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siderophore and organic acid production in root nodule bacteria.nineteen strains of root nodule bacteria were grown under various iron regimes (0.1, 1.0 and 20 microm added iron) and tested for catechol and hydroxamate siderophore production and the excretion of malate and citrate. the growth response of the strains to iron differed markedly. for 12 strains (bradyrhizobium strains nc92b and 32h1, b. japonicum usda110 and cb1809, b. lupini wu8, cowpea rhizobium ngr234, rhizobium meliloti strains u45 and cc169, rhizobium leguminosarum bv viciae wu235 and rhizo ...19921387306
characterisation of rhizobium isolates by amplification of dna polymorphisms using random primers.the use of single random primers, selected in the absence of target sequence information, has been shown to be effective in producing dna amplifications that provide fingerprints which are unique to individual organisms. dna amplification by random priming was applied to the dna from isolates of rhizobium leguminosarum biovar trifolii. amplification products were produced using a number of primers, and the resulting fingerprints allowed strain differentiation. however, the effectiveness of prime ...19921477784
characterization of an aromatic amino acid aminotransferase from rhizobium leguminosarum biovar trifolii.the most abundant aromatic amino acid aminotransferase of rhizobium leguminosarum biovar trifolii was partially purified. the molecular mass of the enzyme was estimated to be 53 kda by gel filtration. the enzyme transaminated aromatic amino acids and histidine. it used aromatic keto acids and alpha-ketoglutaric and oxalacetic acids as amino-group acceptors. the optimum temperature was 35 degrees c. using phenylalanine and alpha-ketoglutaric acid as substrates the activation energy was 46.2 kj.mo ...19921520732
production and epitope analysis of monoclonal antibodies against a rhizobium leguminosarum biovar trifolii strain.heat-treated cells of rhizobium leguminosarum biovar trifolii strain 162x95 were used to produce monoclonal antibodies (mabs). the fusion produced three cross-reactive mabs and eight mabs specific for the immunizing strain and a group of five other r. trifolii strains from the same geographic region where 162x95 was isolated (california). seven mabs were analyzed by competitive enzyme-linked immunosorbent assay to determine the number of different epitopes detectable on strain 162x95. the result ...19901697150
identification of a nifa-like regulatory gene of azospirillum brasilense sp7 expressed under conditions of nitrogen fixation and in the presence of air and ammonia.a gene bank of azospirillum lipoferum br17 constructed in the vector lambda gem11 was screened with a bradyrhizobium japonicum nifa gene probe. a 7.3 kb ecori fragment carrying a nifa-like gene was thereby isolated and subsequently used to screen a gene bank of azospirillum brasilense sp7 constructed in puc18. two ecori fragments of 5.6 kb and 3.6 kb covering the nifa-homology region were found. mutants with nif- phenotype were obtained by site-directed tn5 mutagenesis of the 5.6 kb fragment and ...19911779763
the 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
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
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
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
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
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
the region for exopolysaccharide synthesis in rhizobium leguminosarum biovar trifolii is located on the non-symbiotic plasmid.an exo- mutant of rhizobium leguminosarum biovar trifolii was isolated which did not produce acidic exopolysaccharide and induced defective, non-fixing nodules on clover plants. the nodules were defective at a late stage of development, they contained infection threads and bacteria were released into the host cells. cosmid parf136 capable of complementing the exo- mutation was isolated from a cosmid bank made from total r. trifolii dna. hybridization between dna of parf136 and plasmids of r. tri ...19911814135
a cultivar-specific interaction between rhizobium leguminosarum bv. trifolii and subterranean clover is controlled by nodm, other bacterial cultivar specificity genes, and a single recessive host gene.insertion mutagenesis identified two negatively acting gene loci which restrict the ability of rhizobium leguminosarum bv. trifolii ta1 to infect the homologous host trifolium subterraneum cv. woogenellup. one locus was confirmed by dna sequence analysis as the nodm gene, while the other locus, designated csn-1 (cultivar-specific nodulation), is not located on the symbiosis plasmid. the presence of these cultivar specificity loci could be suppressed by the introduction of the nodt gene from anu8 ...19911673458
phylogenetic relationships among rhizobium species nodulating the common bean (phaseolus vulgaris l.).the phylogenetic relationships among rhizobium species that nodulate phaseolus vulgaris (common bean) were determined by directly sequencing the amplified 16s ribosomal dna genes of these organisms. the bean strains formed four separate clusters. one cluster was composed of rhizobium leguminosarum bv. trifolii, r. leguminosarum bv. viciae, and r. leguminosarum bv. phaseoli. two other clusters comprised rhizobium etli and rhizobium tropici, and the fourth cluster contained a single bean-nodulatin ...19968573502
combined subtraction hybridization and polymerase chain reaction amplification procedure for isolation of strain-specific rhizobium dna sequences.a novel subtraction hybridization procedure, incorporating a combination of four separation strategies, was developed to isolate unique dna sequences from a strain of rhizobium leguminosarum bv. trifolii. sau3a-digested dna from this strain, i.e., the probe strain, was ligated to a linker and hybridized in solution with an excess of pooled subtracter dna from seven other strains of the same biovar which had been restricted, ligated to a different, biotinylated, subtracter-specific linker, and am ...19921637166
cell-associated pectinolytic and cellulolytic enzymes in rhizobium leguminosarum biovar trifolii.the involvement of rhizobium enzymes that degrade plant cell wall polymers has long been an unresolved question about the infection process in root nodule symbiosis. here we report the production of enzymes from rhizobium leguminosarum bv. trifolii that degrade carboxymethyl cellulose and polypectate model substrates with sensitive methods that reliably detect the enzyme activities: a double-layer plate assay, quantitation of reducing sugars with a bicinchoninate reagent, and activity gel electr ...19921622257
slow rehydration improves the recovery of dried bacterial populations.slow rehydration of bacteria from dried inoculant formulations provided higher viable counts than did rapid rehydration. estimates were higher when clay and peat powder formulations of rhizobium meliloti, rhizobium leguminosarum biovar trifolii, and pseudomonas putida, with water activities between 0.280 and 0.650, were slowly rehydrated to water activities of approximately 0.992 before continuing the dilution plating sequence. rhizobium meliloti populations averaged 6.8 x 10(8) cfu/g and 1328 c ...19921504917
evaluation of acidic heteropolysaccharide structures in rhizobium leguminosarum biovars altered in nodulation genes and host range.1h-nmr spectroscopy showed that the extracellular heterpolysaccharides (eps) from derivatives of rhizobium leguminosarum bv. trifolii anu843 altered in psym nod composition or function (transposon insertions, deletion of psym, induction by flavone, and introduction of cloned psym nod regions from anu843 and r. l. bv. viciae 248 on recombinant plasmids into the psym-cured background of anu843) differed only in 3-hydroxybutyrate stoichiometry per octaglycosyl unit. this change in eps was likely to ...19921477403
exopolysaccharides of rhizobium leguminosarum biovar trifolii harbouring cloned exo region.rhizobium leguminosarum bv. trifolii produces an acidic exopolysaccharide (eps) which plays an important role in the development of nitrogen-fixing nodules. tn5 mutant of r. trifolii 93 defective in eps production (exo-) forms ineffective (fix-) nodules on red clover. this exo- mutation is complemented by the parf1368 and parf25 cosmids isolated from gene bank of rhizobium trifolii ta1, but the complementation is not correlated with restoration of fix+ phenotype. furthermore, these cosmids intro ...19921441845
synthesis of cyclic beta-(1,2)-glucans by rhizobium leguminosarum biovar trifolii ta-1: factors influencing excretion.the synthesis of cyclic beta-(1,2)-glucans from udp-[14c]glucose by a crude membrane preparation and whole cells of rhizobium leguminosarum bv. trifolii ta-1 was investigated. the crude membrane system needed mn2+, atp, and nad+ for optimal activity. hardly any difference in biosynthetic activity between membrane fractions of ta-1 cells grown in the presence (200 mm) or absence of nacl was observed. whole ta-1 cells grown in the presence of nacl excreted labeled, neutral cyclic beta-(1,2)-glucan ...19921400186
rhizobium inoculation and physical wounding result in the rapid induction of the same chalcone synthase copy in trifolium subterraneum.the gene or genes encoding chalcone synthase (chs) in the legume trifolium subterraneum (subterranean clover) were induced within 6 hr after inoculation with rhizobium leguminosarum bv. trifolii strain anu843. no induction was found in uninoculated controls or plants inoculated with either the nodulation-deficient r. l. bv. trifolii strain anu845 (psym-) or r. meliloti strain 1021, which is capable of nodulating alfalfa but not clover. morphological examination of the interaction between the leg ...19948075422
flavone-enhanced accumulation and symbiosis-related biological activity of a diglycosyl diacylglycerol membrane glycolipid from rhizobium leguminosarum biovar trifolii.rhizobium leguminosarum bv. trifolii is the bacterial symbiont which induces nitrogen-fixing root nodules on the leguminous host, white clover (trifolium repens l.). in this plant-microbe interaction, the host plant excretes a flavone, 4',7-dihydroxyflavone (dhf), which activates expression of modulation genes, enabling the bacterial symbiont to elicit various symbiosis-related morphological changes in its roots. we have investigated the accumulation of a diglycosyl diacylglycerol (bf-7) in wild ...19948021221
the adaptive acid tolerance response in root nodule bacteria and escherichia coli.root nodule bacteria and escherichia coli show an adaptive acid tolerance response when grown under mildly acidic conditions. this is defined in terms of the rate of cell death upon exposure to acid shock at ph 3.0 and expressed in terms of a decimal reduction time, d. the d values varied with the strain and the ph of the culture medium. early exponential phase cells of three strains of rhizobium leguminosarum (wu95, 3001 and wsm710) had d values of 1, 6 and 5 min respectively when grown at ph 7 ...19948002711
development of an acute and chronic ecotoxicity assay using lux-marked rhizobium leguminosarum biovar trifolii.a soil isolate of rhizobium leguminosarum bv. trifolii was marked with a lux cdabe gene cassette to enable the expression of bioluminescence. the suitability of the bacterium as a soil pollution biosensor was assessed using acute and chronic assays. bacterial bioluminescence responded sensitively to the metals studied. the order of sensitivity was found to be cd > ni = zn > cu for the acute test and cd > ni = zn = cu for the chronic test. the sensitive response of the biosensor highlighted its p ...19979134778
expression of the symbiotic plasmid from rhizobium leguminosarum biovar trifolii in sphingobacterium multivorum.an inoculant strain of rhizobium leguminosarum biovar trifolii containing a tn5 marked symbiotic plasmid transferred this plasmid by conjugation to sphingobacterium multivorum, an organism that can be found in soil. the transconjugant bacteria nodulated the roots of white clover (trifolium repens) seedlings but did not fix atmospheric nitrogen. microscopic examination revealed abnormal nodule structures. bacteria isolated from the nodules were shown to be closely related to the recipient s. mult ...19948000966
structurally diverse chitolipooligosaccharide nod factors accumulate primarily in membranes of wild type rhizobium leguminosarum biovar trifolii.the general view on rhizobium chitolipooligosaccharides (clos) is that they are made in very low levels as diffusible molecules and are primarily secreted by the bacteria into the extracellular milieu where they interact with the host. however, the structural and predicted physicochemical properties of these amphiphilic molecules led us to postulate that they should normally be targeted to bacterial membranes after synthesis. thus, we analyzed membrane lipid extracts of rhizobium leguminosarum b ...19957893680
oxygen sensitivity and metal ion-dependent transcriptional activation by nifa protein from rhizobium leguminosarum biovar trifolii.the nifa protein from rhizobium leguminosarum biovar trifolii (r. trifolii) strain anu843 lacks an n-terminal domain present in homologous nifa proteins from other diazotrophs. the r. trifolii nifa gene product is unstable when expressed in escherichia coli under both aerobic and microaerobic conditions. stability is increased by fusion of additional amino acids to the n-terminus of the protein or by expression of nifa in sno mutant (presumed protease deficient) strains of e. coli. transcription ...19947816041
long-term effects of metals in sewage sludge on soils, microorganisms and plants.this paper reviews the evidence for impacts of metals on the growth of selected plants and on the effects of metals on soil microbial activity and soil fertility in the long-term. less is known about adverse long-term effects of metals on soil microorganisms than on crop yields and metal uptake. this is not surprising, since the effects of metals added to soils in sewage sludge are difficult to assess, and few long-term experiments exist. controlled field experiments with sewage sludges exist in ...19957766215
mutation or increased copy number of node has no effect on the spectrum of chitolipooligosaccharide nod factors made by rhizobium leguminosarum bv. trifolii.the bacterial gene node is the key determinant of host specificity in the rhizobium leguminosarum-legume symbiosis and has been proposed to determined unique polyunsaturated fatty acyl moieties in chitolipooligosaccharides (clos) made by the bacterial symbiont. we evaluated node function by examining clos structures made by wild-type r. leguminosarum bv. trifolii anu843, an isogenic node::tn5 mutant, and a recombinant strain containing multiple copies of the psym nod region of anu843. 1h-nmr, el ...19957673121
supraoperonic clustering of pca genes for catabolism of the phenolic compound protocatechuate in agrobacterium tumefaciens.the protocatechuate branch of the beta-ketoadipate pathway comprises the last six enzymatic steps in the catabolism of diverse phenolic compounds to citric acid cycle intermediates. in this paper, the regulation and tight supraoperonic clustering of the protocatechuate (pca) genes from agrobacterium tumefaciens a348 are elucidated. a previous study found that the pcad gene is controlled by an adjacent regulatory gene, pcaq, which encodes an activator. the activator responded to beta-carboxy-cis, ...19957601847
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
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
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
influence of growth conditions on production of capsular and extracellular polysaccharides by rhizobium leguminosarum.the influence of growth rate and medium composition on exopolymer production by rhizobium leguminosarum was studied. when grown in medium containing 10 g/l mannitol and 1 g/l glutamic acid, rhizobium leguminosarum biovar trifolii ta-1 synthesized up to 2.0 g/l of extracellular polysaccharide (eps), and up to 1.6 g/l of capsular polysaccharide (cps). under non-growing cell conditions in medium without glutamic acid, cps synthesis by strain ta-1 could proceed to 2.1 g/l, while eps-production remai ...19938273998
phospholipid and fatty acid compositions of rhizobium leguminosarum biovar trifolii anu843 in relation to flavone-activated psym nod gene expression.the phospholipid and associated fatty acid compositions of the bacterial symbiont of clover, rhizobium leguminosarum biovar trifolii wild-type anu843, was analyzed by two-dimensional silica thin-layer chromatography, fast atom bombardment-mass spectrometry, flame-ionization detection gas-liquid chromatography and combined gas-liquid chromatography/mass spectrometry. the phospholipid composition included phosphatidylethanolamine (15%), n-methylphosphatidylethanolamine (47%), n,n-dimethylphosphati ...19938277828
methoxylated fatty acids reported in rhizobium isolates arise from chemical alterations of common fatty acids upon acid-catalyzed transesterification procedures.we obtained from a phospholipid extract of wild-type rhizobium leguminosarum bv. trifolii anu843 methoxylated fatty acids that had been previously reported as constitutive unusual rhizobium fatty acids. the use of deuterated reagents and subsequent gas-liquid chromatography-mass spectrometry analyses showed that these methoxylated fatty acid derivatives are the products of chemical alterations of common cyclopropane-containing and unsaturated fatty acids occurring during various acid-catalyzed t ...19938335647
characterization and symbiotic importance of acidic extracellular polysaccharides of rhizobium sp. strain grh2 isolated from acacia nodules.rhizobium sp. wild-type strain grh2 was originally isolated from root nodules of the leguminous tree acacia cyanophylla and has a broad host range which includes herbaceous legumes, e.g., trifolium spp. we examined the extracellular exopolysaccharides (epss) produced by strain grh2 and found three independent glycosidic structures: a high-molecular-weight acidic heteropolysaccharide which is very similar to the acidic eps produced by rhizobium leguminosarum biovar trifolii anu843, a low-molecula ...19938491702
cloning, sequencing, and characterization of the cgmb gene of sinorhizobium meliloti involved in cyclic beta-glucan biosynthesis.periplasmic cyclic beta-glucans of rhizobium species provide important functions during plant infection and hypo-osmotic adaptation. in sinorhizobium meliloti (also known as rhizobium meliloti), these molecules are highly modified with phosphoglycerol and succinyl substituents. we have previously identified an s. meliloti tn5 insertion mutant, s9, which is specifically impaired in its ability to transfer phosphoglycerol substituents to the cyclic beta-glucan backbone (m. w. breedveld, j. a. hadl ...199910419956
positive regulation of phenolic catabolism in agrobacterium tumefaciens by the pcaq gene in response to beta-carboxy-cis,cis-muconate.an escherichia coli system for generating a commercially unavailable catabolite in vivo was developed and was used to facilitate molecular genetic studies of phenolic catabolism. introduction of the plasmid-borne acinetobacter pcahg genes, encoding the 3,4-dioxygenase which acts on protocatechuate, into e. coli resulted in bioconversion of exogenously supplied protocatechuate into beta-carboxy-cis,cis-muconate. this compound has been shown to be an inducer of the protocatechuate (pca) genes requ ...19938501056
dna sequence and mutational analysis of genes involved in the production and resistance of the antibiotic peptide trifolitoxin.the 7.1-kb fragment of rhizobium leguminosarum bv. trifolii t24 dna which confers trifolitoxin production and resistance to nonproducing, sensitive rhizobium strains (e. w. triplett, m. j. schink, and k. l. noeldner, mol. plant-microbe interact. 2:202-208, 1989) was subcloned, sequenced, and mutagenized with a transcriptional fusion cassette. the sequence of this fragment revealed seven complete open reading frames, tfxabcdefg, all transcribed in the same direction. tfxa has an 11-amino-acid car ...19938509324
modulation of development, growth dynamics, wall crystallinity, and infection sites in white clover root hairs by membrane chitolipooligosaccharides from rhizobium leguminosarum biovar trifolii.we used bright-field, time-lapse video, cross-polarized, phase-contrast, and fluorescence microscopies to examine the influence of isolated chitolipooligosaccharides (closs) from wild-type rhizobium leguminosarum bv. trifolii on development of white clover root hairs, and the role of these bioactive glycolipids in primary host infection. clos action caused a threefold increase in the differentiation of root epidermal cells into root hairs. at maturity, root hairs were significantly longer becaus ...19968655563
survival and nodulating ability of indigenous and inoculated rhizobium leguminosarum biovar trifolii in sterilized and unsterilized soil treated with sewage sludge.rhizobium leguminosarum biovar trifolii was detected in soil from 41 of 47 plots, within nine sewage sludge-treated sites with different soil characteristics and heavy metal contents. however, although population size varied widely, there was no consistent correlation with soil heavy metal concentration. indigenous populations in 20 plots within four selected sites retained their ability to induce effective nodule formation after incubation of soil in the dark for 165 days. in sterilized (gamma- ...200111116399
a hierarchical analysis of population genetic structure in rhizobium leguminosarum bv. trifolii.little is known about the population processes that shape the genetic diversity in natural populations of rhizobia. a sample of 912 rhizobium leguminosarum biovar trifolii isolates were collected from naturalized red clover populations (trifolium pratense) and analysed for 15 allozyme loci to determine the levels and distribution of genetic diversity. hierarchical analyses compared different sampling levels, geographical separation, and temporal separation. total genetic diversity across all iso ...19968673267
a newly discovered gene, tfua, involved in the production of the ribosomally synthesized peptide antibiotic trifolitoxin.trifolitoxin (tfx) is a gene-encoded, posttranslationally modified peptide antibiotic. previously, we have shown that tfxabcdefg from rhizobium leguminosarum bv. trifolii t24 is sufficient to confer tfx production and resistance to nonproducing strains within a distinct taxonomic group of the alpha-proteobacteria (e. w. triplett, b. t. breil, and g. a. splitter, appl. environ. microbiol. 60:4163-4166, 1994). here we describe strain tn5-2, a tn5 mutant of t24 defective in the production of tfx, w ...19968763943
rhizobium leguminosarum bv. trifolii produces lipo-chitin oligosaccharides with node-dependent highly unsaturated fatty acyl moieties. an electrospray ionization and collision-induced dissociation tandem mass spectrometric study.the lipo-chitin oligosaccharides (lco) or nodulation factors synthesized by rhizobium leguminosarum bv. trifolii were analyzed using positive mode fast atom bombardment and positive and negative mode electrospray ionization mass spectrometry. from their mass spectrometric behavior it is clearly possible to distinguish between the [m + na]+ pseudomolecular ion of the node-independent molecule iv(c18:1,ac) and the [m + h]+ pseudomolecular ion of the node-dependent molecule iv(c20:4,ac), although t ...19968798424
deletion analysis of the 5' untranslated region of the rhizobium meliloti nodf gene.efficient establishment of the symbiosis between rhizobia and their host plants requires precise regulation of bacterial nod genes. the nod gene transcripts in rhizobium meliloti have approximately 200 nucleotides of untranslated sequence 5' of the start codon (5' utr). we measured the significance of this region by constructing fusions between deletion derivatives of nodf and the reporter beta-glucuronidase (gus). flavonoid-inducible expression of the fusions in r. meliloti was evident when ext ...19968969536
cloning and characterization of four genes of rhizobium leguminosarum bv. trifolii involved in exopolysaccharide production and nodulation.four different genes of rhizobium leguminosarum bv. trifolii strain rbl5599 involved in exopolysaccharide (eps) production were identified by complementation of tn5-induced eps-deficient mutants (exo mutants) with a cosmid bank. on one cosmid pssa was located, which was found to be almost identical to the pss4 gene from r. leguminosarum bv. viciae vf39 and highly homologous to a family of glycosyl transferases. two pssa mutants, exo2 and exo4, were characterized and found to produce 19 and 1% of ...19979057334
direct amplification of nodd from community dna reveals the genetic diversity of rhizobium leguminosarum in soil.sequences of nodd, a gene found only in rhizobia, were amplified from total community dna isolated from a pasture soil. the polymerase chain reaction (pcr) primers used, y5 and y6, match nodd from rhizobium leguminosarum biovar trifolii, r. leguminosarum biovar viciae and sinorhizobium meliloti. the pcr product was cloned and yielded 68 clones that were identified by restriction pattern as derived from biovar trifolii [11 restriction fragment length polymorphism (rflp) types] and 15 clones ident ...200111472501
identification of genes in rhizobium leguminosarum bv. trifolii whose products are homologues to a family of atp-binding proteins.the specific interaction between rhizobia and their hosts requires many genes that influence both early and late steps in symbiosis. three new genes, designated prsd, prse (protein secretion) and orf3, were identified adjacent to the exo133 mutation in a cosmid carrying the genomic dna of rhizobium leguminosarum bv. trifolii ta1. the prsde genes share significant homology to the genes encoding abc transporter proteins prtde from erwinia chrysanthemi and aprde from pseudomonas aeruginosa which ex ...19979141701
root colonization of different plants by plant-growth-promoting rhizobium leguminosarum bv. trifolii r39 studied with monospecific polyclonal antisera.monospecific polyclonal antisera raised against rhizobium leguminosarum bv. trifolii r39, a bacterium which was isolated originally from red clover nodules, were used to study the colonization of roots of leguminous and nonleguminous plants (pisum sativum, lupinus albus, triticúm aestivum, and zea mays) after inoculation. eight weeks after inoculation of soil-grown plants, between 0.1 and 1% of the total bacterial population in the rhizospheres of all inoculated plants were identified as r. legu ...19979143133
structure and role in symbiosis of the exob gene of rhizobium leguminosarum bv trifolii.the rhizobium leguminosarum bv trifolii exob gene has been isolated by heterologous complementation of an exob mutant of r. meliloti. we have cloned a chromosomal dna fragment from the r. leguminosarum bv trifolii genome that contains an open reading frame of 981 bp showing 80% identity at the amino acid level to the udp-glucose 4-epimerase of r. meliloti. this enzyme produces udp-galactose, the donor of galactosyl residues for the lipid-linked oligosaccharide repeat units of various heteropolys ...19979236769
a rhizobium leguminosarum biovar trifolii locus not localized on the sym plasmid hinders effective nodulation on plants of the pea cross-inoculation group.introduction of the sym plasmid prl1ji into the cured rhizobium leguminosarum bv. trifolii strain rcr5 resulted in a strain, designated rbl5523, that was expected to nodulate plants of the pea cross-inoculation group. however, effective nodulation occurred only on vicia sativa plants, not on v. hirsuta or pisum sativum. after random tn5 mutagenesis, a derivative of rbl5523 was isolated that effectively nodulated and fixed nitrogen on p. sativum and v. hirsuta. characterization of the mutant, rbl ...19979304865
sequence and phylogenetic analysis of the rhizobium leguminosarum biovar trifolii pyre gene, overproduction, purification and characterization of orotate phosphoribosyltransferase.the pyre gene of rhizobium leguminosarum biovar trifolii (rl) was subcloned and its sequence is presented. the nucleotide sequence analysis suggests that this gene is not regulated by transcriptional attenuation as seen for the pyre and pyrb genes of escherichia coli (ec) and salmonella typhimurium. the rl pyre gene was subcloned into ec at2538 pyre60 where the rl pyre gene product, orotate phosphoribosyltransferase (oprtase), was overproduced. using ec at2538 pyre60 overproducing rl oprtase, th ...19979305779
synthesis of the unique trisaccharide repeating unit, isolated from lipopolysaccharides rhizobium leguminosarum bv. trifolii 24, and its analogue.the synthesis of trisaccharide: 6-d-alpha-l-talp(1-->2)-alpha-l-rhap(1-->5)-dha, and its analogue: 6-d-alpha-l-talp(1-->2)-beta-l-rhaf(1-->5)dha is described. in the first step a disaccharide, composed of 6-d-l-talp and l-rhap was obtained. this, in turn, was converted to the corresponding 1-trichloroacetimidate and coupled with dha alcohol to afford the required trisaccharide. its analogue was achieved by the conversion of the above disaccharide to the glycosyl bromide, involving the rhamnopyra ...19989648246
determination of plasmid-encoded functions in rhizobium leguminosarum biovar trifolii using proteome analysis of plasmid-cured derivatives.we have used proteome analysis of derivatives of r. leguminosarum biovar trifolii strain anu843, cured of indigenous plasmids by a direct selection system, to investigate plasmid-encoded functions. under the conditions used, the plasmid-encoded gene products contributed to only a small proportion of the 2000 proteins visualised in the two-dimensional (2-d) protein map of strain anu843. the level of synthesis of thirty-nine proteins was affected after curing of either plasmid a, c or e. the diffe ...19989740057
molecular characterization of psscde genes of rhizobium leguminosarum bv. trifolii strain ta1: pssd mutant is affected in exopolysaccharide synthesis and endocytosis of bacteria.we have identified the three genes psscde in rhizobium leguminosarum bv. trifolii ta1. even though they were almost identical to earlier identified psscde genes of r. leguminosarum, they differed in gene lengths and gene overlaps. the predicted gene products of psscde genes shared significant homology to prokaryotic glycosyl transferases involved in exopolysaccharide synthesis. the tn5 insertion in pssd created the nonmucoid mutant that induced non-nitrogen-fixing nodules. the microscopic analys ...19989805402
feasibility of using prokaryote biosensors to assess acute toxicity of polycyclic aromatic hydrocarbons.the aim of this study was to assess the acute toxicity of polycyclic aromatic hydrocarbons using lux-marked bacterial biosensors. standard solutions of phenanthrene, pyrene and benzo[a]pyrene were produced using 50 mm hydroxpropyl-beta-cyclodextrin solution which contained each respective polycyclic aromatic hydrocarbon at 6.25 times the aqueous solubility limit of the compound. the polycyclic aromatic hydrocarbon solutions were incubated with each of the biosensors for 280 min and the biolumine ...19989868766
cloning and characterization of edwardsiella ictaluri proteins expressed and recognized by the channel catfish ictalurus punctatus immune response during infection.an edwardsiella ictaluri expression library was screened for clones expressing antigenic e. ictaluri proteins using anti-e. ictaluri serum, which resulted in the isolation of 32 clones. the clones were partially characterized and 4 were selected for complete analysis. sodium dodecyl sulfate polyacrylamide gel electrophoresis (sds-page), 2-dimensional page, western blotting, and dna sequencing were used to analyze expressed antigenic proteins and encoded genes. sequence analysis identified 4 puta ...200212542086
the pssb gene product of rhizobium leguminosarum bv. trifolii is homologous to a family of inositol monophosphatases.the rhizobium leguminosarum bv. trifolii region encoding pssa and pssb genes was cloned. the pssb gene located upstream of the pssa encoded a 28.36-kda protein which displayed 97.5% identity with the pssb of r. leguminosarum bv. viciae. inactivation of the pssb gene by insertion of the lacz-gmr cassette resulted in the significant increased production of exopolysaccharide in comparison to the wild-type level. a mutant strain was also defective in nitrogen fixation suggesting a regulatory role of ...199910227162
structural and putative regulatory genes involved in cellulose synthesis in rhizobium leguminosarum bv. trifolii.six genes involved in cellulose synthesis in rhizobium leguminosarum bv. trifolii were identified using tn5 mutagenesis. four of them displayed homology to the previously cloned and sequenced agrobacterium tumefaciens cellulose genes cela, celb, celc and cele. these genes are organized similarly in r. leguminosarum bv. trifolii. in addition, there were strong indications that two tandemly located genes, celr1 and celr2, probably organized as one operon, are involved in the regulation of cellulos ...199910376842
occurrence of lipopolysaccharide alterations among tn5 mutants of rhizobium leguminosarum bv. trifolii strain 24.1 with altered colony morphology.transposon mutants of rhizobium leguminosarum bv. trifolii 24.1 showing less glossy or smaller colonies were screened for properties usually associated with lipopolysaccharide (lps) defects in r. leguminosarum, i.e. motility, growth rate, tendency to agglutination in liquid media and symbiotic efficiency. neither any of the above mutants nor the earlier isolated 24.12 strain, defective in lps, showed all these properties changed simultaneously. according to page/sodium deoxycholate analysis the ...199810397346
molecular characterization and symbiotic importance of prsd gene of rhizobium leguminosarum bv. trifolii ta1.the prsd, prse and orf3 genes of rhizobium leguminosarum bv. trifolii strain ta1 encode the proteins which are significantly related to the family of bacterial abc transporters type i secretion systems. the prsd:km(r) mutant of strain ta1 induced non-nitrogen-fixing nodules on trifolium pratense. microscopic analysis of the nodules induced by prsd mutant did not reveal major abberations in the bacteroid appearance. the exopolysaccharide of prsd mutant was produced in increased amount and its lev ...199810397353
temporal and spatial order of events during the induction of cortical cell divisions in white clover by rhizobium leguminosarum bv. trifolii inoculation or localized cytokinin addition.we examined the timing and location of several early root responses to rhizobium leguminosarum bv. trifolii infection, compared with a localized addition of cytokinin in white clover, to study the role of cytokinin in early signaling during nodule initiation. induction of enod40 expression by either rhizobia or cytokinin was similar in timing and location and occurred in nodule progenitor cells in the inner cortex. inoculation of rhizobia in the mature root failed to induce enod40 expression and ...200010830261
infection of clover by plant growth promoting pseudomonas fluorescens strain 267 and rhizobium leguminosarum bv. trifolii studied by mtn5-gusa.plant growth promoting pseudomonas fluorescens strain 267, isolated from soil, produced pseudobactin a, 7-sulfonic acid derivatives of pseudobactin a and several b group vitamins. in coinoculation with rhizobium leguminosarum bv. trifolii strain 24.1, strain 267 promoted clover growth and enhanced symbiotic nitrogen fixation under controlled conditions. to better understand the beneficial effect of p. fluorescens 267 on clover inoculated with rhizobia, the colonization of clover roots by mtn5-gu ...200011016690
identification and characterization of a novel transcriptional regulator, matr, for malonate metabolism in rhizobium leguminosarum bv. trifolii.a novel gene, matr, located upstream of matabc, transcribed in the opposite direction, and encoding a putative regulatory protein by sequence analysis was discovered from rhizobium leguminosarum bv. trifolii. the mata, matb, and matc genes encode malonyl-coa decarboxylase, malonyl-coa synthetase, and a presumed malonate transporter, respectively. together, these enzymes catalyze the uptake and conversion of malonate to acetyl-coa. the deduced amino-acid sequence of matr showed sequence similarit ...200011106435
cloning and characterization of ce/8a gene from rhizobium leguminosarum bv. trifolii 1536.to isolate the cellulase gene from rhizobium leguminosarum bv. trifolii 1536.200415214728
a unipolarly located, cell-surface-associated agglutinin, rapa, belongs to a family of rhizobium-adhering proteins (rap) in rhizobium leguminosarum bv. trifolii.the phage-display cloning technique was used to find rhizobial proteins that bind to receptors located on the bacterial cell surface. the aim was to clone the gene(s) encoding rhicadhesin, a universal rhizobial adhesion protein, and/or other cell-surface-binding proteins. four such rhizobium-adhering proteins (rap) were revealed in rhizobium leguminosarum bv. trifolii strain r200. the binding is mediated by homologous ra domains in these proteins. one member of the rap protein family, named rapa ...200111238962
proteome analysis of cultivar-specific interactions between rhizobium leguminosarum biovar trifolii and subterranean clover cultivar woogenellup.proteome analysis was used to identify proteins that are involved in the early stages of nodulation between the subterranean clover cultivar woogenellup and the rhizobium leguminosarum bv. trifolii strains anu843 and anu794. strain anu843 induces nitrogen-fixing nodules whereas strain anu794 forms aberrant nodules on the roots of cv. woogenellup that fail to develop beyond an early stage. our aim was to identify proteins that might be involved in the early stages of nodulation over a 48 h period ...200111258772
the "missing" typical rhizobium leguminosarum o antigen is attached to a fatty acylated glycerol in r. leguminosarum bv. trifolii 4s, a strain that also lacks the usual tetrasaccharide "core" component.rhizobium leguminosarum bv. trifolii 4s has a lipopolysaccharide o antigen that lacks galactose and many of the typical glycosyl components found in related strains. here, we show that it also lacks the typical core tetrasaccharide but synthesizes an alternative glycolipid that contains galactose and the typical o-antigen glycosyl components, suggesting that in this strain, the o antigen is transferred to an alternative lipid acceptor.19968808946
the in vitro biosynthesis of the exopolysaccharide produced by rhizobium leguminosarum bv. trifolii, strain na 30.rhizobium leguminosarum bv. trifolii, strain na 30 nodulates both red (trifolium pratense) and white (t. repens) clover and produces an acidic exopolysaccharide (eps) containing glucose, galactose, glucuronic acid, acetate and ketalpyruvate residues in a 5:1:2:1:2 molar ratio. the in vitro synthesis of this eps as well as the characterization of five structurally related lipid linked oligosaccharides is described employing edta treated cells as enzyme preparation and 14c-labelled udp-glc, udp-gl ...19968832106
the fructokinase from rhizobium leguminosarum biovar trifolii belongs to group i fructokinase enzymes and is encoded separately from other carbohydrate metabolism enzymes.the rhizobium leguminosarum bv. trifolii bal fructokinase (frk) gene was isolated on a 2 center dot 4 kb bamhi fragment from the cosmid pla72 by complementation analysis of the tn5-induced frk mutant bal79, and confirmed by hybridization analysis. the nucleotide sequence of the frk gene was found to contain an open reading frame consisting of 978 bp encoding 326 amino acids, which was then compared to known fructokinase sequences. the fructokinase gene was not contained in an operon and is encod ...19968932706
a genetic locus necessary for rhamnose uptake and catabolism in rhizobium leguminosarum bv. trifolii.rhizobium leguminosarum bv. trifolii mutants unable to catabolize the methyl-pentose rhamnose are unable to compete effectively for nodule occupancy. in this work we show that the locus responsible for the transport and catabolism of rhamnose spans 10,959 bp. mutations in this region were generated by transposon mutagenesis, and representative mutants were characterized. the locus contains genes coding for an abc-type transporter, a putative dehydrogenase, a probable isomerase, and a sugar kinas ...200415576793
[effects of inoculation with rhizobium leguminosarum biovar trifolii on wheat cultivated in clover crop rotation agricultural soil in morocco].one hundred strains of rhizobium leguminosarum bv. trifolii were isolated from roots of wheat cultivated in rotation with clover in two different regions of morocco. the isolates were first screened for their effect on the growth of the cultivar rihane of wheat cultivated in an agricultural soil under greenhouse conditions. after 5 weeks of growth, 14 strains stimulating the fresh or dry matter yield of shoots were selected and used in a second pot inoculation trial performed with two different ...200111469254
effects of microgravity on the binding of acetylsalicylic acid by rhizobium leguminosarum bv. trifolii.bacteroids can be induced in vitro by treating growing rhizobium leguminosarum bv. trifolii with succinic acid or succinic acid structural analogs like acetysalicylic acid. quantitating bacteroid induction by measuring acetylsalicylic binding under normal (1 g) conditions showed two forms of binding to occur. in one form of binding cells immediately bound comparatively high levels of acetylsalicylic acid, but the binding was quickly reversed. the second form of binding increased with time by fir ...199511540747
genetic data indicate that proteins containing the ggdef domain possess diguanylate cyclase activity.a conserved domain, called ggdef (referring to a conserved central sequence pattern), is detected in many procaryotic proteins, often in various combinations with putative sensory-regulatory components. most sequenced bacterial genomes contain several different ggdef proteins. the function of this domain has so far not been experimentally shown. through genetic complementation using genes from three different bacteria encoding proteins with ggdef domains as the only element in common, we present ...200111682196
isolation and sequencing of rhizobium leguminosarum bv. trifolii pssn, psso and pssp genes encoding the proteins involved in polymerization and translocation of exopolysaccharide.rhizobium leguminosarum bv. trifolii produces an acidic exopolysaccharide (eps) that plays an important role in symbiotic interaction with clover plants. the sequence of 6.0-kb dna fragment located upstream of the previously described prsdeorf3 and psscde genes involved in exopolysaccharide biosynthesis revealed three new genes designated pssn, psso and pssp. the predicted protein product of pssp gene shares a significant homology to members of the membrane-periplasmic auxiliary (mpa1) family, t ...200111697141
rhizobium leguminosarum bv. trifolii pssp protein is required for exopolysaccharide biosynthesis and polymerization.rhizobium leguminosarum bv. trifolii produces an acidic exopolysaccharide (eps) that is important for the induction of nitrogen-fixing nodules on clover. recently, three genes, pssn, psso, and pssp, possibly involved in eps biosynthesis and polymerization were identified. the predicted protein product of the pssp gene shows a significant sequence similarity to other proteins belonging to the pcp2a family that are involved in the synthesis of high-molecular-weight eps. an r. leguminosarum bv. tri ...200212026178
transcription of matr gene in rhizobium leguminosarum bv. trifolii.a transcriptional regulator, matr, encoded on rhizobium leguminosarum bv. trifolii matr gene was reported to repress mat operon gene expression by binding the upstream operator site. also, matr activated its own gene expression by binding the same site that caused the transcriptional repression of the mat operon. this report suggests that matr plays a dual role in the transcription of matr and matabc with malonate as a positive effector.200212186746
symbiotic effects of deltamatb rhizobium leguminosarum bv. trifolii mutant on clovers.the role of malonate in symbiotic nitrogen metabolism has long been controversial, although it is known to occur in legume roots, especially in the nodules. here we report that malonate metabolism plays a key role in the differentiation of bacteroids rhizobium leguminosarum bv. trifolii in clover nodules. an operon, mat, that consists of three consecutive genes (matabc) has been discovered. mat encodes enzymes that catalyze the uptake and conversion of malonate to acetyl-coa through malonyl-coa. ...200212442899
crystallization and preliminary x-ray crystallographic analysis of malonyl-coa decarboxylase from rhizobium leguminosarum bv. trifolii.malonyl-coa decarboxylase (mcd), which catalyzes the conversion of malonyl-coa to acetyl-coa, is an evolutionarily distinct and highly conserved enzyme. mcd does not share sequence homology with other known decarboxylases, while the enzymes from different species exhibit at least >30% sequence identity to each other. in order to provide a canonical structure of the enzyme for detailed study of its structure-function relationship, the mcd of rhizobium leguminosarum bv. trifolii was overexpressed ...200312499559
transfer of the symbiotic plasmid from rhizobium leguminosarum biovar trifolii to agrobacterium tumefaciens.this study examined the symbiotic properties of agrobacterium transconjugants isolated by transferring a tn5-mob-marked derivative of the 315 kb megaplasmid prt4sa from rhizobium leguminosarum bv. trifolii 4s (wild-type strain) to agrobacterium tumefaciens a136 as the recipient. the genetic characteristics of the at4s transconjugant strains were ascertained by random amplified polymorphic dna (rapd) analyses and southern hybridization using tn5-mob and nod genes as probes. several of these at4s ...199812501295
integration of the temperate phage phiu into the putative trna gene on the chromosome of its host rhizobium leguminosarum biovar trifolii.the plasmid pci6, carrying the attp site of the temperate phage phiu, integrates into the attb site on the chromosome of rhizobium leguminosarum biovar trifolii strain 4s. the 4 kb ecori-hindiii region of pci6 involved in site-specific integration was subcloned as the attp fragment of phage phiu and sequenced. the attl fragment, one of the new dna junctions generated from the insertion of pci6 into the chromosome of the host rhizobium, was used as a hybridization probe for isolation of the attb ...199812501298
a white clover nodulin gene, dd23b, encoding a cysteine cluster protein, is expressed in roots during the very early stages of interaction with rhizobium leguminosarumbiovar trifolii and after treatment with chitolipooligosaccharide nod factors.an early nodulin cdna, dd23b, was isolated from white clover root tissue by differential display rt-pcr. its full-length sequence of 340 nucleotides encodes a predicted 72-amino-acid protein of molecular mass 8.3 kda, with a polypeptide region containing cysteine pairs spaced in the manner of a cysteine cluster protein. this feature, which is shared by some other late and early nodulins from pea and broad bean, suggests a role in metal ion binding and membrane transport. temporal and spatial exp ...200212579447
membrane topology of psst, the transmembrane protein component of the type i exopolysaccharide transport system in rhizobium leguminosarum bv. trifolii strain ta1.the psst gene was identified as the fourth gene located upstream of the pssnop gene cluster possibly involved in the biosynthesis, polymerization, and transport of exopolysaccharide (eps) in rhizobium leguminosarum bv. trifolii strain ta1. the hydropathy profile and homology searches indicated that psst belongs to the polysaccharide-specific transport family of proteins, a component of the type i system of the polysaccharide transport. the predicted membrane topology of the psst protein was exam ...200312670974
isolation of rhizobium leguminosarum (biovar trifolii) strains from ethiopian soils and symbiotic effectiveness on african annual clover species.strains of rhizobium leguminosarum (biovar trifolii) isolated from two ethiopian soils or obtained from a commercial source were evaluated for symbiotic effectiveness on five african annual clover species. numerous rhizobium trifolii strains that exhibited varying levels of symbiotic effectiveness were isolated from both soils (a nitosol and a vertisol), and it was possible to identify strains that were highly effective for each clover species. the soil isolates were, as a group, superior to the ...199016348157
exopolysaccharide synthesis in rhizobium leguminosarum bv. trifolii is related to various metabolic pathways.rhizobium leguminosarum bv. trifolii synthesizes extracellular polysaccharide (eps) that is postulated to be a biologically active signalling molecule in clover symbiosis. a group of seven exopolysaccharide-deficient (exo), non-nitrogen-fixing mutants of r. leguminosarum bv. trifolii strain 24.1 isolated by transposon mutagenesis were complemented to mucoid phenotype by a low-copy plasmid carrying the pssa gene encoding the first glucosyl-ip-transferase. some of these mutants were not corrected ...200312892850
synthesis and characterization of carboxymethylated cyclosophoraose, and its inclusion complexation behavior.carboxymethylated cyclosophoraoses (cm-cys) were synthesized by chemical modification of a family of neutral cyclosophoraoses isolated from rhizobium leguminosarum biovar trifolii. structural analyses of the cm-cys were carried out using nmr and ftir spectroscopies, and the molecular weight distributions were confirmed with maldi-tof mass spectrometry. based on structural characterization, native cyclosophoraoses were successfully substituted with carboxymethyl groups at the oh-4 and oh-6 of the ...200415013389
regulation of pssa and pssb gene expression in rhizobium leguminosarum bv. trifolii in response to environmental factors.exopolysaccharide (eps) produced by rhizobium leguminosarum plays an important role in indeterminate-type nodulation. the pssa gene, encoding the first glycosyl transferase and pssb, encoding inositol monophosphatase, are involved in eps synthesis and regulation in r. leguminosarum bv. trifolii. using pssa-lacz and pssb-lacz plasmid-borne transcriptional fusions, a stimulating effect of phosphate on the transcription of both genes was observed. the increase in the transcription of pssa and pssb ...200415031650
the effect of heavy metals on dinitrogen fixation by rhizobium-white clover in a range of long-term sewage sludge amended and metal-contaminated soils.an investigation was conducted to determine whether effective strains of rhizobium leguminosarum biovar. trifolii capable of symbiotic n2 fixation with white clover (trifolium repens) were present in a range of metal-contaminated soils. a number of historically sewage-amended sites (including experimental, pasture grassland and arable sites) were selected and compared with highly contaminated samples from abandoned heavy metal mines. many sites had metal concentrations above the limits establish ...199315091894
environmental modulation of the psstnop gene expression in rhizobium leguminosarum bv. trifolii.exopolysaccharide production by rhizobium leguminosarum bv. trifolii is required for successful establishment of nitrogen-fixing symbiosis with clover (trifolium pratense l.). using plasmid-borne transcriptional fusions of promoters of pss genes with promoterless lacz the effect of root exudate, phosphate, and ammonia on expression of psst, pssn, psso, and pssp genes in wild-type strain rtta1 background was determined. a stimulating effect of these environmental factors on psso and pssp gene exp ...200415105887
control of nodule number by the phytohormone abscisic acid in the roots of two leguminous species.the effects of the phytohormone abscisic acid (aba) on plant growth and root nodule formation were analyzed in trifolium repense (white clover) and lotus japonicus, which form indeterminate and determinate nodules, respectively. in t. repense, although the number of nodules formed after inoculation with rhizobium leguminosarum bv. trifolii strain 4s (wild type) was slightly affected by exogenous aba, those formed by strain h1(pc4s8), which forms ineffective nodules, were dramatically reduced 28 ...200415295075
complexity of phenotypes and symbiotic behaviour of rhizobium leguminosarum biovar trifolii exopolysaccharide mutants.rhizobium leguminosarum biovar trifolii strain ta1 polysaccharide synthesis (pss) mutants in the pssd, pssp, psst and psso genes and altered in exopolysaccharide (eps) synthesis were investigated. eps-deficient mutants were also changed in lipopolysaccharide structure. all mutants exhibited varied sensitivities to detergents, ethanol and antibiotics, thus indicating changes in bacterial membrane integrity. using pss mutants marked with the gusa gene, eps-deficient mutants were found to have abno ...200415349716
enantioseparation using sulfated cyclosophoraoses as a novel chiral additive in capillary electrophoresis.highly sulfated cyclosophoraoses (hs-cys) were synthesized by the chemical modification of a family of neutral cyclosophoraoses isolated from rhizobium leguminosarum bv. trifolii. the hs-cys were then analytically characterized using fourier transform-infrared spectroscopy and elemental analysis. these hs-cys were successfully used as a novel chiral additive, in low-ph aqueous background electrolytes, for capillary electrophoretic separation of five basic chiral drugs such as arterenol, atenolol ...200415351997
the rhizobium leguminosarum bv. trifolii pssb gene product is an inositol monophosphatase that influences exopolysaccharide synthesis.the pssb gene of rhizobium leguminosarum bv. trifolii encodes a protein of 284 amino acids with sequence similarity to eukaryotic inositol monophosphatases. the gene was cloned and overexpressed in escherichia coli. the purified gene product of pssb showed inositol monophosphatase activity with a km of 0.23 mm, and a vmax of 3.27 mumol pi min-1 (mg protein)-1. its substrate specificity, mg+2 requirement, li+ inhibition, and subunit association (dimerization) were studied and compared to those of ...200111285742
cloning and expression of a down-regulated gene (trenoddr1) of white clover responded by the nod genes derived from rhizobium leguminosarum bv. trifolii strain 4s.the nodulation genes of rhizobium leguminosarum bv. trifolii 4s (strain 4s) were cloned into cosmid vector plafr1 named pc4s8 which was contained nodnmlfedabcij and a part of nodt as an insert. the pc4s8 was transferred to strain h1, sym plasmid (prt4sa) cured strain of strain 4s, and isolated as tc resistant and nodulation restored mutant, strain h1(pc4s8). during infection process of this strain, visible symbiotic features, such as root hair curling (hac), root hair deformation (had) and infec ...200111290421
topological and transcriptional analysis of pssl gene product: a putative wzx-like exopolysaccharide translocase in rhizobium leguminosarum bv. trifolii ta1.an identified pssl gene is yet another one, besides the psst, pssn and pssp genes, encoding for a protein engaged in polysaccharide polymerization and export in rhizobium leguminosarum bv. trifolii strain ta1 (rtta1). amino acid sequence similarity and hypothetical protein secondary structure placed the pssl protein within wzx (rfbx) translocases with putative flippase function that belong to the polysaccharide specific transport (pst) family. the predicted secondary structure of the pssl membra ...200516044265
environmental factors influencing numbers of rhizobium leguminosarum biovar trifolii and its bacteriophages in two field soils.fluctuations in numbers of rhizobium leguminosarum biovar trifolii and its bacteriophages in two fields with different soil types were followed during a 17-month period in 1981 and 1982. mean levels of both phage and rhizobia varied significantly (p < 0.05) on different occasions, with rhizobial levels varying from 1.6 x 10 to 2.0 x 10 cell per g of soil and phage from 0 to 1.7 x 10 pfu/g of soil. multivariate regression analysis showed rhizobial levels to be significantly and positively related ...198716347339
evidence for genetic exchange and recombination of rhizobium symbiotic plasmids in a soil population.a soil population of 16 rhizobium leguminosarum bv. trifolii isolates was characterized by using three sym (for symbiotic) plasmid-specific dna hybridization probes: (i) an r. leguminosarum bv. trifolii-specific, repeated-sequence probe; (ii) a nifhdk gene probe, and (iii) a nod gene probe. a predominant sym plasmid family was identified among the isolates. three other unrelated sym plasmid families were also identified. the isolates were also classified either by using a chromosomal dna hybridi ...198716347509
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