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floc formation by azospirillum lipoferum grown on poly-beta-hydroxybutyrate.azospirillum lipoferum rg6xx was grown under conditions similar to those resulting in encystment of azotobacter spp. a. lipoferum produced cells of uniform shape when grown on nitrogen-free beta-hydroxybutyrate agar. cells accumulated poly-beta-hydroxybutyrate and often grew as chains or filaments that eventually lost motility and formed capsules. within 1 week, vegetative a. lipoferum inocula were converted into microflocs arising from filaments or chains. cells within microflocs were pleomorph ...198816347792
isolation and characterization of azospirillum brasilense loci that correct rhizobium meliloti exob and exoc mutations.the occurrence in azospirillum brasilense of genes that code for exopolysaccharide (eps) synthesis was investigated through complementation studies of rhizobium meliloti exo- mutants. these mutants are deficient in the synthesis of the major acidic eps of rhizobium species and form empty, non-nitrogen-fixing root nodules on alfalfa (j. a. leigh, e. r. signer, and g. c. walker, proc. natl. acad. sci. usa 82:6231-6235, 1985). we demonstrated that the exoc mutation of r. meliloti could be corrected ...19883182731
[response of maize to inoculation with azospirillum brasilense]. 19883244926
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
influence of amino acids on nitrogen fixation ability and growth of azospirillum spp.the utilization of amino acids for growth and their effects on nitrogen fixation differ greatly among the several strains of each species of azospirillum spp. that were examined. a. brasiliense grew poorly or not at all on glutamate, aspartate, serine, or histidine as the sole nitrogen and carbon sources. nitrogen fixation by most a. brasiliense strains was inhibited only slightly even by 10 mm concentrations of these amino acids. in contrast, a. lipoferum and a. amazonense grew very well on glu ...19882894202
identification of the klebsiella pneumoniae glnb gene: nucleotide sequence of wild-type and mutant alleles.the glnb gene of klebsiella pneumoniae, which encodes the nitrogen regulation protein pii, has been cloned and sequenced. the gene encodes a 12429 dalton polypeptide and is highly homologous to the escherichia coli glnb gene. the sequences of a glnb mutation which causes glutamine auxotrophy and of a tn5 induced gln+ suppressor of this mutation were also determined. the glutamine auxotrophy was deduced to be the result of a modification of the uridylylation site of pii, and the suppression was s ...19882907369
ferrochelatase activity in azospirillum brasilense with reference to the influence of metal cations.ferrochelatase in membrane preparations from azospirillum brasilense displayed an activity of 2.17 mumol protoheme formed.h-1.mg protein-1 which is 10-fold greater than previous reports for other bacteria. this ferrochelatase showed an apparent km of 20.9 microm for fe2+, a ph optimum of 6.0-6.5, and stimulation by oleic or stearic acids. co2+, cu2+ and zn2+ inhibited the incorporation of fe2+ into protoporphyrin ix while ni2+ and mg2+ had no effect on protoheme synthesis. activity with fe2+ and ...19892485650
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
posttranslational regulatory system for nitrogenase activity in azospirillum spp.the mechanism for "nh4+ switch-off/on" of nitrogenase activity in azospirillum brasilense and a. lipoferum was investigated. a correlation was established between the in vivo regulation of nitrogenase activity by nh4cl or glutamine and the reversible covalent modification of dinitrogenase reductase. dinitrogenase reductase adp-ribosyltransferase (drat) activity was detected in extracts of a. brasilense with nad as the donor molecule. dinitrogenase reductase-activating glycohydrolase (drag) activ ...19892504694
effect of monocrotophos and quinalphos on soil population and nitrogen-fixing activity of azospirillum sp.the effects of monocrotophos and quinalphos on population and nitrogen-fixing activity of azospirillum sp. in four agricultural soils were determined in a laboratory study. concentrations of the two insecticides up to a 5 kg ha-1 level were either stimulatory or innocuous to the population of azospirillum in the soils. four successive applications of the insecticides to soils resulted in a significant increase in the population density. cultures of azospirillum sp., isolated from insecticide-tre ...19892513838
temperature inhibition of siderophore production in azospirillum brasilense.the effect of growth at 42 degrees c on the different components of the siderophore-mediated iron transport that are induced by iron limitation in azospirillum brasilense was examined. biosynthesis of the siderophore spirilobactin was strongly inhibited (20-fold) by growth at 42 degrees c, whereas the transport of iron by the ferric-spirilobactin transport system and the induction of the iron-regulated outer membrane proteins were unaffected.19892525551
plasmid localization and mapping of two azospirillum brasilense loci that affect exopolysaccharide synthesis.two azospirillum brasilense loci that correct rhizobium meliloti exob and exoc mutants for exopolysaccharide (eps) synthesis have been identified previously (k. w. michiels, j. vanderleyden, a. p. van gool, e. r. signer, j. bacteriol., 1988b). a. brasilense exo mutants produce eps of lower molecular weight than the wild type strain. here, we show by hybridization that these exo loci are located on a 90-mda plasmid in a. brasilense sp7. in four other azospirillum strains but not in a. lipoferum s ...19892544914
[the role of chemotaxis genes in establishing the associative relations between azospirillum brasilense and wheat].the chemotactic properties of a number of azospirillum brasilense natural strains have been studied. azospirillum demonstrate the positive chemotactic reaction towards the organic acids salts but a poor reaction towards the presence of the attractants like hydrocarbons and aminoacids except for arabinose and glutamic acid. the series of che- mutants deficient in general chemotaxis has been selected by introducing the transposon tn5 into the cells of rifampicinresistant mutant strain azospirillum ...19892546068
identification of a regulatory nifa type gene and physical mapping of cloned new nif regions of azospirillum brasilense.three new tn5-mutagenized nif genes of azospirillum brasilense were characterized. the sizes of the restriction fragments and the restriction maps of the cloned nif dna regions showed that these nif genes are distinct from those reported earlier, e.g. nifhdk, nife, nifus, fixabc. the nif27 mutant was identified as a nifa type regulatory gene of a. brasilense (a) by genetic complementation with nifa of klebsiella pneumoniae, (b) by the absence of nitrogenase iron protein in western protein blots ...19892559312
nucleotide sequence of the gene encoding the nitrogenase iron protein (nifh) of azospirillum brasilense and identification of a region controlling nifh transcription.the dna sequence was determined for the azospirillum brasilense nifh gene and part of the nifd gene. the nifh gene is 885 bp long and encodes 293 amino acid residues. the region upstream of the nifh open reading frame contains a putative promoter whose sequence shows perfect homology with promoters of other diazotrophic bacteria and two putative upstream activator sequences. experiments with the promoter-probe vector paf300 showed that this region promotes transcription in response to the nitrog ...19892608029
regulation of transcription and promoter mapping of the structural genes for nitrogenase (nifhdk) of azospirillum brasilense sp7.transcription of the structural genes for nitrogenase (nifhdk) in azospirillum brasilense sp7 was analysed using northern blots of total rna extracted from cultures grown under nitrogen-fixing conditions. hybridization with an internal nifh probe revealed two transcripts, a major one (by concentration) of 1.1 kb corresponding to nifh and a minor one of 5.6 kb corresponding to nifhdk. hybridization with nifd or nifk probes revealed the minor transcript of 5.6 kb. this confirms that the nifhdk gen ...19892608030
azospirillum irakense sp. nov., a nitrogen-fixing bacterium associated with rice roots and rhizosphere soil.a new species of nitrogen-fixing bacteria, azospirillum irakense, was found associated with roots and the rhizosphere of rice in the region of diwaniyah (qadisya), iraq. the seven isolates, on which the species description is based, have vibrioid to s-shaped cells with one polar flagellum in liquid medium. additional lateral flagella are seen on cells grown on nutrient agar. poly-beta-hydroxybutyrate granules are present in cells. nitrogen fixation occurs in microaerobic conditions. the phenotyp ...19892626596
membrane protein patterns of three azospirillum species and herbaspirillum seropedicae.membrane protein patterns in sds-page clearly characterized azospirillum amazonense, a. brasilense, a. lipoferum, and herbaspirillum seropedicae. each species showed also a typical major band with approximate molecular weights (amws) of 44, 39.5, 35.5, and 37.5 kdaltons for the four species respectively. characteristic lighter bands with amws of 63.5 and 19 kdaltons were shown by a. amazonense. similar bands of 54, 24 and 24.5 kdaltons were typical of a. brazilense, a. lipoferum and h. seropedic ...19892629550
cloning of histidine genes of azospirillum brasilense: organization of the abfh gene cluster and nucleotide sequence of the hisb gene.a cluster of four azospirillum brasilense histidine biosynthetic genes, hisa, hisb, hisf and hish, was identified on a 4.5 kb dna fragment and its organization studied by complementation analysis of escherichia coli mutations and nucleotide sequence. the nucleotide sequence of a 1.3 kb fragment that complemented the e. coli hisb mutation was determined and an orf of 624 nucleotides which can code for a protein of 207 amino acids was identified. a significant base sequence homology with the carbo ...19892664449
cloning and expression in escherichia coli of the azospirillum brasilense sp7 gene encoding ampicillin resistance.the azospirillum brasilense atcc 29145 gene coding for beta-lactamase was cloned in escherichia coli. the gene was expressed in e. coli from its own promoter as a 30-kilodalton protein, conferring resistance to high levels of beta-lactam antibiotics. the dna sequence containing the beta-lactamase gene was found to be highly amplified in the azospirillum genome, scattered in the chromosomal as well as in the plasmidic dna.19892675764
identification of dna regions homologous to nitrogen fixation genes nife, nifus and fixabc in azospirillum brasilense sp7.a 30 kb dna region from azospirillum brasilense sp7, containing the nitrogenase structural genes (nifhdk), has been cloned. the presence of nif genes, in the 20 kb located next to nifhdk, was explored by tn5 mutagenesis after subcloning various restriction fragments in the broad-host-range suicide vehicle psup202. over 25 mutations due to tn5 random insertions were obtained in the 20 kb and each recombined into the genome of strain sp7. four new nif loci were identified, located at about 4, 9, 1 ...19892695597
lack of expression of rp4-specified beta-lactamase in azospirillum brasilense.plasmid rp4, which normally confers resistance to ampicillin (apr), tetracycline (tcr), and kanamycin (kmr) to its hosts, failed to express enhanced apr when transferred from escherichia coli to azospirillum brasilense which has its own intrinsic beta-lactamase. even in a beta-lactamase-deficient mutant, a. brasilense rg-d16, no increase in beta-lactamase or significant apr appeared following transfer of rp4. however, a. brasilense rg (rp4) and a. brasilense rg-d16 (rp4) did exhibit tcr kmr. whe ...19892699042
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
[formation of pas8-1213 cointegrate with one of the plasmids of azospirillum brasilense sp245].inheritance of the plasmid vector pas8-1213 in azospirillum brasilense sp245 cells has been studied. the plasmid pas8-1213 is shown to be uncapable of autonomous replication in the new host but able to integrate into the genetic structures of azospirillum with high frequency. 90-95% of kmr-transconjugants of a. brasilense harbor pas8-1213 cointegrated with the smaller host plasmid pabsp245c(85md). the formed cointegrate can be transferred into azospirillum spp. 75 and reca- strains of e. coli (h ...19892811907
intact soil-core microcosms for evaluating the fate and ecological impact of the release of genetically engineered microorganisms.intact soil-core microcosms were studied to determine their applicability for evaluating the transport, survival, and potential ecosystem effects of genetically engineered microorganisms before they are released into the environment. soil-core microcosms were planted with wheat and maize seeds and inoculated with azospirillum lipoferum spbr17 and sprg20a tn5 mutants, respectively. microcosm leachate, rhizosphere soil, plant endorhizosphere, insects, and xylem exudate were sampled for a. lipoferu ...198916347823
survival of azorhizobium caulinodans in the soil and rhizosphere of wetland rice under sesbania rostrata-rice rotation.the survival of indigenous and introduced strains of azorhizobium caulinodans in flooded soil and in the rice rhizosphere, where in situ sesbania rostrata was incorporated before the rice crop, is reported. the azorhizobia studied were both root and stem nodulating. in a pot experiment, two crop cycles each of inoculated and noninoculated sesbania-rice were compared with two crop cycles of flooded fallow-rice. in a field experiment, the effect of repeated incorporation of in situ s. rostrata in ...198916347853
floc formation by azospirillum lipoferum grown on beta-hydroxybutyrate.[this corrects the article on p. 2986 in vol. 54.].198916347889
n(2) fixation by bacteria associated with maize roots at a low partial o(2) pressure.nitrogen fixation by bacteria associated with roots of intact maize plants was measured by exposing the roots to n(2) at a partial o(2) pressure (po(2)) of 2 or 10 kpa. the plants were grown in a mixture of weswood soil and sand and then transferred to plastic cylinders containing an n-free plant nutrient solution. the solution was sparged continuously with a mixture of air and n(2) at a po(2) of 2 or 10 kpa. acetylene reduction was measured after the roots were exposed to the low po(2) overnigh ...198916347968
intracellular location and o(2) sensitivity of uptake hydrogenase in azospirillum spp.uptake hydrogenase activity of azospirillum brasilense in vitro (cell-free extract) was very much more sensitive to o(2) than was that of a. amazonense, and the o(2) pressure optima for uptake hydrogenase activities were 0.01 and 0.4 to 3 kpa for a. brasilense and a. amazonense, respectively. the addition of superoxide dismutase did not increase uptake hydrogenase activity of a. brasilense either in vivo or in vitro. the o(2) uptake rates of a. brasilense and a. amazonense were nearly the same. ...198916348011
identification of gibberellins a(1), a(3), and iso-a(3) in cultures of azospirillum lipoferum.gibberellins a(1), a(3), and iso-a(3) were identified from aseptic cultures of azospirillum lipoferum strain op 33 by capillary gas chromatography-mass spectrometry (gc-ms) and gc-ms-selected ion monitoring. there were 20 to 40 picograms (in ga(3) equivalents, estimated from bioassay) of gibberellins a(1) and a(3) per milliliter of cell culture (containing 10(9) cells).198916666766
enhanced growth of wheat and soybean plants inoculated with azospirillum brasilense is not necessarily due to general enhancement of mineral uptake.the capacity of azospirillum brasilense to enhance the accumulation of k, p, ca, mg, s, na, mn, fe, b, cu, and zn in inoculated wheat and soybean plants was evaluated by using two different analytical methods with five a. brasilense strains originating from four distinct geographical regions. a pseudomonas isolate from the rhizosphere of zea mays seedlings was included as a control. all a. brasilense strains significantly improved wheat and soybean growth by increasing root and shoot dry weight ...199016348150
nitrogen fixation in continuous culture with nh(4)cl-containing media.n balance and n dilution were determined from growth of azospirillum brasilense sp7 and two unidentified gram-negative nitrogen-fixing microorganisms in continuous culture supplied with nh(4)cl. at the 1.1 and 2.2 mm nh(4)cl steady states (n-to-c ratios of 1:68 and 1:34, respectively), the organisms grew with nh(4)cl and n(2) as n sources simultaneously under carbon limitation. no ammonium could be detected in the supernatant of these cultures.199016348161
interaction of rhizosphere bacteria, fertilizer, and vesicular-arbuscular mycorrhizal fungi with sea oats.plants must be established quickly on replenished beaches in order to stabilize the sand and begin the dune-building process. the objective of this research was to determine whether inoculation of sea oats (uniola paniculata l.) with bacteria (indigenous rhizosphere bacteria and n(2) fixers) alone or in combination with vesicular-arbuscular mycorrhizal fungi would enhance plant growth in beach sand. at two fertilizer-n levels, klebsiella pneumoniae and two azospirillum spp. did not provide the p ...199016348236
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 ...199016348295
effects of partial o(2) pressure, partial co(2) pressure, and agitation on growth kinetics of azospirillum lipoferum under fermentor conditions.azospirillum lipoferum crt1 was grown in batch cultures under standard conditions at 85% saturation of dissolved oxygen (do) and 30-g/liter glucose concentrations. kinetic studies revealed nutritional limitations of growth and the presence of an initial lag phase prior to consumption of glucose. the influences of various gaseous environments and shear stress on growth, i.e., various conditions of agitation-aeration, were characterized. faster growth in the first stages of the culture and shorter ...199016348331
dna restriction fingerprint analysis of the soil bacterium azospirillum.total dnas of 18 strains of azospirillum from different sources and geographical areas were compared by restriction endonuclease pattern analysis. fragments obtained with hindiii or bglii were separated by page and stained with silver nitrate. each strain possessed a unique and reproducible fingerprint with each enzyme, thereby facilitating strain recognition. upgma analysis recovered clusters of band patterns that were compared to the distribution of species within the genus azospirillum.19901696613
characterization of three different nitrogen-regulated promoter regions for the expression of glnb and glna in azospirillum brasilense.the complete nucleotide sequence of the open reading frame (orf) located upstream of the glna structural gene for glutamine synthetase (gs) in azospirillum brasilense sp7 was determined. this orf, which codes for a 12 kda protein, was identified as glnb, the structural gene for the pii protein, a component of the adenylylation cascade involved in the regulation of gs activity in some gram-negative bacteria. transcription analysis and mrna mapping of glnb and glna of a. brasilense was performed w ...19901702507
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
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
characterization of two azospirillum brasilense sp7 plasmid genes homologous to rhizobium meliloti nodpq.bacteria belonging to the azospirillum genus are nitrogen fixers that colonize the roots of grasses, but do not cause the formation of differentiated structures. sequences from total dna of several azospirillum strains are homologous to restriction fragments containing rhizobium meliloti nodulation genes. a 10-kilobase (kb) ecori fragment from a. brasilense sp7, sharing homology with a 6.8-kb ecori fragment carrying nodgefh and part of nodp of r. meliloti 41, was cloned in puc18 to yield pab502. ...19902131098
production of bacteriocins and siderophore-like activity by azospirillum brasilense.sixty azospirillum strains were tested for their bacteriocin production ability; twenty-seven (45%) were able to produce bacteriocins and inhibited the growth of one or more indicator strains in solid medium. mitomycin c treatment enhanced the proportion to 80%. sometimes large growth inhibition zones were formed, but not when fecl3 was added in the medium. these inhibition zones probably result from the activity of siderophores. partially purified bacteriocins produced by four strains were inac ...19902148964
[transposon mutagenesis, elimination and mobilization of plasmids in nitrogen-fixating bacterium azospirillum brasilense sp245].the expressed difference in the plasmid profile of a. brasilense sp245 is registered as a result of tn5-mob-mutability. integration of the vector psup5011 into one of the a. brasilense sp245 plasmid and using of the tn5-mob transposon to mobilize the 85md cryptic plasmid are reported. the properties of a. brasilense sp245 with the mutant plasmids composition (surface structure, acetylene and nitrate reduction, ability to a number of carbohydrates utilization, formation of melanin, antibiotics re ...19902159109
isolation of behavioral mutants of azospirillum brasilense by using tn5 lacz.tn5 lacz mutants were generated with azospirillum brasilense 7030 by mating that strain with escherichia coli strains carrying suicide plasmid pcib100 or pcib110. kanamycin-resistant azospirillum colonies were obtained with a maximum frequency of 10(-6) per recipient cell. the potential of tn5 lacz for random transposon mutagenesis coupled to transcription analysis in a. brasilense 7030 was demonstrated. sixty percent of all kmr a. brasilense 7030 mutants expressed beta-galactosidase activity. m ...19902160221
construction of an azospirillum brasilense sp7 reca mutant.cosmid clones encoding the reca gene of azospirillum brasilense were isolated by intergeneric complementation of an escherichia coli reca mutant. site-directed tn5 mutagenesis and subcloning of one complementing cosmid clone allowed us to localize the a. brasilense reca gene on a 1.2 kb dna fragment. one tn5 insertion that inactivates the cloned reca gene was crossed into the chromosome of a. brasilense by marker exchange. the resulting a. brasilense reca mutant showed increased sensitivity to t ...19902175386
structural studies on the subunits of glutamate synthase from azospirillum brasilense.the amino acid composition and the n-terminal sequences of the two dissimilar subunits of glutamate synthase from azospirillum brasilense have been determined along with the sequences of selected cnbr peptides. comparison of our data with those available for escherichia coli glutamate synthase revealed an overall good homology between the enzymes from the two sources. this is more evident for the heavy subunits where the highly conserved n-terminal sequence containing cys-1, suggests that this r ...19902198943
physical map and properties of a 90-mda plasmid of azospirillum brasilense sp7.homology was previously detected between the dna restriction fragments containing rhizobium meliloti nodulation genes and the 90-mda plasmid, p90, of azospirillum brasilense sp7. two dna loci from sp7 genome that complement mutations in the exopolysaccharide synthesis genes, exob and exoc, of r. meliloti were also shown to be present on the plasmid. a more detailed characterization of the plasmid was undertaken to establish its physical map and to localize the nod homologies and other specific r ...19902217570
nucleotide sequence of the nodg gene of azospirillum brasilense. 19902243795
involvement of azospirillum brasilense plasmid dna in the production of indole acetic acid.indole acetic acid (iaa) production in azospirillum brasilense strain sp245 is controlled by a 85 mda plasmid naturally present in this bacterium. in the presence of l-tryptophan, anthranilic acid production and almost no iaa production occurs in a derivative strain harbouring a tn5-mob insertion in the 85 mda plasmid. agrobacterium tumefaciens strain gm19023, upon transfer of tn5-mob labelled 85 mda plasmid of a. brasilense sp245, gains the ability to produce anthranilic acid.19902283026
expression of the agrobacterium tumefaciens chvb virulence region in azospirillum spp.inner membranes of azospirillum brasilense incubated with udp-glucose were unable to synthesize beta-(1-2) glucan and lacked the 235-kilodalton intermediate protein known to be involved in the synthesis of beta-(1-2) glucan in agrobacterium tumefaciens and rhizobium meliloti. inner membranes of a. brasilense strains carrying a cosmid containing the chromosomal virulence genes chva and chvb of agrobacterium tumefaciens formed beta-(1-2) glucan in vitro and synthesized the 235-kilodalton intermedi ...19902332404
characterization of an osmoregulated periplasmic glycine betaine-binding protein in azospirillum brasilense sp7.azospirillum brasilense is able to use glycine betaine as a powerful osmoprotectant; the uptake of this compound is strongly stimulated by salt stress, but significantly reduced by cold osmotic shock. non-denaturing page in the presence of [methyl-14c] glycine betaine and autoradiography demonstrated the presence of one glycine betaine-binding protein (gbbp) in periplasmic shock fluid obtained from high-osmolarity-grown cells. the binding activity was absent in periplasmic fractions from cells g ...19911747385
identification and mapping of loci involved in motility, adsorption to wheat roots, colony morphology, and growth in minimal medium on the azospirillum brasilense sp7 90-mda plasmid.we have constructed a cosmid library of the azospirillum brasilense sp7 90-mda plasmid (p90) and established the ecori restriction map of this plasmid. the central regions of cloned p90 dna fragments from several recombinant cosmids were deleted by restriction endonuclease digestion and replaced by a dna cassette encoding kanamycin resistance. using these in vitro constructed deletions for marker exchange in sp7, we made six different p90 deletion derivatives spanning all together 50% of the tot ...19911749822
[transfer of transformation and conjugation plasmids from escherichia coli to bacillus subtilis and azospirillum brasilense].the conjugative transfer of rp4 plasmid from escherichia coli to azospirillum brasilense was detected after introduction and subsequent incubation of these microorganisms in soil. the plasmid transfer via transformation from escherichia coli to bacillus subtilis was observed in case both bacteria were growing together in sand containing sucrose solution. the possible reason for low frequency interspecies plasmid transformation under conditions close to natural habitats is poor survival of "domes ...19911758472
the production and utilization of nitric oxide by a new, denitrifying strain of pseudomonas aeruginosa.when a new strain of pseudomonas aeruginosa was grown aerobically and then transferred to anaerobic conditions, cells reduced no3- quantitatively to no2- in no3(-)-respiration. in the absence of nitrate, no2- was immediately reduced to no or n2o but not to n2 indicating that no2(-)-reductase but not n2o-reductase was active. the formation of the products no or n2o depended on the ph in the medium and the concentration of no2- present. when p. aeruginosa was grown anaerobically for at least three ...19911772347
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
1,8-naphthalic anhydride antidote enhances the toxic effects of captan and thiram fungicides on azospirillum brasilense cells.the effects of ten fungicides, six herbicides and four insecticides on the nitrogen-fixing bacterium azospirillum brasilense were examined. the fungicides captan and thiram were the most toxic among the compounds tested. cell growth and nitrogenase activity of the bacterium were markedly inhibited by low concentrations of the two fungicides. antidote 1,8-naphthalic anhydride increased by a factor of 2 the cellular level of glutathione. the addition of the antidote in the presence of captan or th ...19911805302
plasmid coding for aerobactin production and drug resistance is involved in virulence of escherichia coli avian strains. 19911817706
the nifhdk operon in the free-living nitrogen-fixing bacteria azospirillum brasilense sequentially comprises genes h, d, k, an 353 bp orf and gene y.1. the complete nucleotide sequence of the nitrogenase structural genes from azospirillum brasilense was determined. two additional open reading frames of 353 and 683 base pairs were detected downstream of the nifk gene, one of which shows homology to the nify gene. 2. structures resembling the consensus nif promoter and nifa-binding motif were found only upstream from the nifh region and an inverted repeat structure located downstream of the nify gene may be a potential stem-and-loop transcript ...19911823284
relationship between tryptophan biosynthesis and indole-3-acetic acid production in azospirillum: identification and sequencing of a trpgdc cluster.screening the tryptophan (trp)-dependent indole-3-acetic acid (iaa) production of different azospirillum species revealed that a. irakense ka3 released 10 times less iaa into the medium than a. brasilense sp7. a cosmid library of strain sp7 was transferred into a. irakense ka3 with the aim of characterizing genes involved in iaa biosynthesis. trp-dependent iaa production was increased in two transconjugants which both contained an identical 18.5 kb hindiii fragment from sp7. after tn5 mutagenesi ...19911896020
cloning and characterization of the nifa gene from herbaspirillum seropedicae strain z78.a genomic library of herbaspirillum seropedicae was constructed and screened for the nifa gene by complementation of a nifa mutant of azospirillum brasilense (fp10). a recombinant plasmid, pems1, capable of restoring acetylene reduction activity in the mutant fp10, was isolated and found to hybridize to the nifa gene of klebsiella pneumoniae. the results suggest that nifa is involved in the regulation of nif genes in h. seropedicae.19911913346
the kinetic mechanism of the reactions catalyzed by the glutamate synthase from azospirillum brasilense.the reactions catalyzed by glutamate synthase from azospirillum brasilense have been investigated by a combination of absorption spectroscopy, steady-state kinetic measurements and experiments with stereospecifically labelled substrate. the data show that both l-glutamine-dependent and ammonia-dependent reactions of the glutamate synthase from a. brasilense follow an identical two-site uni-uni bi-bi kinetic mechanism, in which the enzyme is alternately reduced by nadph and oxidized by the iminog ...19911935975
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. ...19911987127
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
mechanistic studies on azospirillum brasilense glutamate synthase.the reaction mechanism of azospirillum brasilense glutamate synthase has been investigated by several approaches. 15n nuclear magnetic resonance studies demonstrate that the amide nitrogen of glutamine is reductively transferred to 2-oxoglutarate in an irreversible manner with no release of the transferred ammonia group into the medium. identical results were obtained using thio-nadph and acetylpyridine-nadph, which are shown to be less efficient substrates of the enzyme than nadph. similarly, n ...19911683791
nh(4)-excreting azospirillum brasilense mutants enhance the nitrogen supply of a wheat host.spontaneous ethylenediamine-resistant mutants of azospirillum brasilense were selected on the basis of their excretion of nh(4). two mutants exhibited no repression of their nitrogenase enzyme systems in the presence of high (20 mm) concentrations of nh(4). the nitrogenase activities of these mutants on nitrogen-free minimal medium were two to three times higher than the nitrogenase activity of the wild type. the mutants excreted substantial amounts of ammonia when they were grown either under o ...199116348569
effect of endosulfan on azospirillum lipoferum growth, morphology, nitrogenase activity, and protein binding.the organochlorine thiodan ce inhibited growth and nitrogenase activity of azospirillum lipoferum. the active ingredient, endosulfan, was nonspecifically bound to proteins and mainly adsorbed to the cell envelope with small amounts transported into cytosol. the involvement of the external membrane and cyst formation in protection against hazardous substances is discussed.199216348777
[azospirillum brasilense sp245 mutants in production of anthranilic and indolyl-3-acetic acids].the mutants of azospirillum brasilense sp245 altered in the production of anthranilic (ant) and indolyl-3-acetic (iaa) acids were selected after the chemical or transposon facilitated mutagenesis and divided into the following three classes: ant+iaa+, ant+iaa- and ant-iaa-. a hypothesis on the existence of a pattern for tryptophan conversion to anthranilate that is different from the classic pattern, and on the connection of the indolyl-3-acetic synthesis with this process is suggested.19921298884
[plasmid p85 from azospirillum brasilense sp245: study of the circle of possible hosts and incompatibility with plasmids from azospirillum brasilense sp7].the possibility of the stable inheritance of the plasmid p85 mobilized derivatives from azospirillum brasilense sp245 in the cells of the bacterial genera rizobiaceae (agrobacterium tumfaciens) and pseudomonadaceae (pseudomonas putida) has been shown. the plasmid p85 participates in coding for the physiologically active products (the plant hormones). it is not inherited by the escherichia coli strains. for the first time the incompatibility of azospirillium plasmids has been demonstrated on the ...19921298886
nitrogenase activity in wheat seedlings bearing para-nodules induced by 2,4-dichlorophenoxyacetic acid (2,4-d) and inoculated with azospirillum.nitrogenase activity (c2h2 reduction) was demonstrated in seedlings of wheat roots bearing para-nodules induced by 2,4-dichlorophenoxyacetic acid (2,4-d) and inoculated with azospirillum brasilense. increased nitrogenase activity was observed in inoculated para-nodulated seedlings as compared to inoculated roots not treated by 2,4-d under the conditions of assay used. 2,4-d had no stimulating effect on plant ethylene production in the absence of acetylene. when inoculation was performed with a n ...19921299838
characterization of the flavins and the iron-sulfur centers of glutamate synthase from azospirillum brasilense by absorption, circular dichroism, and electron paramagnetic resonance spectroscopies.azospirillum brasilense glutamate synthase has been studied by absorption, electron paramagnetic resonance, and circular dichroism spectroscopies in order to determine the type and number of iron-sulfur centers present in the enzyme alpha beta protomer and to gain information on the role of the flavin and iron-sulfur centers in the catalytic mechanism. the fmn and fad prosthetic groups are demonstrated to be non-equivalent with respect to their reactivities with sulfite. sulfite reacts with only ...19921316154
regulation of nitrogen fixation in azospirillum brasilense sp7: involvement of nifa, glna and glnb gene products.the expression of nifa-, nih- and nifb-lacz fusions was examined in different mutants of azospirillum brasilense. mutations in nifa, glna and glnb severely impaired the expression of nifh- and nifb-lacz fusions. by contrast, a nifa-lacz fusion was not affected in a nifa or a glnb background and was only partially impaired in glna mutants. it is proposed that in a. brasilense, the pii protein and glutamine synthetase are involved in a post-translational modification of nifa.19921362170
in vitro protein synthesis is affected by the herbicide 2,4-dichlorophenoxyacetic acid in azospirillum brasilense.the effects of 2,4-dichlorophenoxyacetic acid (2,4-d) on growth and protein, dna and rna synthesis of azospirillum brasilense cd were studied. at a concentration of 1 mm, 2,4-d inhibited cell growth, an effect that was reversed either by transferring bacteria to a control (2,4-d-free) medium or to a 2,4-d-treated medium supplemented with polyamines. the herbicide also affected in vitro protein synthesis, either when azospirillum brasilense cd's own cellular mrna or an artificial mrna was used. t ...19921375402
the serotyping of azospirillum spp. by cell-gold immunoblotting.ten azospirillum strains were serotyped using the method of cell-gold immunoblotting (dot-blot immune-overlay assay). colloidal gold-protein a conjugate was used. antibodies raised against the whole cells showed strain specificity and interacted mainly with carbohydrate antigens on the cell surface. immunological identity for a. brasilense sp 245 and sp 107 strains was found. cell-gold immunoblotting can be recommended for serotyping of a wide variety of bacterial strains.19921398026
degradation of selected insecticides by bacteria isolated from soil. 19921450557
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
the hit protein family: a new family of proteins present in prokaryotes, yeast and mammals.by comparing the sequence of a putative translation product from a saccharomyces cerevisiae split gene with several data-bases, i have uncovered a new protein family. members of this family are found in prokaryotes as well as in lower and higher eukaryotes. the function of these proteins is unknown but they share a characteristic histidine triad that may be involved in zinc binding. this group of protein has been named the hit protein family.19921472710
[conjugative transfer of plasmid dna between bacteria in soil].conjugative transfer of plasmid rp4 between populations of azospirilla and between escherichia coli and azospirillum brasilense in nonsterile soil has been investigated. the process of genetic exchange was realized at the early stages of interpopulational interactions, further on the process intensity was obviously rather low. population dynamics of azospirilla transconjugates in soil depends on the presence or the absence of additional food substrate.19921474945
characterization of an azospirillum brasilense sp7 gene homologous to alcaligenes eutrophus phbb and to rhizobium meliloti nodg.a 4 kb sali fragment from azospirillum brasilense sp7 that shares homology with a 6.8 kb ecori fragment carrying nodgefh and part of nodp of rhizobium meliloti 41 was cloned in puc18 to yield pab503. the nucleotide sequence of a 2 kb sali-smai fragment of the pab503 insert revealed an open reading frame, named orf3, encoding a polypeptide sharing 40% identity with r. meliloti nodg. the deduced polypeptide also shared 60% identity with the alcaligenes eutrophus nadph-dependent acetoacetyl-coa (aa ...19921538694
transcription of the azospirillum brasilense nifh gene is positively regulated by nifa and ntra and is negatively controlled by the cellular nitrogen status.the expression of a translational azospirillum brasilense nifh-uida fusion was studied in a. brasilense and in rhizobium meliloti strains with mutations in nifa, ntra and ntrc. induction of the fusion was observed in the r. meliloti wild-type and ntrc- strains on incubation under microaerobic conditions but not in the nifa- and ntra- strains, showing the absolute requirement of both sigma 54 and nifa for activation of the nifh promoter. histochemical analysis of the root nodules elicited by r. m ...19921557035
cloning, sequencing, mutagenesis, and functional characterization of drat and drag genes from azospirillum brasilense.the azospirillum brasilense drat gene, encoding dinitrogenase reductase atp-ribosyltransferase, and drag gene, encoding dinitrogenase reductase activating glycohydrolase, were cloned and sequenced. two genes were contiguous on the a. brasilense chromosome and showed extensive similarity to the same genes from rhodospirillum rubrum. analysis of mutations introduced into the dra region on the a. brasilense chromosome showed that mutants affected in drat were incapable of regulating nitrogenase act ...19921577701
isolation of a glutamate synthase (gogat)-negative, pleiotropically n utilization-defective mutant of azospirillum brasilense: cloning and partial characterization of gogat structural gene.an azospirillum brasilense mutant (n12) pleiotropically defective in the assimilation of nitrogenous compounds (asm-) was isolated and found lacking in the glutamate synthase (gogat-). the glt (gogat) locus of a. brasilense was identified by isolating a broad-host-range plafr1 cosmid clone from a gene library of the bacterium that rectified asm- and gogat- defects (full recovery of activities of the nitrogenase, the assimilatory nitrate and nitrite reductases, and the glutamate synthase). a 7.5- ...19937902833
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
rapd fingerprinting is useful for identification of azospirillum strains.in vitro amplification of genomic dna fragments with single primers of arbitrary sequence was used as a rapid and sensitive method to obtain fingerprints of ten strains belonging to three of the azospirillum species: brasilense, lipoferum and amazonense. each strain showed a distinctive pattern of bands that permitted its unequivocal identification. closely related strains produced almost identical fingerprints. pairwise comparison and cluster analysis of the amplification patterns allowed group ...19937904224
functional organization of the glnb-glna cluster of azospirillum brasilense.the functional organization of the glnb-a cluster of azospirillum brasilense, which codes for the pii protein and glutamine synthetase, respectively, was studied with the aid of lacz fusions, deletion mapping, site-directed mutagenesis, and complementation. it was shown previously by mrna mapping that the cluster contains two tandemly organized promoters, glnbp1 and glnbp2, of the sigma 70 and sigma 54 types, respectively, upstream of glnb and a third unidentified promoter upstream of glna. data ...19938097514
the histidine operon of azospirillum brasilense: organization, nucleotide sequence and functional analysis.a 3457-base pair fragment of azospirillum brasilense dna which complemented mutations in the hisa and hisf genes of escherichia coli was sequenced. the sequence analysis revealed the presence of six major contiguous open reading frames (orf). the comparison of the predicted amino acid sequence of these orf with those encoded by the eubacterial, archaebacterial and eukaryotic his genes sequenced thus far revealed that four of them have a significant degree of homology with the e. coli hish, hisa, ...19938210676
posttranslational regulation of nitrogenase activity by anaerobiosis and ammonium in azospirillum brasilense.in the microaerophilic diazotroph azospirillum brasilense, the addition of fixed nitrogen or a shift to anaerobic conditions leads to a rapid loss of nitrogenase activity due to adp-ribosylation of dinitrogenase reductase. the product of drat (drat) is shown to be necessary for this modification, and the product of drag (drag) is shown to be necessary for the removal of the modification upon removal of the stimulus. drag and drat are themselves subject to posttranslational regulation, and this r ...19938226619
the interaction of 2,4-dichlorophenoxyacetic acid, ribosomes and polyamines in azospirillum brasilense.2,4-dichlorophenoxyacetic acid (2,4-d) is an herbicide used extensively in agriculture. we had previously determined that 1 mm 2,4-d could inhibit cell growth, dna and protein synthesis of azospirillum brasilense. the present work was designed to determine if these alterations are a consequence of 2,4-d action on polyamine biosynthesis and if the protein synthesis inhibition is a result of ribosomal impairment. in this paper we demonstrate that 2,4-d alters the metabolism of polyamines and, thus ...19938248945
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
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
effect on wheat root development of inoculation with an azospirillum brasilense mutant with altered indole-3-acetic acid production.to evaluate the involvement of indole-3-acetic acid (iaa) in promotion of root development, the effects of inoculation of wheat seedlings with azospirillum brasilense spm7918, a very low-iaa producer, were estimated. compared with the wild-type strain sp6, spm7918 showed a reduced ability to promote root system development in terms both of number and length of lateral roots and of distribution of root hairs.19938327784
characterization of the ntrbc genes of azospirillum brasilense sp7: their involvement in the regulation of nitrogenase synthesis and activity.a 7.1 kb ecori fragment from azospirillum brasilense, that hybridized with a probe carrying the ntrbc genes from bradyrhizobium japonicum, was cloned. the nucleotide sequence of a 3.8 kb subfragment was established. this led to the identification of two open reading frames, encoding polypeptides of 401 and 481 amino acids, that were similar to ntrb and ntrc, respectively. a broad host range plasmid containing the putative azospirillum ntrc gene was shown to restore nitrogen fixation under free-l ...19938355653
glutamate synthase genes of the diazotroph azospirillum brasilense. cloning, sequencing, and analysis of functional domains.a 10-kilobase ecori fragment of azospirillum brasilense genomic dna was cloned in escherichia coli. two open reading frames of 4548 and 1446 base pairs (bp) were identified within the fragment as the structural genes for the alpha and beta subunits (gltb and gltd, respectively) of a. brasilense glts. the organization of the gltbd region of a. brasilense differs from that of the corresponding region in e. coli: in a. brasilense, gltd is upstream relative to gltb, and its stop codon is separated b ...19938428988
motility, chemokinesis, and methylation-independent chemotaxis in azospirillum brasilense.observations of free-swimming and antibody-tethered azospirillum brasilense cells showed that their polar flagella could rotate in both clockwise and counterclockwise directions. rotation in a counterclockwise direction caused forward movement of free-swimming cells, whereas the occasional change in the direction of rotation to clockwise caused a brief reversal in swimming direction. the addition of a metabolizable chemoattractant, e.g., malate or proline, had two distinct effects on the swimmin ...19938432718
azospirillum brasilense locus coding for phosphoenolpyruvate:fructose phosphotransferase system and global regulation of carbohydrate metabolism.mutants of azospirillum brasilense unable to grow on fructose include ones affected only on fructose (fru-) and others impaired on many or all carbohydrates through interference with induction of their specific pathways (car-). both types of mutants could be complemented by a cosmid in broad-host-range vector plafr1 containing a 27.5-kb genomic insert, car(-)-complementing activity depending on a 2.2-kb fragment, and fru(-)-complementing activity depending on an overlapping 9.6-kb fragment.19938491742
identification of a nifw-like gene in azospirillum brasilense.a small orf, 5' upstream of the fixabc operon in azospirillum brasilense sp7, has been identified. sequence comparison shows significant homology to the azotobacter vinelandii and azorhizobium caulinodans nifw gene.19938504172
production of b-group vitamins by azospirillum spp. grown in media of different ph at different temperatures.studies were carried out on b-group vitamin (thiamine, biotin, nicotinic acid, riboflavin, pantothenic acid) production by 3 strains of azospirillum (one derived from coniferous ectomycorrhizae and two--from sporocarps of ectomycorrhizal fungi) grown in media of different ph (5.5, 6.5, 7.5) at different temperatures (10 degrees c, 20 degrees c, 26 degrees c). riboflavin was produced in largest amounts by all the strains studied; biotin was not detected in culture filtrates at all. qualitative-qu ...19938511977
use of random amplified polymorphic dna (rapd) for generating specific dna probes for microorganisms.we report the rapid generation of dna probes for several azospirillum strains. this method does not require any knowledge of the genetics and/or the molecular biology of the organism (genome) to be investigated. the procedure is based on the generation of random amplified polymorphic dna (rapd) fingerprints using primers with an embedded restriction site. the amplification product(s) peculiar to one strain or common to two or more strains can be purified, cloned, sequenced and used as molecular ...19938167854
chemotaxis of azospirillum species to aromatic compounds.chemotaxis of azospirillum lipoferum sp 59b and azospirillum brasilense sp 7 and sp cd to malate and to the aromatic substrates benzoate, protocatechuate, 4-hydroxybenzoate, and catechol was assayed by the capillary method and direct cell counts. a. lipoferum required induction by growth on 4-hydroxybenzoate for positive chemotaxis to this compound. chemotaxis of azospirillum spp. to all other substrates did not require induction. maximum chemotactic responses for most aromatic compounds occurre ...199316349041
root-to-root travel of the beneficial bacterium azospirillum brasilense.the root-to-root travel of the beneficial bacterium azospirillum brasilense on wheat and soybean roots in agar, sand, and light-textured soil was monitored. we used a motile wild-type (mot) strain and a motility-deficient (mot) strain which was derived from the wild-type strain. the colonization levels of inoculated roots were similar for the two strains. mot cells moved from inoculated roots (either natural or artificial roots in agar, sand, or light-textured soil) to noninoculated roots, where ...199416349297
isolation of azospirillum lipoferum 4t tn5 mutants affected in melanization and laccase activity.azospirillum lipoferum 4t has original properties such as nonmotility, melanin synthesis, and laccase activity. following random tn5 mutagenesis in a. lipoferum 4t, we obtained 10 mutants which were affected in melanization and laccase activity. the class 1 mutants, with intermediate levels of laccase activity, showed some coloration; the class 2 mutants, which were completely negative for laccase activity, were also colorless. the tn5 localization on the chromosome or on the cryptic 300-mda pla ...199416349390
[effect of plasmid composition on the chemotaxis reaction of azospirillum brasilense sp245 associated with gramineae].correlation between the loss of the 120 and/or 130 kb plasmids by the spontaneous azospirillum brasilense mutant and appearance of the che(-)-phenotype towards 9-mono- and disaccharides has been established. the plasmid rearrangement is concomitant with the appearance of a new 44 kda protein among the membrane proteins of azospirilli. chemotaxis to alanine, glutamic acid, and to organic acids is not impaired.19948183305
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