both by molecular and culture-based methods. | 2003 | 14640202 |
| substrate specificities and electron paramagnetic resonance properties of benzylsuccinate synthases in anaerobic toluene and m-xylene metabolism. | the anaerobic degradation pathways of toluene and m-xylene are initiated by addition of a fumarate cosubstrate to the methyl group of the hydrocarbon, yielding (r)-benzylsuccinate and (3-methylbenzyl)succinate, respectively, as first intermediates. these reactions are catalyzed by a novel glycyl-radical enzyme, (r)-benzylsuccinate synthase. substrate specificities of benzylsuccinate synthases were analyzed in azoarcus sp. strain t and thauera aromatica strain k172. the enzyme of azoarcus sp. str ... | 2004 | 14689166 |
| improvement of comparative modeling by the application of conserved motifs amongst distantly related proteins as additional restraints. | protein comparative modeling has useful applications in large-scale structural initiatives and in rational design of drug targets in medicinal chemistry. the reliability of a homology model is dependent on the sequence identity between the query and the structural homologue used as a template for modeling. here, we present a method for the utilization and conservation of important structural features of template structures by providing additional spatial restraints in comparative modeling progra ... | 2004 | 14691673 |
| x-ray absorption spectroscopy of selenate reductase. | the metal sites of selenate reductase from thauera selenatis have been characterized by mo, se, and fe k-edge x-ray absorption spectroscopy. the mo site of the oxidized enzyme has 3 to 4 sulfur ligands at 2.33 a from two molybdopterin cofactors, one mo=o group at 1.68 a and one mo-o with an intermediate bond length of 1.81 a. the reduced enzyme has a des-oxo active site, again with about four mo-s ligands (at 2.32 a) and possibly one oxygen ligand at 2.22 a. the enzyme was found to contain se in ... | 2004 | 14730999 |
| genes involved in the anaerobic degradation of toluene in a denitrifying bacterium, strain ebn1. | the organization of all genes required for the anaerobic conversion of toluene to benzoyl-coa was investigated in denitrifying azoarcus-like strain ebn1. all of these genes are clustered within 25.3 kb of contiguous dna sequence, which includes only a few intervening sequences. the toluene-catabolic genes are organized in two apparent operons. one contains the genes ( bsscab) for the three subunits of benzylsuccinate synthase, which initiates anaerobic toluene degradation by converting toluene t ... | 2004 | 14735297 |
| crystallization of 4-hydroxybenzoyl-coa reductase and the structure of its electron donor ferredoxin. | 4-hydroxybenzoyl-coa reductase (4-hbcr) is a central enzyme in the metabolism of phenolic compounds in anaerobic bacteria. the enzyme catalyzes the reductive removal of the phenolic hydroxyl group from 4-hydroxybenzoyl-coa, yielding benzoyl-coa and water. 4-hbcr belongs to the xanthine oxidase (xo) family of molybdenum enzymes which occur as heterodimers, (alphabetagamma)(2). 4-hbcr contains two molybdopterins, four [2fe-2s] and two [4fe-4s] clusters and two fads. a low-potential allochromatium ... | 2004 | 14747735 |
| substrate binding and reduction of benzoyl-coa reductase: evidence for nucleotide-dependent conformational changes. | benzoyl-coa reductase (bcr) from the denitrifying bacterium thauera aromatica catalyzes the atp driven two-electron reduction of the aromatic moiety of benzoyl-coa (bcoa) to a nonaromatic cyclic diene (2 atp/2 e(-)). the enzyme contains two similar but nonidentical atp-binding sites of the acetate kinase/sugar kinase/hsp70/actin family. to obtain further insights into the overall catalytic cycle of bcr, the binding affinities and stoichiometries of all substrates as well as their effects on redu ... | 2004 | 14756575 |
| role of benzylsuccinate in the induction of the tute tutfdgh gene complex of t. aromatica strain t1. | expression of the tute tutfdgh gene cluster of thauera aromatica strain t1 was examined by northern and western analysis in a wild-type strain and chromosomally deleted strains with or without in-frame deletion plasmids. while expression was observed when the wild-type strain was induced with toluene, various chromosomally deleted strains exhibited little or no expression of the tut genes. in contrast, both wild-type and chromosomally deleted strains expressed the tut genes when induced with ben ... | 2004 | 14987773 |
| aerobic and anaerobic toluene degradation by a newly isolated denitrifying bacterium, thauera sp. strain dnt-1. | a newly isolated denitrifying bacterium, thauera sp. strain dnt-1, grew on toluene as the sole carbon and energy source under both aerobic and anaerobic conditions. when this strain was cultivated under oxygen-limiting conditions with nitrate, first toluene was degraded as oxygen was consumed, while later toluene was degraded as nitrate was reduced. biochemical observations indicated that initial degradation of toluene occurred through a dioxygenase-mediated pathway and the benzylsuccinate pathw ... | 2004 | 15006757 |
| n-acyl-l-homoserine lactones (ahls) affect microbial community composition and function in activated sludge. | the role of intercellular signalling in the regulation of genes and phenotypes in a broad range of bacterial species is now firmly established. in contrast, the impact of intercellular signalling on microbial community parameters, such as species diversity and function, is less well understood. in this study the role of n-acyl-l-homoserine lactones (ahls) in microbial community dynamics in an industrial wastewater treatment system is addressed. seven proteobacterial strains producing compounds w ... | 2004 | 15008819 |
| identification of a novel steroid inducible gene associated with the beta hsd locus of comamonas testosteroni. | comamonas testosteroni is a soil bacterium, which can use a variety of steroids as carbon and energy source. even if it can be estimated that the complete degradation of the steroid nucleus requires more than 20 enzymatic reactions, the complete molecular characterization of the genes encoding these steroid degradative enzymes as well as the genetic organization of them remain to be elucidated. we have previously reported the cloning and nucleotide sequence of two steroid-inducible genes, beta h ... | 2004 | 15026087 |
| selenocysteine-containing proteins in anaerobic benzoate metabolism of desulfococcus multivorans. | the sulfate-reducing bacterium desulfococcus multivorans uses various aromatic compounds as sources of cell carbon and energy. in this work, we studied the initial steps in the aromatic metabolism of this strictly anaerobic model organism. an atp-dependent benzoate coenzyme a (coa) ligase (amp plus ppi forming) composed of a single 59-kda subunit was purified from extracts of cells grown on benzoate. specific activity was highest with benzoate and some benzoate derivatives, whereas aliphatic car ... | 2004 | 15028701 |
| phenylphosphate carboxylase: a new c-c lyase involved in anaerobic phenol metabolism in thauera aromatica. | the anaerobic metabolism of phenol in the beta-proteobacterium thauera aromatica proceeds via carboxylation to 4-hydroxybenzoate and is initiated by the atp-dependent conversion of phenol to phenylphosphate. the subsequent para carboxylation of phenylphosphate to 4-hydroxybenzoate is catalyzed by phenylphosphate carboxylase, which was purified and studied. this enzyme consists of four proteins with molecular masses of 54, 53, 18, and 10 kda, whose genes are located adjacent to each other in the ... | 2004 | 15231788 |
| analysis and glycosyl composition of the exopolysaccharide isolated from the floc-forming wastewater bacterium thauera sp. mz1t. | conditions were developed for the reproducible production, isolation and characterization of a novel microbial extracellular polysaccharide believed to be involved in transient viscous bulking at an industrial wastewater treatment plant. the exopolysaccharide was extracted from cell-free culture supernatants of thauera sp. strain mz1t grown on a minimal medium with succinate. the purified polymer was found to be approximately 260 kda in size by gel-permeation chromatography. the gc-ms analysis o ... | 2004 | 15250880 |
| microbial characterization of toluene-degrading denitrifying consortia obtained from terrestrial and marine ecosystems. | the degradation characteristics of toluene coupled to nitrate reduction were investigated in enrichment culture and the microbial communities of toluene-degrading denitrifying consortia were characterized by denaturing gradient gel electrophoresis (dgge) technique. anaerobic nitrate-reducing bacteria were enriched from oil-contaminated soil samples collected from terrestrial (rice field) and marine (tidal flat) ecosystems. enriched consortia degraded toluene in the presence of nitrate as a termi ... | 2004 | 15278317 |
| the bzd gene cluster, coding for anaerobic benzoate catabolism, in azoarcus sp. strain cib. | we report here that the bzd genes for anaerobic benzoate degradation in azoarcus sp. strain cib are organized as two transcriptional units, i.e., a benzoate-inducible catabolic operon, bzdnopqmstuvwxyza, and a gene, bzdr, encoding a putative transcriptional regulator. the last gene of the catabolic operon, bzda, has been expressed in escherichia coli and encodes the benzoate-coenzyme a (coa) ligase that catalyzes the first step in the benzoate degradation pathway. the bzda enzyme is able to acti ... | 2004 | 15317781 |
| dehydration of (r)-2-hydroxyacyl-coa to enoyl-coa in the fermentation of alpha-amino acids by anaerobic bacteria. | several clostridia and fusobacteria ferment alpha-amino acids via (r)-2-hydroxyacyl-coa, which is dehydrated to enoyl-coa by syn-elimination. this reaction is of great mechanistic interest, since the beta-hydrogen, to be eliminated as proton, is not activated (pk 40-50). a mechanism has been proposed, in which one high-energy electron acts as cofactor and transiently reduces the electrophilic thiol ester carbonyl to a nucleophilic ketyl radical anion. the 2-hydroxyacyl-coa dehydratases are two-c ... | 2004 | 15374661 |
| enzymatic reactions in anaerobic 2-methylnaphthalene degradation by the sulphate-reducing enrichment culture n 47. | the upper pathway of anaerobic degradation of 2-methylnaphthalene was studied with a sulphate-reducing enrichment culture, which is able to grow with naphthalene or 2-methylnaphthalene as sole carbon source and electron donor. anaerobic degradation of 2-methylnaphthalene is initiated by an addition of fumarate to the methyl-group producing the first intermediate, naphthyl-2-methyl-succinate. in a subsequent beta-oxidation of the original methyl atom, the central metabolite 2-naphthoic acid is ge ... | 2004 | 15500985 |
| phenylphosphate synthase: a new phosphotransferase catalyzing the first step in anaerobic phenol metabolism in thauera aromatica. | the anaerobic metabolism of phenol in the beta-proteobacterium thauera aromatica proceeds via para-carboxylation of phenol (biological kolbe-schmitt carboxylation). in the first step, phenol is converted to phenylphosphate which is then carboxylated to 4-hydroxybenzoate in the second step. phenylphosphate formation is catalyzed by the novel enzyme phenylphosphate synthase, which was studied. phenylphosphate synthase consists of three proteins whose genes are located adjacent to each other on the ... | 2004 | 15547277 |
| genetic diversity of benzoyl coenzyme a reductase genes detected in denitrifying isolates and estuarine sediment communities. | benzoyl coenzyme a (benzoyl-coa) reductase is a central enzyme in the anaerobic degradation of organic carbon, which utilizes a common intermediate (benzoyl-coa) in the metabolism of many aromatic compounds. the diversity of benzoyl-coa reductase genes in denitrifying bacterial isolates capable of degrading aromatic compounds and in river and estuarine sediment samples from the arthur kill in new jersey and the chesapeake bay in maryland was investigated. degenerate primers were developed from t ... | 2005 | 15812036 |
| development of a pcr method for the detection and quantification of benzoyl-coa reductase genes and its application to monitored natural attenuation. | benzoyl coenzyme a reductase (bcr) catalyzes dearomatization of benzoyl coenzyme a (benzoyl-coa), which is the central step in the anaerobic degradative pathways for a variety of aromatic compounds. this study developed a pcr method for the detection and quantification of bcr genes in bacterial strains and environmental samples. pcr primers were designed by aligning known bcr genes in thauera, azoarcus and rhodopseudomonas species, and their utility was assessed by amplifying bcr fragments from ... | 2005 | 15865350 |
| functional genomics of an anaerobic aromatic-degrading denitrifying bacterium, strain ebn1. | nitrate-reducing bacteria of the recently recognized azoarcus/thauera group within the betaproteobacteria contribute significantly to the biodegradation of aromatic and other refractory compounds in anoxic waters and soils. strain ebn1 belongs to a distinct cluster (new genus) and is the first member of this phylogenetic group, the genome of which has been determined (4.7 mb; one chromosome, two plasmids) by [rabus r, kube m, heider j, beck a, heitmann k, widdel f, reinhardt r (2005) the genome ... | 2005 | 16041578 |