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[chemotaxis of azospirillum lipoferum and azospirillum brasiliensis toward gramineae root exudates. i. corn, wheat and sorghum activity]. 19807209175
[chemotaxis of azospirillum lipoferum and azospirillum brasiliensis. ii. activity of the amino acids contained in gramineae root exudates]. 19807209176
fructose catabolism in azospirillum brasilense and azospirillum lipoferum.the pathways for catabolism of fructose were investigated in the type strains of azospirillum lipoferum and azospirillum brasilense grown aerobically with (nh4)2so4 as the nitrogen source. when grown on fructose, the former species possessed a complete entner-doudoroff pathway, whereas the latter species lacked activity for glucose-6-phosphate dehydrogenase. both species possessed a complete catabolic embden-meyerhof-parnas pathway. neither species possessed the key enzyme of the hexose monophos ...19846735986
morphological and physiological characteristics and lipopolysaccharide composition of n2-fixing (c2h2-reducing) root-associated pseudomonas sp.a dinitrogen-fixing pseudomonas sp. was isolated from the roots of the grass deschampsia caespitosa. the motile organism, which had 4 to 10 polar flagella, was gram negative, obligately aerobic, oxidase positive, arginine dihydrolase positive, and fluorescent. to verify api20b, api20e, and oxi-ferm identifications, as well as results from standard microbiological tests and electron microscopic examinations, which all indicated the organism to be a pseudomonas, we analyzed its lipopolysaccharide. ...19836652578
immunological techniques to identify azospirillum associated with wetland rice.azospirilla associated with wetland rice were isolated and characterized by employing immunodiffusion and immunofluorescence techniques. antisera against two strains belonging to azospirillum lipoferum produced at least one heat-labile precipitation band with most isolates of a. lipoferum and a. brasilense. antisera against two strains belonging to a. lipoferum and one strain belonging to a. brasilense produced one band only with strains of their respective species. fluorescent antibody reaction ...19826809301
intermediary carbon metabolism of azospirillum brasilense.azospirillum brasilense sp 7 grew rapidly in azo medium containing reduced nitrogen and succinate as an energy source, with a doubling time of 43 min. no growth was measured with glucose as the sole carbon source. in contrast, azospirillum lipoferum sp 59b could grow in media containing either succinate or glucose with a doubling time of 69 min and 223 min, respectively. warburg-barcroft respirometry showed that the rate of oxygen consumption by a. brasilense sp 7 on glucose medium (0.034 mumol ...19846425263
degradation of carbofuran by azospirillum lipoferum and streptomyces spp. isolated from flooded alluvial soil. 19846498360
the behaviour of azospirillum spp. in the presence of plant growth hormones.tests were carried out to determine the effects of commercial preparations of indole-3-acetic acid (iaa), gibberellin (ga) and kinetin, separately and in combination, on azospirillum lipoferum and a. brasilense. these hormones showed no effect upon morphology, growth rate, or oxygen uptake. some random effects of ga, kinetin and the combination of hormones--but not of iaa alone--were observed on the number of viable cells. iaa, in the concentrations 0.001-1.0 microgram/ml, inhibited nitrogenase ...19836579879
regulation of nitrogenase activity by ammonium chloride in azospirillum spp.ammonium chloride (greater than or equal to 0.05 mm) effectively and reversibly inhibited the nitrogenase activity of azospirillum brasilense, azospirillum lipoferum and azospirillum amazonense. the glutamine synthetase inhibitor l-methionine-dl- sulfoximine abolished this "switch-off" in a. lipoferum and a. brasilense, but not in a. amazonense. azaserine, an inhibitor of glutamate synthase, inhibited nitrogenase activity itself. this provides further evidence for glutamine as a metabolite of re ...19863081492
regulation of nitrogenase activity by oxygen in azospirillum brasilense and azospirillum lipoferum.the nitrogenase activity of the microaerophilic bacteria azospirillum brasilense and a. lipoferum was completely inhibited by 2.0 kpa of oxygen (approximately 0.02 atm of o2) in equilibrium with the solution. the activity could be partially recovered at optimal oxygen concentrations of 0.2 kpa. in contrast to the nh4+ switch off, no covalent modification of the nitrogenase reductase (fe protein) was involved, as demonstrated by western-blotting and 32p-labeling experiments. however, the inhibiti ...19872880836
mobilization and transfer of azospirillum lipoferum plasmid by the tn5-mob transposon into a plasmid-free agrobacterium tumefaciens strain.azospirillum lipoferum 4b harbors five cryptic plasmids. several suicide plasmids were used to transfer tn5-mob to a. lipoferum 4b. tn5-mob insertion mutations of this strain could be obtained at frequencies of 10(-8)-10(-7) per recipient cell. one hundred tn5-mob a. lipoferum 4b mutants were used in bacterial matings with a plasmid-free agrobacterium tumefaciens recipient strain. this is the first report of mobilization, transfer, and replication of an azospirillum plasmid in agrobacterium tume ...19882852995
catabolism of carbohydrates and organic acids and expression of nitrogenase by azospirilla.fructose, galactose, l-arabinose, gluconate, and several organic acids support rapid growth and n2 fixation of azospirillum brasiliense atcc 29145 (strain sp7) as a sole source of carbon and energy. growth of azospirillum lipoferum atcc 29707 (strain sp59b) is also supported by glucose, mannose, mannitol, and alpha-ketoglutarate. oxidation of fructose and gluconate by a. brasiliense sp7 and of glucose, gluconate, and fructose by a. lipoferum sp59b was achieved through inducible enzymatic mechani ...19846588050
ammonium inhibition of nitrogenase activity in herbaspirillum seropedicae.the effect of oxygen, ammonium ion, and amino acids on nitrogenase activity in the root-associated n2-fixing bacterium herbaspirillum seropedicae was investigated in comparison with azospirillum spp. and rhodospirillum rubrum. h. seropedicae is microaerophilic, and its optimal dissolved oxygen level is from 0.04 to 0.2 kpa for dinitrogen fixation but higher when it is supplied with fixed nitrogen. no nitrogenase activity was detected when the dissolved o2 level corresponded to 4.0 kpa. ammonium, ...19892498287
cloning and expression of dratg genes from azospirillum lipoferum.a genomic library of azospirillum lipoferum was constructed with phage lambda embl4 as vector. from this library, the genes encoding dinitrogenase reductase adp-ribosyltransferase (drat), drat, and dinitrogenase reductase-activating glycohydrolase (drag), drag, were cloned by hybridization with the heterologous probes of rhodospirillum rubrum. as in r. rubrum, drat is located between drag and nifh, the gene encoding dinitrogenase reductase (a substrate for the drag/drat system). in the crude ext ...19902107127
flocculation in azospirillum brasilense and azospirillum lipoferum: exopolysaccharides and cyst formation.the phenomena of flocculation and floc formation by azospirillum brasilense sp7 (atcc 29145) and azospirillum lipoferum sp59b (atcc 29707) were studied in aerobic liquid cultures. carbon sources representative of various entry pathways in combination with various nitrogen sources induced flocculation in both species of azospirilla. noticeably, the combination of fructose and nitrate was the most effective in terms of floc yields. phase-contrast microscopic observations revealed a transition in c ...19853894333
calcofluor- and lectin-binding exocellular polysaccharides of azospirillum brasilense and azospirillum lipoferum.extracellular polysaccharides synthesized by azospirillum brasilense and a. lipoferum were shown on agar plates and liquid flocculating cultures. the six strains used in this work expressed a mucoid phenotype, yielding positive calcofluor fluorescence under uv light. the calcofluor-binding polysaccharides were distributed between the capsular and exopolysaccharide fractions, suggesting exocellular localization. no calcofluor fluorescence was observed in residual cells after separation of the cap ...19892722757
isolation, characterization, and transfer of cryptic gene-mobilizing plasmids in the wheat rhizosphere.a set of self-transmissible plasmids with incq plasmid-mobilizing capacity was isolated by triparental exogenous isolation from the wheat rhizosphere with an escherichia coli incq plasmid host and a ralstonia eutropha recipient. three plasmids of 38 to 45 kb, denoted pipo1, pipo2, and pipo3, were selected for further study. no selectable traits (antibiotic or heavy-metal resistance) were identified in these plasmids. the plasmids were characterized by replicon typing via pcr and hybridization wi ...19989501428
identification of a promoter dependent on nifa and sigma 54 upstream of nifh in azospirillum lipoferum.southern hybridization experiments strongly indicate that the regulatory region of the azospirillum lipoferum nifh gene is located on a cloned 1.1 kb bamhi-xhoi restriction fragment. by cloning this fragment into a promoter-probe plasmid in escherichia coli, a promoter was identified oriented towards the nifh gene. using a set of several bacterial strains and plasmids, both nifa and the alternative sigma factor, sigma 54, from klebsiella pneumoniae were shown to be required for the induction of ...19912046661
reversible adp-ribosylation is demonstrated to be a regulatory mechanism in prokaryotes by heterologous expression.the primary product of biological nitrogen fixation, ammonia, reversibly regulates nitrogenase activity in a variety of diazotrophs by a process called "nh4(+)-switch-off/on." strong correlative evidence from work in azospirillum lipoferum and rhodospirillum rubrum indicates that this regulation involves both the inactivation of dinitrogenase reductase by dinitrogenase reductase adp-ribosyltransferase and the reactivation by dinitrogenase reductase activating glycohydrolase. the genes encoding t ...19902106680
identification of a nifa-like regulatory gene of azospirillum brasilense sp7 expressed under conditions of nitrogen fixation and in the presence of air and ammonia.a gene bank of azospirillum lipoferum br17 constructed in the vector lambda gem11 was screened with a bradyrhizobium japonicum nifa gene probe. a 7.3 kb ecori fragment carrying a nifa-like gene was thereby isolated and subsequently used to screen a gene bank of azospirillum brasilense sp7 constructed in puc18. two ecori fragments of 5.6 kb and 3.6 kb covering the nifa-homology region were found. mutants with nif- phenotype were obtained by site-directed tn5 mutagenesis of the 5.6 kb fragment and ...19911779763
the dratg gene region of rhodobacter capsulatus is required for post-translational regulation of both the molybdenum and the alternative nitrogenase.synthetic oligonucleotides, which were designed according to amino acid sequences conserved between rhodospirillum rubrum and azospirillum brasilense drat and drag, respectively, were used to identify the corresponding genes of rhodobacter capsulatus. sequence analysis of a 1904 bp dna fragment proved the existence of r. capsulatus drat and drag. these two genes were separated by 11 bp only, suggesting that r. capsulatus drat and drag were part of one transcriptional unit. in contrast to r. rubr ...19938277250
identification of azospirillum species by rflp and pulsed-field gel electrophoresis.pulsed-field gel electrophoresis (pfge) was applied to analyse the restriction fragment length polymorphism of azospirillum brasilense and azospirillum lipoferum strains. genomic dna was digested by rarely cutting restriction enzymes and subjected to pfge using the rotaphor system. the restrictions with spei produced 10-20 fragments with sizes from about 10 kb to 900 kb. the separation resulted in a strain-specific banding pattern in almost every case. after southern blotting and hybridization w ...19937903193
pectin decomposition and associated nitrogen fixation by mixed cultures of azospirillum and bacillus species.cocultures of different azospirillum species with bacillus polymyxa or bacillus subtilis allow the efficient utilization of pectin as carbon and energy sources for nitrogen fixation. the nitrogenase activity obtained with cocultures was as high as 30-80 nmol c2h4 h-1 ml-1, a much higher value than that obtained with pure cultures of either azospirillum (up to 13 nmol c2h4 h-1 ml-1) or b. polymyxa (up to 2 nmol c2h4 h-1 ml-1) alone. to establish to what extent each partner contributed to nitrogen ...19921458371
selective infection of maize roots by streptomycin-resistant azospirillum lipoferum and other bacteria.the percentage of low-level streptomycin-resistant (20 microgram/ml) bacteria in surface-sterilized or washed maize roots was more than a thousand times higher than that in soil populations. there was also a higher incidence of resistant bacteria in rhizosphere as compared with non-rhizosphere soil and bacteria isolated from maize roots were relatively tolerant to several other antibiotics. azospirillum lipoferum was predominant in surface-sterilized roots of field-grown maize and was low-level ...1979540253
cloning and characterization of a cluster of genes coding for 5s rrna and three trnas from azospirillum lipoferum.a genomic library was constructed from a hindiii digest of azospirillum lipoferum chromosomal dna in the hindiii site of puc19. from the library, a clone, palh64, which showed strong hybridization with 3' end labeled a. lipoferum total trnas and which contains a 2.9 kb insert was isolated and restriction map of the insert established. the nucleotide sequence of a 490 bp hindiii-hincii subfragment containing a cluster of genes coding for 5s rrna, trna(val)(uac), trna(thr)(uga) and trna(lys)(uuu) ...19947526923
differences in the levels of aminoacylation and contents of modified nucleotides between total trnas from n2- and nh4(+)-grown azospirillum lipoferum cells.total trnas isolated from n2- and nh4(+)-grown azospirillum lipoferum cells were compared with respect to amino acid acceptance, isoacceptor trna species levels and extent of nucleotide modifications. amino-acylation of these two trna preparations with ten different amino acids indicated differences in the relative acceptor activities. comparison of aminoacyl-trna patterns by rpc-5 column chromatography revealed no qualitative differences in the elution profiles. however, quantitative difference ...19947875713
cloning, sequencing and transcriptional regulation of the drat and drag genes of azospirillum lipoferum fs.from azospirillum lipoferum (al) fs, a nitrogen-fixing bacterium isolated from the rhizosphere of rice, we cloned and sequenced drat, encoding dinitrogenase reductase adp-ribosyltransferase, and drag, encoding dinitrogenase reductase-activating glycohydrolase. the nucleotide sequences of dratg showed extensive similarity to the same genes from azospirillum brasilense, rhodospirillum rubrum and rhodobacter capsulatus, and they are assumed to be co-transcribed as a single operon. when this dratg o ...19968621068
isolation and characterization of azospirillum lipoferum locus that complements rhizobium meliloti dcta and dctb mutations.a dna probe containing the structural gene for dicarboxylate transport (dct a) of rhizobium meliloti hybridized strongly with the fragments of azospirillum lipoferum genomic dna. a genomic library of a. lipoferum was screened for the dct a gene by complementation of a dct a mutant of rhizobium meliloti. a recombinant cosmid, p37d, capable of restoring growth of the dct a mutant on dicarboxylates was isolated and found to hybridize to the dcta probe. the ability of p37d to complement the dct b mu ...19968640608
mutagenesis and functional characterization of the glnb, glna, and nifa genes from the photosynthetic bacterium rhodospirillum rubrum.nitrogen fixation is tightly regulated in rhodospirillum rubrum at two different levels: transcriptional regulation of nif expression and posttranslational regulation of dinitrogenase reductase by reversible adp-ribosylation catalyzed by the drat-drag (dinitrogenase reductase adp-ribosyltransferase-dinitrogenase reductase-activating glycohydrolase) system. we report here the characterization of glnb, glna, and nifa mutants and studies of their relationship to the regulation of nitrogen fixation. ...200010648524
azospirillum lipoferum trnas: fractionation and identification of trna species and the nucleotide sequence of trna(asn) (quu).transfer rnas of azospirillum lipoferum were separated by two-dimensional gel electrophoresis and identified by aminoacylation. thirty-six trna spots were resolved by this technique and twenty-six trna species have been identified. there are five trnas for leu, four for val, three for pro, two each for arg, ile, lys and tyr, and one each for ala, asp, his, phe, ser and thr. the trna (asn) (quu) was purified and its nucleotide sequence was determined. the a. lipoferum trna (asn) (quu) is 92% simi ...19968988334
oxygen sensitivity of nifa protein of azospirillum lipoferum fs as suggested by gene cloning and expression in escherichia coli.we cloned and sequenced a 2.8-kb sali fragment of azospirillum lipoferum fs as a homologue of the klebsiella oxytoca nifa gene. the amino acid sequence deduced from an open reading frame of 1872 bases showed 91% identity to that of the a. brasilense nifa, and the putative central sigma54 interaction domain was conserved as well as the c-terminal dna-binding domain. the nifa function on the nifh promoter was examined in escherichia coli using a combination of a nifa driver plasmid and a nifh-lacz ...19979178550
a taxonomic study of the spirillum lipoferum group, with descriptions of a new genus, azospirillum gen. nov. and two species, azospirillum lipoferum (beijerinck) comb. nov. and azospirillum brasilense sp. nov.sixty-one strains of the root-associated nitrogen fixer spirillum lipoferum exhibited a similar morphology in peptone--succinate salts medium: vibrioid cells having a diameter of 1.0 micrometer. when grown in broth the cells had a single polar flagellum, but when grown on agar at 30 degrees c lateral flagella of shorter wavelength were also formed. the dna base composition was 69--71 mol% guanine + cytosine when determined by thermal denaturation. dna homology experiments indicated the occurrenc ...1978356945
overproduction of indole acetic acid in azospirillum lipoferum using the escherichia coli trp operon.a recombinant plasmid carrying the trp operon from escherichia coli, which synthesizes tryptophan from chorismate, was constructed by using a broad host range plasmid vector prk290; a mutant trp plasmid for tryptophan overproduction was then selected. the physiological, biochemical, and genetic properties of the azospirillum lipoferum ky6, a potential nitrogen fixer of rice, harbouring the recombinant trp plasmid pmjc1 and its mutant pmjc101, were compared with those of the wild-type bacteria. a ...19938281358
(methyl)ammonium transport in the nitrogen-fixing bacterium azospirillum brasilense.an ammonium transporter of azospirillum brasilense was characterized. in contrast to most previously reported putative prokaryotic nh4+ transporter genes, a. brasilense amtb is not part of an operon with glnb or glnz which, in a. brasilense, encode nitrogen regulatory proteins pii and pz, respectively. sequence analysis predicts the presence of 12 transmembrane domains in the deduced amtb protein and classifies amtb as an integral membrane protein. nitrogen regulates the transcription of the amt ...19989573149
isolation and cloning of a azospirillum lipoferum locus that complements escherichia coli prou mutant.glycine betaine relieved sodium chloride-mediated inhibition of growth in azospirillum lipoferum atcc 29708. 35s-methionine labelling of proteins after salinity up-shock revealed strong induction of a 30 kda protein which cross-reacted with the anti-glycine betaine binding protein antibody from escherichia coli. this suggested that a. lipoferum had a salinity-induced prou-like high-affinity glycine betaine transport system. a genomic library of a. lipoferum atcc 29708 was screened for the prou-l ...19989627959
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 ...19989687429
molecular relationship of an atypical azospirillum strain 4t to other azospirillum species.dna/dna hybridization, plasmid content and partial 16s rdna sequence were determined to confirm the relationship between two azospirillum strains, 4b and 4t, isolated from the same rice rhizosphere. the partial 16s rdna sequence was determined for 9 strains belonging to 5 azospirillum species which included azospirillum lipoferum strains 4b and 4t, and was compared to a set of ribosomal sequences from other bacteria of the alpha subdivision of the proteobacteria. four azospirillum species sequen ...19947871242
a cytochrome cbb3 (cytochrome c) terminal oxidase in azospirillum brasilense sp7 supports microaerobic growth.spectral analysis indicated the presence of a cytochrome cbb3 oxidase under microaerobic conditions in azospirillum brasilense sp7 cells. the corresponding genes (cytnoqp) were isolated by using pcr. these genes are organized in an operon, preceded by a putative anaerobox. the phenotype of an a. brasilense cytn mutant was analyzed. under aerobic conditions, the specific growth rate during exponential phase (mu(e)) of the a. brasilense cytn mutant was comparable to the wild-type specific growth r ...19989791120
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 ...19989797277
molecular characterization of epiphytic bacterial communities on charophycean green algaeepiphytic bacterial communities within the sheath material of three filamentous green algae, desmidium grevillii, hyalotheca dissiliens, and spondylosium pulchrum (class charophyceae, order zygnematales), collected from a sphagnum bog were characterized by pcr amplification, cloning, and sequencing of 16s ribosomal dna. a total of 20 partial sequences and nine different sequence types were obtained, and one sequence type was recovered from the bacterial communities on all three algae. by phyloge ...19989797295
azospirillum irakense produces a novel type of pectate lyase.the pela gene from the n2-fixing plant-associated bacterium azospirillum irakense, encoding a pectate lyase, was isolated by heterologous expression in escherichia coli. nucleotide sequence analysis of the region containing pela indicated an open reading frame of 1,296 bp, coding for a preprotein of 432 amino acids with a typical amino-terminal signal peptide of 24 amino acids. n-terminal amino acid sequencing confirmed the processing of the protein in e. coli at the signal peptidase cleavage si ...199910198006
occurrence of choline and glycine betaine uptake and metabolism in the family rhizobiaceae and their roles in osmoprotectionthe role of glycine betaine and choline in osmoprotection of various rhizobium, sinorhizobium, mesorhizobium, agrobacterium, and bradyrhizobium reference strains which display a large variation in salt tolerance was investigated. when externally provided, both compounds enhanced the growth of rhizobium tropici, sinorhizobium meliloti, sinorhizobium fredii, rhizobium galegae, agrobacterium tumefaciens, mesorhizobium loti, and mesorhizobium huakuii, demonstrating their utilization as osmoprotectan ...199910224003
mutational inactivation of a gene homologous to escherichia coli ptsp affects poly-beta-hydroxybutyrate accumulation and nitrogen fixation in azotobacter vinelandii.strain ds988, an azotobacter vinelandii mutant with a reduced capacity to accumulate poly-beta-hydroxybutyrate, was isolated after mini-tn5 mutagenesis of the uw136 strain. cloning and nucleotide sequencing of the affected locus revealed a gene homologous to escherichia coli ptsp which encodes enzyme intr, a homologue of enzyme i of the phosphoenol pyruvate-sugar phosphotransferase system with an n-terminal domain similar to the n-terminal domain of some nifa proteins. strain ds988 was unable to ...19989733679
[effect of inoculation with azospirillum spp on forage grasses in highland pastures of the sierras de córdoba, argentian].a field assay was performed in an impoverished hill grassland of the sierras of córdoba, with the objective of evaluating the effects of azospirillum spp on gramineous plants. native grasses were inoculated with different strains of azospirillum lipoferum and azospirillum brasilense, during two consecutive years. the inoculation effect on yield, nitrogen content and number of azospirillum spp was evaluated in three annual harvests. the first and the second inoculation increased significantly the ...19979424624
interaction of azospirillum lipoferum with wheat germ agglutinin stimulates nitrogen fixation.in vitro, the nitrogen fixation capability of a. lipoferum is efficiently increased in the presence of wheat germ agglutinin (wga). a putative wga-binding receptor, a 32-kda protein, was detected in the cell capsule. the stimulatory effect required n-acetyl-d-glucosamine dimer (glcnacdi) terminated sugar side chains of the receptor and was dependent on the number of glcnacdi links involved in receptor-wga interface. binding to the primary sugar binding sites on wga had a larger stimulatory effec ...199910383962
characterization of the dominant and rare members of a young hawaiian soil bacterial community with small-subunit ribosomal dna amplified from dna fractionated on the basis of its guanine and cytosine composition.the small-subunit ribosomal dna (rdna) diversity was found to be very high in a hawaiian soil community that might be expected to have lower diversity than the communities in continental soils because the hawaiian soil is geographically isolated and only 200 years old, is subjected to a constant climate, and harbors low plant diversity. since an underlying community structure could not be revealed by analyzing the total eubacterial rdna, we first fractionated the dna on the basis of guanine-plus ...19989546163
emergence of a laccase-positive variant of azospirillum lipoferum occurs via a two-step phenotypic switching process.two variants have been isolated from the wild-type azospirillum lipoferum strain 4b. the first variant, 4v(i), spontaneously emerged from the wild-type at frequencies in the order of 10(-4) to 10(-3) per cell generation. compared to the wild-type, the 4v(i) variant gained (production of a carotenoid-like pigment, assimilation of certain carbohydrates) and lost (swimming motility, reduction of triphenyl tetrazolium chloride, acid production from certain sugars) apparently unrelated phenotypic cha ...199910339830
ubiquity and diversity of dissimilatory (per)chlorate-reducing bacteria.environmental contamination with compounds containing oxyanions of chlorine, such as perchlorate or chlorate [(per)chlorate] or chlorine dioxide, has been a constantly growing problem over the last 100 years. although the fact that microbes reduce these compounds has been recognized for more than 50 years, only six organisms which can obtain energy for growth by this metabolic process have been described. as part of a study to investigate the diversity and ubiquity of microorganisms involved in ...199910583970
importance of pfka for rapid growth of enterobacter cloacae during colonization of crop seeds.enterobacter cloacae a-11 is a prototrophic, glycolytic mutant of strain 501r3 with a single transposon insertion in pfka. the populations of strain a-11 on cucumber and radish seeds were smaller than the populations of strain 501r3 in natural soil, but the populations of these two strains on pea, soybean, sunflower, and sweet corn seeds were similar (d. p. roberts, p. d. dery, i. yucel, j. buyer, m. a. holtman, and d. y. kobayashi, appl. environ. microbiol. 65:2513-2519, 1999). the net effect o ...200010618207
the ntrb and ntrc genes are involved in the regulation of poly-3-hydroxybutyrate biosynthesis by ammonia in azospirillum brasilense sp7.azospirillum brasilense sp7 and its ntra (rpon), ntrbc, and ntrc mutants have been evaluated for their capabilities of poly-3-hydroxybutyrate (phb) accumulation in media with high and low ammonia concentrations. it was observed that the ntrbc and ntrc mutants can produce phb in both low- and high-c/n-ratio media, while no significant phb production was observed for the wild type or the ntra mutant in low-c/n-ratio media. further investigation by fermentation analysis indicated that the ntrbc and ...200010618211
growth of azospirillum irakense kbc1 on the aryl beta-glucoside salicin requires either sala or salb.the rhizosphere nitrogen-fixing bacterium azospirillum irakense kbc1 is able to grow on pectin and beta-glucosides such as cellobiose, arbutin, and salicin. two adjacent genes, sala and salb, conferring beta-glucosidase activity to escherichia coli, have been identified in a cosmid library of a. irakense dna. the sala and salb enzymes preferentially hydrolyzed aryl beta-glucosides. a delta(sala-salb) a. irakense mutant was not able to grow on salicin but could still utilize arbutin, cellobiose, ...199910321999
a phase variant of azospirillum lipoferum lacks a polar flagellum and constitutively expresses mechanosensing lateral flagella.flagellation of a nonswimming variant of the mixed flagellated bacterium azospirillum lipoferum 4b was characterized by electron microscopy, and polyclonal antibodies were raised against polar and lateral flagellins. the variant cells lacked a polar flagellum due to a defect in flagellin synthesis and constitutively expressed lateral flagella. the variant cells were able to respond to conditions that restricted the rotation of lateral flagella by producing more lateral flagella, suggesting that ...199910508112
loss of cytochrome c oxidase activity and acquisition of resistance to quinone analogs in a laccase-positive variant of azospirillum lipoferum.laccase, a p-diphenol oxidase typical of plants and fungi, has been found recently in a proteobacterium, azospirillum lipoferum. laccase activity was detected in both a natural isolate and an in vitro-obtained phase variant that originated from the laccase-negative wild type. in this study, the electron transport systems of the laccase-positive variant and its parental laccase-negative forms were compared. during exponential (but not stationary) growth under fully aerobic (but not under microaer ...199910542175
16s ribosomal dna characterization of nitrogen-fixing bacteria isolated from banana (musa spp.) and pineapple (ananas comosus (l.) merril).nitrogen-fixing bacteria isolated from banana (musa spp.) and pineapple (ananas comosus (l.) merril) were characterized by amplified 16s ribosomal dna restriction analysis and 16s rrna sequence analysis. herbaspirillum seropedicae, herbaspirillum rubrisubalbicans, burkholderia brasilensis, and burkholderia tropicalis were identified. eight other types were placed in close proximity to these genera and other alpha and beta proteobacteria.200111319127
the cela gene, encoding a glycosyl hydrolase family 3 beta-glucosidase in azospirillum irakense, is required for optimal growth on cellobiosides.the cela beta-glucosidase of azospirillum irakense, belonging to glycosyl hydrolase family 3 (ghf3), preferentially hydrolyzes cellobiose and releases glucose units from the c(3), c(4), and c(5) oligosaccharides. the growth of a deltacela mutant on these cellobiosides was affected. in a. irakense, the ghf3 beta-glucosidases appear to be functional alternatives for the ghf1 beta-glucosidases in the assimilation of beta-glucosides by other bacteria.200111319128
mutants with enhanced nitrogenase activity in hydroponic azospirillum brasilense-wheat associations.the effect of a mutation affecting flocculation, differentiation into cyst-like forms, and root colonization on nitrogenase expression by azospirillum brasilense is described. the gene flca of strain sp7 restored these phenotypes in spontaneous mutants of both strains sp7 and sp245. employing both constitutive pla-lacz and nifh-lacz reporter fusions expressed in situ, the colony morphology, colonization pattern, and potential for nitrogenase activity of spontaneous mutants and flca tn5-induced m ...200010788397
effects of perturbations of the nitrogenase electron transfer chain on reversible adp-ribosylation of nitrogenase fe protein in klebsiella pneumoniae strains bearing the rhodospirillum rubrum dra operon.the redox state of nitrogenase fe protein is shown to affect regulation of adp-ribosylation in klebsiella pneumoniae strains transformed by plasmids carrying dra genes from rhodospirillum rubrum. the dra operon encodes dinitrogenase reductase adp-ribosyltransferase and dinitrogenase reductase-activating glycohydrolase, enzymes responsible for the reversible inactivation, via adp-ribosylation, of nitrogenase fe protein in r. rubrum. in bacteria containing the dra operon in their chromosomes, inac ...200010850982
mutational analysis of a role for salicylic acid in iron metabolism of mycobacterium smegmatis.the role of salicylic acid in iron metabolism was examined in two wild-type strains (mc(2)155 and ncimb 8548) and three mutant strains (mc(2)1292 [lacking exochelin], sm3 [lacking iron-dependent repressor protein ider] and s99 [a salicylate-requiring auxotroph derived in this study]) of mycobacterium smegmatis. synthesis of salicylate in sm3 was derepressed even in the presence of iron, as was synthesis of the siderophores exochelin, mycobactin, and carboxymycobactin. s99 was dependent on salicy ...200010629169
marinomonas mediterranea mmb-1 transposon mutagenesis: isolation of a multipotent polyphenol oxidase mutant.marinomonas mediterranea is a melanogenic marine bacterium expressing a multifunctional polyphenol oxidase (ppo) able to oxidize substrates characteristic for laccases and tyrosinases, as well as produce a classical tyrosinase. a new and quick method has been developed for screening laccase activity in culture plates to detect mutants differentially affected in this ppo activity. transposon mutagenesis has been applied for the first time to m. mediterranea by using different minitransposons load ...200010850991
genome structure of the genus azospirillum.azospirillum species are plant-associated diazotrophs of the alpha subclass of proteobacteria. the genomes of five of the six azospirillum species were analyzed by pulsed-field gel electrophoresis. all strains possessed several megareplicons, some probably linear, and 16s ribosomal dna hybridization indicated multiple chromosomes in genomes ranging in size from 4.8 to 9.7 mbp. the nifhdk operon was identified in the largest replicon.200010869094
effect of model sorptive phases on phenanthrene biodegradation: molecular analysis of enrichments and isolates suggests selection based on bioavailability.reduced bioavailability of nonpolar contaminants due to sorption to natural organic matter is an important factor controlling biodegradation of pollutants in the environment. we established enrichment cultures in which solid organic phases were used to reduce phenanthrene bioavailability to different degrees (r. j. grosser, m. friedrich, d. m. ward, and w. p. inskeep, appl. environ. microbiol. 66:2695-2702, 2000). bacteria enriched and isolated from contaminated soils under these conditions were ...200010877758
role of molybdate and other transition metals in the accumulation of protochelin by azotobacter vinelandii.both molybdate and iron are metals that are required by the obligately aerobic organism azotobacter vinelandii to survive in the nutrient-limited conditions of its natural soil environment. previous studies have shown that a high concentration of molybdate (1 mm) affects the formation of a. vinelandii siderophores such that the tricatecholate protochelin is formed to the exclusion of the other catecholate siderophores, azotochelin and aminochelin. it has been shown previously that molybdate comb ...200010742245
starvation-induced changes in the cell surface of azospirillum lipoferum.three starvation regimes (a deficient culture medium, a saline buffer solution and distilled water) were evaluated for their possible effect on cell surface characteristics of azospirillum lipoferum 1842 related to the initial adsorption of the bacterium to surfaces. the bacteria survived for 7 days in all media although they did not multiply. upon transfer from a rich growth medium (nutrient agar) to starvation conditions, cell surface hydrophobicity dropped sharply but recovered its initial va ...200010922497
bacterial diversity and community structure in an aerated lagoon revealed by ribosomal intergenic spacer analyses and 16s ribosomal dna sequencing.we investigated the bacterial community structure in an aerated plug-flow lagoon treating pulp and paper mill effluent. for this investigation, we developed a composite method based on analyses of pcr amplicons containing the ribosomal intergenic spacer (ris) and its flanking partial 16s rrna gene. community percent similarity was determined on the basis of ris length polymorphism. a community succession was evident in the lagoon, indicated by a progressive community transition through seven sam ...200111282606
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 ...200010966395
role of respiratory nitrate reductase in ability of pseudomonas fluorescens yt101 to colonize the rhizosphere of maize.selection of the denitrifying community by plant roots (i.e., increase in the denitrifier/total heterotroph ratio in the rhizosphere) has been reported by several authors. however, very few studies to evaluate the role of the denitrifying function itself in the selection of microorganisms in the rhizosphere have been performed. in the present study, we compared the rhizosphere survival of the denitrifying pseudomonas fluorescens yt101 strain with that of its isogenic mutant deficient in the abil ...200010966422
azospirillum, a free-living nitrogen-fixing bacterium closely associated with grasses: genetic, biochemical and ecological aspects.azospirillum represents the best characterized genus of plant growth-promoting rhizobacteria. other free-living diazotrophs repeatedly detected in association with plant roots, include acetobacter diazotrophicus, herbaspirillum seropedicae, azoarcus spp. and azotobacter. four aspects of the azospirillum-plant root interaction are highlighted: natural habitat, plant root interaction, nitrogen fixation and biosynthesis of plant growth hormones. each of these aspects is dealt with in a comparative ...200010978548
energy taxis is the dominant behavior in azospirillum brasilense.energy taxis encompasses aerotaxis, phototaxis, redox taxis, taxis to alternative electron acceptors, and chemotaxis to oxidizable substrates. the signal for this type of behavior is originated within the electron transport system. energy taxis was demonstrated, as a part of an overall behavior, in several microbial species, but it did not appear as the dominant determinant in any of them. in this study, we show that most behavioral responses proceed through this mechanism in the alpha-proteobac ...200011029423
decolorization and detoxification of textile dyes with a laccase from trametes hirsuta.trametes hirsuta and a purified laccase from this organism were able to degrade triarylmethane, indigoid, azo, and anthraquinonic dyes. initial decolorization velocities depended on the substituents on the phenolic rings of the dyes. immobilization of the t. hirsuta laccase on alumina enhanced the thermal stabilities of the enzyme and its tolerance against some enzyme inhibitors, such as halides, copper chelators, and dyeing additives. the laccase lost 50% of its activity at 50 mm nacl while the ...200010919791
role of pfka and general carbohydrate catabolism in seed colonization by enterobacter cloacae.enterobacter cloacae a-11 is a transposon mutant of strain 501r3 that was deficient in cucumber spermosphere colonization and in the utilization of certain carbohydrates (d. p. roberts, c. j. sheets, and j. s. hartung, can. j. microbiol. 38:1128-1134, 1992). in vitro growth of strain a-11 was reduced or deficient on most carbohydrates that supported growth of strain 501r3 but was unaffected on fructose, glycerol, and all amino acids and organic acids tested. colonization by strain a-11 was signi ...199910347036
comparison of fungal laccases and redox mediators in oxidation of a nonphenolic lignin model compound.several fungal laccases have been compared for the oxidation of a nonphenolic lignin dimer, 1-(3, 4-dimethoxyphenyl)-2-(2-methoxyphenoxy)propan-1,3-diol (i), and a phenolic lignin model compound, phenol red, in the presence of the redox mediators 1-hydroxybenzotriazole (1-hbt) or violuric acid. the oxidation rates of dimer i by the laccases were in the following order: trametes villosa laccase (tvl) > pycnoporus cinnabarinus laccase (pcl) > botrytis cinerea laccase (bcl) > myceliophthora thermop ...199910347057
effect of associative bacteria on element composition of barley seedlings grown in solution culture at toxic cadmium concentrations.the response of barley seedlings to inoculation with associative rhizobacteria azospirillum lipoferum 137, arthrobacter mysorens 7, agrobacterium radiobacter 10 and flavobacterium sp. l30 was studied in hydroponic and quartz sand cultures in the presence of 50 microm cdcl2. cadmium caused severe inhibition in the growth and uptake of nutrient elements by the plants. inoculation with the bacteria slightly stimulated root length and biomass of hydroponically grown cd-treated seedlings. the bacteri ...200010950194
effect of p(ii) and its homolog glnk on reversible adp-ribosylation of dinitrogenase reductase by heterologous expression of the rhodospirillum rubrum dinitrogenase reductase adp-ribosyl transferase-dinitrogenase reductase-activating glycohydrolase regulatory system in klebsiella pneumoniae.reversible adp-ribosylation of dinitrogenase reductase, catalyzed by the dinitrogenase reductase adp-ribosyl transferase-dinitrogenase reductase-activating glycohydrolase (drat-drag) regulatory system, has been characterized in rhodospirillum rubrum and other nitrogen-fixing bacteria. to investigate the mechanisms for the regulation of drat and drag activities, we studied the heterologous expression of r. rubrum dratg in klebsiella pneumoniae glnb and glnk mutants. in k. pneumoniae wild type, th ...200111160092
oleomonas sagaranensis gen. nov., sp. nov., represents a novel genus in the alpha-proteobacteria.a gram-negative bacterium was previously isolated from an oil field in shizuoka, japan, and designated strain hd-1. here we have performed detailed characterization of the strain, and have found that it represents a novel genus. the 16s rrna sequence of strain hd-1 displayed highest similarity to various uncultured species (86.7-99.7%), along with 86.2-88.2% similarity to sequences from azospirillum, methylobacterium, rhizobium, and hyphomicrobium, all members of the alpha-proteobacteria. phylog ...200212480113
azospirillum doebereinerae sp. nov., a nitrogen-fixing bacterium associated with the c4-grass miscanthus.a new group of nitrogen-fixing azospirillum sp. bacteria was isolated from the roots of the c4-gramineous plant miscanthus. polyphasic taxonomy was performed, including auxanography using api galleries, physiological tests and 16s rrna sequence comparison. the ability of the isolates to fix dinitrogen was evaluated by amplification of the nifd gene, immunodetection of the dinitrogenase reductase and acetylene-reduction assay. on the basis of these results, the nitrogen-fixing isolates represent ...200111211255
more than one way to sense chemicals. 200111466269
recovery and analysis of formyltetrahydrofolate synthetase gene sequences from natural populations of acetogenic bacteria.primers for pcr amplification of partial (1,102 of 1,680 bp) formyltetrahydrofolate synthetase (fthfs) gene sequences were developed and tested. partial fthfs sequences were successfully amplified from dna from pure cultures of known acetogens, from other fthfs-producing organisms, from the roots of the smooth cordgrass, spartina alterniflora, and from fresh horse manure. the amplimers recovered were cloned, their nucleotide sequences were determined, and their translated amino acid sequences we ...200111229939
polyclonal antibodies recognizing the amob protein of ammonia oxidizers of the beta-subclass of the class proteobacteria.a 41-kda protein of nitrosomonas eutropha was purified, and the n-terminal amino acid sequence was found to be nearly identical with the sequence of amob, a subunit of ammonia monooxygenase. this protein was used to develop polyclonal antibodies, which were highly specific for the detection of the four genera of ammonia oxidizers of the beta-subclass of proteobacteria (nitrosomonas, including nitrosococcus mobilis, which belongs phylogenetically to nitrosomonas; nitrosospira; nitrosolobus; and n ...200111133435
comparative 16s rrna analysis of lake bacterioplankton reveals globally distributed phylogenetic clusters including an abundant group of actinobacteria.in a search for cosmopolitan phylogenetic clusters of freshwater bacteria, we recovered a total of 190 full and partial 16s ribosomal dna (rdna) sequences from three different lakes (lake gossenköllesee, austria; lake fuchskuhle, germany; and lake baikal, russia). the phylogenetic comparison with the currently available rdna data set showed that our sequences fall into 16 clusters, which otherwise include bacterial rdna sequences of primarily freshwater and soil, but not marine, origin. six of t ...200011055963
azospirillum brasilense and azospirillum lipoferum hydrolyze conjugates of ga20 and metabolize the resultant aglycones to ga1 in seedlings of rice dwarf mutants.azospirillum species are plant growth-promotive bacteria whose beneficial effects have been postulated to be partially due to production of phytohormones, including gibberellins (gas). in this work, azospirillum brasilense strain cd and azospirillum lipoferum strain usa 5b promoted sheath elongation growth of two single gene ga-deficient dwarf rice (oryza sativa) mutants, dy and dx, when the inoculated seedlings were supplied with [17,17-2h2]ga20-glucosyl ester or [17,17- 2h2]ga20-glucosyl ether ...200111299384
evidence for the presence of dna-binding proteins involved in regulation of the gene expression of indole-3-pyruvic acid decarboxylase, a key enzyme in indole-3-acetic acid biosynthesis in azospirillum lipoferum fs.we isolated the ipdc gene coding for indole-3-pyruvic acid decarboxylase (ipdc), a key enzyme in the indole-3-pyruvic acid pathway for indole-3-acetic acid biosynthesis, in the plant growth-promoting rhizobacterium azospirillum lipoferum fs. gel mobility-shift assay showed the presence of two dna-binding proteins that might be involved in regulation of the ipdc gene expression.200111440156
analysis of the pmsceab gene cluster involved in biosynthesis of salicylic acid and the siderophore pseudomonine in the biocontrol strain pseudomonas fluorescens wcs374.mutants of pseudomonas fluorescens wcs374 defective in biosynthesis of the fluorescent siderophore pseudobactin still display siderophore activity, indicating the production of a second siderophore. a recombinant cosmid clone (pmb374-07) of a wcs374 gene library harboring loci necessary for the biosynthesis of salicylic acid (sa) and this second siderophore pseudomonine was isolated. the salicylate biosynthesis region of wcs374 was localized in a 5-kb ecori fragment of pmb374-07. the sa and pseu ...200111222588
oxidation of phenolate siderophores by the multicopper oxidase encoded by the escherichia coli yack gene.a gene (yack) encoding a putative multicopper oxidase (mco) was cloned from escherichia coli, and the expressed enzyme was demonstrated to exhibit phenoloxidase and ferroxidase activities. the purified protein contained six copper atoms per polypeptide chain and displayed optical and electron paramagnetic resonance (epr) spectra consistent with the presence of type 1, type 2, and type 3 copper centers. the strong optical a(610) (e(610) = 10,890 m(-1) cm(-1)) and copper stoichiometry were taken a ...200111466290
quantitative analysis of bacterial gene expression by using the gusa reporter gene system.an azospirillum brasilense sp7 strain containing a plasmid-borne translational cytn-gusa fusion was grown in a continuous culture to quantitatively evaluate the influence of extracellular signals (such as o(2)) on expression of the cytnoqp operon. the dissolved oxygen concentration was shifted at regular time intervals before the steady state was reached. the measured beta-glucuronidase activity was used to monitor cytn gene expression. however, as the beta-glucuronidase activity in the experime ...200111472903
azospirillum spp. metabolize [17,17-2h2]gibberellin a20 to [17,17-2h2]gibberellin a1 in vivo in dy rice mutant seedlings.azospirillum spp. are endophytic bacteria with beneficial effects on cereals--effects partially attributed to gibberellin production by the microorganisms. azospirillum lipoferum and azospirillum brasilense inoculated to rice dy mutant reversed dwarfism in seedlings incubated with [17,17-2h2]ga20 with formation of [17,17-2h2]ga1, showing the in vivo capacity to perform the 3beta-hydroxylation. when prohexadione-ca, an inhibitor of late steps in gibberellin biosynthesis, was added to the culture ...200111479384
cota of bacillus subtilis is a copper-dependent laccase.the spore coat protein cota of bacillus subtilis displays similarities with multicopper oxidases, including manganese oxidases and laccases. b. subtilis is able to oxidize manganese, but neither cota nor other sporulation proteins are involved. we demonstrate that cota is a laccase. syringaldazine, a specific substrate of laccases, reacted with wild-type spores but not with deltacota spores. cota may participate in the biosynthesis of the brown spore pigment, which appears to be a melanin-like p ...200111514528
enzymatic manganese(ii) oxidation by a marine alpha-proteobacterium.a yellow-pigmented marine bacterium, designated strain sd-21, was isolated from surface sediments of san diego bay, san diego, calif., based on its ability to oxidize soluble mn(ii) to insoluble mn(iii, iv) oxides. 16s rrna analysis revealed that this organism was most closely related to members of the genus erythrobacter, aerobic anoxygenic phototrophic bacteria within the alpha-4 subgroup of the proteobacteria (alpha-4 proteobacteria). sd-21, however, has a number of distinguishing phenotypic ...200111526000
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 ...200111571174
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.200111673445
p(ii) signal transduction proteins, pivotal players in microbial nitrogen control.the p(ii) family of signal transduction proteins are among the most widely distributed signal proteins in the bacterial world. first identified in 1969 as a component of the glutamine synthetase regulatory apparatus, p(ii) proteins have since been recognized as playing a pivotal role in control of prokaryotic nitrogen metabolism. more recently, members of the family have been found in higher plants, where they also potentially play a role in nitrogen control. the p(ii) proteins can function in t ...200111238986
possible roles of nitrogen fixation and mineral uptake induced by rhizobacterial inoculation on salt tolerance of maize.pot experiments were conducted to evaluate the possible roles of nitrogen fixation and/or enhanced mineral uptake by azospirillum lipoferum and bacillus polymexa inoculation in improving salt tolerance of maize plants. plants were inoculated and grown under salt stress (osmotic potential: -0.3, -0.6, -0.9 and -1.2 mpa). both microorganisms were able to fix nitrogen up to -0.9 mpa salinity level accompanied with increased total n-yield compared with the control plants. in order to investigate the ...200415330268
[relationship between lectin, alpha-, beta-glucosidase, and beta-galactosidase activities of azospirillum].the activities of alpha-glucosidase, beta-glucosidase, and beta-galactosidase were studied during the isolation and purification of lectins from azospirillum brasilense sp7 and azospirillum lipoferum 59b cells. these enzymatic activities were revealed in crude extracts of surface proteins, protein fraction precipitated with ammonium sulfate or ethanol-acetone mixture, and protein fraction obtained by gel filtration on sephadex g-75. the distribution of the enzymes between different protein fract ...200111763784
transformation studies of bacillus thuringiensis cryic gene into a nitrogen-fixing azospirillum lipoferum.a lepidopteran toxin gene, cryic (psb607) from entomopathogenic bacillus thuringiensis subsp. aizawai was introduced into nitrogen-fixing azospirillum lipoferum by transformation. regeneration of spheroplasts was achieved at 99% with 39% frequency of regeneration. transformants were screened on nb kanamycin with ampicillin plates and 4 transformants were selected after ten generations. sds-page and western blot analysis confirmed the presence of a 68 kda protein in the transformants. studies on ...200111371015
enriching vermicompost by nitrogen fixing and phosphate solubilizing bacteria.the effect of inoculation of vermicompost with nitrogen-fixing azotobacter chroococcum strains, azospirillum lipoferum and the phosphate solubilizing pseudomonas striata on n and p contents of the vermicompost was assessed. inoculation of n2 fixing bacteria into vermicompost increased contents of n and p. enriching vermicompost with rock phosphate improved significantly the available p when inoculated with p. striata. during the incubation period, the inoculated bacterial strains proliferated ra ...200111131802
endophytic colonization and in planta nitrogen fixation by a herbaspirillum sp. isolated from wild rice species.nitrogen-fixing bacteria were isolated from the stems of wild and cultivated rice on a modified rennie medium. based on 16s ribosomal dna (rdna) sequences, the diazotrophic isolates were phylogenetically close to four genera: herbaspirillum, ideonella, enterobacter, and azospirillum. phenotypic properties and signature sequences of 16s rdna indicated that three isolates (b65, b501, and b512) belong to the herbaspirillum genus. to examine whether herbaspirillum sp. strain b501 isolated from wild ...200111679357
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 ...200111679360
kraft pulp biobleaching and mediated oxidation of a nonphenolic substrate by laccase from streptomyces cyaneus cect 3335.a new laccase (ec 1.10.3.2) produced by streptomyces cyaneus cect 3335 in liquid media containing soya flour (20 g per liter) was purified to homogeneity. the physicochemical, catalytic, and spectral characteristics of this enzyme, as well as its suitability for biobleaching of eucalyptus kraft pulps, were assessed. the purified laccase had a molecular mass of 75 kda and an isoelectric point of 5.6, and its optimal ph and temperature were 4.5 and 70 degrees c, respectively. the activity was stro ...200312676669
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 ...200111114923
catalytic properties of an endogenous beta-lactamase responsible for the resistance of azospirillum lipoferum to beta-lactam antibiotics.azospirillum lipoferum rg20, a nitrogen-fixing bacterium found in all kind of soils, was found to be naturally resistant to penicillins and cephalosporins. 6-beta-bromopenicillanic acid, an irreversible inhibitor of serine-beta-lactamases, completely abolished this resistance. a beta-lactamase was purified 518-fold from a cell-free extract of a. lipoferum rg20. a single band on sds-page (apparent molecular mass 31000 da) and on isoelectric focussing (pi9.35) was observed with the purified protei ...200312624206
[search for conjugative plasmids in azospirillum brasilense and azospirillum lipoferum associated with plants].the conjugative plasmids in azospirillum brasilense strains s17. sp107, sp245, spbr14, jm6b2, jm82al, uq1794, uqi796 and in azospirillum lipoferum strain rg20 were prove to exist for the first time in connection with their potency to mobilize a non-conjugative incq-plasmid pvz361 from incq-group (ori rsf1010, kmr, sur. 11.4 kb) for conjugated transfer to aplasmid strains agrobacterium tumefaciens and pseudomonas putida at high frequencies.200212243065
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