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roles of flagella, lipopolysaccharide, and a ca2+-dependent cell surface protein in attachment of rhizobium leguminosarum biovar viciae to pea root hair tips.the relationship between ca2+-dependent cell surface components of rhizobium leguminosarum biovar viciae, motility, and ability to attach to pea root hair tips was investigated. in contrast to flagella and lipopolysaccharide, a small protein located on the cell surface was identified as the ca2+-dependent adhesin.19892914856
host-range related structural features of the acidic extracellular polysaccharides of rhizobium trifolii and rhizobium leguminosarum.proton nuclear magnetic resonance (1h nmr) and fast atom bombardment mass spectrometric analyses were performed on enzymatically derived oligosaccharides from the acidic excreted polysaccharides (eps) from representative bacterial strains of the pea-nodulating symbiont, rhizobium leguminosarum (128c53, 128c63, and 300) and the clover-nodulating symbiont, rhizobium trifolii (na-30, anu843, 0403, ta-1, lpr5035, usda20.102, and 4s). the results revealed structural similarities and differences betwe ...19892912966
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
tight linkage of glna and a putative regulatory gene in rhizobium leguminosarum.rhizobium leguminosarum, biovar viceae, strain rcc1001 contains two glutamine synthetase activities, gsi and gsii. we report here the identification of glna, the structural gene for gsi. a 2 kb fragment of dna was shown to complement the gln- phenotype of klebsiella pneumoniae glna mutant strains. dna sequence analysis revealed an open reading frame (orf) of 469 codons specifying a polypeptide of 52,040 daltons. its deduced amino acid sequence was found to be highly homologous to other glutamine ...19872882467
characterization and cloning of two rhizobium leguminosarum genes coding for glutamine synthetase activities.we have demonstrated that rhizobium leguminosarum strain lpr1105 contains a heat stable and a heat labile glutamine synthetase (ec 6.3.1.2) activity similar to those described for other rhizobiaceae. most of the activity is heat stable when this strain is grown on glutamine as sole nitrogen source, but most is heat labile when grown on nitrate. using a gene bank of r. leguminosarum dna we have isolated two clones, which code for heat stable (p7d9) and heat labile (p4f7) glutamine synthetase acti ...19862878969
[mutation, transfer and location of symbiotic genes of rhizobium leguminosarum biovar phaseoli by insertion of tn5-mob]. 19882856224
construction of a tn5 derivative encoding bioluminescence and its introduction in pseudomonas, agrobacterium and rhizobium.a simple method based upon the use of a tn5 derivative, tn5-lux, has been devised for the introduction and stable expression of the character of bioluminescence in a variety of gram-negative bacteria. in tn5-lux, the luxab genes of vibrio harveyi encoding luciferase are inserted on a sali--bglii fragment between the kanamycin resistance (kmr) gene and the right insertion sequence. the transposon derivative was placed on a transposition suicide vehicle by in situ recombination with the tn5 suicid ...19882851709
analysis of pss genes of rhizobium leguminosarum required for exopolysaccharide synthesis and nodulation of peas: their primary structure and their interaction with psi and other nodulation genes.strains of rhizobium leguminosarum (r.l.) biovar viciae containing pss mutations fail to make the acidic exopolysaccharides (eps) and are unable to nodulate peas. it was found that they also failed to nodulate vicia hirsuta, another host of this biovar. when peas were co-inoculated with pss mutant derivatives of a strain of r.l. by viciae containing a sym plasmid plus a cured strain lacking a sym plasmid (and which is thus nod-, but for different reasons) but which makes the acidic eps, normal n ...19882851702
interference between rhizobium meliloti and rhizobium trifolii nodulation genes: genetic basis of r. meliloti dominance.transfer of an incp plasmid carrying the rhizobium meliloti nodfe, nodg, and nodh genes to rhizobium trifolii enabled r. trifolii to nodulate alfalfa (medicago sativa), the normal host of r. meliloti. using transposon tn5-linked mutations and in vitro-constructed deletions of the r. meliloti nodfe, nodg, and nodh genes, we showed that r. meliloti nodh was required for r. trifolii to elicit both root hair curling and nodule initiation on alfalfa and that nodh, nodfe, and nodg were required for r. ...19882848012
transcriptional regulation of the vira and virg genes of agrobacterium tumefaciens.we have used transcriptional and translational fusions between various vir gene promoters and the lacz gene to study the regulation of vir genes. like other vir promoters, the vira promoter was induced by acetosyringone in a vira virg-dependent fashion. in addition to being induced by acetosyringone, the virg promoter was partially induced by acidic growth conditions and by starvation for inorganic phosphate. these two conditions appeared to act synergistically. the response to low ph and to pho ...19882842300
genetic characterization and sequence analysis of the duplicated nifa/nifb gene region of rhodobacter capsulatus.a dna region showing homology to klebsiella pneumoniae nifa and nifb is duplicated in rhodobacter capsulatus. the two copies of this region are called nifa/nifb copy i and nifa/nifb copy ii. deletion mutagenesis demonstrated that either of the two copies is sufficient for growth in nitrogen-free medium. in contrast, a double deletion mutant turned out to be deficient in nitrogen fixation. the complete nucleotide sequence of a 4838 bp fragment containing nifa/nifb copy i was determined. two open ...19882836706
rhizobium japonicum usda 191 has two nodd genes that differ in primary structure and function.several rhizobium genes (designated nod genes) are involved in early steps in nodule formation. here we present the results of dna sequence and functional analysis of two nodd genes from the symbiotic plasmid of usda 191, a fast-growing strain that forms nitrogen-fixing nodules on soybeans. both genes encoded full-length nodd-related polypeptides, which were 69% homologous to each other. one of these genes, nodd1, complemented a rhizobium trifolii nodd::tn5 mutant for clover nodulation; the othe ...19882826389
cloning and characterization of hydrogen uptake genes from rhizobium leguminosarum.a gene library of genomic dna from the hydrogen uptake (hup)-positive strain 128c53 of rhizobium leguminosarum was constructed by using the broad-host-range mobilizable cosmid vector plafr1. the resulting recombinant cosmids contained insert dna averaging 21 kilobase pairs (kb) in length. two clones from the above gene library were identified by colony hybridization with dna sequences from plasmid phu1 containing hup genes of bradyhizobium japonicum. the corresponding recombinant cosmids, pal618 ...19872822654
[utilization of nitrate by bacteroids and cytosol of nodules formed by rhizobium leguminosarum].nitrite production by nodules and roots of pea plants (pisum sativum l., cultivar alaska) inoculated with rhizobium leguminosarum strain 3855 has been studied. nitrate reductase (nr) activity and nitrite reductase (nir) activity of the bacteroidal and cytosolic fractions of the nodules were also determined, as well as the nitrite content of the nodules cytosol. nitrite production by nodules and roots from plants treated with 5 mm kno3 was higher than that of nodules and roots from plants not tre ...19892803636
conservation between coding and regulatory elements of rhizobium meliloti and rhizobium leguminosarum dct genes.complementation of rhizobium leguminosarum dct mutants with a cosmid bank yielded rhizobium meliloti homologs of the dcta, dctb, and dctd genes. the genes dctb and dctd are thought to form a two-component system which responds to the presence of c4-dicarboxylates to regulate expression of a transport protein encoded by dcta. dna sequence analysis showed that dct coding and intergenic regions, including putative binding sites for the dctd protein and sigma 54-rna polymerase, were highly conserved ...19892793824
genetic derepression of a developmentally regulated lipopolysaccharide antigen from rhizobium leguminosarum 3841.monoclonal antibody afrc mac 203 recognizes a developmentally regulated lipopolysaccharide antigen in rhizobium leguminosarum bv. viciae 3841. transposon-induced mutants that constitutively expressed mac 203 antigen were isolated. these strains were morphologically normal, showed no gross abnormalities in lipopolysaccharide size distribution on sodium dodecyl sulfate-polyacrylamide gels, and induced normal nitrogen-fixing nodules. however, the mutants lacked lipopolysaccharide epitopes recognize ...19892768182
expression of a cell surface antigen from rhizobium leguminosarum 3841 is regulated by oxygen and ph.rhizobium leguminosarum bv. viciae 3841 was grown in liquid suspension culture to investigate how culture conditions could affect the expression of a developmentally regulated cell surface antigen associated with lipopolysaccharide. the antigen, which is recognized by monoclonal antibody afrc mac 203, was expressed when cultures were grown at neutral ph under low-oxygen conditions (less than 7.5% [vol/vol] o2 in the gas phase). antigen was also expressed in aerobically grown cultures at ph value ...19892768181
developmental regulation of a rhizobium cell surface antigen during growth of pea root nodules.a monoclonal antibody, afrc mac 203, was used to examine the expression of a nodule-induced cell surface antigen associated with lipopolysaccharide in rhizobium leguminosarum bv. viciae 3841. silver-enhanced immunogold-labeled tissue sections revealed that, in very young tissues of pea root nodules, the nodule-induced form of lipopolysaccharide antigen was not expressed either by rhizobia in the infection thread or by bacteria recently released into the plant cell cytoplasm. in the more mature r ...19892768180
accumulation of a nod gene inducer, the flavonoid naringenin, in the cytoplasmic membrane of rhizobium leguminosarum biovar viciae is caused by the ph-dependent hydrophobicity of naringenin.most sym plasmid-localized nodulation genes of rhizobium leguminosarum bv. viciae are only expressed upon activation of the nodd protein by plant flavonoids, e.g., naringenin (s. a. j. zaat, c. a. wijffelman, h. p. spaink, a. a. n. van brussel, and b. j. j. lugtenberg, j. bacteriol, 169:198-204, 1987). as part of a study on the mechanism of nodd protein activation, the mechanism of uptake and the intracellular fate of [3h]naringenin were studied. naringenin was accumulated by rhizobium cells wit ...19892753859
purification and partial characterization of the rhizobium leguminosarum biovar viciae ca2+-dependent adhesin, which mediates the first step in attachment of cells of the family rhizobiaceae to plant root hair tips.the ca2+-dependent adhesin which mediates the first step in attachment of bacteria of the family rhizobiaceae to plant root hair tips was isolated from the surface of rhizobium leguminosarum biovar viciae cells; its ability to inhibit attachment of r. leguminosarum to pea root hair tips was used as a bioassay. isolated adhesin was found to be able to inhibit attachment of both carbon-limited and manganese-limited r. leguminosarum cells. a multicolumn purification procedure was developed which re ...19892738027
the central domain of rhizobium meliloti nifa is sufficient to activate transcription from the r. meliloti nifh promoter.the rhizobium meliloti nifa product (nifa) shares extensive homology in its central region and at its c-terminal end with rhizobium leguminosarum dctd and with ntrc from several species. all three proteins are transcriptional activators of ntra (rpon)-rna polymerase-dependent promoters. several large deletions of r. meliloti nifa were constructed to investigate the role of the conserved and divergent domains of nifa in transcriptional activity and posttranscriptional regulation by oxygen. the ab ...19892722751
transcription of rhia, a gene on a rhizobium leguminosarum bv. viciae sym plasmid, requires rhir and is repressed by flavanoids that induce nod genes.strains of rhizobium leguminosarum biovar viciae specifically make an abundant protein (rhi) in free-living culture but not in bacteroids. genes needed for rhi synthesis are on a sym plasmid and here we show that one of these genes, rhia, is the structural gene that specifies this polypeptide. transcription of rhia requires a regulatory gene, rhir, located close to rhia and to nod genes involved in nodulation. mutations in rhia or rhir do not appear to affect symbiotic nitrogen fixation. transcr ...19892716520
genetic analysis and regulation of the rhizobium meliloti genes controlling c4-dicarboxylic acid transport.the genes controlling the transport of c4-dicarboxylic acids from rhizobium meliloti have been cloned and analysed. the nucleotide sequence of the control region of the structural dcta and the regulatory dctbd genes has been determined. comparison with the rhizobium leguminosarum dct genes revealed a high degree of homology. gene fusions to the enteric laczy reporter gene were constructed and the expression of the dcta and dctbd genes studied under various physiological conditions. in free-livin ...19892695394
nucleotide sequence of the regulatory nifa gene of rhizobium leguminosarum pre: transcriptional control sites and expression in escherichia coli.we report the sequence of the regulatory nifa gene of rhizobium leguminosarum pre. the transcription initiation and termination sites of nifa were mapped and a potential promoter and a rho-independent terminator identified. the nifa gene has two possible translation start sites, both of which are used in an escherichia coli background, resulting in proteins with apparent molecular weights of 58 kd and 57 kd; initiation at the second site is preferred over initiation at the first. the nifa-nifb i ...19892693897
nodo, a new nod gene of the rhizobium leguminosarum biovar viciae sym plasmid prl1ji, encodes a secreted protein.the region of the rhizobium leguminosarum biovar viciae sym plasmid prl1ji, responsible for the production and secretion of a previously described 50-kilodalton protein (r. a. de maagd, c. a. wijffelman, e. pees, and b. j. j. lugtenberg, j. bacteriol. 170:4424-4427, 1988), was cloned and its nucleotide sequence was determined. a new nod gene, nodo, preceded by a poorly conserved nod box, was identified and its transcriptional start site was determined. comparison of its predicted protein product ...19892687250
genetic analysis and cellular localization of the rhizobium host specificity-determining node protein.the nucleotide sequence of the node gene of rhizobium trifolii strain anu843 was determined. like the node gene of r. leguminosarum strain 248 it encodes a protein with a predicted mol. wt of 42.0 kd. the predicted node proteins of r.trifolii and r.leguminosarum have a homology of 78%. using antibodies raised against the node protein of r.trifolii it was shown that the node products of r.leguminosarum and r.trifolii are localized in the cytoplasmic membrane. furthermore, these node proteins are ...19892684629
subcellular localization of the nodd gene product in rhizobium leguminosarum.in rhizobium strains the transcription of symbiosis plasmid-localized nod genes, except nodd, is induced by plant flavonoids and requires the nodd gene product. in order to localize nodd protein in r. leguminosarum, a nodd protein-specific antiserum was raised against a lacz'-'nodd gene fusion product. using these antibodies, we determined that the nodd protein is located exclusively in the cytoplasmic membrane of wild-type r. leguminosarum biovar viciae cells. this localization is independent o ...19892670892
localization and symbiotic function of a region on the rhizobium leguminosarum sym plasmid prl1ji responsible for a secreted, flavonoid-inducible 50-kilodalton protein.a previously described (r. a. de maagd, c. a. wijffelman, e. pees, and b. j. j. lugtenberg, j. bacteriol. 170:4424-4427, 1988) sym plasmid-dependent, naringenin-inducible 50-kilodalton protein of rhizobium leguminosarum biovar viciae is further characterized in this paper. the protein was overproduced by constructing a strain containing multiple copies of the r. meliloti nodd gene, which facilitated its purification. an antiserum was used to screen tn5 insertion mutants located in the prl1ji reg ...19892644226
rhizobium leguminosarum cfn42 genetic regions encoding lipopolysaccharide structures essential for complete nodule development on bean plants.eight symbiotic mutants defective in lipopolysaccharide (lps) synthesis were isolated from rhizobium leguminosarum biovar phaseoli cfn42. these eight strains elicited small white nodules lacking infected cells when inoculated onto bean plants. the mutants had undetectable or greatly diminished amounts of the complete lps (lps i), whereas amounts of an lps lacking the o antigen (lps ii) greatly increased. apparent lps bands that migrated between lps i and lps ii on sodium dodecyl sulfate-polyacry ...19892644215
the structures of the lipopolysaccharide core components from rhizobium leguminosarum biovar phaseoli ce3 and two of its symbiotic mutants, ce109 and ce309.the structures for the core regions of the lipopolysaccharides (lpss) from r. leguminosarum bv. phaseoli ce3 and two symbiotic mutants were determined by g.l.c.-m.s., proton nuclear magnetic resonance spectroscopy (n.m.r.), fast-atom-bombardment mass spectrometry (f.a.b.-m.s.), and by comparison with known structures from the lps of r. leguminosarum bv. trifolii anu843. the core oligosaccharides were separated into two components, p2-2 and p2-3, by gel-filtration chromatography using bio-gel p2. ...19892636039
quantitative comparison of the laboratory and field competitiveness of rhizobium leguminosarum biovar phaseoli.rhizobium leguminosarum bv. phaseoli kim5s outcompeted strain ce3 in bean (phaseolus vulgaris l.) root nodulation when plants were grown at any of three field sites, each with a different soil type and indigenous population, or in the laboratory in a sterilized sand, a sterilized peat-vermiculite mixture, or a nonsterile field soil. a mathematical model describing nodulation competitiveness was empirically derived to evaluate the relative competitiveness of the two strains under these conditions ...19892624457
molecular linkage of the nif/fix and nod gene regions in rhizobium leguminosarum biovar trifolii.nucleotide sequence analysis of a 2.5kb region downstream of the nifa gene from rhizobium leguminosarum biovar trifolii has resulted in linkage, at the dna sequence level, of the nifen, nifhdk, fixabcx, nifa gene cluster with the nodef, nodd, nodabcij genes. four genes have been identified within this intervening region. immediately 3' to the nifa gene is the nifb gene and the nifb-linked ferredoxin-encoding fdxn gene. downstream of fdxn in r. leguminosarum bv. trifolii and in rhizobium meliloti ...19892622339
the nodl gene from rhizobium leguminosarum is homologous to the acetyl transferases encoded by laca and cyse.the predicted protein sequence of the nodl gene from rhizobium leguminosarum was screened against translations of the genbank dna sequence database. a very strong homology was found to laca, which encodes thiogalactoside transferase; homology between nodl and the cyse gene product (serine acetyl transferase) was also found. comparison of the conserved regions of the three protein sequences indicated a domain that may be an active site of the enzymes.19892615659
single and multiple mutations affecting properties of the regulatory gene nodd of rhizobium.nodd of rhizobium leguminosarum has two regulatory properties: it autoregulates and, in cells grown with specific flavonoids, activates other nod genes. we isolated mutations in nodd affecting one or both properties. those abolishing autoregulation and nod gene induction were at the 5' end of nodd, as were those which only affected autoregulation. mutations affecting nod gene activation are at the 3' end of nodd. eleven mutations in this region of nodd were isolated: some had little effect on th ...19892615655
construction of a gene bank of rhizobium leguminosarum rld 164.the total genomic dna of r. leguminosarum rld164 (trp, sms, azi) was cloned in the ecor1 site of the wide host and conjugally transferable cosmid vector plafr1. the average insert size in the gene clones of the bank was found to be 21.3 kb. the strain r. leguminosarum rld7 (leu-1) was employed as recepient to conjugally transfer and thus isolate the complementary leu+ allele carrying clones from the gene bank.19892606538
additional nodulation genes on the sym plasmid of rhizobium leguminosarum biovar viciae.a rhizobium leguminosarum biovar viciae strain lacking a 40 kb dna region of the sym plasmid prl1ij to the left (3' side) of gene node failed to nodulate vicia sativa plants. therefore this dna region was investigated for the presence of additional nodulation genes. complementation experiments indicated that the dna region to the left (3' side) of node is functionally homologous between r. leguminosarum bv. viciae and r. leguminosarum bv. trifolii. in this dna region, three nodulation genes were ...19892562395
transposon mutagenesis and complementation of the fructokinase gene in rhizobium leguminosarum biovar trifolii.transposon tn5 was used to generate a fructokinase mutation in rhizobium leguminosarum biovar trifolii bal. the section of the genome containing tn5 was cloned into the ecori site of the vector phc79 and isolated by direct selection on medium containing kanamycin and tetracycline. total ecori digestion was used to obtain a single fragment containing tn5 and flanking dna sequences. the flanking dna was used as a probe to isolate an intact fructokinase gene from a plafr1 cosmid clone bank of the p ...19892561289
transposable elements for efficient manipulation of a wide range of gram-negative bacteria: promoter probes and vectors for foreign genes.we describe here the construction and use of a series of modified transposons based on the insertion sequence is1. like their parent, omegon-km [fellay et al., gene 76 (1989) 215-226], these elements permit efficient insertional mutagenesis of a variety of gram-negative bacteria. the presence of a functional pbr322 origin of replication within the transposable element facilitates subsequent cloning of the mutated gene. the omegon-km system was previously shown to function in pseudomonas putida, ...19892559879
characterization and nucleotide sequence of a novel gene fixw upstream of the fixabc operon in rhizobium leguminosarum.on the rhizobium leguminosarum pre sym plasmid, fixabc and a novel gene fixw were identified upstream of the regulatory gene nifa. the molecular masses of fixabc, 29, 44 and 50 kda respectively, were estimated by polyacrylamide gel electrophoresis (page) and of fixw, 25 kda, by page and nucleotide sequencing. hybridization studies using bacteroid mrna as a probe showed that fixabc is one operon which can be transcribed independently of fixw. nucleotide sequencing revealed that both fixw and fixa ...19892555670
genes involved in lipopolysaccharide production and symbiosis are clustered on the chromosome of rhizobium leguminosarum biovar viciae vf39.four mutants of rhizobium leguminosarum biovar viciae vf39 altered in lipopolysaccharide (lps) synthesis were isolated upon random tn5 mutagenesis. these mutants produced matt colonies on ty medium and showed autoagglutination and loss of motility. on sodium dodecyl sulfate-polyacrylamide gels, they lacked a slow-migrating carbohydrate band, corresponding to the complete lps (lpsi). all four mutants formed small white nodules on vicia hirsuta. these nodules were infected but showed no nitrogen-f ...19892553672
the nifa gene product from rhizobium leguminosarum biovar trifolii lacks the n-terminal domain found in other nifa proteins.the nifa gene has been identified between the fixx and nifb genes in the clover microsymbiont rhizobium leguminosarum biovar trifolii (r.i. bv. trifolii) strain anu843. expression of the nifa gene is induced in the symbiotic state and site-directed mutagenesis experiments indicate that nifa expression is essential for symbiotic nitrogen fixation. interestingly, the predicted r.i. bv. trifolii nifa protein lacks an n-terminal domain that is present in the homologous proteins from r.i. bv. viciae, ...19892552256
comparative study of the symbiotic plasmid dna in free living bacteria and bacteroids of rhizobium leguminosarum.the symbiotic plasmid (psym) dna present in bacteroids of strain rcr1001 of rhizobium leguminosarum biovar viceae has been compared qualitatively and quantitatively with that present in free living bacteria by hybridization experiments with appropriate probes. a decrease in the relative amount of psym dna was observed in bacteroids as compared to bacteria. no rearrangements of the symbiotically expressed psym borne genes were detected in bacteroids.19892551770
rhizobium leguminosarum exopolysaccharide mutants: biochemical and genetic analyses and symbiotic behavior on three hosts.ten independently generated mutants of rhizobium leguminosarum biovar phaseoli cfn42 isolated after tn5 mutagenesis formed nonmucoid colonies on all agar media tested and lacked detectable production of the normal acidic exopolysaccharide in liquid culture. the mutants were classified into three groups. three mutants harbored tn5 insertions on a 3.6-kilobase-pair ecori fragment and were complemented to have normal exopolysaccharide production by cosmids that shared an ecori fragment of this size ...19892549002
direct selection for curing and deletion of rhizobium plasmids using transposons carrying the bacillus subtilis sacb gene.we have constructed derivatives of the transposon tn5 carrying the mob site (orit) of plasmid rp4, and an npti-sacb-sacr cassette [ried and collmer, gene 57 (1987) 239-246]. the mob site, in conjunction with the antibiotic-resistance markers carried on the transposons, allows identification of transposon inserts in cryptic plasmids by mobilisation to other strains. the sacb-sacr genes allow direct selection for the loss or curing of plasmids, because only strains which no longer contain an activ ...19892548927
omegon-km: a transposable element designed for in vivo insertional mutagenesis and cloning of genes in gram-negative bacteria.to combine the features of the omega interposons with the advantages of in vivo transposition mutagenesis, we have constructed an artificial transposon, called omegon-km. the omegon-km transposon is carried on the plasmid pjff350 which can be conjugally mobilized into a broad range of gram-negative bacteria. omegon-km is flanked, in inverted orientation, by synthetic 28-bp repeats derived from the ends of is1. in addition, each end of omegon-km has the very efficient transcription and translatio ...19892546859
the rhizobium meliloti host range nodq gene encodes a protein which shares homology with translation elongation and initiation factors.the rhizobium meliloti nod region iib is involved in host-range determination: (i) the presence of region iib is necessary for transfer of alfalfa root hair curling ability to rhizobium leguminosarum biovar trifolii; (ii) a mutation in region iib extends the r. meliloti infection host range to vicia sativa nigra; (iii) dominance of r. meliloti nod genes over r. leguminosarum biovar viciae nod genes is abolished by mutations in region iib. the nucleotide sequence of this region has been determine ...19892546009
symbiotic properties of rhizobia containing a flavonoid-independent hybrid nodd product.a hybrid nodd gene consisting of 75% of the nodd1 gene of rhizobium meliloti at the 5' end and 27% of the nodd gene of rhizobium trifolii at the 3' end activates the six tested inducible nod promoters of rhizobium leguminosarum, r. trifolii, or r. meliloti to maximal levels, even in the absence of flavonoids. in strains containing such a constitutive activating nodd gene, transcription of nod genes started at the same site as in flavonoid-induced strains containing a wild-type nodd gene. in cont ...19892544568
isolation and characterization of mutants of rhizobium leguminosarum bv. viciae 248 with altered lipopolysaccharides: possible role of surface charge or hydrophobicity in bacterial release from the infection thread.effects of alterations in lipopolysaccharide (lps) structure of rhizobium leguminosarum bv. viciae on effective symbiosis and on a number of cell surface characteristics were studied. tn5 mutants with altered lpss were screened for their inability to bind monoclonal antibody 3, one of three monoclonal antibodies to the tentative o-antigenic part of the wild-type lps of strain 248. ten class i lps mutants completely lacked the o-antigen-containing lps species. the class ii lps mutant had a severe ...19892536673
extension of host range of rhizobium leguminosarum bv. trifolii caused by point mutations in nodd that result in alterations in regulatory function and recognition of inducer molecules.the positive activation of several nodulation genes in strain anu843 of rhizobium leguminosarum biovar trifolii is mediated by the product of the nodd gene and by the interaction of nodd with plant-secreted inducer and anti-inducer compounds. we have mutagenized the nodd gene of strain anu843 with nitrosoguanidine and have found that the ability of the mutated nodd products to interact with inducer and anti-inducer compounds is affected by the amino acid sequence in at least two key regions, inc ...19892520822
analysis of the major inducers of the rhizobium noda promoter from vicia sativa root exudate and their activity with different nodd genes.root exudate of vicia sativa contains 7 inducers for the noda promoter of rhizobium leguminosarum biovar viciae. six of these inducers are flavanones. one inducer was identified as 3,5,7,3'-tetrahydroxy-4'-methoxyflavanone, and a second inducer most likely is 7,3'-dihydroxy-4'-methoxyflavanone. the inducing activity of these compounds and the other inducers depends on the nodd gene present in the test strains, which originated either from r. leguminosarum biovars viciae or trifolii, or from r. m ...19892519112
construction of a lacz-kanamycin-resistance cassette, useful for site-directed mutagenesis and as a promoter probe.a lacz gene without a promoter, but containing its ribosome-binding site, was cloned next to the kanamycin-resistance (kmr) gene of plasmid puc4k, yielding a lacz-kmr cassette. from the resulting plasmid, pkok5, the lacz-kmr cassette was recloned by means of bamhi into plasmid pkok4, a mobilizable derivative of pbr322 which mediates ampicillin, chloramphenicol and tetracycline resistance. the lacz-kmr cassette can be excised from pkok5 or pkok6 by digestion with bamhi, sali or psti. it can be us ...19892515118
evidence for divalent cation (ca2+)-stabilized oligomeric proteins and covalently bound protein-peptidoglycan complexes in the outer membrane of rhizobium leguminosarum.two unusual characteristics of some outer membrane proteins of rhizobium leguminosarum are described. first, most of the major outer membrane proteins could only be visualized by sodium dodecyl sulfate-polyacrylamide gel electrophoresis after lysozyme treatment of the isolated cell envelopes, suggesting a very strong, possibly covalent, interaction of these proteins with the peptidoglycan. these peptidoglycan-associated outer membrane proteins belonged to two distinct groups of immunologically r ...19892500420
two host-inducible genes of rhizobium fredii and characterization of the inducing compound.random transcription fusions with mu d1(kan lac) generated three mutants in rhizobium fredii (strain usda 201) which showed induction of beta-galactosidase when grown in root exudate of the host plants glycine max, phaseolus vulgaris, and vigna ungliculata. two genes were isolated from a library of total plasmid dna of one of the mutants, 3f1. these genes, present in tandem on a 4.2-kilobase hindiii fragment, appear in one copy each on the symbiotic plasmid and do not hybridize to the rhizobium ...19882447061
genetic organization of the hydrogen uptake (hup) cluster from rhizobium leguminosarum.in symbiosis with peas, rhizobium leguminosarum upm791 induces the synthesis of a hydrogen uptake (hup) system that recycles hydrogen generated in nodules by nitrogenase. a cosmid (pal618) containing hup genes from this strain on a 20-kilobase-pair (kb) dna insert has previously been isolated in our laboratory (a. leyva, j. m. palacios, t. mozo, and t.ruiz-argüeso, j. bacteriol. 169:4929-4934, 1987). here we show that cosmid pal618 contains all of the genetic information required to confer high ...19902407728
determination of viability within serotypes of a soil population of rhizobium leguminosarum bv. trifolii.concern has been raised about the percentage of viable cells within soil rhizobia populations measured by the immunofluorescence direct count method. the purpose of this study was to evaluate a direct viable count technique which is based on the fact that viable bacteria in natural populations undergo cell elongation when they are exposed to a combination of substrate and the inhibitor of dna gyrase, nalidixic acid. a soil extraction procedure was developed to recover a high proportion of soil b ...19902407187
a rhizobium leguminosarum mutant defective in symbiotic iron acquisition.iron acquisition by symbiotic rhizobium spp. is essential for nitrogen fixation in the legume root nodule symbiosis. rhizobium leguminosarum 116, an ineffective mutant strain with a defect in iron acquisition, was isolated after nitrosoguanidine mutagenesis of the effective strain 1062. the pop-1 mutation in strain 116 imparted to it a complex phenotype, characteristic of iron deficiency: the accumulation of porphyrins (precursors of hemes) so that colonies emitted a characteristic pinkish-red f ...19902404949
dna sequence encoding the two structural genes for the uptake hydrogenase of rhizobium leguminosarum bv. viciae b10. 19902402452
a biovar-specific signal of rhizobium leguminosarum bv. viciae induces increased nodulation gene-inducing activity in root exudate of vicia sativa subsp. nigra.flavonoids in root exudate of leguminous plants activate the transcription of rhizobium genes involved in the formation of root nodules (nod genes). we report that inoculation with the homologous symbiont r. leguminosarum bv. viciae results in an increased nod gene-inducing activity (ini) in root exudate of v. sativa subsp. nigra, whereas inoculation with heterologous rhizobium strains results in exudates with nod gene-inducing activity comparable to that of uninfected plants. ini can be demonst ...19902394688
molecular characterization of the nodulation gene, nodt, from two biovars of rhizobium leguminosarum.dna sequencing of the nodij region from rhizobium leguminosarum biovar trifolii revealed the nodt gene immediately downstream of nodj. dna hybridizations using a nodt-specific probe showed that nodt is present in several r. leguminosarum strains. interestingly, a flavonoid-inducible nodt gene homologue in r. leguminosarum bv. viciae is not in the nodabcij operon but is located downstream of nodmn. the sequence of the nodt gene from bv. viciae was determined and a comparison of the predicted amin ...19902338917
immunochemical analysis of lipopolysaccharides from free-living and endosymbiotic forms of rhizobium leguminosarum.rhizobium leguminosarum b556 and 8002 differ only with respect to carrying symbiotic plasmids with specificity for pisum or phaseolus hosts, respectively. protease-treated samples derived from free-living cultures of both strains revealed a ladder of lipopolysaccharide (lps-1) bands after periodate-silver staining of sodium dodecyl sulfate-polyacrylamide gels. these bands were arranged as doublets. after western (immuno-) blotting, all lps-1 bands reacted with monoclonal antibody jim 21, whereas ...19902318803
the rhizobium nodulation gene nodo encodes a ca2(+)-binding protein that is exported without n-terminal cleavage and is homologous to haemolysin and related proteins.nodulation and host-specific recognition of legumes such as peas and vicia spp. are encoded by the nodulation (nod) genes of rhizobium leguminosarum biovar viciae. one of these genes, nodo, has been shown to encode an exported protein that contains a multiple tandem repeat of a nine amino acid domain. this domain was found to be homologous to repeated sequences in a group of bacterial exported proteins that includes haemolysin, cyclolysin, leukotoxin and two proteases. these proteins are secrete ...19902303029
expression of rhizobium leguminosarum cfn42 genes for lipopolysaccharide in strains derived from different r. leguminosarum soil isolates.two mutant derivatives of rhizobium leguminosarum anu843 defective in lipopolysaccharide (lps) were isolated. the lps of both mutants lacked o antigen and some sugar residues of the lps core oligosaccharides. genetic regions previously cloned from another rhizobium leguminosarum wild-type isolate, strain cfn42, were used to complement these mutants. one mutant was complemented to give lps that was apparently identical to the lps of strain anu843 in antigenicity, electrophoretic mobility, and sug ...19902298697
the enod12 gene product is involved in the infection process during the pea-rhizobium interaction.the pea cdna clone ppsenod12 represents a gene involved in the infection process during pisum sativum l.-rhizobium leguminosarum bv. viciae symbiosis. the enod12 protein is composed of pentapeptides containing two hydroxyprolines. the expression of the enod12 gene is induced in cells through which the infection thread is migrating, but also in cells that do not yet contain an infection thread. soluble compounds from rhizobium are involved in eliciting enod12 gene expression. rhizobium common and ...19902297789
structure of the extracellular polysaccharide secreted by rhizobium leguminosarum var. phaseoli ciat 899.the structure of the extracellular polysaccharide secreted by rhizobium leguminosarum var. phaseoli ciat 899 has been studied by methylation analysis. 1h-n.m.r. spectroscopy, and partial acid hydrolysis. the repeating unit is an octasaccharide made up of d-glucose, d-galactose, pyruvic acid, and acetic acid in the molar ratios 6:2:1.5:1.5. half of the terminal gal groups are 4,6-substituted by pyruvic acid acetal groups and the other half by o-acetyl groups at position 3. also, one of the 3-link ...19902279241
[construction of frankia genomic libraries and isolation of clones homologous to nodulation genes from rhizobium leguminosarum].high molecular genomic dnas were isolated by using the lysozyme plus achromopeptidase system from frankia strains at4, ccol and hr16, the root nodule endophytes of alnus, casuarina and hippophae respectively, and used to construct genomic libraries in plafr1, a broad host range cosmid vector within many gram-negative hosts. the genomic libraries were screened by in situ colony hybridization to identify clones homologous to common nodulation genes of rhizobium leguminosarum, based on the sequence ...19902268450
rleai: a novel class-iis restriction endonuclease from rhizobium leguminosarum recognizing 5'-cccaca(n)12-3' 3'-gggtgt(n)9-5'. 19902253885
rhizobium leguminosarum exob mutants are deficient in the synthesis of udp-glucose 4'-epimerase.rhizobium leguminosarum bv. viciae exo- mutant strains rbl5523,exo7::tn5,rbl5523,exo8::tn5 and rbl5523,exo52::tn5 are affected in nodulation and in the syntheses of lipopolysaccharide, capsular polysaccharide, and exocellular polysaccharide. these mutants were complemented for nodulation and for the syntheses of these polysaccharides by plasmid pmp2603. the gene in which these mutants are defective is functionally homologous to the exob gene of rhizobium meliloti. the repeating unit of the resid ...19902250016
either of two nod gene loci can complement the nodulation defect of a nod deletion mutant of rhizobium leguminosarum bv viciae.a deletion mutant of rhizobium leguminosarum biovar viciae lacking the host-specific nodulation (nod) gene region (nodfel nodmnt and nodo) but retaining the other nod genes (nodd nodabcij) was unable to nodulate peas or vicia hirsuta, although it did induce root hair deformation. the mutant appeared to be blocked in its ability to induce infection threads and could be rescued for nodulation of v. hirsuta in mixed inoculation experiments with an exopolysaccharide deficient mutant (which is also n ...19902233683
analysis of three nodd genes in rhizobium leguminosarum biovar phaseoli; nodd1 is preceded by noie, a gene whose product is secreted from the cytoplasm.in a strain of rhizobium leguminosarum biovar phaseoli, three copies of the regulatory nodulation gene nodd were identified on the sym plasmid and sequenced. two were closely linked to each other and the third was near, but not adjacent, to the nodabc genes. each of these nodd genes could correct the nod- defect of a nodd mutant strain of r. leguminosarum biovar viciae on peas. a truncated form of nodd2 could also correct this mutant, indicating that the c-terminus of nodd2 is not needed for ind ...19902215216
subcellular localization of the rhizobium leguminosarum nodi gene product.by the use of antibodies raised against a fusion protein of lacz'-nodi (produced in escherichia coli) which specifically react with nodi protein, it was shown that in wild-type rhizobium leguminosarum biovar viciae nodi protein (i) is recovered with the cytoplasmic membrane fraction and (ii) is translated as part of the nodabcij operon. in addition, it was found that the bacterial chromosomal background strongly influences the expression of several nod genes.19902203755
rhizobium meliloti and rhizobium leguminosarum dctd gene products bind to tandem sites in an activation sequence located upstream of sigma 54-dependent dcta promoters.free-living rhizobia transport external c4-dicarboxylates to use as sole carbon sources, and uptake of these compounds is essential for nitrogen fixation by rhizobial bacteroids. in both rhizobium leguminosarum and rhizobium meliloti, the genes dctb and dctd are believed to form an ntrb/ntrc-like two-component system which regulates the synthesis of a c4-dicarboxylate transport protein encoded by dcta. here we confirm the identity of sigma 54-dependent promoters previously hypothesized for the r ...19902193923
the nifh promoter region of rhizobium leguminosarum: nucleotide sequence and promoter elements controlling activation by nifa protein.the nucleotide (nt) sequence of the rhizobium leguminosarum nifh promoter region contains a consensus promoter, a consensus upstream activator sequence (uas), a pseudo (psi) promoter and a psi uas. we mapped the transcription start point for the consensus promoter sequence by primer extension. this promoter differs from the consensus in one of the four supposedly invariant nt and can be activated by the klebsiella pneumoniae nifa product in escherichia coli. under these conditions the psi promot ...19902185138
an fnr-like protein encoded in rhizobium leguminosarum biovar viciae shows structural and functional homology to rhizobium meliloti fixk.a 1.9 kb dna region of rhizobium leguminosarum biovar viciae strain vf39 capable of promoting microaerobic and symbiotic induction of the rhizobium meliloti fixn gene was identified by heterologous complementation. sequence analysis of this dna region revealed the presence of two complete open reading frames, orf240 and orf114. the deduced amino acid sequence of orf240 showed significant homology to escherichia coli fnr and r. meliloti fixk. the major difference between orf240 and fixk is the pr ...19902175385
differential expression of hydrogen uptake (hup) genes in vegetative and symbiotic cells of rhizobium leguminosarum.the genetic determinants responsible for h2-uptake (hup genes) in rhizobium leguminosarum are organized in six transcriptional units, designated regions hupi to hupvi, with region hupi coding for the hydrogenase structural genes (leyva et al. 1990). regulation of the expression of hup genes from r. leguminosarum was examined by using hup-lacz fusions and mrna dot-blot analysis. none of the six hup regions is transcribed in vegetative cells grown under normal aerobic conditions, whereas all six r ...19902166228
two plasmids other than the nodulation plasmid are necessary for formation of nitrogen-fixing nodules by rhizobium leguminosarum.a system which allows direct selection for curing of plasmids in gram-negative bacteria was used to generate derivatives of rhizobium leguminosarum vf39 cured of each of six plasmids present in this strain. phenotypes could be correlated with the absence of five of the six plasmids. the smallest plasmid, prlevf39a, carries genes for the production of a melanin-like pigment as has been previously reported. plasmid prlevf39d carries nodulation and nitrogen fixation genes. curing of the plasmids pr ...19902161988
two genes that regulate exopolysaccharide production in rhizobium sp. strain ngr234: dna sequences and resultant phenotypes.two closely linked genes involved in the regulation of exopolysaccharide (eps) production in rhizobium sp. strain ngr234, exox and exoy, were sequenced, and their corresponding phenotypes were investigated. inhibition of eps synthesis occurred in wild-type strains when extra copies of exox were introduced, but only when exoy had been deleted or mutated or was present at a lower copy number. normal eps synthesis occurred in rhizobium sp. when both exox and exoy were introduced on the same replico ...19902152899
identification of nods and nodu, two inducible genes inserted between the bradyrhizobium japonicum nodyabc and nodij genes.the so-called common nodulation (nod) gene cluster of bradyrhizobium japonicum is characterized by a unique composition of genes that are arranged in the following order: nody, noda, nodb, nodc, nods, nodu, nodi, nodj. as reported here, the identification of the two new genes nods and nodu resulted from the dna sequencing of a 4.5-kilobase nodc-downstream region covering nods, nodu, nodi, and nodj. the predicted nods, nodu, nodi, and nodj proteins had the following respective amino acid (aa) len ...19902134855
regulatory functions of the three nodd genes of rhizobium leguminosarum biovar phaseoli.the three nodd genes of a strain of rhizobium leguminosarum biovar phaseoli were cloned to study their effects on transcription of themselves and of the nodc genes of biovars phaseoli and viciae. efficient transcription of nodd1 required nodd1 and was enhanced by exposure of the cells to bean exudate consistent with the presence of a nod-box preceding the noie-nodd1 operon. transcription of nodd2 and nodd3 was constitutive. nodc of r. leguminosarum biovar phaseoli was activated by each of the no ...19902120543
excessive excretion of cyclic beta-(1,2)-glucan by rhizobium trifolii ta-1.at 25 degrees c, the optimal temperature for growth of rhizobium trifolii ta-1, extracellular and capsular polysaccharide (eps and cps) were the main carbohydrate products synthesized in mannitol-rich medium (10 g of mannitol and 1 g of glutamic acid per liter). in the same medium at 33 degrees c, eps and cps production was inhibited, and up to 3.9 g of cyclic beta-(1,2)-glucan was produced during an incubation period of 20 days with a total biomass of 0.55 g of protein. in a medium containing 5 ...19902117876
a new family of rsf1010-derived expression and lac-fusion broad-host-range vectors for gram-negative bacteria.a series of broad-host-range expression and lac fusion vectors, based on rsf1010 derivatives, was constructed. the expression vectors contain various promoters (pnm, plac, ptac and ps1) for expression of foreign genes. the efficiency of the promoters was determined in escherichia coli, rhizobium meliloti, rhizobium leguminosarum and pseudomonas putida by beta-galactosidase activity measurements. of the promoters assayed in e. coli, the most effective is the tac promoter, whereas in soil bacteria ...19902115488
nucleotide sequence of the hydrogenase structural genes from rhizobium leguminosarum. 19902103457
identification and cloning of nodulation genes and host specificity determinants of the broad host-range rhizobium leguminosarum biovar phaseoli strain ciat899.rhizobium leguminosarum biovar phaseoli type ii strain ciat899 nodulates a wide range of hosts: phaseolus vulgaris (beans), leucaena esculenta (leucaena) and macroptilium atropurpureum (siratro). a nodulation region from the symbiotic plasmid has been isolated and characterized. this region, which is contained in the overlapping cosmid clones pcv38 and pcv117, is able to induce nodules in beans, leucaena and siratro roots when introduced in strains cured for the symbiotic plasmid, psym. in addit ...19902082147
transcriptional analysis of the glnb-glna region of rhizobium leguminosarum biovar viciae.we report that the glnb and glna genes of rhizobium leguminosarum biovar viciae are preceded by promoters located upstream of each gene. we find the presence of a glnb-glna and a glna mrna whose intracellular concentration changes two- to three-fold when r. leguminosarum is grown on different nitrogen sources. primer extension analysis shows unique transcriptional initiation sites upstream of glnb and glna. the glnb promoter is rpon(ntra)-dependent, while the glna promoter does not contain a typ ...19902077357
distribution of o-acetyl groups in the exopolysaccharide synthesized by rhizobium leguminosarum strains is not determined by the sym plasmid.the patterns of o-acetylation of the exopolysaccharide (eps) from the sym plasmid-cured derivatives of rhizobium leguminosarum bv. trifolii strain lpr5, r. leguminosarum bv. trifolii strain anu843 and r. leguminosarum bv. viciae strain 248 were determined by 1h and 13c nmr spectroscopy. beside a site indicative of the chromosomal background, these strains have one site of o-acetylation in common, namely residue b of the repeating unit. the o-acetyl esterification pattern of eps of the sym plasmi ...19912033052
the degree of esterification and points of substitution by o-acetyl and o-(3-hydroxybutanoyl) groups in the acidic extracellular polysaccharides secreted by rhizobium leguminosarum biovars viciae, trifolii, and phaseoli are not related to host range.rhizobium leguminosarum biovars viciae, trifolii, and phaseoli have been grown in the presence and absence of 4',5,7-trihydroxyflavonone (naringenin) or 4',5,7-trihydroxyflavone (apigenin), which induce the expression of nodulation genes of the bacteria. the acidic polysaccharides secreted by the rhizobium were isolated from the culture media and purified. the polysaccharides were cleaved with a bacteriophage enzyme and the octasaccharide repeating units formed were isolated. the glycosyl sequen ...19912033051
isolation of the rhizobium leguminosarum nodf nodulation protein: nodf carries a 4'-phosphopantetheine prosthetic group.rhizobium species produce a protein product of the nodf gene that has a limited but recognizable homology to the well-characterized acyl carrier protein (acp) of escherichia coli. nodf functions together with node in generating a host-specific response to the plant host in the interchange of signals leading to the effective nodulation of roots (h.p. spaink, j. weinman, m.a. djordjevic, c.a. wijffelman, r.j.h. okker, and b. j.j. lugtenberg, embo j. 8:2811-2818, 1989; b. scheres, c. van de wiel, a ...19912019559
genetic and physical analysis of the nodd3 region of rhizobium meliloti.the nodulation (nod) genes of the symbiont rhizobium meliloti are transcriptionally controlled by protein activators in the nodd gene family. while nodd1 and nodd2 act in concert with small molecular weight inducers provided by the host legume plant, nodd3 is an inducer-independent activator of the nod promoters. we determined the sequence of the nodd3 gene, confirmed the expression of a 35 kda protein in vitro, and determined the insertion points of five tn5 insertions in the region of the nodd ...19912017373
partial deletion of the rhizobium phaseoli cfn23 symbiotic plasmid implies a concomitant amplification of plasmid dna sequences.rhizobium leguminosarum biovar phaseoli cfn23 loses its ability to nodulate beans at a high frequency because of a deletion of part of its symbiotic (psym) plasmid (soberón-chávez et al., 1986). we report here that at least 80 kb of psym are deleted upon loss of the symbiotic phenotype; the deletion removes the nitrogenase structural nifhdk and the common nodabc genes. the size of the deleted psym is not reduced, since it is accompanied by an amplification of other psym plasmid sequences. this g ...19912014006
structural complexity of the symbiotic plasmid of rhizobium leguminosarum bv. phaseoli.the complete physical map of the symbiotic plasmid of rhizobium leguminosarum bv. phaseoli strain cfn42 was established. the data support the concept that rhizobium symbiotic genes are part of a complex genomic structure which contains a large amount of reiterated dna sequences. this plasmid is a circular structure of 390 kb with approximately 10 families of internally reiterated dna sequences of two to three elements each. one family includes two directly oriented nitrogenase operons situated 1 ...19912013564
construction of a mobilizable cloning vector for site-directed mutagenesis of gram-negative bacteria: application to rhizobium leguminosarum.a mobilizable cloning vector was constructed from defined fragments to serve as a suicide plasmid for site-directed mutagenesis. the new vector, pkok4, closely resembles plasmid pbr325. however, the inverted duplication existing in the latter was not introduced. the useful cloning sites of pbr325 (ecori, hindiii, ecorv, bamhi, sali, psti and pvui) were retained and are located in one of the three resistance markers, apr, cmr or tcr, respectively. also, in pkok4 the cmr gene retains its own promo ...19912013412
occurrence of lipid a variants with 27-hydroxyoctacosanoic acid in lipopolysaccharides from members of the family rhizobiaceae.lipopolysaccharides (lpss) isolated from several strains of rhizobium, bradyrhizobium, agrobacterium, and azorhizobium were screened for the presence of 27-hydroxyoctacosanoic acid. the lpss from all strains, with the exception of azorhizobium caulinodans, contained various amounts of this long-chain hydroxy fatty acid in the lipid a fractions. analysis of the lipid a sugars revealed three types of backbones: those containing glucosamine (as found in rhizobium meliloti and rhizobium fredii), tho ...19912007543
high-frequency rearrangements in rhizobium leguminosarum bv. phaseoli plasmids.high-frequency genomic rearrangements affecting the plasmids of rhizobium leguminosarum bv. phaseoli cfn42 were analyzed. this strain contains six large plasmids ranging in size from 200 to 600 kb. in the absence of any selective pressure, we found 11 strains from 320 analyzed colonies that presented different kinds of plasmid-borne rearrangements, including sequence amplification, deletion, cointegration, and loss of plasmids. these data support the concept that the r. leguminosarum bv. phaseol ...19911991727
novel organization of the common nodulation genes in rhizobium leguminosarum bv. phaseoli strains.nodulation by rhizobium, bradyrhizobium, and azorhizobium species in the roots of legumes and nonlegumes requires the proper expression of plant genes and of both common and specific bacterial nodulation genes. the common nodabc genes form an operon or are physically mapped together in all species studied thus far. rhizobium leguminosarum bv. phaseoli strains are classified in two groups. the type i group has reiterated nifhdk genes and a narrow host range of nodulation. the type ii group has a ...19911991718
a previously unrecognized glutamine synthetase expressed in klebsiella pneumoniae from the glnt locus of rhizobium leguminosarum.using glnt dna of rhizobium meliloti as a hybridization probe we identified a r. leguminosarum biovar phaseoli (r. l. phaseoli) locus (glnt) expressing a glutamine synthetase activity in klebsiella pneumoniae. a 2.2 kb dna fragment from r. l. phaseoli was cloned to give plasmid pmw5a, which shows interspecific complementation of a k. pneumoniae glna mutant. the cloned sequence did not show cross-hybridization to glna or glnii, the genes coding for two glutamine synthetase isozymes of rhizobium s ...19901980142
a novel highly unsaturated fatty acid moiety of lipo-oligosaccharide signals determines host specificity of rhizobium.in rhizobium leguminosarum biovar viciae, the nodabc and nodfel operons are involved in the production of lipo-oligosaccharide signals which mediate host specificity. the structure of these metabolites and those produced in nod mutants links the node and nodl genes to specific chemical features of the signal molecules. a node-determined, highly unsaturated fatty acid and a nodl-determined o-acetyl substituent are essential for the ability of the signals to induce nodule meristems on the host pla ...19911944592
six nodulation genes of nod box locus 4 in rhizobium meliloti are involved in nodulation signal production: nodm codes for d-glucosamine synthetase.the nucleotide sequence of the nod box locus n4 in rhizobium meliloti was determined and revealed six genes organized in a single transcriptional unit, which are induced in response to a plant signal such as luteolin. mutations in these genes influence the early steps of nodule development on medicago, but have no detectable effect on melilotus, another host for r. meliloti. based on sequence homology, the first open reading frame (orf) corresponds to the nodm gene and the last to the nodn gene ...19911909418
characterization of reca genes and reca mutants of rhizobium meliloti and rhizobium leguminosarum biovar viciae.dna fragments carrying the reca genes of rhizobium meliloti and rhizobium leguminosarum biovar viciae were isolated by complementing a uv-sensitive reca- escherichia coli strain. sequence analysis revealed that the coding region of the r. meliloti reca gene consists of 1044 bp coding for 348 amino acids whereas the coding region of the r. leguminosarum bv. viciae reca gene has 1053 bp specifying 351 amino acids. the r. meliloti and r. leguminosarum bv. viciae reca genes show 84.8% homology at th ...19911896024
regulation of phenolic catabolism in rhizobium leguminosarum biovar trifolii.in members of the family rhizobiaceae, many phenolic compounds are degraded by the protocatechuate branch of the beta-ketoadipate pathway. in this paper we describe a novel pattern of induction of protocatechuate (pca) genes in rhizobium leguminosarum biovar trifolii. isolation of pca mutant strains revealed that 4-hydroxybenzoate, quinate, and 4-coumarate are degraded via the protocatechuate pathway. at least three inducers govern catabolism of 4-hydroxybenzoate to succinyl coenzyme a and acety ...19911885531
rhizobium lipopolysaccharide modulates infection thread development in white clover root hairs.the interaction between rhizobium lipopolysaccharide (lps) and white clover roots was examined. the limulus lysate assay indicated that rhizobium leguminosarum bv. trifolii (hereafter called r. trifolii) released lps into the external root environment of slide cultures. immunofluorescence and immunoelectron microscopy showed that purified lps from r. trifolii 0403 bound rapidly to root hair tips and infiltrated across the root hair wall. infection thread formation in root hairs was promoted by p ...19911885517
nodt, a positively-acting cultivar specificity determinant controlling nodulation of trifolium subterraneum by rhizobium leguminosarum biovar trifolii.rhizobium leguminosarum biovar trifolii strain ta1 nodulates a range of trifolium plants including red, white and subterranean clovers. nitrogen-fixing nodules are promptly initiated on the tap roots of these plants at the site of inoculation. in contrast to these associations, strain ta1 has a 'nod-' phenotype on a particular cultivar of subterranean clover called woogenellup (a.h. gibson, aust j agric sci 19: (1968) 907-918) where it induces rare, poorly developed, slow-to-appear and ineffecti ...19911868196
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