| direct electrochemistry of two genetically distinct flavodoxins isolated from azotobacter chroococcum grown under nitrogen-fixing conditions. | two genetically distinct flavodoxins, designated acflda and acfldb, were isolated from azotobacter chroococcum (mcd1155) grown under nitrogen-fixing conditions. acflda and acfldb differ in their midpoint potentials for the semiquinone-hydroquinone couple (em -305 mv and -520 mv respectively). only acfldb was competent to act as an electron donor to the mo-containing nitrogenase of a. chroococcum. the n-terminal amino acid sequence (20 residues) of acfldb was identical with that predicted from th ... | 1991 | 1859358 |
| hydrazine is a product of dinitrogen reduction by the vanadium-nitrogenase from azotobacter chroococcum. | during the enzymic reduction of n2 to nh3 by mo-nitrogenase, free hydrazine (n2h4) is not detectable, but an enzyme-bound intermediate can be made to yield n2h4 by quenching the enzyme during turnover [thorneley, eady & lowe (1978) nature (london) 272, 557-558]. in contrast, we show here that the v-nitrogenase of azotobacter chroococcum produces a small but significant amount of free n2h4 (up to 0.5% of the electron flux resulting in n2 reduction) as a product of the reduction of n2. the amount ... | 1991 | 1859374 |
| nucleotide sequence and genetic analysis of the azotobacter chroococcum nifusvwzm gene cluster, including a new gene (nifp) which encodes a serine acetyltransferase. | nucleotide sequence was obtained for a region of 7,099 bp spanning the nifu, nifs, nifv, nifw, nifz, and nifm genes from azotobacter chroococcum. chromosomal mutations constructed at several sites within the locus confirmed a requirement for this region for expression of the molybdenum nitrogenase in this organism. the genes are tightly clustered and ordered as in klebsiella pneumoniae except for two additional open reading frames (orfs) between nifv and nifw. the arrangement of genes in a. chro ... | 1991 | 1885524 |
| detection of alternative nitrogenases in aerobic gram-negative nitrogen-fixing bacteria. | strains of aerobic, microaerobic, nonsymbiotic, and symbiotic dinitrogen-fixing bacteria were screened for the presence of alternative nitrogenase (n2ase) genes by dna hybridization between genomic dna and dna encoding structural genes for components 1 of three different enzymes. a nifdk gene probe was used as a control to test for the presence of the commonly occurring mo-fe n2ase, a vnfdgk gene probe was used to show the presence of v-fe n2ase, and an anfdgk probe was used to detect fe n2ase. ... | 1991 | 1987127 |
| iron k-edge x-ray-absorption spectroscopy of the iron-vanadium cofactor of the vanadium nitrogenase from azotobacter chroococcum. | iron k-edge e.x.a.f.s. data for the iron-vanadium cofactor (fevaco) from azotobacter chroococcum vanadium nitrogenase reported here provide further evidence for the structural similarity between this and the iron-molybdenum nitrogenase cofactor (femoco) from klebsiella pneumoniae molybdenum nitrogenase [arber, flood, garner, gormal, hasnain & smith (1988) biochem. j. 252, 421-425]. the e.x.a.f.s. data are consistent with the vanadium being present in a v-fe-s cluster, thus confirming that the n- ... | 1990 | 2327976 |
| completed sequence of the region encoding the structural genes for the vanadium nitrogenase of azotobacter chroococcum. | | 1990 | 2388847 |
| molybdenum nitrogenase of azotobacter chroococcum. tight binding of mgadp to the mofe protein. | the dye-oxidized or dithionite-reduced forms of the mofe protein of molybdenum nitrogenase of azotobacter chroococcum were shown to bind 2 mol of mgadp/mol of protein, as determined by column equilibrium techniques. the gel-filtration elution profile of unbound mg[14c]adp was not symmetrical, consistent with a low rate of dissociation from the protein. symmetrical elution profiles were observed for the oxidized fe protein of nitrogenase, which bound 2 mol of mgadp/mol of protein. the low rate of ... | 1989 | 2597127 |
| nucleotide sequence and mutational analysis of the structural genes (anfhdgk) for the second alternative nitrogenase from azotobacter vinelandii. | the nucleotide sequence of a region of the azotobacter vinelandii genome exhibiting sequence similarity to nifh has been determined. the order of open reading frames within this 6.1-kilobase-pair region was found to be anfh (alternative nitrogen fixation, nifh-like gene), anfd (nifd-like gene), anfg (potentially encoding a protein similar to the product of vnfg from azotobacter chroococcum), anfk (nifk-like gene), followed by two additional open reading frames. the 5'-flanking region of anfh con ... | 1989 | 2644222 |
| oxidation of nitrogenase iron protein by dioxygen without inactivation could contribute to high respiration rates of azotobacter species and facilitate nitrogen fixation in other aerobic environments. | the kinetics of oxidation of the fe proteins of nitrogenases from klebsiella pneumoniae (kp2) and azotobacter chroococcum (ac2) by o2 and h2o2 have been studied by stopped-flow spectrophotometry at 23 degrees c, ph 7.4. with excess o2, one-electron oxidation of kp2 and ac2 and their 2 mgatp or 2 mgadp bound forms occurs with rate constants (k) in the range 5.3 x 10(3) m-1.s-1 to 1.6 x 10(5) m-1.s-1. a linear correlation between log k and the mid-point potentials (em) of these protein species ind ... | 1989 | 2673213 |
| vanadium k-edge x-ray-absorption spectroscopy of the functioning and thionine-oxidized forms of the vfe-protein of the vanadium nitrogenase from azotobacter chroococcum. | vanadium k-edge x-ray-absorption spectra were collected for samples of thionine-oxidized, super-reduced (during enzyme turnover) and dithionite-reduced vfe-protein of the vanadium nitrogenase of azotobacter chroococcum (acl*). both the e.x.a.f.s and the x.a.n.e.s. (x-ray-absorption near-edge structure) are consistent with the vanadium being present as part of a vfes cluster; the environment of the vanadium is not changed significantly in different oxidation states of the protein. the vanadium at ... | 1989 | 2730564 |
| structural genes for the vanadium nitrogenase from azotobacter chroococcum. | structural genes for the vfe-protein (ac1v) of the vanadium nitrogenase from azotobacter chroococcum were cloned and sequenced. the vfe-protein contains three subunit types with mr of 53,793 (alpha), 52,724 (beta) and 13,274 (delta). alpha and beta subunits show 18 and 15% sequence identity respectively, with alpha and beta subunits of the mofe-protein of a.chroococcum molybdenum nitrogenase. the genes for the three subunits vnfd (alpha), vnfg (delta) and vnfk (beta) are contiguous and form an o ... | 1989 | 2743980 |
| vanadium nitrogenase of azotobacter chroococcum. mgatp-dependent electron transfer within the protein complex. | the kinetics of mgatp-induced electron transfer from the fe protein (ac2v) to the vfe protein (aclv) of the vanadium-containing nitrogenase from azotobacter chroococcum were studied by stopped-flow spectrophotometry at 23 degrees c at ph 7.2. they are very similar to those of the molybdenum nitrogenase of klebsiella pneumoniae [thorneley (1975) biochem. j. 145, 391-396]. extrapolation of the dependence of kobs. on [mgatp] to infinite mgatp concentration gave k = 46 s-1 for the first-order electr ... | 1989 | 2784670 |
| the vanadium nitrogenase of azotobacter chroococcum. purification and properties of the vfe protein. | 1. nitrogenase activity of a strain of azotobacter chroococcum lacking the structural genes for conventional nitrogenase (nifhdk) was separated into two components: an fe-containing protein and a vanadoprotein. 2. the larger protein was purified to homogeneity by the criterion of electrophoresis of 10% (w/v) acrylamide gels in the presence of sds. two types of subunit, of mr 50,000 and 55,000, were present in equal amounts. 3. the protein had an mr of 210,000 and contained 2 v atoms, 23 fe atoms ... | 1987 | 2821997 |
| the vanadium-iron protein of vanadium nitrogenase from azotobacter chroococcum contains an iron-vanadium cofactor. | n-methylformamide extracts of acid-treated precipitated vfe protein of the v-nitrogenase of azotobacter chroococcum are yellow-brown in colour and contain vanadium, iron and acid-labile sulphur in the approximate proportions 1:6:5. e.p.r. spectra of the extracts exhibit a weak signal with g values near 4.5, 3.6 and 2.0 characteristic of an s = 3/2 metal-containing centre. the n-methylformamide extracts activated the mofe protein polypeptides from mutants of nitrogen-fixing bacteria unable to syn ... | 1988 | 2833236 |
| the vanadium nitrogenase of azotobacter chroococcum. purification and properties of the fe protein. | 1. nitrogenase activity of a strain of azotobacter chroococcum lacking the structural genes of monitrogenase (nifhdk) was associated with a v + fe-containing protein and an fe-containing protein [robson, eady, richardson, miller, hawkins & postgate (1986) nature (london) 322, 388-390; eady, robson, richardson, miller & hawkins (1987) biochem. j. 244, 197-207]. 2. the fe protein was purified to homogeneity by the criterion of coomassie blue staining after electrophoresis in 10% or 17% (w/v) polya ... | 1988 | 2851977 |
| electron-transfer studies involving flavodoxin and a natural redox partner, the iron protein of nitrogenase. conformational constraints on protein-protein interactions and the kinetics of electron transfer within the protein complex. | the kinetics of electron-transfer reactions involving flavodoxins from klebsiella pneumoniae (kpfld), azotobacter chroococcum (acfld), anacystis nidulans (anfld) and megasphaera elsdenii (mefld), the free, mgadp-bound and mgatp-bound forms of the fe protein component of nitrogenase from k. pneumoniae [kp2, kp2(mgadp)2 and kp2(mgatp)2] and na2s2o4 were studied by stopped-flow spectrophotometry. kinetic evidence was obtained for the formation of binary protein complexes involving kpfldsq (semiquin ... | 1988 | 3140782 |
| the vanadium nitrogenase of azotobacter chroococcum. reduction of acetylene and ethylene to ethane. | 1. the vanadium (v-) nitrogenase of azobacter chroococcum transfers up to 7.4% of the electrons used in acetylene (c2h2) reduction for the formation of ethane (c2h6). the apparent km for c2h2 (6 kpa) is the same for either ethylene (c2h4) or ethane (c2h6) formation and much higher than the reported km values for c2h2 reduction to c2h4 by molybdenum (mo-) nitrogenases. reduction of c2h2 in 2h2o yields predominantly [cis-2h2]ethylene. 2. the ratio of electron flux yielding c2h6 to that yielding c2 ... | 1988 | 3162672 |
| the vanadium- and molybdenum-containing nitrogenases of azotobacter chroococcum. comparison of mid-point potentials and kinetics of reduction by sodium dithionite of the iron proteins with bound magnesium adenosine 5'-diphosphate. | the mid-point potentials of the fe protein components (ac2 and ac2* respectively) of the mo nitrogenase and v nitrogenase from azotobacter chroococcum were determined in the presence of mgadp to be -450 mv (nhe) [ac2(mgadp)2-ac2*ox.(mgadp)2 couple] and -463 mv (nhe) [ac2* (mgadp)2-ac2*ox.(adp)2 couple] at 23 degrees c at ph 7.2. these values are consistent with a flavodoxin characterized by deistung & thorneley [(1986) biochem. j. 239, 69-75] with em = -522 mv (nhe) being an effective electron d ... | 1988 | 3164616 |
| molybdenum and vanadium nitrogenases of azotobacter chroococcum. low temperature favours n2 reduction by vanadium nitrogenase. | a comparison of the effect of temperature on the reduction of n2 by purified molybdenum nitrogenase and vanadium nitrogenase of azotobacter chroococcum showed differences in behaviour. as the assay temperature was lowered from 30 degrees c to 5 degrees c n2 remained an effective substrate for v nitrogenase, but not mo nitrogenase, since the specific activity for n2 reduction by mo nitrogenase decreased 10-fold more than that of v nitrogenase. activity cross-reactions between nitrogenase componen ... | 1988 | 3223922 |
| short-term nitrate (nitrite) inhibition of nitrogen fixation in azotobacter chroococcum. | nitrate-grown azotobacter chroococcum atcc 4412 cells lack the ability to fix n2. nitrogenase activity developed after the cells were suspended in a combined nitrogen-free medium and was paralleled by a concomitant decrease in nitrate assimilation capacity. in such treated cells exhibiting transitory nitrate assimilation and n2-fixation capacity, nitrate or nitrite caused a short-term inhibitory effect on nitrogenase activity which ceased once the anion was exhausted from the medium. the analog ... | 1986 | 3455689 |
| electron transfer to nitrogenase. characterization of flavodoxin from azotobacter chroococcum and comparison of its redox potentials with those of flavodoxins from azotobacter vinelandii and klebsiella pneumoniae (niff-gene product). | flavodoxin in the hydroquinone state acts as an electron donor to nitrogenase in several nitrogen-fixing organisms. the mid-point potentials for the oxidized-semiquinone and semiquinone-hydroquinone couples of flavodoxins isolated from facultative anaerobe klebsiella pneumoniae (niff-gene product, kpfld) and the obligate aerobe azotobacter chroococcum (acfld) were determined as a function of ph. the mid-point potentials of the semiquinone-hydroquinone couples of kpfld and acfld are essentially i ... | 1986 | 3541922 |
| lesions in citrate synthase that affect aerobic nitrogen fixation by azotobacter chroococcum. | a class of azotobacter chroococcum mutants induced by tn1 that were defective in normal aerobic nitrogen fixation when grown on sugars (fos-) were corrected by provision of alpha-ketoglutarate or glutamate. in a representative mutant, fos252, rates of evolution of 14co2 from [14c]acetate or [14c]glucose were 5% of the parental values, although uptake and incorporation were normal for both substrates. the results suggest that a lesion affects the entry of substrates into the tricarboxylic acid cy ... | 1985 | 3988712 |
| azotobacter chroococcum 7fe ferredoxin. two ph-dependent forms of the reduced 3fe clusters and its conversion to a 4fe cluster. | ferredoxin from azotobacter chroococcum has been studied by low-temperature magnetic-circular-dichroism and electron-paramagnetic-resonance spectroscopy. when aerobically isolated ferredoxin contains a [3fe-4s] and [4fe-4s] cluster. anaerobic treatment with dithionite in the presence of ethanediol reduces the [3fe-4s] cluster to give two spectroscopically distinct forms ri and rii which are reversibly interconvertible with a pka approximately 7.5. the higher-ph form, rii, has a high affinity for ... | 1984 | 6095817 |
| roles of niff and nifj gene products in electron transport to nitrogenase in klebsiella pneumoniae. | crude extracts of the wild-type klebsiella pneumoniae reduced c2h2 with either pyruvate or formate as reductant (specific activity, 3 nmol min-1 mg of protein-1), whereas crude extracts of niff mutant were almost inactive (specific activity, 0.05). however, activity in the latter extracts was stimulated by adding azotobacter chroococcum flavodoxin (specific activity, 10). thus, niff mutants may lack an electron transport factor. crude extracts of nifj mutants had about 20% of the wild-type level ... | 1980 | 6988383 |
| effect of chelating agents on hydrogenase in azotobacter chroococcum. evidence that nickel is required for hydrogenase synthesis. | the chelating agents edta, o-phenanthroline, nitrilotriacetic acid (nta), ethylenediamine-bis(o-hydroxyphenylacetic acid) (edda) or dimethylglyoxime prevented the expression of hydrogenase activity in batch cultures of nitrogen-fixing azotobacter chroococcum, but did not inhibit preformed enzyme. the inhibition was reversed either by adding a mixture of trace elements (cu2+, mn2+, zn2+, co2+) or ni2+ or, to a lesser degree, co2+ alone. ni2+ or ni2+ + fe2+ also enhanced the rate of hydrogenase de ... | 1982 | 7052066 |
| homologous structural genes and similar induction patterns in azotobacter spp. and pseudomonas spp. | intergeneric comparison of the three enzymes that initiate metabolism of protocatechuate in azotobacter and pseudomonas species revealed close immunological relatedness of isofunctional proteins. furthermore, beta-ketoadipate induces all of the enzymes of the protocatechuate pathway (except protocatechuate oxygenase) in azotobacter and in pseudomonas species of the "fluorescent" and "cepacia" groups. this regulatory property sets the organisms apart from other bacteria. protocatechuate oxygenase ... | 1980 | 7204335 |
| in vivo modification of azotobacter chroococcum glutamine synthetase. | a monospecific anti-(glutamine synthetase) antibody raised against glutamine synthetase of the unicellular cyanobacterium synechocystis sp. strain pcc 6803 immunoreacted with glutamine synthetase from the n2-fixing heterotrophic bacterium azotobacter chroococcum. in western-blotting experiments this antibody recognized a single protein of a molecular mass of 59 kda corresponding to glutamine synthetase subunit. this protein was in vivo-labelled in response to addition of ammonium, both [3h]adeni ... | 1994 | 7908189 |
| effects of mn2+ and mg2+ on assimilation of no3- and nh4+ by soil microorganisms. | although it has been demonstrated that mn2+ and mg2+ can influence the activity of glutamine synthetase in various organisms, there is little information concerning the effects of these cations on the activity of this enzyme in soil microorganisms or on ability of these microorganisms to assimilate no3- and nh4+. we studied the effects of different concentrations of mn2+ and mg2+ on assimilatory no3- reduction and nh4+ assimilation in cultures of two microorganisms commonly found in soil [pseudo ... | 1993 | 8415713 |
| the molybdenum and vanadium nitrogenases of azotobacter chroococcum: effect of elevated temperature on n2 reduction. | during the reduction of n2 by v-nitrogenase at 30 degrees c, some hydrazine (n2h4) is formed as a product in addition to nh3 [dilworth and eady (1991) biochem. j. 277, 465-468]. we show here the following. (1) that over the temperature range 30-45 degrees c the apparent km for the reduction of n2 to yield these products is the same, but increases from 30 to 58 kpa of n2. on increasing the temperature from 45 degrees c to 50 degrees c, little change occurred in the rate of reduction of protons to ... | 1993 | 8424785 |
| expression from the nifb promoter of azotobacter vinelandii can be activated by nifa, vnfa, or anfa transcriptional activators. | in azotobacter vinelandii, nifb is required for the activity of all three nitrogenases. expression of a nifb-lacz fusion was examined to determine which regulatory gene products are important for nifb expression and how its transcription is regulated in response to metals. in all conditions, expression in a. vinelandii was eliminated by an rpon mutation, confirming the absolute requirement for sigma n. in the wild type, nifb-lacz expression was approximately twofold higher in cells grown with mo ... | 1996 | 8550514 |
| alkylresorcinols are abundant lipid components in different strains of azotobacter chroococcum and pseudomonas spp. | the occurrence of various amounts of 5-n-alkylresorcinols was shown in lipids extracted from 14 bacterial strains of azotobacter chroococcum as well as from strains of pseudomonas aureofaciens, p. chlororapsis, and p. fluorescens. the amount of alkylresorcinols found varied from 2.3 to 56.2 microg/mg (dry weight) of cells in a. chroococum and from 0.2 to 0.8 microg/mg (dry weight) of cells in pseudomonas spp. strains of both genera produce saturated homologs with c13 to c27 side chains. c19, c21 ... | 1996 | 8763927 |
| cloning and sequencing of a 2,5-dichlorohydroquinone reductive dehalogenase gene whose product is involved in degradation of gamma-hexachlorocyclohexane by sphingomonas paucimobilis. | sphingomonas (formerly pseudomonas) paucimobilis ut26 utilizes gamma-hexachlorocyclohexane (gamma-hch), a halogenated organic insecticide, as a sole carbon and energy source. in a previous study, we showed that gamma-hch is degraded to 2,5-dichlorohydroquinone (2,5-dchq) (y. nagata, r. ohtomo, k. miyauchi, m. fukuda, k. yano, and m. takagi, j. bacteriol. 176:3117-3125, 1994). in the present study, we cloned and characterized a gene, designated lind, directly involved in the degradation of 2,5-dc ... | 1998 | 9515900 |
| unusual organization of the genes coding for hydsl, the stable [nife]hydrogenase in the photosynthetic bacterium thiocapsa roseopersicina bbs. | the characterization of a hyd gene cluster encoding the stable, bidirectional [nife]hydrogenase 1 enzyme in thiocapsa roseopersicina bbs, a purple sulfur photosynthetic bacterium belonging to the family chromatiaceae, is presented. the heterodimeric hydrogenase 1 had been purified to homogeneity and thoroughly characterized (k. l. kovacs et al., j. biol. chem. 266:947-951, 1991; c. bagyinka et al., j. am. chem. soc. 115:3567-3585, 1993). as an unusual feature, a 1,979-bp intergenic sequence (is) ... | 1998 | 9515914 |
| characterization of the glnk-amtb operon of azotobacter vinelandii. | to determine whether in azotobacter vinelandii the pii protein influences the regulation of nif gene expression in response to fluxes in the ammonium supply, the gene encoding pii was isolated and characterized. its deduced translation product was highly similar to pii proteins from other organisms, with the greatest degree of relatedness being exhibited to the escherichia coli glnk gene product. a gene designated amtb was found downstream of and was contranscribed with glnk as in e. coli. the a ... | 1998 | 9620984 |
| biochemical properties and substrate specificities of a recombinantly produced azotobacter vinelandii alginate lyase. | alginate is a polysaccharide composed of beta-d-mannuronic acid (m) and alpha-l-guluronic acid (g). an azotobacter vinelandii alginate lyase gene, algl, was cloned, sequenced, and expressed in escherichia coli. the deduced molecular mass of the corresponding protein is 41.4 kda, but a signal peptide is cleaved off, leaving a mature protein of 39 kda. sixty-three percent of the amino acids in this mature protein are identical to those in algl from pseudomonas aeruginosa. algl was partially purifi ... | 1998 | 9683471 |
| genetic diversity of nifh gene sequences in paenibacillus azotofixans strains and soil samples analyzed by denaturing gradient gel electrophoresis of pcr-amplified gene fragments. | the diversity of dinitrogenase reductase gene (nifh) fragments in paenibacillus azotofixans strains was investigated by using molecular methods. the partial nifh gene sequences of eight p. azotofixans strains, as well as one strain each of the close relatives paenibacillus durum, paenibacillus polymyxa, and paenibacillus macerans, were amplified by pcr by using degenerate primers and were characterized by dna sequencing. we found that there are two nifh sequence clusters, designated clusters i a ... | 1998 | 9687429 |
| heterologous expression of the desulfovibrio gigas [nife] hydrogenase in desulfovibrio fructosovorans mr400. | the ability of desulfovibrio fructosovorans mr400 deltahynabc to express the heterologous cloned [nife] hydrogenase of desulfovibrio gigas was investigated. the [nife] hydrogenase operon from d. gigas, hynabcd, was cloned, sequenced, and introduced into d. fructosovorans mr400. a portion of the recombinant heterologous [nife] hydrogenase was totally matured, exhibiting catalytic and spectroscopic properties identical to those of the native d. gigas protein. a chimeric operon containing hynab fro ... | 1998 | 9733707 |
| physiological diversity of the rhizosphere diazotroph assemblages of selected salt marsh grasses. | rhizosphere diazotroph assemblages of salt marsh grasses are thought to be influenced by host plant species and by a number of porewater geochemical parameters. several geochemical variables can adversely affect plant productivity and spatial distributions, resulting in strong zonation of plant species and growth forms. this geochemically induced stress may also influence the species compositions and distributions of rhizosphere diazotroph assemblages, but little is currently known about these o ... | 1998 | 9797277 |
| combined physical and genetic map of the pseudomonas putida kt2440 chromosome. | a combined physical and genetic map of the pseudomonas putida kt2440 genome was constructed from data obtained by pulsed-field gel electrophoresis techniques (pfge) and southern hybridization. circular genome size was estimated at 6.0 mb by adding the sizes of 19 swai, 9 pmei, 6 paci, and 6 i-ceui fragments. a complete physical map was achieved by combining the results of (i) analysis of pfge of the dna fragments resulting from digestion of the whole genome with pmei, swai, i-ceui, and paci as w ... | 1998 | 9829947 |
| the signal transduction protein glnk is required for nifl-dependent nitrogen control of nif gene expression in klebsiella pneumoniae. | in klebsiella pneumoniae, transcription of the nitrogen fixation (nif) genes is regulated in response to molecular oxygen or availability of fixed nitrogen by the coordinated activities of the nifa and nifl gene products. nifa is a nif-specific transcriptional activator, the activity of which is inhibited by interaction with nifl. nitrogen control of nifl occurs at two levels: transcription of the nifla operon is regulated by the global ntr system, and the inhibitory activity of nifl is controll ... | 1999 | 9973341 |
| cloning and expression of the algl gene, encoding the azotobacter chroococcum alginate lyase: purification and characterization of the enzyme. | the alginate lyase-encoding gene (algl) of azotobacter chroococcum was localized to a 3.1-kb ecori dna fragment that revealed an open reading frame of 1,116 bp. this open reading frame encodes a protein of 42.98 kda, in agreement with the value previously reported by us for this protein. the deduced protein has a potential n-terminal signal peptide that is consistent with its proposed periplasmic location. the analysis of the deduced amino acid sequence indicated that the gene sequence has a hig ... | 1999 | 10049370 |
| the a modules of the azotobacter vinelandii mannuronan-c-5-epimerase alge1 are sufficient for both epimerization and binding of ca2+. | the industrially important polysaccharide alginate is composed of the two sugar monomers beta-d-mannuronic acid (m) and its epimer alpha-l-guluronic acid (g). in the bacterium azotobacter vinelandii, the g residues originate from a polymer-level reaction catalyzed by one periplasmic and at least five secreted mannuronan c-5-epimerases. the secreted enzymes are composed of repeats of two protein modules designated a (385 amino acids) and r (153 amino acids). the modular structure of one of the ep ... | 1999 | 10322003 |
| chemoselective nitro group reduction and reductive dechlorination initiate degradation of 2-chloro-5-nitrophenol by ralstonia eutropha jmp134. | ralstonia eutropha jmp134 utilizes 2-chloro-5-nitrophenol as a sole source of nitrogen, carbon, and energy. the initial steps for degradation of 2-chloro-5-nitrophenol are analogous to those of 3-nitrophenol degradation in r. eutropha jmp134. 2-chloro-5-nitrophenol is initially reduced to 2-chloro-5-hydroxylaminophenol, which is subject to an enzymatic bamberger rearrangement yielding 2-amino-5-chlorohydroquinone. the chlorine of 2-amino-5-chlorohydroquinone is removed by a reductive mechanism, ... | 1999 | 10347008 |
| ni(2+) transport and accumulation in rhodospirillum rubrum. | the cooctj gene products are coexpressed with co-dehydrogenase (codh) and facilitate in vivo nickel insertion into codh. a ni(2+) transport assay was used to monitor uptake and accumulation of (63)ni(2+) into r. rubrum and to observe the effect of mutations in the cooc, coot, and cooj genes on (63)ni(2+) transport and accumulation. cells grown either in the presence or absence of co transported ni(2+) with a k(m) of 19 +/- 4 microm and a v(max) of 310 +/- 22 pmol of ni/min/mg of total protein. i ... | 1999 | 10419953 |
| interstrain variation of the polysaccharide b biosynthesis locus of bacteroides fragilis: characterization of the region from strain 638r. | the sequence and analysis of the capsular polysaccharide biosynthesis locus, ps b2, of bacteroides fragilis 638r are described, and the sequence is compared with that of the ps b1 biosynthesis locus of b. fragilis nctc 9343. two genes of the region, wcgd and wcgc, are shown by complementation to encode a udp-n-acetylglucosamine 2-epimerase and a udp-n-acetylmannosamine dehydrogenase, respectively. | 1999 | 10498737 |
| the respiratory system and diazotrophic activity of acetobacter diazotrophicus pal5. | the characteristics of the respiratory system of acetobacter diazotrophicus pal5 were investigated. increasing aeration (from 0.5 to 4.0 liters of air min(-1) liter of medium(-1)) had a strong positive effect on growth and on the diazotrophic activity of cultures. cells obtained from well-aerated and diazotrophically active cultures possessed a highly active, membrane-bound electron transport system with dehydrogenases for nadh, glucose, and acetaldehyde as the main electron donors. ethanol, suc ... | 1999 | 10559164 |
| ralstonia eutropha tf93 is blocked in tat-mediated protein export. | ralstonia eutropha (formerly alcaligenes eutrophus) tf93 is pleiotropically affected in the translocation of redox enzymes synthesized with an n-terminal signal peptide bearing a twin arginine (s/t-r-r-x-f-l-k) motif. immunoblot analyses showed that the catalytic subunits of the membrane-bound [nife] hydrogenase (mbh) and the molybdenum cofactor-binding periplasmic nitrate reductase (nap) are mislocalized to the cytoplasm and to the inner membrane, respectively. moreover, physiological studies s ... | 2000 | 10633089 |
| dual roles of bradyrhizobium japonicum nickelin protein in nickel storage and gtp-dependent ni mobilization. | the hydrogenase accessory protein hypb, or nickelin, has two functions in the n(2)-fixing, h(2)-oxidizing bacterium bradyrhizobium japonicum. one function of hypb involves the mobilization of nickel into hydrogenase. hypb also carries out a nickel storage/sequestering function in b. japonicum, binding nine nickel ions per monomer. here we report that the two roles (nickel mobilization and storage) of hypb can be separated in vitro and in vivo using molecular and biochemical approaches. the role ... | 2000 | 10692376 |
| flavodoxin mutants of escherichia coli k-12. | the flavodoxins are flavin mononucleotide-containing electron transferases. flavodoxin i has been presumed to be the only flavodoxin of escherichia coli, and its gene, flda, is known to belong to the soxrs (superoxide response) oxidative stress regulon. an insertion mutation of flda was constructed and was lethal under both aerobic and anaerobic conditions; only cells that also had an intact (flda(+)) allele could carry it. a second flavodoxin, flavodoxin ii, was postulated, based on the sequenc ... | 2000 | 10714981 |
| role of the azotobacter vinelandii nitrogenase-protective shethna protein in preventing oxygen-mediated cell death. | azotobacter vinelandii strains lacking the nitrogenase-protective shethna protein lost viability upon carbon-substrate deprivation in the presence of oxygen. this viability loss was dependent upon the n(2)-fixing status of cultures (n(2)-fixing cells lost viability, while non-n(2)-fixing cells did not) and on the ambient o(2) level. supra-atmosheric o(2) tensions (40% partial pressure) decreased the viable cell number of the mutant further, and the mutant had a slightly higher spontaneous mutati ... | 2000 | 10851006 |
| the hydrogenase cytochrome b heme ligands of azotobacter vinelandii are required for full h(2) oxidation capability. | the hydrogenase in azotobacter vinelandii, like other membrane-bound [nife] hydrogenases, consists of a catalytic heterodimer and an integral membrane cytochrome b. the histidines ligating the hemes in this cytochrome b were identified by h(2) oxidation properties of altered proteins produced by site-directed mutagenesis. four fully conserved and four partially conserved histidines in hoxz were substituted with alanine or tyrosine. the roles of these histidines in hoxz heme binding and hydrogena ... | 2000 | 10852874 |
| molecular analysis of diazotroph diversity in the rhizosphere of the smooth cordgrass, spartina alterniflora. | n(2) fixation by diazotrophic bacteria associated with the roots of the smooth cordgrass, spartina alterniflora, is an important source of new nitrogen in many salt marsh ecosystems. however, the diversity and phylogenetic affiliations of these rhizosphere diazotrophs are unknown. denaturing gradient gel electrophoresis (dgge) of pcr-amplified nifh sequence segments was used in previous studies to examine the stability and dynamics of the spartina rhizosphere diazotroph assemblages in the north ... | 2000 | 10966395 |
| effect of oxygen on formation and structure of azotobacter vinelandii alginate and its role in protecting nitrogenase. | the activity of nitrogenase in the nitrogen-fixing bacterium azotobacter vinelandii grown diazotrophically under aerobic conditions is generally considered to be protected against o(2) by a high respiration rate. in this work, we have shown that a high rate of respiration is not the prevailing mechanism for nitrogenase protection in a. vinelandii grown in phosphate-limited nitrogen-free chemostat culture. instead, the formation of alginate appeared to play a decisive role in protecting the nitro ... | 2000 | 10966426 |
| characterization of alginate lyase from pseudomonas syringae pv. syringae. | the gene encoding alginate lyase (algl) in pseudomonas syringae pv. syringae was cloned, sequenced, and overexpressed in escherichia coli. alginate lyase activity was optimal when the ph was 7.0 and when assays were conducted at 42 degrees c in the presence of 0.2 m nacl. in substrate specificity studies, algl from p. syringae showed a preference for deacetylated polymannuronic acid. sequence alignment with other alginate lyases revealed conserved regions within algl likely to be important for t ... | 2000 | 11029455 |
| persistence of selected spartina alterniflora rhizoplane diazotrophs exposed to natural and manipulated environmental variability. | rhizoplane-rhizosphere nitrogen-fixing microorganisms (diazotrophs) are thought to provide a major source of biologically available nitrogen in salt marshes dominated by spartina alterniflora. compositional and functional stability has been demonstrated for this important functional group; however, the quantitative responses of specific diazotroph populations to environmental variability have not been assessed. changes in the relative abundances of selected rhizoplane diazotrophs in response to ... | 2000 | 11055903 |
| key aromatic-ring-cleaving enzyme, protocatechuate 3,4-dioxygenase, in the ecologically important marine roseobacter lineage. | aromatic compound degradation in six bacteria representing an ecologically important marine taxon of the alpha-proteobacteria was investigated. initial screens suggested that isolates in the roseobacter lineage can degrade aromatic compounds via the beta-ketoadipate pathway, a catabolic route that has been well characterized in soil microbes. six roseobacter isolates were screened for the presence of protocatechuate 3,4-dioxygenase, a key enzyme in the beta-ketoadipate pathway. all six isolates ... | 2000 | 11055908 |
| purification and properties of an enzyme capable of degrading the sheath of sphaerotilus natans. | microorganisms which can degrade and grow on the purified sheath of a sheathed bacterium sphaerotilus natans were collected from soil and river water. two bacterial strains were isolated from the soil and designated strains tb and tk. both strains are rod shaped, negatively stained by gram staining, facultatively anaerobic, and formed ellipsoidal endospores. these characteristics suggested that the isolates belong to the genus paenibacillus, according to ash et al. (c. ash, f. g. priest, and m. ... | 2000 | 11055955 |
| characterization of a major cluster of nif, fix, and associated genes in a sugarcane endophyte, acetobacter diazotrophicus. | a major 30.5-kb cluster of nif and associated genes of acetobacter diazotrophicus (syn. gluconacetobacter diazotrophicus), a nitrogen-fixing endophyte of sugarcane, was sequenced and analyzed. this cluster represents the largest assembly of contiguous nif-fix and associated genes so far characterized in any diazotrophic bacterial species. northern blots and promoter sequence analysis indicated that the genes are organized into eight transcriptional units. the overall arrangement of genes is most ... | 2000 | 11092875 |
| coliform bacteria and nitrogen fixation in pulp and paper mill effluent treatment systems. | the majority of pulp and paper mills now biotreat their combined effluents using activated sludge. on the assumption that their wood-based effluents have negligible fixed n, and that activated-sludge microorganisms will not fix significant n, these mills routinely spend large amounts adding ammonia or urea to their aeration tanks (bioreactors) to permit normal biomass growth. n(2) fixation in seven eastern canadian pulp and paper mill effluent treatment systems was analyzed using acetylene reduc ... | 2000 | 11097883 |
| role of the dinitrogenase reductase arginine 101 residue in dinitrogenase reductase adp-ribosyltransferase binding, nad binding, and cleavage. | dinitrogenase reductase is posttranslationally regulated by dinitrogenase reductase adp-ribosyltransferase (drat) via adp-ribosylation of the arginine 101 residue in some bacteria. rhodospirillum rubrum strains in which the arginine 101 of dinitrogenase reductase was replaced by tyrosine, phenylalanine, or leucine were constructed by site-directed mutagenesis of the nifh gene. the strain containing the r101f form of dinitrogenase reductase retains 91%, the strain containing the r101y form retain ... | 2001 | 11114923 |
| glnd and mvin are genes of an essential operon in sinorhizobium meliloti. | to evaluate the role of uridylyl-transferase, the sinorhizobium meliloti glnd gene was isolated by heterologous complementation in azotobacter vinelandii. the glnd gene is cotranscribed with a gene homologous to salmonella mvin. glnd1::omega or mvin1::omega mutants could not be isolated by a powerful sucrose counterselection procedure unless a complementing cosmid was provided, indicating that glnd and mvin are members of an indispensable operon in s. meliloti. | 2001 | 11274131 |
| role of a ferredoxin gene cotranscribed with the nifhdk operon in n(2) fixation and nitrogenase "switch-off" of azoarcus sp. strain bh72. | the endophytic diazotroph azoarcus sp. strain bh72 is capable of infecting rice roots and of expressing the nitrogenase (nif) genes there. in order to study the genetic background for nitrogen fixation in strain bh72, the structural genes of nitrogenase (nifhdk) were cloned and sequenced. the sequence analysis revealed an unusual gene organization: downstream of nifhdk, a ferredoxin gene (fdxn; 59% amino acid sequence identity to r. capsulatus fdxn) and open reading frames showing 52 and 36% ami ... | 2001 | 11371540 |
| response of the endophytic diazotroph gluconacetobacter diazotrophicus on solid media to changes in atmospheric partial o(2) pressure. | gluconacetobacter diazotrophicus is an n(2)-fixing endophyte isolated from sugarcane. g. diazotrophicus was grown on solid medium at atmospheric partial o(2) pressures (po(2)) of 10, 20, and 30 kpa for 5 to 6 days. using a flowthrough gas exchange system, nitrogenase activity and respiration rate were then measured at a range of atmospheric po(2) (5 to 60 kpa). nitrogenase activity was measured by h(2) evolution in n(2)-o(2) and in ar-o(2), and respiration rate was measured by co(2) evolution in ... | 2001 | 11571174 |
| control of nitrogenase reactivation by the glnz protein in azospirillum brasilense. | the glnz mutant of azospirillum brasilense (strain 7611) showed only partial recovery (20 to 40%) after 80 min of ammonia-induced nitrogenase switch-off, whereas the wild type recovered totally within 10 min. in contrast, the two strains showed identical anoxic-induced switch-on/switch-off, indicating no cross talk between the two reactivation mechanisms. | 2001 | 11673445 |
| purification and properties of a glucuronan lyase from sinorhizobium meliloti m5n1cs (ncimb 40472). | a glucuronan lyase extracted from sinorhizobium meliloti strain m5n1cs was purified to homogeneity by anion-exchange chromatography. the purified enzyme corresponds to a monomer with a molecular mass of 20 kda and a pi of 4.9. a specific activity was found only for polyglucuronates leading to the production of 4,5-unsaturated oligoglucuronates. the enzyme activity was optimal at ph 6.5 and 50 degrees c. zn(2+), cu(2+), and hg(2+) (1 mm) inhibited the enzyme activity. no homology of the enzyme n- ... | 2001 | 11679345 |
| recovery and phylogenetic analysis of nifh sequences from diazotrophic bacteria associated with dead aboveground biomass of spartina alterniflora. | dna was extracted from dry standing dead spartina alterniflora stalks as well as dry spartina wrack from the north inlet (south carolina) and sapelo island (georgia) salt marshes. partial nifh sequences were pcr amplified, the products were separated by denaturing gradient gel electrophoresis (dgge), and the prominent dgge bands were sequenced. most sequences (109 of 121) clustered with those from alpha-proteobacteria, and 4 were very similar (>99%) to that of azospirillum brasilense. seven sequ ... | 2001 | 11679360 |
| noncoupled nadh:ubiquinone oxidoreductase of azotobacter vinelandii is required for diazotrophic growth at high oxygen concentrations. | the gene encoding the noncoupled nadh:ubiquinone oxidoreductase (ndh ii) from azotobacter vinelandii was cloned, sequenced, and used to construct an ndh ii-deficient mutant strain. compared to the wild type, this strain showed a marked decrease in respiratory activity. it was unable to grow diazotrophically at high aeration, while it was fully capable of growth at low aeration or in the presence of nh(4)(+). this result suggests that the role of ndh ii is as a vital component of the respiratory ... | 2001 | 11698376 |
| involvement of the twin-arginine translocation system in protein secretion via the type ii pathway. | the general secretory pathway (gsp) is a two-step process for the secretion of proteins by gram-negative bacteria. the translocation across the outer membrane is carried out by the type ii system, which involves machinery called the secreton. this step is considered to be an extension of the general export pathway, i.e. the export of proteins across the inner membrane by the sec machinery. here, we demonstrate that two substrates for the pseudomonas aeruginosa secreton, both phospholipases, use ... | 2001 | 11726509 |
| rubredoxins involved in alkane oxidation. | rubredoxins (rds) are essential electron transfer components of bacterial membrane-bound alkane hydroxylase systems. several rd genes associated with alkane hydroxylase or rd reductase genes were cloned from gram-positive and gram-negative organisms able to grow on n-alkanes (alk-rds). complementation tests in an escherichia coli recombinant containing all pseudomonas putida gpo1 genes necessary for growth on alkanes except rd 2 (alkg) and sequence comparisons showed that the alk-rds can be divi ... | 2002 | 11872724 |
| characterization of a nifs-like chloroplast protein from arabidopsis. implications for its role in sulfur and selenium metabolism. | nifs-like proteins catalyze the formation of elemental sulfur (s) and alanine from cysteine (cys) or of elemental selenium (se) and alanine from seleno-cys. cys desulfurase activity is required to produce the s of iron (fe)-s clusters, whereas seleno-cys lyase activity is needed for the incorporation of se in selenoproteins. in plants, the chloroplast is the location of (seleno) cys formation and a location of fe-s cluster formation. the goal of these studies was to identify and characterize chl ... | 2002 | 12427997 |
| the sac mutants of chlamydomonas reinhardtii reveal transcriptional and posttranscriptional control of cysteine biosynthesis. | algae and vascular plants are cysteine (cys) prototrophs. they are able to import, reduce, and assimilate sulfate into cys, methionine, and other organic sulfur-containing compounds. characterization of genes encoding the enzymes required for cys biosynthesis from the unicellular green alga chlamydomonas reinhardtii reveals that transcriptional and posttranscriptional mechanisms regulate the pathway. the derived amino acid sequences of the c. reinhardtii genes encoding 5'-adenylylsulfate (aps) r ... | 2002 | 12481091 |
| mrna extraction and reverse transcription-pcr protocol for detection of nifh gene expression by azotobacter vinelandii in soil. | the study of free-living nitrogen-fixing organisms in bulk soil is hampered by the great diversity of soil microbial communities and the difficulty of relating nitrogen fixation activities to individual members of the diazotroph populations. we developed a molecular method that allows analysis of nifh mrna expression in soil in parallel with determinations of nitrogen-fixing activity and bacterial growth. in this study, azotobacter vinelandii growing in sterile soil and liquid culture served as ... | 2003 | 12676666 |
| prediction of reduction potential changes in rubredoxin: a molecular mechanics approach. | predicting the effects of mutation on the reduction potential of proteins is crucial in understanding how reduction potentials are modulated by the protein environment. previously, we proposed that an alanine vs. a valine at residue 44 leads to a 50-mv difference in reduction potential found in homologous rubredoxins because of a shift in the polar backbone relative to the iron site due to the different side-chain sizes. here, the aim is to determine the effects of mutations to glycine, isoleuci ... | 2003 | 14581187 |
| hybf, a zinc-containing protein involved in nife hydrogenase maturation. | hypa and hypb are maturation proteins required for incorporation of nickel into the hydrogenase large subunit. to examine the functions of these proteins in nickel insertion, the hybf gene, which is a homolog of hypa essential for maturation of hydrogenases 1 and 2 from escherichia coli, was overexpressed, and the product was purified. this protein behaves like a monomer in gel filtration and contains stoichiometric amounts of zinc but insignificant or undetectable amounts of nickel and iron. in ... | 2004 | 15090500 |
| bacterial transcriptional regulators for degradation pathways of aromatic compounds. | human activities have resulted in the release and introduction into the environment of a plethora of aromatic chemicals. the interest in discovering how bacteria are dealing with hazardous environmental pollutants has driven a large research community and has resulted in important biochemical, genetic, and physiological knowledge about the degradation capacities of microorganisms and their application in bioremediation, green chemistry, or production of pharmacy synthons. in addition, regulation ... | 2004 | 15353566 |
| second gene (nifh*) coding for a nitrogenase iron protein in azotobacter chroococcum is adjacent to a gene coding for a ferredoxin-like protein. | azotobacter chroococcum mcd1 contains a cluster of nitrogen fixation (nif) genes coding for the structural polypeptides for nitrogenase (nifh for the fe-protein and nifd and nifk for the mofe protein) and a second sequence in the genome homologous to nifh. dna fragments bearing this second nifh-like sequence were cloned and the dna sequence around the homologous region determined. two open reading frames were identified in this region. one codes for a protein of 289 amino acid residues and is hi ... | 1986 | 15966103 |
| nitrogenase switch-off by ammonium ions in azospirillum brasilense requires the glnb nitrogen signal-transducing protein. | nitrogenase activity in several diazotrophs is switched off by ammonium and reactivated after consumption. the signaling pathway to this system in azospirillum brasilense is not understood. we show that ammonium-dependent switch-off through adp-ribosylation of fe protein was partial in a glnb mutant of a. brasilense but absent in a glnb glnz double mutant. triggering of inactivation by anaerobic conditions was not affected in either mutant. the results suggest that glnb is necessary for full amm ... | 2005 | 16151168 |
| nitrogenase reactivity with p-cluster variants. | nitrogenase is a multicomponent metalloenzyme that catalyzes the conversion of atmospheric dinitrogen to ammonia. for decades, it has been generally believed that the [8fe-7s] p-cluster of nitrogenase component 1 is indispensable for nitrogenase activity. in this study, we identified two catalytically active p-cluster variants by activity assays, metal analysis, and epr spectroscopic studies. further, we showed that both p-cluster variants resemble [4fe-4s]-like centers based on x-ray absorption ... | 2005 | 16166259 |
| comparative cytochrome oxidase and superoxide dismutase analyses on strains of azotobacter vinelandii and other related free-living nitrogen-fixing bacteria. | quantitative n,n,n',n'-tetramethyl-p-phenylenediamine (tmpd) oxidase and superoxide dismutase (sod) analyses were performed on representative organisms of the family azotobacteraceae. azotobacter vinelandii, azotobacter chroococcum, azotobacter paspali, and derxia gummosa exhibited high quantitative tmpd oxidase activities, and their extracts possessed very active and electrophoretically homogeneous (single gel band) fe-type sods. azomonas macrocytogenes extracts had similar single fe-type sods, ... | 1984 | 16346548 |
| root hair deformation, bacterial attachment, and plant growth in wheat-azospirillum associations. | seven azospirillum strains induced more deformation of root hairs of wheat than did strains of rhizobium leguminosarum, azotobacter chroococcum, or escherichia coli. azospirillum sp. strain sp245 caused the most deformation. strain sp245 (isolated from surface sterile roots of wheat) and strain sp7 (isolated from the rhizosphere of a forage grass) were compared with regard to their effects on root hair deformation, their attachment to roots, and their effects on the growth of four wheat cultivar ... | 1984 | 16346680 |
| survival of azotobacter spp. in dry soils. | dry soils stored in glass containers in the laboratory and protected from contamination for periods of 22 to 24 years yielded numerous colonies of azotobacter chroococcum and other members of the family azotobacteraceae. these results were compared with those reported in 1974, and the findings are uniformly consistent in terms of surviving populations. the data prove that these bacteria remain viable after prolonged periods of dormancy in much the same way as do the endospores of gram-positive b ... | 1986 | 16346962 |
| sodium-dependent growth of azotobacter chroococcum. | the majority of azotobacter chroococcum strains in a collection obtained from alberta soils were absolutely dependent on na for growth. two strains from the american type culture collection also were either na dependent or were stimulated by na. optimal growth required 0.8 mm na and was limited at 0.2 to 0.35 mm na. growth promoted by 0.8 mm na was inhibited by rb > k >> nh(4) but was not affected by li. growth inhibition by rb and k was overcome by increasing the na concentration present in the ... | 1986 | 16347013 |
| iron-dependent production of hydroxamate by sodium-dependent azotobacter chroococcum. | the sodium-dependent strain 184 of azotobacter chroococcum was unable to grow significantly in iron-limited medium, but did produce iron-repressible outer membrane proteins. siderophores were not produced under these conditions. citric acid was excreted, but not in response to iron limitation. this strain, however, was able to grow in insoluble mineral iron sources, and under these conditions the cells produced a hydroxamate. growth on minerals and hydroxamate production was dependent on a low l ... | 1987 | 16347372 |
| sodium-dependent azotobacter chroococcum strains are aeroadaptive, microaerophilic, nitrogen-fixing bacteria. | na -dependent strains of azotobacter chroococcum were observed to have very low reactivities with the h(2)o(2) spot test for catalase. the cell extract of the representative na -dependent strain 184 contained a catalase specific activity that was 10-to 600-fold lower than those found in na -independent strains of a. chroococcum. peroxidase and superoxide dismutase activities existed in all strains, although only certain na -dependent strains contained a peroxidase reactive with p-phenylenediamin ... | 1988 | 16347721 |
| isolation and preliminary characterization of hydroxamic acids formed by nitrogen-fixing azotobacter chroococcum b-8. | the free-living diazotroph azotobacter chroococcum b-8 responded to iron-limited growth conditions by forming hydroxamic acids and an 85,000-dalton outer membrane protein. the fe(iii)-binding hydroxamate compounds stimulated the growth of arthrobacter flavescens jg-9 and gave a positive csaky reaction for bound hydroxylamines. the hydroxamates were isolated from liquid cultures by benzyl alcohol extraction and purified by size exclusion chromatography and high-performance liquid chromatography. ... | 1989 | 16347843 |
| catechol formation and melanization by na -dependent azotobacter chroococcum: a protective mechanism for aeroadaptation? | aeroadaptive microaerophilic azotobacter chroococcum 184 produced a cell-associated black pigment when grown at high aeration rates under nitrogen-fixing conditions. this pigment was shown to be a catechol melanin. polyphenol oxidase activity was detected in cell extracts of cells grown for 72 h. melanin formation was optimal in the later stages of growth, and there was no correlation between nitrogenase activity and melanization. nitrogenase activity in strain 184 was optimal at 10% o(2), and m ... | 1989 | 16347974 |
| preferential osmolyte accumulation: a mechanism of osmotic stress adaptation in diazotrophic bacteria. | a common cellular mechanism of osmotic-stress adaptation is the intracellular accumulation of organic solutes (osmolytes). we investigated the mechanism of osmotic adaptation in the diazotrophic bacteria azotobacter chroococcum, azospirillum brasilense, and klebsiella pneumoniae, which are adversely affected by high osmotic strength (i.e., soil salinity and/or drought). we used natural-abundance c nuclear magnetic resonance spectroscopy to identify all the osmolytes accumulating in these strains ... | 1990 | 16348295 |
| phenolic lipid synthesis by type iii polyketide synthases is essential for cyst formation in azotobacter vinelandii. | cysts of azotobacter vinelandii are resting cells that are surrounded by a protective coat, conferring resistance to various chemical and physical agents. the major chemical components of the cyst coat are alkylresorcinols, which are amphiphilic molecules possessing an aromatic ring with a long aliphatic carbon chain. although alkylresorcinols are widely distributed in bacteria, fungi, plants, and animals, no enzyme systems for their biosynthesis are known. we report here an ars operon in a. vin ... | 2006 | 16597676 |
| the obligate human pathogen, neisseria gonorrhoeae, is polyploid. | we show using several methodologies that the gram-negative, diplococcal-bacterium neisseria gonorrhoeae has more than one complete genome copy per cell. gene dosage measurements demonstrated that only a single replication initiation event per chromosome occurs per round of cell division, and that there is a single origin of replication. the region containing the origin does not encode any genes previously associated with bacterial origins of replication. quantitative pcr results showed that ther ... | 2006 | 16719561 |
| biology of pseudomonas stutzeri. | pseudomonas stutzeri is a nonfluorescent denitrifying bacterium widely distributed in the environment, and it has also been isolated as an opportunistic pathogen from humans. over the past 15 years, much progress has been made in elucidating the taxonomy of this diverse taxonomical group, demonstrating the clonality of its populations. the species has received much attention because of its particular metabolic properties: it has been proposed as a model organism for denitrification studies; many ... | 2006 | 16760312 |
| involvement of the cynabds operon and the co2-concentrating mechanism in the light-dependent transport and metabolism of cyanate by cyanobacteria. | the cyanobacteria synechococcus elongatus strain pcc7942 and synechococcus sp. strain utex625 decomposed exogenously supplied cyanate (nco-) to co2 and nh3 through the action of a cytosolic cyanase which required hco3- as a second substrate. the ability to metabolize nco- relied on three essential elements: proteins encoded by the cynabds operon, the biophysical activity of the co2-concentrating mechanism (ccm), and light. inactivation of cyns, encoding cyanase, and cyna yielded mutants unable t ... | 2007 | 17122352 |
| involvement of the cynabds operon and the co2-concentrating mechanism in the light-dependent transport and metabolism of cyanate by cyanobacteria. | the cyanobacteria synechococcus elongatus strain pcc7942 and synechococcus sp. strain utex625 decomposed exogenously supplied cyanate (nco-) to co2 and nh3 through the action of a cytosolic cyanase which required hco3- as a second substrate. the ability to metabolize nco- relied on three essential elements: proteins encoded by the cynabds operon, the biophysical activity of the co2-concentrating mechanism (ccm), and light. inactivation of cyns, encoding cyanase, and cyna yielded mutants unable t ... | 2007 | 17122352 |
| role of soil rhizobacteria in phytoremediation of heavy metal contaminated soils. | heavy metal pollution of soil is a significant environmental problem and has its negative impact on human health and agriculture. rhizosphere, as an important interface of soil and plant, plays a significant role in phytoremediation of contaminated soil by heavy metals, in which, microbial populations are known to affect heavy metal mobility and availability to the plant through release of chelating agents, acidification, phosphate solubilization and redox changes, and therefore, have potential ... | 2007 | 17323432 |
| nitrogen fixation in eukaryotes--new models for symbiosis. | nitrogen, a component of many bio-molecules, is essential for growth and development of all organisms. most nitrogen exists in the atmosphere, and utilisation of this source is important as a means of avoiding nitrogen starvation. however, the ability to fix atmospheric nitrogen via the nitrogenase enzyme complex is restricted to some bacteria. eukaryotic organisms are only able to obtain fixed nitrogen through their symbiotic interactions with nitrogen-fixing prokaryotes. these symbioses involv ... | 2007 | 17408485 |
| alterations in seedling vigour and antioxidant enzyme activities in catharanthus roseus under seed priming with native diazotrophs. | an experiment was conducted on catharanthus roseus to study the effect of seed treatments with native diazotrophs on its seedling growth and antioxidant enzyme activities. the treatments had significant influence on various seedling parameters. there is no significant influence on dry matter production with the diazotrophs, azospirillum and azotobacter. however, the vital seedling parameters such as germination percentage and vigour index were improved. azotobacter treatment influenced maximum o ... | 2007 | 17610323 |
| burkholderia cenocepacia c5424 produces a pigment with antioxidant properties using a homogentisate intermediate. | burkholderia cenocepacia is a gram-negative opportunistic pathogen that belongs to the burkholderia cepacia complex. b. cenocepacia can survive intracellularly within phagocytic cells, and some epidemic strains produce a brown melanin-like pigment that can scavenge free radicals, resulting in the attenuation of the host cell oxidative burst. in this work, we demonstrate that the brown pigment produced by b. cenocepacia c5424 is synthesized from a homogentisate (hga) precursor. the disruption of ... | 2007 | 17933889 |
| effects of disruption of homocitrate synthase genes on nostoc sp. strain pcc 7120 photobiological hydrogen production and nitrogenase. | in the case of nitrogenase-based photobiological hydrogen production systems of cyanobacteria, the inactivation of uptake hydrogenase (hup) leads to significant increases in hydrogen production activity. however, the high-level-activity stage of the hup mutants lasts only a few tens of hours under air, a circumstance which seems to be caused by sufficient amounts of combined nitrogen supplied by active nitrogenase. the catalytic femo cofactor of nitrogenase binds homocitrate, which is required f ... | 2007 | 17933939 |
| characterization of diazotrophs containing mo-independent nitrogenases, isolated from diverse natural environments. | molybdenum-independent nitrogenases were first described in the nitrogen-fixing bacterium azotobacter vinelandii and have since been described in other diazotrophic bacteria. previously, we reported the isolation of seven diazotrophs with mo-independent nitrogenases from aquatic environments. in the present study, we extend these results to include diazotrophs isolated from wood chip mulch, soil, "paraffin dirt," and sediments from mangrove swamps. mo-deficient, n-free media under both aerobic a ... | 2008 | 18378646 |
| genome sequence of azotobacter vinelandii, an obligate aerobe specialized to support diverse anaerobic metabolic processes. | azotobacter vinelandii is a soil bacterium related to the pseudomonas genus that fixes nitrogen under aerobic conditions while simultaneously protecting nitrogenase from oxygen damage. in response to carbon availability, this organism undergoes a simple differentiation process to form cysts that are resistant to drought and other physical and chemical agents. here we report the complete genome sequence of a. vinelandii dj, which has a single circular genome of 5,365,318 bp. in order to reconcile ... | 2009 | 19429624 |
| unique features of the nitrogenase vfe protein from azotobacter vinelandii. | nitrogenase is an essential metalloenzyme that catalyzes the biological conversion of dinitrogen (n(2)) to ammonia (nh(3)). the vanadium (v)-nitrogenase is very similar to the "conventional" molybdenum (mo)-nitrogenase, yet it holds unique properties of its own that may provide useful insights into the general mechanism of nitrogenase catalysis. so far, characterization of the vanadium iron (vfe) protein of azotobacter vinelandii v-nitrogenase has been focused on 2 incomplete forms of this prote ... | 2009 | 19478062 |