Publications

oxidation of methyl fluoride and dimethyl ether by ammonia monooxygenase in nitrosomonas europaea.	methyl fluoride and dimethyl ether were previously identified as inhibitors of ammonia oxidation and n2o production in autotrophic nitrifying bacteria. we demonstrate that methyl fluoride and dimethyl ether are substrates for ammonia monooxygenase and are converted to formaldehyde and a mixture of methanol and formaldehyde, respectively.	1994	8085841
molecular analysis of enrichment cultures of marine ammonia oxidisers.	marine ammonia oxidising bacteria were enriched by incubation of sea water, amended with ammonium sulphate, and subsequent subculture in liquid inorganic medium. pcr primers were designed to be specific for rdna sequences from ammonia oxidisers belonging to the beta-sub-group of the proteobacteria. these primers were then used to amplify rrna genes from ammonia oxidiser enrichment cultures containing heterotrophs. pcr products were recovered from all cultures in which complete ammonia oxidation ...	1994	8076810
identification of axial ligands of cytochrome c552 from nitrosomonas europaea.	cytochrome c552 from nitrosomonas europaea was analyzed by visible, epr and mcd spectroscopies. the visible and mcd data show that histidine and methionine are the axial ligands to the heme iron of the ferric protein. the epr spectrum of the cytochrome shows an atypical highly axial low spin (hals) type signal with g-values that make it difficult to identify the axial ligands. these results reinforce the value of near-infrared mcd spectroscopy for assigning ligands in ferric heme systems and poi ...	1994	8143881
a di-heme cytochrome c peroxidase from nitrosomonas europaea catalytically active in both the oxidized and half-reduced states.	a di-c-heme containing cytochrome (cytochrome c553 peroxidase) has been isolated from the chemoautotrophic bacterium nitrosomonas europaea. sequence analysis of the n terminus and the two heme-containing peptides generated by digestion of the enzyme with trypsin show 40% homology overall to sequences reported for the di-heme peroxidase from pseudomonas aeruginosa (rönnberg, m., kalkkinen, n., and ellfolk, n. (1989) febs lett. 250, 175-178). at room temperature and ph 7.0, one heme is low spin wi ...	1994	8163487
organization of the hao gene cluster of nitrosomonas europaea: genes for two tetraheme c cytochromes.	the organization of genes for three proteins involved in ammonia oxidation in nitrosomonas europaea has been investigated. the amino acid sequence of the n-terminal region and four heme-containing peptides produced by proteolysis of the tetraheme cytochrome c554 of n. europaea were determined by edman degradation. the gene (cyca) encoding this cytochrome is present in three copies per genome (h. mctavish, f. laquier, d. arciero, m. logan, g. mundfrom, j.a. fuchs, and a. b. hooper, j. bacteriol. ...	1994	8195067
the use of a hollow fiber membrane module in sample conditioning prior to electrophoresis.	a new method to continuously change the buffer conditions in samples prior to electrophoresis by counter-current dialysis has been developed using a hollow fiber membrane module (variperm m, bitop, witten). it is demonstrated that the collected fractions of a column eluate after hydrophobic interaction chromatography cannot be analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (sds-page) due to the high content of ammonium sulfate. in contrast, when the hollow fiber membrane m ...	1994	7859717
crystallization and preliminary x-ray analysis of cytochrome c-552 from nitrosomonas europaea.	cytochrome c-552 from nitrosomonas europaea was crystallized by the sandwiched drop, vapor diffusion method, with anmmonium sulfate as the precipitant. the crystals were found to belong to the space group p2(1)2(1)2(1), having unit cell dimensions of a = 106.1 a, b = 126.1 a, and c = 57.7 a. the crystals diffracted x-rays at greater than 3.0 a resolution.	1994	7896754
biological nitrogen removal from wastewater.	a review of the research on the kinetics of nitrification and denitrification is presented including an explanation of reaction engineering models. the results of laboratory scale experiments with high rate nitrification processes are discussed using kinetic results for oxygen limitation as well as for substrate limitation and inhibition. it can be demonstrated that reaction engineering models are helpful for a better understanding of the processes and for the design of reactors. pilot scale inv ...	1994	8165950
the primary structure of cytochrome p460 of nitrosomonas europaea: presence of a c-heme binding motif.	cytochrome p460 and hydroxyamine oxidoreductase of nitrosomonas europaea both catalyze the oxidation of hydroxylamine and contain a 460 nm-absorbing chromophore. the gene (cyp) encoding cytochrome p460 was cloned and sequenced. the predicted amino acid sequence contains a single c-heme binding motif (cxxch) near the carboxy-terminus. cytochrome p460 shows little sequence homology to other c-cytochromes including hydroxyamine oxidoreductase. the presence of a signal peptide and a possible c-heme ...	1994	7957885
the dynamic progression of evolved character states for aromatic amino acid biosynthesis in gram-negative bacteria.	a systematic analysis of the evolution of aromatic amino acid biosynthesis in the proteobacteria, previously focussed mainly upon the gamma subdivision, has now been extended to the beta subdivision. five lineages were studied, represented by neisseria gonorrhoeae, nitrosomonas europaea, alcaligenes faecalis, rrna group-iii pseudomonads/rubrivivax gelatinosus, and rrna group-ii pseudomonads/rhodocyclus tenuis. within the phenylalanine pathway, the bifunctional p-protein (chorismate mutase/prephe ...	1994	7533594
sequence of the gene, amob, for the 43-kda polypeptide of ammonia monoxygenase of nitrosomonas europaea.	the sequence for the 3' portion of amob, a gene encoding a 43-kda polypeptide component ammonia monooxygenase of nitrosomonas europaea, is presented. the derived polypeptide has no homology with other known proteins. amoa and amob are the only open reading frames in the putative amo operon.	1994	7980540
enzyme immunoassay detection of nitrosomonas europaea.	an exploratory effort to selectively detect the presence of a nitrifying bacterium, nitrosomonas europaea, successfully demonstrated the fundamental utility of an enzyme-based immunoassay protocol. the applied polyclonal antibody test seemingly offered a marked improvement over the available analytical options, including plating, activity, and fluorescence immunoassay techniques. following an initial purification step to enhance overall specificity, this procedure had an apparent lower limit of ...	1994	16349287
transformations of aromatic compounds by nitrosomonas europaea.	benzene and a variety of substituted benzenes inhibited ammonia oxidation by intact cells of nitrosomonas europaea. in most cases, the inhibition was accompanied by transformation of the aromatic compound to a more oxidized product or products. all products detected were aromatic, and substituents were often oxidized but were not separated from the benzene ring. most transformations were enhanced by (nh(4))(2)so(4) (12.5 mm) and were prevented by c(2)h(2), a mechanism-based inactivator of ammoni ...	1994	16349282
co-immobilized nitrosomonas europaea and nitrobacter agilis cells: validation of a dynamic model for simultaneous substrate conversion and growth in kappa-carrageenan gel beads.	a dynamic model for two microbial species immobilized in a gel matrix is presented and validated with experiments. the model characterizes the nitrification of ammonia with nitrosomonas europaea and nitrobacter agilis co-immobilized in k-carrageenan gel beads. the model consists of kinetic equations for the microorganisms and mass transfer equations for the substrates and products inside and outside the gel beads. the model predicts reactor bulk concentrations together with the substrate consump ...	1994	18615529
a cometabolic kinetics model incoroporating enzyme inhibition, inactivation, and recovery: ii. trichloroethylene degradaation experiments.	a cometabolism enzyme kinetics model has been presented which takes into account changes in bacterial activity associated with enzyme inhibitiion, inactivation, inactivation of enzyme resulting from product toxicty, and respondent synthesis of new enzyme. although this process is inherently unsteady-state, the model assumes that cometabolic degradation of a compound exhibiting product toxicity can be modeled as pseudo-steady-staate under certain conditions. in its simplified from, the model also ...	1995	18623307
effects of diffusion limitation on immobilized nitrifying microorganisms at low temperatures.	activation energies of suspended and immobilized nitrifying bacteria were determined and compared to determine if diffusion limitation results in decreased sensitivity for temperature. the activation energy for the respiration activity of suspended nitrosomonas europaea and nitrobacter agilis was found to be 86.4 and 58.4 kj mol(-1), respectively. the activation energy for oxygen diffusion in the support material, kappa-carrageenan, determined from the effect of temperature on the effective diff ...	1995	18623045
inhibition, inactivation, and recovery of ammonia-oxidizing activity in cometabolism of trichloroethylene by nitrosomonas europaea.	the kinetics of the cometabolism of trichloroethylene (tce) by the ammonia-oxidizing soil bacterium nitrosomonas europaea in short-term (<10-min) incubations were investigated. three individual effects of tce cometabolism on this bacterium were characterized. first, we observed that tce is a potent competitive inhibitor of ammonia oxidation by n. europaea. the k(infi) value for tce (30 (mu)m) is similar to the k(infm) for ammonia (40 (mu)m). second, we examined the toxicity associated with tce c ...	1995	16534997
detection of ammonium-oxidizing bacteria of the beta-subclass of the class proteobacteria in aquatic samples with the pcr.	the pcr was used as the basis for the development of a sensitive and specific assay for the detection of ammonium-oxidizing bacteria belonging to the beta-subclass of the class proteobacteria. pcr primers were selected on the basis of nucleic acid sequence data available for seven species of nitrifiers in this subclass. the specificity of the ammonium oxidizer primers was evaluated by testing known strains of nitrifiers, several serotyped environmental nitrifier isolates, and other members of th ...	1995	7538277
nih shift in the hydroxylation of aromatic compounds by the ammonia-oxidizing bacterium nitrosomonas europaea. evidence against an arene oxide intermediate.	the migration of deuterium and hydrogen was observed in the aromatic hydroxylation of specifically deuterated, monosubstituted benzenes catalyzed by ammonia monooxygenase of nitrosomonas europaea. the phenolic products of the hydroxylation of aromatics containing ortho-/para-directing substituents (f, cl, br, i, oh, nh2, ch3, ch2ch3, and och3) were primarily para-phenols. in contrast, with aromatics containing meta-directing substituents (no2 and cn), the phenolic products were a more even mixtu ...	1995	7547906
sequence of an ammonia monooxygenase subunit a-encoding gene from nitrosospira sp. npav.	one of three gene copies encoding ammonia monooxygenase subunit a (amoa) and flanking sequences was isolated from genomic dna of the chemolithotrophic soil bacterium nitrosospira sp. npav using oligodeoxyribonucleotide primers and the polymerase chain reaction (pcr). the gene (amoa) encodes a 274-amino-acid polypeptide which has similarity to the ammonia monooxygenase acetylene-binding protein from nitrosomonas europaea.	1995	7557469
amplification of the amoa gene from diverse species of ammonium-oxidizing bacteria and from an indigenous bacterial population from seawater.	because the chemolithotrophic ammonium-oxidizing bacteria are an integral component of nitrogen biogeochemistry, a sensitive and accurate method to detect this ecologically important group of microorganisms is needed. the amoa gene of these organisms encodes the active site of ammonia monooxygenase, an enzyme unique to this group of nitrifying bacteria. we report here the use of the pcr technique to detect the amoa gene from pure cultures of chemolithotrophic ammonium-oxidizing bacteria, ammoniu ...	1995	7618882
suicide inactivation of hydroxylamine oxidoreductase of nitrosomonas europaea by organohydrazines.	in the presence of a suitable electron acceptor such as mammalian cytochrome c, hydroxylamine oxidoreductase (hao) from the chemolithotrophic bacterium nitrosomonas europaea catalyzes the oxidation of hydroxylamine or hydrazine to nitrite or dinitrogen, respectively. each subunit of hao contains 7 c-hemes and a chromophore of the active site called heme p460, a c-heme bridged from a methylene carbon to a ring carbon of a tyrosine of the peptide chain. reaction with either substrate results in re ...	1995	7619827
generation of polymerase chain reaction-specific probes for library screening using single degenerate primers.	degenerate oligonucleotide primers were made to peptide sequences from hydroxylamine oxidoreductase (hao) from nitrosomonas europaea. the primers were used singly in pcr reactions to amplify portions of the gene for hao from genomic dna. southern hybridizations using fragments amplified with each primer showed that they labeled the same genomic dna fragments. the pcr-amplified fragments were successfully used to screen a gene library for clones containing the hao gene. the method of isolating ge ...	1995	7648471
the amino acid sequence of nitrosomonas europaea cytochrome c-552.	the complete amino acid sequence of cytochrome c-552 derived from the chemoautotrophic ammonia-oxidizing bacterium nitrosomonas europaea was determined. the cytochrome consisted of 81 amino acid residues, and its molecular weight was calculated to be 9098 including heme c. although the sequence of cytochrome c-552 was highly homologous to those of cytochromes c-551, which were known as the electron-donating components to dissimilatory nitrite reductase in pseudomonads, cytochrome c-552 differed ...	1995	7767224
interaction with membranes of cytochrome c554 from nitrosomonas europaea.	two c-cytochromes extrinsically bound to the membranes of nitrosomonas europaea have been identified. one is the tetraheme cytochrome c554, a protein previously described as soluble and periplasmic. depending on the concentration of fe and cu in the growth medium, from 50 to 100% of the total cellular cytochrome c554 is membrane-associated. the cytochromes c554 found in the soluble or membrane fractions are identical in the spectroscopic, chromatographic, or primary structural properties examine ...	1995	7503559
effects of ammonia on the de novo synthesis of polypeptides in cells of nitrosomonas europaea denied ammonia as an energy source.	the effects of ammonium on the de novo synthesis of polypeptides in the soil-nitrifying bacterium nitrosomonas europaea have been investigated. cells were incubated in the presence of both acetylene and nh4+. under these conditions, the cells were unable to utilize nh4+ as an energy source. energy to support protein synthesis was supplied by the oxidation of hydroxylamine or other alternative substrates for hydroxylamine oxidoreductase. de novo protein synthesis was detected by 14c incorporation ...	1995	7665474
anaerobic oxidation of ammonium is a biologically mediated process.	a newly discovered process by which ammonium is converted to dinitrogen gas under anaerobic conditions (the anammox process) has now been examined in detail. in order to confirm the biological nature of this process, anaerobic batch culture experiments were used. all of the ammonium provided in the medium was oxidized within 9 days. in control experiments with autoclaved or raw wastewater, without added sludge or with added sterilized (either autoclaved or gamma irradiated) sludge, no changes in ...	1995	7747947
reaction with cyanide of hydroxylamine oxidoreductase of nitrosomonas europaea.	hydroxylamine oxidoreductase (hao) catalyzes the reaction nh2oh+h2o-->hno2+4e- + 4h+, a step in the energy-generating oxidation of ammonia to nitrite by the bacterium nitrosomonas europaea. each subunit of hao contains 7 c-hemes and 1 heme p460. the latter, c-heme cross-linked from a methylene carbon to the ring of a protein tyrosine, forms part of the active site. the iron of heme p460 is probably linked by a bridging ligand to the iron of a c-heme. here, the reaction of cyanide with ferric hao ...	1995	7619802
amplification of 16s ribosomal rna genes of autotrophic ammonia-oxidizing bacteria demonstrates the ubiquity of nitrosospiras in the environment.	oligonucleotide sequences selected from the 16s rrna genes of various species of ammonia-oxidizing bacteria were evaluated as specific pcr amplification primers and probes. the specificities of primer pairs for eubacterial, nitrosospira and nitrosomonas rrna genes were established with sequence databases, and the primer pairs were used to amplify dna from laboratory cultures and environmental samples. eubacterial rrna genes amplified from samples of soil and activated sludge hybridized with an o ...	1995	8535507
crystallization and preliminary x-ray analysis of cytochrome c-554 from nitrosomonas europaea.	cytochrome c-554 from nitrosomonas europaea was crystallized by the batch method utilizing ammonium sulfate as the precipitant. the crystals belong to the space group, p21, with unit cell dimensions of a = 64.8 a, b = 44.7 a, c = 78.7 a, and beta = 99.0 degrees. the crystals diffracted x-rays beyond 2.5 a resolution.	1995	8586634
roles of bovine serum albumin and copper in the assay and stability of ammonia monooxygenase activity in vitro.	we investigated the effects of bovine serum albumin (bsa) on both the assay and the stability of ammonia-oxidizing activity in cell extracts of nitrosomonas europaea. ammonia-dependent o2 uptake activity of freshly prepared extracts did not require bsa. however, a dependence on bsa developed in extracts within a short time. the role of bsa in the assay of ammonia-oxidizing activity apparently is to absorb endogenous free fatty acids which are present in the extracts, because (i) only proteins wh ...	1995	7665467
comparative analysis of nitrifying bacteria associated with freshwater and marine aquaria.	three nucleic acid probes, two for autotrophic ammonia-oxidizing bacteria of the beta subdivision of the class proteobacteria and one for alpha subdivision nitrite-oxidizing bacteria, were developed and used to study nitrifying bacterial phylotypes associated with various freshwater and seawater aquarium biofilters. nitrosomonas europaea and related species were detected in all nitrifying seawater systems and accounted for as much as 20% of the total eubacterial rrna. in contrast, nitrifying bac ...	1996	8702281
phylogenetic probes for analyzing abundance and spatial organization of nitrifying bacteria.	a hierarchical set of five 16s rrna-targeted oligonucleotide dna probes for phylogenetically defined groups of autotrophic ammonia- and nitrite-oxidizing bacteria was developed for environmental and determinative studies. hybridization conditions were established for each probe by using temperature dissociation profiles of target and closely related nontarget organisms to document specificity. environmental application was demonstrated by quantitative slot blot hybridization and whole-cell hybri ...	1996	8787412
crystallization and preliminary crystallographic analysis of cytochrome c553 peroxidase from nitrosomonas europaea.	the di-heme peroxidase (cytochrome c553 peroxidase) from nitrosomonas europaea has been crystallized in a form suitable for high-resolution x-ray structure determination. a complete data set was obtained to 2.5a and the data were indexed in space group p2(1) with a = 88.79 a, b = 55.93 a, c = 144.37 a, beta = 103.87 degrees. the self-rotation function indicates one homodimer per asymmetric unit.	1996	8813001
isolation and characterization of a functional promoter from nitrosomonas europaea.	a functional promoter from the obligate autotrophic ammonia oxidizing bacterium nitrosomonas europaea was identified by expression in escherichia coli, using a promoterless reporter gene. transcription initiation site of this promoter was determined by primer extension analysis. the sequences at -35 and -10 have low similarity to the -10/-35 consensus sequence of known prokaryotic promoters.	1996	8935651
mutagenesis of hydroxylamine oxidoreductase in nitrosomonas europaea by transformation and recombination.	mutagenesis of nitrosomonas europaea was achieved by electroporation and recombination. to demonstrate this, an aminoglycoside 3'-phosphotransferase (kan) gene was specifically inserted into each of the three gene copies of hao individually. southern hybridizations and pcr analysis showed the incorporation of the kan gene at the chosen genetic loci. the isolation of mutant strains was achieved in 7 to 14 days when the strains were grown on solid medium. the induced mutations were stable even in ...	1996	8682770
structure and function of a nitrifying biofilm as determined by in situ hybridization and the use of microelectrodes.	microprofiles of o2 and no3- were measured in nitrifying biofilms from the trickling filter of an aquaculture water recirculation system. by use of a newly developed biosensor for no3-, it was possible to avoid conventional interference from other ions. nitrification was restricted to a narrow zone of 50 microns on the very top of the film. in the same biofilms, the vertical distributions of members of the lithoautotrophic ammonia-oxidizing genus nitrosomonas and of the nitrite-oxidizing genus n ...	1996	8953735
the purification of ammonia monooxygenase from paracoccus denitrificans.	the heterotrophic nitrifier paracoccus denitrificans expresses a membrane-associated ammonia monooxygenase. the active enzyme has been solubilized in the detergent dodecyl-beta-d-maltoside and purified by standard chromatographic techniques. this is the first purification of an ammonia monooxygenase. the enzyme consists of two subunits with molecular masses of 38 and 46 kda. the purified enzyme is a quinol oxidase, is inhibited by light and a variety of chelating agents and is activated by cupri ...	1996	8654570
the biochemical characterization of a novel non-haem-iron hydroxylamine oxidase from paracoccus denitrificans gb17.	the characterization of the hydroxylamine oxidase from the heterotrophic nitrifier paracoccus denitrificans gb17 indicates the enzyme to be entirely distinct from the hydroxylamine oxidase from the autotrophic nitrifier nitrosomonas europaea. hydroxylamine oxidase from p. denitrificans contains three to five non-haem, non-iron-sulphur iron atoms as prosthetic groups, predominantly co-ordinated by carboxylate ligands. the interaction of the enzyme with the electron-accepting proteins cytochrome c ...	1996	8920986
molecular diversity of soil and marine 16s rrna gene sequences related to beta-subgroup ammonia-oxidizing bacteria.	we have conducted a preliminary phylogenetic survey of ammonia-oxidizing beta-proteobacteria, using 16s rrna gene libraries prepared by selective pcr and dna from acid and neutral soils and polluted and nonpolluted marine sediments. enrichment cultures were established from samples and analyzed by pcr. analysis of 111 partial sequences of c. 300 bases revealed that the environmental sequences formed seven clusters, four of which are novel, within the phylogenetic radiation defined by cultured au ...	1996	8900005
nitrogen removal by tubular gel containing nitrosomonas europaea and paracoccus denitrificans.	a new bioreactor for the removal of nitrogen from wastewater is described which consists of a tubular polymeric gel containing nitrosomonas europaea and paracoccus denitrificans. the outer surface of the tube is in aerobic contact with wastewater containing ammonia, while the inside of the tube is in anaerobic contact with ethanol flowing through the tube. n. europaea oxidizes ammonia to nitrite in the gel, and then p. denitrificans reduces the nitrite to nitrogen gas in the same gel. this conce ...	1996	8900015
induction of ammonia monooxygenase and hydroxylamine oxidoreductase mrnas by ammonium in nitrosomonas europaea.	in nitrosomonas europaea, ammonia monooxygenase (amo) and hydroxylamine oxidoreductase (hao) catalyse the oxidation of ammonia (nh3) to nitrite (no2-). a transcript of 3500 bases hybridizes to probes for amoa and amob (genes that code for amo proteins). a transcript of 2100 bases hybridizes to probes for hao (the gene that codes for hao). induction of the mrnas detected by amo and hao probes required the presence of ammonium (nh4+). to correlate new levels of mrna with de novo activity, existent ...	1996	8736533
the gene encoding ammonia monooxygenase subunit a exists in three nearly identical copies in nitrosospira sp. npav.	the gene encoding ammonia monooxygenase subunit a (amoa) was found in three copies of the genome of the chemolithotrophic soil bacterium, nitrosospira sp. npav. the open reading frame and flanking regions of the three copies were isolated from digested size fractionated genomic dna using oligodeoxyribonucleotide primers and polymerase chain reaction. the three gene copies of amoa were sequenced and the sequences compared to each other. the open reading frames and the upstream and downstream flan ...	1996	8674986
evidence for an iron center in the ammonia monooxygenase from nitrosomonas europaea.	binding of the ligand, nitric oxide, in the presence of reductant was used to identify a ferrous s = 3/2 signal, characteristic of a ferrous nitrosyl complex, and a g= 2.03 copper or iron signal in membranes of the ammonia-oxidizing bacterium, nitrosomonas europaea. the same ferrous s = 3/2 signal is thought to be a component of the membrane-associated methane monooxygenase (pmmo) of methylococcus capsulatus bath, since it is seen in the membrane fraction of cells expressing pmmo and in the puri ...	1996	8941709
a bioreactor system for the nitrogen loop in a controlled ecological life support system.	as space missions become longer in duration, the need to recycle waste into useful compounds rises dramatically. this problem can be addressed by the development of controlled ecological life support systems (celss) (i.e., engineered closed/controlled eco-systems (ecces)), consisting of human and plant modules. one of the waste streams leaving the human module is urine. in addition to the reclamation of water from urine, recovery of the nitrogen is important because it is an essential nutrien ...	1996	11538973
steady-state solution of a two-species biofilm problem.	through a thorough investigation of the boundary conditions for a general two-species biofilm model, a simple and fast method for solving the steady-state case is developed and presented. the methods used may be extended to biofilm models in which more than two species are considered. four different sets of boundary conditions are possible for the two-species biofilm model. each set is shown to be asymptotically stable. a biofilm model describing the competition between autotrophic and heterotro ...	1996	18627076
cometabolism of chlorinated solvents by nitrifying bacteria: kinetics, substrate interactions, toxicity effects, and bacterial response.	pure cultures of ammonia-oxidizing bacteria, nitrosomonas europaea, were exposed to trichloroethylene (tce), 1,1-dichloroethylene (1,1-dce), chloroform (cf), 1,2-dichloroethane (1,2-dca), or carbon tetrachloride (ct), in the presence of ammonia, in a quasi-steady-state bioreactor. estimates of enzyme kinetics constants, solvent inactivation constants, and culture recovery constants were obtained by simultaneously fitting three model curves to experimental data using nonlinear optimization techni ...	1997	18636408
production of no and n(inf2)o by pure cultures of nitrifying and denitrifying bacteria during changes in aeration.	peak emissions of no and n(inf2)o are often observed after wetting of soil. the reactions to sudden changes in the aeration of cultures of nitrifying and denitrifying bacteria with respect to no and n(inf2)o emissions were compared to obtain more information about the microbiological aspects of peak emissions. in continuous culture, the nitrifier nitrosomonas europaea and the denitrifiers alcaligenes eutrophus and pseudomonas stutzeri were cultured at different levels of aeration (80 to 0% air s ...	1997	16535707
regulation of the synthesis and activity of ammonia monooxygenase in nitrosomonas europaea by altering ph to affect nh(inf3) availability.	the obligately ammonia-oxidizing bacterium nitrosomonas europaea was incubated in medium containing 50 mm ammonium. changes in the concentration of nitrite, the ph, and the nh(inf4)(sup+)- and nh(inf2)oh-dependent o(inf2) uptake activities of the cell suspension were monitored. the nh(inf4)(sup+)-dependent o(inf2) uptake activity doubled over the first 3 h of incubation and then slowly returned to its original level over the following 5 h. the extent of stimulation of nh(inf4)(sup+)-dependent o( ...	1997	16535741
dynamics of artificially immobilized nitrosomonas europaea: effect of biomass decay.	the dynamics of growth and death of immobilized nitrosomonas europaea were studied. for this, the death rate of suspended cells was determined in the absence of ammonium or oxygen by following the loss of respiration activity and by fluorescein-diacetate (fda)/lissamine-green staining techniques. the death rates obtained (1.06 x 10(-6) s(-1) or 4.97 x 10(-6) s(-1) in the absence of oxygen or ammonium, respectively) were incorporated in a dynamic growth model and the effects on the performance of ...	1997	18636573
analysis of ammonia-oxidizing bacteria of the beta subdivision of the class proteobacteria in coastal sand dunes by denaturing gradient gel electrophoresis and sequencing of pcr-amplified 16s ribosomal dna fragments.	denaturing gradient gel electrophoresis (dgge) is a powerful and convenient tool for analyzing the sequence diversity of complex natural microbial populations. dgge was evaluated for the identification of ammonia oxidizers of the beta subdivision of the proteobacteria based on the mobility of pcr-amplified 16s rdna fragments and for the analysis of mixtures of pcr products from this group generated by selective pcr of dna extracted from coastal sand dunes. degenerate pcr primers, cto189f-gc and ...	1997	9097446
a gene encoding a membrane protein exists upstream of the amoa/amob genes in ammonia oxidizing bacteria: a third member of the amo operon?	the gene cluster encoding ammonia monooxygenase (amo) in the chemolithotrophic soil bacterium nitrosospira sp. npav was found to contain a third open reading frame, termed amoc, upstream of the genes amoa and amob that encode the subunits of amo. the amoc gene and its flanking regions were isolated and sequenced from a 4.4 kb ecori fragment that contains one of three copies of the ammonia monooxygenase gene cluster. the presence of this gene upstream of the other two amoa gene copies in nitrosos ...	1997	9163908
evidence for a crosslink between c-heme and a lysine residue in cytochrome p460 of nitrosomonas europaea.	cytochrome p460 and hydroxylamine oxidoreductase (hao) of nitrosomonas europaea catalyze the oxidation of hydroxylamine. cytochrome p460 contains an unidentified heme-like chromophore whose distinctive spectroscopic properties are similar to those for the p460 heme found in hao. the heme p460 of hao has previously been shown by protein chemistry and nmr structural analysis to be a c-heme with an additional covalent crosslink between the c2 ring carbon of a tyrosine residue of the polypeptide cha ...	1997	9237682
the ammonia monooxygenase structural gene amoa as a functional marker: molecular fine-scale analysis of natural ammonia-oxidizing populations.	the naturally occurring genetic heterogeneity of autotrophic ammonia-oxidizing populations belonging to the beta subclass of the proteobacteria was studied by using a newly developed pcr-based assay targeting a partial stretch of the gene which encodes the active-site polypeptide of ammonia monooxygenase (amoa). the pcr yielded a specific 491-bp fragment with all of the nitrifiers tested, but not with the homologous stretch of the particulate methane monooxygenase, a key enzyme of methane-oxidiz ...	1997	9406389
heterologous expression of heterotrophic nitrification genes.	paracoccus denitrificans is a heterotrophic organism capable of oxidizing ammonia to nitrite during growth on an organic carbon and energy source. this pathway, termed heterotrophic nitrification, requires the concerted action of an ammonia monooxygenase (amo) and hydroxylamine oxidase (hao). the genes required for heterotrophic nitrification have been isolated by introducing a pa. denitrificans genomic library into pseudomonas putida and screening for the accumulation of nitrite. in contrast to ...	1997	9421902
the remarkable complexity of hydroxylamine oxidoreductase.		1997	9095186
the 2.8 a structure of hydroxylamine oxidoreductase from a nitrifying chemoautotrophic bacterium, nitrosomonas europaea.	the 2.8 a crystal structure of hydroxylamine oxidoreductase of a nitrifying chemoautotrophic bacterium, nitrosomonas europaea, is described. twenty-four haems lie in the centre bottom of the trimeric molecule, localized in four clusters within each monomer. the haem clusters within the trimer are aligned to form a ring that has inlet and outlet sites. the inlet is occupied by a novel haem, p460, and there are two possible outlet sites per monomer formed by paired haems lying within a cavity or c ...	1997	9095195
cell density-regulated recovery of starved biofilm populations of ammonia-oxidizing bacteria.	the speed of recovery of cell suspensions and biofilm populations of the ammonia oxidizer nitrosomonas europaea, following starvation was determined. stationary-phase cells, washed and resuspended in ammoniumfree inorganic medium, were starved for periods of up to 42 days, after which the medium was supplemented with ammonium and subsequent growth was monitored by measuring nitrite concentration changes. cultures exhibited a lag phase prior to exponential nitrite production, which increased from ...	1997	9172348
effect of ammonia starvation on hydroxylamine oxidoreductase activity of nitrosomonas europaea.	a technique for detection of the activity of hydroxylamine oxidoreductase (hao) involving denaturing sds-polyacrylamide gels was developed. the activity of hao of nitrosomonas europaea was assayed using this technique, which revealed a single active band of 140 kda. the hao activity of other ammonia-oxidizers was also resistant to sds, the molecular weights being identical to that of n. europaea. n. europaea cells starved of ammonia for up to 72 h retained a considerable amount of hao, as detect ...	1997	9192739
cloning, nucleotide sequence, and regulatory analysis of the nitrosomonas europaea dnak gene.	the dnak gene of an ammonia-oxidizing bacterium, nitrosomonas europaea, was cloned and sequenced. it was found that the dnak gene product was highly homologous to previously analyzed dnak gene products from other organisms at the amino acid level. two partial open reading frames located upstream and downstream of the dnak gene were also found and identified as grpe and dnaj genes, respectively, by the predicted amino acid homology of their gene products to other bacterial grpe and dnaj proteins. ...	1997	9143112
anaerobic ammonia oxidation with nitrogen dioxide by nitrosomonas eutropha	nitrosomonas eutropha, an obligately lithoautotrophic bacterium, was able to nitrify and denitrify simultaneously under anoxic conditions when gaseous nitrogen dioxide (no2) was supplemented to the atmosphere. in the presence of gaseous no2, ammonia was oxidized, nitrite and nitric oxide (no) were formed, and hydroxylamine occurred as an intermediate. between 40 and 60% of the produced nitrite was denitrified to dinitrogen (n2). nitrous oxide (n2o) was shown to be an intermediate of denitrificat ...	1997	9042749
enzymology of the oxidation of ammonia to nitrite by bacteria.	the enzymes which catalyze the oxidation of ammonia to nitrite by autotrophic bacteria are reviewed. a comparison is made with enzymes which catalyze the same reactions in methylotrophs and organotrophic heterotrophic bacteria.	1997	9049018
anaerobic ammonia oxidation with nitrogen dioxide by nitrosomonas eutropha.	nitrosomonas eutropha, an obligately lithoautotrophic bacterium, was able to nitrify and denitrify simultaneously under anoxic conditions when gaseous nitrogen dioxide (no2) was supplemented to the atmosphere. in the presence of gaseous no2, ammonia was oxidized, nitrite and nitric oxide (no) were formed, and hydroxylamine occurred as an intermediate. between 40 and 60% of the produced nitrite was denitrified to dinitrogen (n2). nitrous oxide (n2o) was shown to be an intermediate of denitrificat ...	1997	9133316
metal selectivity of in situ microcolonies in biofilms of the elbe river.	the ultrastructure of natural complex biofilm communities of the elbe river grown in situ on microscopic glass coverslips was studied by using transmission electron microscopy and energy-dispersive x-ray (edx) analysis. characteristic microcolonies which measured between 3.3 and 9.3 microm in diameter were frequently observed. they had an outer envelope and harbored 6 to 30 cells. the cells formed short rods measuring 1.09 +/- 0.28 microm (n = 10) in length and 0.55 + 0.07 microm (n = 21) in wid ...	1997	8981977
linkage of genes encoding enolase (eno) and ctp synthase (pyrg) in the beta-subdivision proteobacterium nitrosomonas europaea.	the gene encoding enolase (eno) from the ammonia oxidising bacterium nitrosomonas europaea has been cloned and sequenced. the deduced amino acid sequence for enolase from n. europaea was 65% identical (76% similar) to its bacillus subtilis orthologue. an incomplete open reading frame located 432 bp 5' of eno was identified as pyrg, which encodes ctp synthase. these two genes are therefore organised in n. europaea, a beta-subdivision proteobacterium, in the same way as in the gamma-subdivision pr ...	1998	9711852
effect of long-term ammonia starvation on the oxidation of ammonia and hydroxylamine by nitrosomonas europaea.	axenic cultures of the ammonia-oxidizing bacterium nitrosomonas europaea were starved of ammonia (energy source) for up to 342 d. during this time the bacteria retained the ability to respond instantly to ammonia (1 mm) or hydroxylamine (0.1 mm) amendment by oxidizing it to nitrite without initial protein synthesis. in vivo, the ability to oxidize amended ammonia stayed almost constant during the starvation period, but a drop in the hydroxylamine oxidation rate (to 33%) was observed after 4 wk o ...	1998	9756628
effects of ph and oxygen and ammonium concentrations on the community structure of nitrifying bacteria from wastewater	shifts in nitrifying community structure and function in response to different ammonium concentrations (50, 500, 1,000, and 3,000 mg of n liter-1), ph values (ph 6.0, 7.0, and 8.2), and oxygen concentrations (1, 7, and 21%) were studied in experimental reactors inoculated with nitrifying bacteria from a wastewater treatment plant. the abilities of the communities selected for these conditions to regain their original structures after conditions were returned to the original conditions were also ...	1998	9758771
loss of ammonia monooxygenase activity in nitrosomonas europaea upon exposure to nitrite	nitrosomonas europaea, an obligate ammonia-oxidizing bacterium, lost an increasing amount of ammonia oxidation activity upon exposure to increasing concentrations of nitrite, the primary product of ammonia-oxidizing metabolism. the loss of activity was specific to the ammonia monooxygenase (amo) enzyme, as confirmed by a decreased rate of nh4+-dependent o2 consumption, some loss of active amo molecules observed by polypeptide labeling with 14c2h2, the protection of activity by substrates of amo, ...	1998	9758853
identification and activities in situ of nitrosospira and nitrospira spp. as dominant populations in a nitrifying fluidized bed reactor.	bacterial aggregates from a chemolithoautotrophic, nitrifying fluidized bed reactor were investigated with microsensors and rrna-based molecular techniques. the microprofiles of o2, nh4+, no2-, and no3- demonstrated the occurrence of complete nitrification in the outer 125 microgram of the aggregates. the ammonia oxidizers were identified as members of the nitrosospira group by fluorescence in situ hybridization (fish). no ammonia- or nitrite-oxidizing bacteria of the genus nitrosomonas or nitro ...	1998	9726900
physiological and molecular biological characterization of ammonia oxidation of the heterotrophic nitrifier pseudomonas putida.	the heterotrophic nitrifier pseudomonas putida aerobically oxidized ammonia to hydroxylamine, nitrite, and nitrate. product formation was accompanied by a small but significant release of no, whereas n2o evolution could not be detected under the assay conditions employed. the isolate reduced nitrate to nitrite and partially further to no under anaerobic conditions. aerobically grown cells utilized gamma-aminobutyrate as a carbon source and as a n-source by ammonification. the physiological exper ...	1998	9732537
a qualitative evaluation of the published oligonucleotides specific for the 16s rrna gene sequences of the ammonia-oxidizing bacteria.	over the past few years, there has been an increasing interest in making oligonucleotides specific for ammonia-oxidizing bacteria (aob), in order to detect and monitor these slow growing bacteria in environmental samples, in enrichment cultures and in wastewater treatment plants. based on 16s rdna sequences, a broad selection of oligonucleotides have been designed, either encompassing all known aob in the beta-subgroup of the proteobacteria (beta aob), or subclasses within beta aob. thirty diffe ...	1998	9741112
transcription of the amoc, amoa and amob genes in nitrosomonas europaea and nitrosospira sp. npav.	nitrifying bacteria such as nitrosomonas europaea and nitrosospira sp. npav use ammonia monooxygenase (amo) for oxidation of their primary growth substrate, ammonia. two polypeptides of amo are coded for by contiguous genes, amoa and amob, which are preceded by a third gene, amoc. the amocab clusters are present in multiple copies in nitrifying bacteria of the beta subdivision. these bacteria also have one amoc copy that is not adjacent to a copy of amoab. the seven known amoc genes in different ...	1998	9785456
heme packing motifs revealed by the crystal structure of the tetra-heme cytochrome c554 from nitrosomonas europaea.	cytochrome c554 (cyt c554), a tetra-heme cytochrome from nitrosomonas europaea, is an essential component in the biological nitrification pathway. in n. europaea, ammonia is converted to hydroxylamine, which is then oxidized to nitrite by hydroxylamine oxidoreductase (hao). cyt c554 functions in the latter process by accepting pairs of electrons from hao and transferring them to a cytochrome acceptor. the crystal structure of cyt c554 at 2.6 a resolution shows a predominantly alpha-helical prote ...	1998	9808046
a bioluminescence assay using nitrosomonas europaea for rapid and sensitive detection of nitrification inhibitors.	an expression vector for the luxab genes, derived from vibrio harveyi, was introduced into nitrosomonas europaea. although the recombinant strain produced bioluminescence due to the expression of the luxab genes under normal growing conditions, the intensity of the light emission decreased immediately, in a time-and dose-dependent manner, with the addition of ammonia monooxygenase inhibitors, such as allylthiourea, phenol, and nitrapyrin. when whole cells were challenged with several nitrificati ...	1998	9758781
consideration of a phlorin structure for haem p-460 of hydroxylamine oxidoreductase and its implications regarding reaction mechanism.		1998	9765884
primary sequence and solution conformation of ferrocytochrome c-552 from nitrosomonas europaea.	cytochrome c-552 from nitrosomonas europaea is a 9.1-kda monoheme protein that is a member of the bacterial cytochrome c-551 family. the gene encoding for c-552 has been cloned and sequenced and the primary sequence of the product deduced. proton resonance assignments were made for all main-chain and most side-chain protons in the diamagnetic, reduced form by two-dimensional nmr techniques. distance constraints (1056) were determined from nuclear overhauser enhancements, and torsion angle constr ...	1998	9746537
combined molecular and conventional analyses of nitrifying bacterium diversity in activated sludge: nitrosococcus mobilis and nitrospira-like bacteria as dominant populations.	the ammonia-oxidizing and nitrite-oxidizing bacterial populations occurring in the nitrifying activated sludge of an industrial wastewater treatment plant receiving sewage with high ammonia concentrations were studied by use of a polyphasic approach. in situ hybridization with a set of hierarchical 16s rrna-targeted probes for ammonia-oxidizing bacteria revealed the dominance of nitrosococcus mobilis-like bacteria. the phylogenetic affiliation suggested by fluorescent in situ hybridization (fish ...	1998	9687471
recovery of a nitrosomonas-like 16s rdna sequence group from freshwater habitats.	in order to study the diversity of ammonia-oxidising bacteria in freshwater habitats, including sediments, a molecular approach focused on the sequencing of 16s rdna was adopted. 16s rdna sequences showing affinity with the beta-subgroup of ammonia-oxidising bacteria were recovered by specific pcr of directly isolated dna from freshwater samples, and samples from brackish water and glyceria maxima rhizosphere were included in the analysis for comparison. the ammonia oxidiser-like sequences recov ...	1998	9704117
application of molecular biological techniques to a seasonal study of ammonia oxidation in a eutrophic freshwater lake	the autotrophic ammonia-oxidizing bacteria in a eutrophic freshwater lake were studied over a 12-month period. numbers of ammonia oxidisers in the lakewater were small throughout the year, and tangential-flow concentration was required to obtain meaningful estimates of most probable numbers. sediments from littoral and profundal sites supported comparatively large populations of these bacteria, and the nitrification potential was high, particularly in summer samples from the littoral sediment su ...	1998	9758784
high rate of aerobic nitrification and denitrification by nitrosomonas eutropha grown in a fermentor with complete biomass retention in the presence of gaseous no2 or no.	a pure culture of the obligately lithoautotrophic ammonia-oxidizer nitrosomonas eutropha was grown in a laboratory-scale bioreactor with complete biomass retention. the air supply was supplemented with nitrogen dioxide (no2; 25 or 50 ppm) or nitric oxide (no; 25 or 50 ppm). compared to cultures grown without these nitrogenous oxides, the addition of no2 or no to the culture resulted in a significant increase of the nitrification rate, specific activity of ammonia oxidation, growth rate, and maxi ...	1998	9531628
mutagenesis and expression of amo, which codes for ammonia monooxygenase in nitrosomonas europaea.	nitrosomonas europaea has two copies of the operon encoding ammonia monooxygenase (amo). the nucleotide sequences of the two copies of amoa were obtained, and they were found to differ by one nucleotide. to determine if both copies of amoa were functional, insertional mutagenesis was performed to inactivate either copy of amoa alone. a dna cassette containing the lacz and kan genes inserted into amoa was constructed. mutagenesis was done by using transformation and homologous recombination to mo ...	1998	9642187
molecular analysis of bacterial communities in a three-compartment granular activated sludge system indicates community-level control by incompatible nitrification processes.	bacterial community structure and the predominant nitrifying activities and populations in each compartment of a three-compartment activated sludge system were determined. each compartment was originally inoculated with the same activated sludge community entrapped in polyethylene glycol gel granules, and ammonium nitrogen was supplied to the system in an inorganic salts solution at a rate of 5.0 g of n liter of granular activated sludge-1 day-1. after 150 days of operation, the system was found ...	1998	9647825
correlation of optical and epr signals with the p460 heme of hydroxylamine oxidoreductase from nitrosomonas europaea.	hydroxylamine oxidoreductase (hao) of nitrosomonas europaea catalyzes the four-electron oxidation of nh2oh to no2-. each subunit of the trimeric enzyme contains seven c-hemes and one heme p460. in previous work [hendrich, m. p., et al. (1994) j. am. chem. soc. 116, 11961-11968], an integer-spin epr signal at g = 7.7 was discovered from the active site of the resting enzyme. this new signal was assigned to an exchange-coupled cluster containing ferric heme p460 and a ferric c-heme. an electrochem ...	1998	9425072
dna-probing for genes coding for denitrification, n2-fixation and nitrification in bacteria isolated from different soils.	bacteria isolated from different layers of four soils of the cologne area were analyzed for denitrifying, nitrifying and n2-fixing isolates by colony hybridization using gene probes. in the soils tested, the percentage of denitrifying bacteria among the total population isolated was 3-8% (in one case exceptionally 15%) and thus small. denitrifying bacteria were particularly enriched in the upper layer (depth approximately 5 cm) and were present only in low amounts at 25 cm depth in two gleysol s ...	1998	9528124
anaerobic ammonia oxidation by cell-free extracts of nitrosomonas eutropha.	cell-free extracts of nitrosomonas eutropha oxidized ammonia to nitrite with no2 (n2o4) as electron acceptor. the ammonia oxidation activity was shown to be sensitive against oxygen. in the absence of oxygen ammonia and no2 were consumed in a ratio of approximately 1:2 and hydroxylamine occurred as an intermediate. no was released in amounts equimolar to the consumption of no2. after passing the cell suspension through a french pressure cell and fractionating it by density gradient centrifugatio ...	1998	9801772
the anaerobic oxidation of ammonium.	from recent research it has become clear that at least two different possibilities for anaerobic ammonium oxidation exist in nature. 'aerobic' ammonium oxidizers like nitrosomonas eutropha were observed to reduce nitrite or nitrogen dioxide with hydroxylamine or ammonium as electron donor under anoxic conditions. the maximum rate for anaerobic ammonium oxidation was about 2 nmol nh4+ min-1 (mg protein)-1 using nitrogen dioxide as electron acceptor. this reaction, which may involve no as an inter ...	1998	9990725
assessment of changes in microbial community structure during operation of an ammonia biofilter with molecular tools.	biofiltration has been used for two decades to remove odors and various volatile organic and inorganic compounds in contaminated off-gas streams. although biofiltration is widely practiced, there have been few studies of the bacteria responsible for the removal of air contaminants in biofilters. in this study, molecular techniques were used to identify bacteria in a laboratory-scale ammonia biofilter. both 16s rrna and ammonia monooxygenase (amoa) genes were used to characterize the heterotrophi ...	1998	9835577
cytochrome p460 genes from the methanotroph methylococcus capsulatus bath.	p460 cytochromes catalyze the oxidation of hydroxylamine to nitrite. they have been isolated from the ammonia-oxidizing bacterium nitrosomonas europaea (r. h. erickson and a. b. hooper, biochim. biophys. acta 275:231-244, 1972) and the methane-oxidizing bacterium methylococcus capsulatus bath (j. a. zahn et al., j. bacteriol. 176:5879-5887, 1994). a degenerate oligonucleotide probe was synthesized based on the n-terminal amino acid sequence of cytochrome p460 and used to identify a dna fragment ...	1998	9851984
functional gene hybridization patterns of terrestrial ammonia-oxidizing bacteria.	abstract the biochemical pathway and genetics of autotrophic ammonia oxidation have been studied almost exclusively in nitrosomonas europaea. terrestrial autotrophic ammonia-oxidizing bacteria (aaos), however, comprise two distinct phylogenetic groups in the beta-proteobacteria, the nitrosomonas and nitrosospira groups. hybridization patterns were used to assess the potential of functional probes in non-pcr-based molecular analysis of natural aao populations and their activity. the objective of ...	1998	9852509
kinetic characterization of the inactivation of ammonia monooxygenase in nitrosomonas europaea by alkyne, aniline and cyclopropane derivatives.	the kinetic mechanisms of seven inactivators of ammonia oxidation activity in cells of the nitrifying bacterium, nitrosomonas europaea were investigated. the effects of the inactivators were specific for ammonia monooxygenase (amo) which oxidizes ammonia to hydroxylamine. the aniline derivatives, 1,3-phenylenediamine and p-anisidine, were potent inactivators of amo while other derivatives were ineffective as inactivators. two cyclopropane derivatives, 1, 2-dimethylcyclopropane and cyclopropyl br ...	1998	9858770
organic halogen removal from chlorinated humic ground water and lake water by nitrifying fluidized-bed biomass characterised by electron microscopy and molecular methods.	the dechlorinating and genotoxicity-removing activities of nitrifying fluidized-bed reactor biomass towards chlorinated organic compounds in water were shown at level below 1 ppm. the removal rates of adsorbable organic halogens were 200 micrograms cl (g vs day)-1 for chlorinated humic ground water and 50 micrograms cl (g vs day)-1 for chlorinated lake water when studied in batch mode. in a sequenced batch mode the removal rates [micrograms cl (g vs day)-1] were 2000 from chlorohumus, 1400-1800 ...	1998	9866179
application of a fine thread beam to the structure analysis of a hemihedrally twinned crystal of hydroxylamine oxidoreductase.	accurate diffraction intensity data have been collected from a twinned p6(3) crystal of the 24-haem protein hydroxylamine oxidoreductase, from a nitrifying chemoautotrophic bacterium nitrosomonas europaea, using synchrotron radiation at station bl6a of the photon factory. estimation of the twinning fraction and deconvoluted intensity data, including native and heavy-atom derivative data, gave an improved patterson function. four diffraction data sets were collected from one crystal and an estima ...	1998	15263716
water purification system by using the biofilter for long-term experiment equipment with aquatic animals for the space station.	we have developed a water purification system that enables long-term experiment with aquatic animals for 90 days or more on the space station. we designed the system that combined a biofilter for ammonia removal (nitrification) with another for nitrate removal (denitrification). the experiment with goldfish was for 90 days with an aquatic animals' examination device. the equipment consists of a fish tank, a filter module, pumps, and an artificial lung for gas exchange. the goldfish were kept in ...	1998	11876203
analysis of beta-subgroup proteobacterial ammonia oxidizer populations in soil by denaturing gradient gel electrophoresis analysis and hierarchical phylogenetic probing	a combination of denaturing gradient gel electrophoresis (dgge) and oligonucleotide probing was used to investigate the influence of soil ph on the compositions of natural populations of autotrophic beta-subgroup proteobacterial ammonia oxidizers. pcr primers specific to this group were used to amplify 16s ribosomal dna (rdna) from soils maintained for 36 years at a range of ph values, and pcr products were analyzed by dgge. genus- and cluster-specific probes were designed to bind to sequences w ...	1998	9687457
ammonium limitation results in the loss of ammonia-oxidizing activity in nitrosomonas europaea.	the effects of limiting concentrations of ammonium on the metabolic activity of nitrosomonas europaea, an obligate ammonia-oxidizing soil bacterium, were investigated. cells were harvested during late logarithmic growth and were incubated for 24 h in growth medium containing 0, 15, or 50 mm ammonium. the changes in nitrite production and the rates of ammonia- and hydroxylamine-dependent oxygen consumption were monitored. in incubations without ammonium, there was little change in the ammonia oxi ...	1998	16349550
effects of soil on ammonia, ethylene, chloroethane, and 1,1,1-trichloroethane oxidation by nitrosomonas europaea.	ammonia monooxygenase (amo) from nitrosomonas europaea catalyzes the oxidation of ammonia to hydroxylamine and has been shown to oxidize a variety of halogenated and nonhalogenated hydrocarbons. as part of a program focused upon extending these observations to natural systems, a study was conducted to examine the influence of soil upon the cooxidative abilities of n. europaea. small quantities of willamette silt loam (organic carbon content, 1.8%; cation-exchange capacity, 15 cmol/kg of soil) we ...	1998	16349541
vfeu water quality control in sts-95 mission.	in sts-95 space shuttle mission, an aquatic animal research facility, vestibular function experiment unit (vfeu), was flown to perform neurobiological experiment with marine fish, oyster toadfish. for this purpose, we have developed a sea water purification system using highly active nitrifying bacteria at low temperature. with this system, the water quality in the vfeu was maintained in sufficient condition to keep the toadfish in healthy state for 9 days of the mission. this report summarizes ...	1999	11542797
water quality management for low temperature marine fishes in space.	vestibular function experiment unit (vfeu), one of the spacelab facility flown in neurolab mission (sts-90) in april, 1998, was to support neurophysiological research using a marine fish, opsanus tau (oyster toadfish). the functions of the vfeu were primarily a quality management of environmental water during the mission at 14 degrees c and for acquiring physiological signals from implanted micro-electrodes in the otolith nerves as well as the spatial acceleration of the fish. a key element of t ...	1999	11542798
closed water recirculating system for fish rearing equipped with bioreactor capable of simultaneous nitrification and denitrification.	five crucian carp, carassius auratus langsdorfiicarps had been reared in a closed water recirculating system. the system was equipped with the compact bioreactor using the plate gels capable of both nitrification and denitrification in a single unit. ammonia and nitrite concentrations in the rearing water had been maintained below 0.05 mg-n/l, and nitrate concentration also controlled between 2 and 8 mg-n/l with the bioreactor. as concerns nitrogen budget in the closed system, 95.0% of nitrogen ...	1999	11542800
r&d of long-term life support system by using electrochemically activated biofilm reactor of aquatic animals for space examinations.	we have developed the long-term life support system that enables the experiment of aquatic animals breeding for 90 days or more for the future experiments in orbit. in order to enable long-term breeding of wide aquatic animals, it is necessary to remove nitrate produced by biological nitrification. then, we examined a denitrification method to use an electrochemical reaction of biofilm-electrode reactor. in this research, we have not kept the aquatic animals actually but imitated breeding of fiv ...	1999	11542801