Publications
| Title | Abstract | Year Filter | PMID(sorted descending) Filter |
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| identification of a gene cluster for the formation of extracellular polysaccharide precursors in the chemolithoautotroph acidithiobacillus ferrooxidans. | a cluster of five genes, proposed to be involved in the formation of extracellular polysaccharide (eps) precursors via the leloir pathway, have been identified in the acidophilic autotroph acidithiobacillus ferrooxidans. the order of the genes is luxa-gale-galk-pgm-galm, encoding a luxa-like protein, udp-glucose 4-epimerase, galactokinase, phosphoglucomutase, and galactose mutarotase, respectively. the gal cluster forms a single transcriptional unit and is therefore an operon. two other putative ... | 2005 | 15932984 |
| root border-like cells of arabidopsis. microscopical characterization and role in the interaction with rhizobacteria. | plant roots of many species produce thousands of cells that are released daily into the rhizosphere. these cells are commonly termed border cells because of their major role in constituting a biotic boundary layer between the root surface and the soil. in this study, we investigated the occurrence and ultrastructure of such cells in arabidopsis (arabidopsis thaliana) using light and electron microscopy coupled to high-pressure freezing. the secretion of cell wall molecules including pectic polys ... | 2005 | 15908608 |
| alkane-induced expression, substrate binding profile, and immunolocalization of a cytochrome p450 encoded on the nifd excision element of anabaena 7120. | alkanes have been hypothesized to act as universal inducers of bacterial cytochrome p450 gene expression. we tested this hypothesis on an unusual p450 gene (cyp110) found on a conserved 11 kilobase episomal dna element of unknown function found in filamentous cyanobacteria. we also monitored the binding of potential substrates to the p450 protein and explored the distribution of p450 protein in vegetative cells and nitrogen-fixing heterocysts using immuno-electron microscopy. | 2005 | 15790415 |
| protein domains and architectural innovation in plant-associated proteobacteria. | evolution of new complex biological behaviour tends to arise by novel combinations of existing building blocks. the functional and evolutionary building blocks of the proteome are protein domains, the function of a protein being dependent on its constituent domains. we clustered completely-sequenced proteomes of prokaryotes on the basis of their protein domain content, as defined by pfam (release 16.0). this revealed that, although there was a correlation between phylogeny and domain content, ot ... | 2005 | 15715905 |
| nopb, a type iii secreted protein of rhizobium sp. strain ngr234, is associated with pilus-like surface appendages. | rhizobium sp. strain ngr234 possesses a functional type three secretion system (ttss), through which a number of proteins, called nodulation outer proteins (nops), are delivered to the outside of the cell. a major constraint to the identification of nops is their low abundance in the supernatants of ngr234 strains grown in culture. to overcome this limitation, a more sensitive proteomics-based strategy was developed. secreted proteins from wild-type ngr234 were separated by two-dimensional gel e ... | 2005 | 15659692 |
| thermophilic, reversible gamma-resorcylate decarboxylase from rhizobium sp. strain mtp-10005: purification, molecular characterization, and expression. | we found the occurrence of thermophilic reversible gamma-resorcylate decarboxylase (gamma-rdc) in the cell extract of a bacterium isolated from natural water, rhizobium sp. strain mtp-10005, and purified the enzyme to homogeneity. the molecular mass of the enzyme was determined to be about 151 kda by gel filtration, and that of the subunit was 37.5 kda by sodium dodecyl sulfate-polyacrylamide gel electrophoresis; in other words, the enzyme was a homotetramer. the enzyme was induced specifically ... | 2004 | 15466039 |
| characterization of nopp, a type iii secreted effector of rhizobium sp. strain ngr234. | the type three secretion system (ttss) encoded by pngr234a, the symbiotic plasmid of rhizobium sp. strain ngr234, is responsible for the flavonoid- and nodd1-dependent secretion of nodulation outer proteins (nops). abolition of secretion of all or specific nops significantly alters the nodulation ability of ngr234 on many of its hosts. in the closely related strain rhizobium fredii usda257, inactivation of the ttss modifies the host range of the mutant so that it includes the improved glycine ma ... | 2004 | 15231809 |
| engineering the nifh promoter region and abolishing poly-beta-hydroxybutyrate accumulation in rhizobium etli enhance nitrogen fixation in symbiosis with phaseolus vulgaris. | rhizobium etli, as well as some other rhizobia, presents nitrogenase reductase (nifh) gene reiterations. several r. etli strains studied in this laboratory showed a unique organization and contained two complete nifhdk operons (copies a and b) and a truncated nifhd operon (copy c). expression analysis of lacz fusion demonstrated that copies a and b in strain cfn42 are transcribed at lower levels than copy c, although this copy has no discernible role during nitrogen fixation. to increase nitroge ... | 2004 | 15184121 |
| nopl, an effector protein of rhizobium sp. ngr234, thwarts activation of plant defense reactions. | bacterial effector proteins delivered into eukaryotic cells via bacterial type iii secretion systems are important virulence factors in plant-pathogen interactions. type iii secretion systems have been found in rhizobium species that form symbiotic, nitrogen-fixing associations with legumes. one such bacterium, rhizobium sp. ngr234, secretes a number of type iii effectors, including nodulation outer protein l (nopl, formerly y4xl). here, we show that expression of nopl in tobacco (nicotiana taba ... | 2004 | 14966249 |
| an evolutionary hot spot: the pngr234b replicon of rhizobium sp. strain ngr234. | rhizobium sp. strain ngr234 has an exceptionally broad host range and is able to nodulate more than 112 genera of legumes. since the overall organization of the ngr234 genome is strikingly similar to that of the narrow-host-range symbiont rhizobium meliloti strain 1021 (also known as sinorhizobium meliloti), the obvious question is why are the spectra of hosts so different? study of the early symbiotic genes of both bacteria (carried by the syma plasmids) did not provide obvious answers. yet, bo ... | 2004 | 14702322 |
| metabolic reconstruction of sulfur assimilation in the extremophile acidithiobacillus ferrooxidans based on genome analysis. | acidithiobacillus ferrooxidans is a gamma-proteobacterium that lives at ph2 and obtains energy by the oxidation of sulfur and iron. it is used in the biomining industry for the recovery of metals and is one of the causative agents of acid mine drainage. effective tools for the study of its genetics and physiology are not in widespread use and, despite considerable effort, an understanding of its unusual physiology remains at a rudimentary level. nearly complete genome sequences of a. ferrooxidan ... | 2003 | 14675496 |
| quorum sensing in nitrogen-fixing rhizobia. | members of the rhizobia are distinguished for their ability to establish a nitrogen-fixing symbiosis with leguminous plants. while many details of this relationship remain a mystery, much effort has gone into elucidating the mechanisms governing bacterium-host recognition and the events leading to symbiosis. several signal molecules, including plant-produced flavonoids and bacterially produced nodulation factors and exopolysaccharides, are known to function in the molecular conversation between ... | 2003 | 14665677 |
| citrate synthase mutants of sinorhizobium fredii usda257 form ineffective nodules with aberrant ultrastructure. | the tricarboxylic acid (tca) cycle plays an important role in generating the energy required by bacteroids to fix atmospheric nitrogen. citrate synthase is the first enzyme that controls the entry of carbon into the tca cycle. we cloned and determined the nucleotide sequence of the glta gene that encodes citrate synthase in sinorhizobium fredii usda257, a symbiont of soybeans (glycine max [l.] merr.) and several other legumes. the deduced citrate synthase protein has a molecular weight of 48,198 ... | 2003 | 12788763 |
| nod factor and elicitors activate different phospholipid signaling pathways in suspension-cultured alfalfa cells. | lipo-chitooligosaccharides (nod factors) are produced by symbiotic rhizobium sp. bacteria to elicit nod responses on their legume hosts. one of the earliest responses is the formation of phosphatidic acid (pa), a novel second messenger in plant cells. remarkably, pathogens have also been reported to trigger the formation of pa in nonlegume plants. to investigate how host plants can distinguish between symbionts and pathogens, the effects of nod factor and elicitors (chitotetraose and xylanase) o ... | 2003 | 12746536 |
| prediction and overview of the rpon-regulon in closely related species of the rhizobiales. | in the rhizobia, a group of symbiotic gram-negative soil bacteria, rpon (sigma54, sigman, ntra) is best known as the sigma factor enabling transcription of the nitrogen fixation genes. recent reports, however, demonstrate the involvement of rpon in other symbiotic functions, although no large-scale effort has yet been undertaken to unravel the rpon-regulon in rhizobia. we screened two complete rhizobial genomes (mesorhizobium loti, sinorhizobium meliloti) and four symbiotic regions (rhizobium et ... | 2002 | 12537565 |
| quorum sensing in rhizobium sp. strain ngr234 regulates conjugal transfer (tra) gene expression and influences growth rate. | rhizobium sp. strain ngr234 forms symbiotic, nitrogen-fixing nodules on a wide range of legumes via functions largely encoded by the plasmid pngr234a. the pngr234a sequence revealed a region encoding plasmid replication (rep) and conjugal transfer (tra) functions similar to those encoded by the rep and tra genes from the tumor-inducing (ti) plasmids of agrobacterium tumefaciens, including homologues of the ti plasmid quorum-sensing regulators trai, trar, and tram. in a. tumefaciens, trai, a luxi ... | 2003 | 12533456 |
| the rhizobial hema gene is required for symbiosis in species with deficient [delta]-aminolevulinic acid uptake activity. | most rhizobial hema mutants induce root nodules on their respective legume hosts that lack nitrogen fixation activity and leghemoglobin expression. however, a bradyrhizobium japonicum hema mutant elicits effective nodules on soybean, and we proposed previously that synthesis and uptake of the heme precursor [delta]-aminolevulinic acid (ala) by the plant and bacterial symbiont, respectively, allow mutant rescue (i. sangwan, m.r. o'brian [1991] science 251: 1220-1222). in the present work, the b. ... | 1995 | 12228561 |
| rhizobial nodulation factors stimulate mycorrhizal colonization of nodulating and nonnodulating soybeans. | legumes form tripartite symbiotic associations with noduleinducing rhizobia and vesicular-arbuscular mycorrhizal fungi. co-inoculation of soybean (glycine max [l.] merr.) roots with bradyrhizobium japonicum 61-a-101 considerably enhanced colonization by the mycorrhizal fungus glomus mosseae. a similar stimulatory effect on mycorrhizal colonization was also observed in nonnodulating soybean mutants when inoculated with bradyrhizobium japonicum and in wild-type soybean plants when inoculated with ... | 1995 | 12228558 |
| sym2 of pea is involved in a nodulation factor-perception mechanism that controls the infection process in the epidermis. | in pea (pisum sativum) up to 50 nodulation mutants are known, several of which are affected in the early steps of the symbiotic interaction with rhizobium sp. bacteria. here we describe the role of the sym2 gene in nodulation (nod) factor perception. our experiments show that the sym2a allele from the wild pea variety afghanistan confers an arrest in infection-thread growth if the rhizobium leguminosarum bv viciae strain does not produce nod factors with a nodx-mediated acetylation at their redu ... | 1997 | 12223813 |
| degeneracy of antigen recognition as the molecular basis for the high frequency of naive a2/melan-a peptide multimer(+) cd8(+) t cells in humans. | in contrast with the low frequency of most single epitope reactive t cells in the preimmune repertoire, up to 1 of 1,000 naive cd8(+) t cells from a2(+) individuals specifically bind fluorescent a2/peptide multimers incorporating the a27l analogue of the immunodominant 26-35 peptide from the melanocyte differentiation and melanoma associated antigen melan-a. this represents the only naive antigen-specific t cell repertoire accessible to direct analysis in humans up to date. to get insight into t ... | 2002 | 12119345 |
| nucleotide sequence and genetic structure of a novel carbaryl hydrolase gene (ceha) from rhizobium sp. strain ac100. | rhizobium sp. strain ac100, which is capable of degrading carbaryl (1-naphthyl-n-methylcarbamate), was isolated from soil treated with carbaryl. this bacterium hydrolyzed carbaryl to 1-naphthol and methylamine. carbaryl hydrolase from the strain was purified to homogeneity, and its n-terminal sequence, molecular mass (82 kda), and enzymatic properties were determined. the purified enzyme hydrolyzed 1-naphthyl acetate and 4-nitrophenyl acetate indicating that the enzyme is an esterase. we then cl ... | 2002 | 11872471 |
| morphological changes of rhizobia in peat cultures. | morphological changes that take place in peat cultures of several species of rhizobia were examined. these changes seemed to be associated with enhanced survival of cells in peat and after inoculation onto plastic beads, which were used as a model system for seeds. cell wall changes, in which the periplasmic space appeared to be occluded with electron-dense material, were observed in rhizobium sp. strain su343 and bradyrhizobium lupini wu425 cells after 7 and 14 days in peat, respectively. nutri ... | 2002 | 11872451 |
| endogenous nod-factor-like signal molecules promote early somatic embryo development in norway spruce. | embryogenic cultures of norway spruce (picea abies) are composed of pro-embryogenic masses (pems) and somatic embryos of various developmental stages. auxin is important for pem formation and proliferation. in this report we show that depletion of auxin blocks pem development and causes large-scale cell death. extracts of the media conditioned by embryogenic cultures stimulate development of pem aggregates in auxin-deficient cultures. partial characterization of the conditioning factor shows tha ... | 2002 | 11842156 |
| dynamics of genome architecture in rhizobium sp. strain ngr234. | bacterial genomes are usually partitioned in several replicons, which are dynamic structures prone to mutation and genomic rearrangements, thus contributing to genome evolution. nevertheless, much remains to be learned about the origins and dynamics of the formation of bacterial alternative genomic states and their possible biological consequences. to address these issues, we have studied the dynamics of the genome architecture in rhizobium sp. strain ngr234 and analyzed its biological significa ... | 2002 | 11741857 |
| a medicago truncatula homoglutathione synthetase is derived from glutathione synthetase by gene duplication. | glutathione (gsh) and homo-gsh (hgsh) are the major low-molecular weight thiols synthesized in medicago truncatula. two m. truncatula cdnas (gshs1 and gshs2) corresponding to a putative gsh synthetase (gshs) and a putative hgsh synthetase (hgshs) were characterized. heterologous expression of gshs1 and gshs2 cdnas in an escherichia coli strain deficient in gshs activity showed that gshs1 and gshs2 are a gshs and an hgshs, respectively. leucine-534 and proline-535 present in hgshs were substitute ... | 2001 | 11500568 |
| analysis of the chromosome sequence of the legume symbiont sinorhizobium meliloti strain 1021. | sinorhizobium meliloti is an alpha-proteobacterium that forms agronomically important n(2)-fixing root nodules in legumes. we report here the complete sequence of the largest constituent of its genome, a 62.7% gc-rich 3,654,135-bp circular chromosome. annotation allowed assignment of a function to 59% of the 3,341 predicted protein-coding orfs, the rest exhibiting partial, weak, or no similarity with any known sequence. unexpectedly, the level of reiteration within this replicon is low, with onl ... | 2001 | 11481430 |
| specific detection of bradyrhizobium and rhizobium strains colonizing rice (oryza sativa) roots by 16s-23s ribosomal dna intergenic spacer-targeted pcr. | in addition to forming symbiotic nodules on legumes, rhizobial strains are members of soil or rhizosphere communities or occur as endophytes, e.g., in rice. two rhizobial strains which have been isolated from root nodules of the aquatic legumes aeschynomene fluminensis (irbg271) and sesbania aculeata (irbg74) were previously found to promote rice growth. in addition to analyzing their phylogenetic positions, we assessed the suitability of the 16s-23s ribosomal dna (rdna) intergenic spacer (igs) ... | 2001 | 11472944 |
| bacteria mediate methylation of iodine in marine and terrestrial environments. | methyl iodide (ch(3)i) plays an important role in the natural iodine cycle and participates in atmospheric ozone destruction. however, the main source of this compound in nature is still unclear. here we report that a wide variety of bacteria including terrestrial and marine bacteria are capable of methylating the environmental level of iodide (0.1 microm). of the strains tested, rhizobium sp. strain mrcd 19 was chosen for further analysis, and it was found that the cell extract catalyzed the me ... | 2001 | 11375186 |
| phylogenetic relationships among group ii intron orfs. | group ii introns are widely believed to have been ancestors of spliceosomal introns, yet little is known about their own evolutionary history. in order to address the evolution of mobile group ii introns, we have compiled 71 open reading frames (orfs) related to group ii intron reverse transcriptases and subjected their derived amino acid sequences to phylogenetic analysis. the phylogenetic tree was rooted with reverse transcriptases (rts) of non-long terminal repeat retroelements, and the infer ... | 2001 | 11222775 |
| genetic snapshots of the rhizobium species ngr234 genome. | in nitrate-poor soils, many leguminous plants form nitrogen-fixing symbioses with members of the bacterial family rhizobiaceae. we selected rhizobium sp. ngr234 for its exceptionally broad host range, which includes more than i 12 genera of legumes. unlike the genome of bradyrhizobium japonicum, which is composed of a single 8.7 mb chromosome, that of ngr234 is partitioned into three replicons: a chromosome of about 3.5 mb, a megaplasmid of more than 2 mb (pngr234b) and pngr234a, a 536,165 bp pl ... | 2000 | 11178268 |
| identification of legionella pneumophila genes important for infection of amoebas by signature-tagged mutagenesis. | legionella pneumophila is a facultative intracellular gram-negative rod that causes pneumonia in humans. free-living amoebas are thought to serve as a reservoir for legionella infections. signature-tagged mutagenesis was employed to identify legionella pneumophila genes necessary for survival in the amoeba acanthamoeba castellanii. six mutant strains were defective in assays of invasion and intracellular growth. four mutants also exhibited invasion and replication defects in hartmannella vermifo ... | 2001 | 11159993 |
| nod factors and chitooligomers elicit an increase in cytosolic calcium in aequorin-expressing soybean cells. | rhizobial nod factors (nfs) function as nodulation signals that trigger symbiotic responses of leguminous host plants. nfs consist of a chitin oligomer backbone carrying a fatty acid at the non-reducing end. depending on the rhizobial strain, nfs carry additional substituents, which may determine host specificity. transgenic suspension-cultured soybean (glycine max [l.] merr.) cells expressing aequorin have been used to record cytosolic [ca(2+)] changes upon treatment with purified nfs and chiti ... | 2000 | 11027722 |
| rhizosphere soil aggregation and plant growth promotion of sunflowers by an exopolysaccharide-producing rhizobium sp. strain isolated from sunflower roots. | root-adhering soil (ras) forms the immediate environment where plants take up water and nutrients for their growth. we report the effect of an exopolysaccharide (eps)-producing rhizobacterium (strain yas34) on the physical properties of sunflower (helianthus annuus l.) ras, associated with plant growth promotion, under both water stress and normal water supply conditions. strain yas34 was isolated as a major eps-producing bacterium from the rhizoplane of sunflowers grown in a french dystric camb ... | 2000 | 10919797 |
| identification of sinorhizobium meliloti genes regulated during symbiosis. | rna fingerprinting by arbitrarily primed pcr was used to isolate sinorhizobium meliloti genes regulated during the symbiotic interaction with alfalfa (medicago sativa). sixteen partial cdnas were isolated whose corresponding genes were differentially expressed between symbiotic and free-living conditions. thirteen sequences corresponded to genes up-regulated during symbiosis, whereas three were instead repressed during establishment of the symbiotic interaction. seven cdnas corresponded to known ... | 2000 | 10850975 |
| reduction of adenosine-5'-phosphosulfate instead of 3'-phosphoadenosine-5'-phosphosulfate in cysteine biosynthesis by rhizobium meliloti and other members of the family rhizobiaceae. | we have cloned and sequenced three genes from rhizobium meliloti (sinorhizobium meliloti) that are involved in sulfate activation for cysteine biosynthesis. two of the genes display homology to the escherichia coli cysdn genes, which code for an atp sulfurylase (ec 2.7.7.4). the third gene has homology to the e. coli cysh gene, a 3'-phosphoadenosine-5'-phosphosulfate (paps) reductase (ec 1.8.99.4), but has greater homology to a set of genes found in arabidopsis thaliana that encode an adenosine- ... | 1999 | 10464198 |
| purification and characterization of an alpha-glucosidase from rhizobium sp. (robinia pseudoacacia l.) strain usda 4280. | a novel alpha-glucosidase with an apparent subunit mass of 59 +/- 0. 5 kda was purified from protein extracts of rhizobium sp. strain usda 4280, a nodulating strain of black locust (robinia pseudoacacia l), and characterized. after purification to homogeneity (475-fold; yield, 18%) by ammonium sulfate precipitation, cation-exchange chromatography, hydrophobic chromatography, dye chromatography, and gel filtration, this enzyme had a pi of 4.75 +/- 0.05. the enzyme activity was optimal at ph 6.0 t ... | 1999 | 10388682 |
| investigation of two evolutionarily unrelated halocarboxylic acid dehalogenase gene families. | dehalogenases are key enzymes in the metabolism of halo-organic compounds. this paper describes a systematic approach to the isolation and molecular analysis of two families of bacterial alpha-halocarboxylic acid (alphaha) dehalogenase genes, called group i and group ii deh genes. the two families are evolutionarily unrelated and together represent almost all of the alphaha deh genes described to date. we report the design and evaluation of degenerate pcr primer pairs for the separate amplificat ... | 1999 | 10198020 |
| isolation and characterization of alfalfa-nodulating rhizobia present in acidic soils of central argentina and uruguay | we describe the isolation and characterization of alfalfa-nodulating rhizobia from acid soils of different locations in central argentina and uruguay. a collection of 465 isolates was assembled, and the rhizobia were characterized for acid tolerance. growth tests revealed the existence of 15 acid-tolerant (at) isolates which were able to grow at ph 5.0 and formed nodules in alfalfa with a low rate of nitrogen fixation. analysis of those isolates, including partial sequencing of the genes encodin ... | 1999 | 10103231 |
| noll of rhizobium sp. strain ngr234 is required for o-acetyltransferase activity. | following (iso)flavonoid induction, nodulation genes of the symbiotic nitrogen-fixing bacterium rhizobium sp. strain ngr234 elaborate a large family of lipooligosaccharidic nod factors (nodngr factors). when secreted into the rhizosphere of compatible legumes, these signal molecules initiate root hair deformation and nodule development. the nonreducing glucosamine residue of nodngr factors are n acylated, n methylated, and mono- or biscarbamoylated, while position c-6 of the reducing extremity i ... | 1999 | 9922261 |
| three replicons of rhizobium sp. strain ngr234 harbor symbiotic gene sequences. | rhizobium sp. strain ngr234 contains three replicons: the symbiotic plasmid or pngr234a, a megaplasmid (pngr234b), and the chromosome. symbiotic gene sequences not present in pngr234a were analyzed by hybridization. dna sequences homologous to the genes fixljknopqghis were found on the chromosome, while sequences homologous to nodpq and exobdflk were found on pngr234b. | 1998 | 9811668 |
| characterization of a hemoglobin protease secreted by the pathogenic escherichia coli strain eb1. | many pathogenic bacteria can use heme compounds as a source of iron. pathogenic escherichia coli strains are capable of using hemoglobin as an iron source. however, the mechanism of heme acquisition from hemoglobin is not understood for this microorganism. we present the first molecular characterization of a hemoglobin protease (hbp) from a human pathogenic e. coli strain. the enzyme also appeared to be a heme-binding protein. affinity purification of this bifunctional protein enabled us to iden ... | 1998 | 9743528 |
| structure and evolution of ngrrs-1, a complex, repeated element in the genome of rhizobium sp. strain ngr234. | much of the remarkable ability of rhizobium sp. strain ngr234 to nodulate at least 110 genera of legumes, as well as the nonlegume parasponia andersonii, stems from the more than 80 different nod factors it secretes. except for node, nodg, and nodpq, which are on the chromosome, most nod factor biosynthesis genes are dispersed over the 536,165-bp symbiotic plasmid, pngr234a. mosaic sequences and insertion sequences (iss) comprise 18% of pngr234a. many of them are clustered, and these is islands ... | 1997 | 9393715 |
| rhizobium sp. strain ngr234 nodz protein is a fucosyltransferase. | rhizobium sp. strain ngr234 produces a large family of lipochitooligosaccharide nod factors carrying specific substituents. among them are 3-o- (or 4-o-) and 6-o-carbamoyl groups, an n-methyl group, and a 2-o-methylfucose residue which may bear either 3-o-sulfate or 4-o-acetyl substitutions. investigations on the genetic control of host specificity revealed a number of loci which directly affect nod factor structure. here we show that insertion and frameshift mutations in the nodz gene abolish f ... | 1997 | 9260950 |
| sinorhizobium teranga bv. acaciae ors1073 and rhizobium sp. strain ors1001, two distantly related acacia-nodulating strains, produce similar nod factors that are o carbamoylated, n methylated, and mainly sulfated. | we have determined the structures of nod factors produced by strains representative of sinorhizobium teranga bv. acaciae and the so-called cluster u from the rhizobium loti branch, two genetically different symbionts of particular acacia species. compounds from both strains were found to be similar, i.e., mainly sulfated, o carbamoylated, and n methylated, indicating a close relationship between host specificity and nod factor structure, regardless of the taxonomy of the bacterial symbiont. | 1997 | 9139935 |
| cloning and sequence analysis of genes encoding xylanases and acetyl xylan esterase from streptomyces thermoviolaceus opc-520. | three genes encoding two types of xylanases (stx-i and stx-ii) and an acetyl xylan esterase (stx-iii) from streptomyces thermoviolaceus opc-520 were cloned, and their dna sequences were determined. the nucleotide sequences showed that genes stx-ii and stx-iii were clustered on the genome. the stx-i, stx-ii, and stx-iii genes encoded deduced proteins of 51, 35.2, and 34.3 kda, respectively. stx-i and stx-ii bound to both insoluble xylan and crystalline cellulose (avicel). alignment of the deduced ... | 1997 | 9023944 |
| characterization, distribution, and localization of isrl2, and insertion sequence element isolated from rhizobium leguminosarum bv. viciae. | an insertion sequence (is) element, isr12, from rhizobium leguminosarum bv. viciae strain msdj4184 was isolated by insertional inactivation of the sacrb gene of psup104-sac, which allows positive selection. isrl2 is 932 bp long, is flanked by 17-bp imperfect terminal inverted repeats, and generated a 3-bp target site duplication. isrl2 was found to be 63 to 77% homologous to insertion elements of the is5 group of the is4 superfamily. a probe incorporating a full-length copy of isrl2 was used to ... | 1996 | 8593071 |
| 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 ... | 1993 | 8491702 |
| characterization of rfrs9, a second member of the rhizobium fredii repetitive sequence family from the nitrogen-fixing symbiont r. fredii usda257. | the genome of the nitrogen-fixing symbiont, rhizobium fredii usda257, contains nine copies of repetitive sequences known as the r. fredii repetitive sequence (rfrs) family. we previously sequenced rfrs3, which is linked to symbiosis plasmid-borne nodulation genes of this organism and has substantial homology to the t-dna of agrobacterium rhizogenes and lesser homology to reiterated sequences of bradyrhizobium japonicum. here we characterize a second family member, rfrs9. the ecori fragment conta ... | 1993 | 8382462 |
| perception of rhizobium nodulation factors by tomato cells and inactivation by root chitinases. | the bacterial genera rhizobium and bradyrhizobium, nitrogen-fixing symbionts of legumes, secrete specific lipo-chitooligosaccharides that induce the formation of nodules on their host plants. when preparations of such nodulation-inducing factors (nod factors) were added to suspension-cultured tomato cells, a rapid and transient alkalinization of the culture medium occurred. lipo-oligosaccharide preparations from rhizobium or bradyrhizobium treated with flavonoids, known inducers of nod factor sy ... | 1994 | 8134372 |
| rhizobia catabolize nod gene-inducing flavonoids via c-ring fission mechanisms. | gas chromatographic and mass spectrometric analyses of derivatized culture medium extracts were used to identify the products of flavonoid metabolism by rhizobia. a number of rhizobium species and biovars degraded their nod gene-inducing flavonoids by mechanisms which originated in a cleavage of the c-ring of the molecule and which yielded conserved a- and b-ring products among the metabolites. in contrast, pseudomonas putida degraded quercetin via an initial fission in its a-ring, and agrobacte ... | 1994 | 8071218 |
| the nodd proteins of rhizobium sp. strain br816 differ in their interactions with coinducers and in their activities for nodulation of different host plants. | the early steps of symbiotic nodule formation by rhizobium spp. on plants require coordinate expression of several nod gene operons, which is accomplished by the activating protein nodd. rhizobium sp. strain br816, isolated from leucaena leucocephala, contains four nodd genes which differ in their interaction with flavonoids. two of the four nodd proteins, namely, nodd1 and nodd2, obey the lysr rule regarding the need of a coinducer. nodd3 shows hardly any inducing activity, and nodd4 contains a ... | 1994 | 7986038 |
| identification of rhizobium-specific intergenic mosaic elements within an essential two-component regulatory system of rhizobium species. | analysis of the dna regions upstream of the phosphoenolpyruvate carboxykinase gene (pcka) in rhizobium meliloti and rhizobium sp. strain ngr234 identified an open reading frame which was highly homologous to the agrobacterium tumefaciens chromosomal virulence gene product chvi. a second gene product, 500 bp downstream of the chvi-like gene in r. meliloti, was homologous to the a. tumefaciens chvg protein. the homology between the r. meliloti and a. tumefaciens genes was confirmed, because the r. ... | 1995 | 7559334 |
| a rapeseed cold-inducible transcript encodes a phosphoenolpyruvate carboxykinase. | we have isolated a clone corresponding to a new cold-regulated gene from a cdna library made from rapeseed (brassica napus cv samourai) cold-acclimated etiolated seedlings. sequence analysis and homology searches showed that this clone encodes a protein highly homologous to the atp-dependent phosphoenolpyruvate carboxykinase (pepck; ec 4.1.1.49) from saccharomyces cerevisiae, trypanosoma, rhizobium sp., and escherichia coli; we refer to the b. napus clone as bnpepck. a potential atp-binding site ... | 1995 | 7480349 |
| morphology of root nodules and nodule-like structures formed by rhizobium and agrobacterium strains containing a rhizobium meliloti megaplasmid. | we examined expression of the megaplasmid prme41b of rhizobium meliloti in two different rhizobium sp. strains and in agrobacterium tumefaciens. transfer of prme41b into these bacteria was facilitated by insertion of a recombinant plasmid coding for mobilization functions of rp4 into the nif region (kondorosi, a., e. kondorosi, c.e. pankhurst, w. j. broughton, and z. banfalvi, 1982, mol. gen. genet., 188:433-439). in all cases, transconjugants formed nodule-like structures on the roots of medica ... | 1983 | 6885919 |
| methylammonium uptake by rhizobium sp. strain 32h1. | we present evidence that methylammonium is transported into cowpea rhizobium sp. strain 32h1 cells by a membrane carrier whose natural substrate is ammonium. after growth in low (0.2%) oxygen, which is necessary for nitrogen fixation by these cells, respiring rhizobial cells took up [14c]methylammonium to high intracellular levels. cells grown in atmospheric (21%) oxygen did not take up methylammonium. uptake (transport plus metabolism) was maximal in cells harvested in the early stationary phas ... | 1983 | 6826521 |
| pleomorphism and acetylene-reducing activity of free-living rhizobia. | cowpea-type rhizobium sp. strain 32h1 and rhizobium japonicum usda 26 and 110 grown on a glutamate-mannitol-gluconate agar medium showed increases in the number of pleomorphic cells coincident with their acetylene-reducing activity. pleomorphs appeared to be inhibited in growth nonuniformly, because acetylene-reducing cultures were mixtures of rod, branched (v, y, and t), and other irregularly shaped cells. in contrast, strain usda 10 consistently failed to reduce acetylene, even though it also ... | 1983 | 6822472 |
| initial stages in the morphogenesis of nitrogen-fixing stem nodules of sesbania rostrata. | morphogenesis of stem nodules in sesbania rostrata was studied over a period of 6 days after inoculation with an appropriate species of rhizobium. nodulation sites were initially slightly raised, circular areas 0.3 to 0.6 mm in diameter and 4 to 5 mm apart in vertical rows along the length of the stem. each site was underlaid by an adventitious root primordium. a site became susceptible to infection by a specific rhizobium sp. when the root primordium broke through the epidermis, leaving a fissu ... | 1983 | 6630154 |
| properties of six pesticide degradation plasmids isolated from alcaligenes paradoxus and alcaligenes eutrophus. | biophysical and genetic properties of six independently isolated plasmids encoding the degradation of the herbicides 2,4-dichlorophenoxyacetic acid and 4-chloro-2-methylphenoxyacetic acid are described. four of the plasmids, pjp3, pjp4, pjp5, and pjp7, had molecular masses of 51 megadaltons, belonged to the incp1 incompatibility group, and transferred freely to strains of escherichia coli, rhodopseudomonas sphaeroides, rhizobium sp., agrobacterium tumefaciens, pseudomonas putida, pseudomonas flu ... | 1981 | 6257648 |
| h+/atp stoichiometry of cowpea rhizobium sp. strain 32h1 cells grown under nitrogen-fixing and nitrogen-nonfixing conditions. | the obligate aerobe cowpea rhizobium sp. strain 32h1 in axenic culture is able to fix n2 when grown under 0.2% o2 but not when grown under 21% o2. it was, therefore, of interest to investigate atp synthesis in these cells grown under the two conditions. when respiring in buffers having phs ranging from 6 to 8.5, cells grown under either o2 tension maintained an intracellular ph more alkaline than the exterior. the transmembrane chemical gradient of h+ (delta ph) was essentially the same under bo ... | 1984 | 6237099 |
| rhizobium sp. strain ors571 ammonium assimilation and nitrogen fixation. | among rhizobia studied, rhizobium sp. strain ors571 alone grew unambiguously on n2 as sole n source. in ors571 , only the glutamine synthetase (gs)-glutamate synthase ( gogat ) pathway assimilated ammonium. however, ors571 exhibited two unique physiological aspects of this pathway: ors571 had only gs i, whereas all other rhizobiaceae studied had both gs i and gs ii, and both nadph- and nadh-dependent gogat activities were present. ors571 gs-affected and nadph- gogat -affected mutant strains were ... | 1984 | 6144666 |
| comparative properties of glutamine synthetases i and ii in rhizobium and agrobacterium spp. | some properties of glutamine synthetase i (gsi) and gsii are described for a fast-growing rhizobium sp. (rhizobium trifolii t1), a slow-growing rhizobium sp. (rhizobium japonicum usda 83), and agrobacterium tumefaciens c58. gsii of the fast-growing rhizobium sp. and gsii of the agrobacterium sp. were considerably more heat labile than gsii of the slow-growing rhizobium sp. as previously shown in r. japonicum 61a76, gsi became adenylylated rapidly in all species tested in response to ammonium. gs ... | 1980 | 6107288 |
| purification of glutamine synthetase from a variety of bacteria. | we have developed two procedures which allow the very rapid purification of glutamine synthetase (gs) from a diverse variety of bacteria. the first procedure, based upon differential sedimentation, depends upon the association of gs with deoxyribonucleic acid in cell extracts. the second procedure, derived from the method of c. gross et al (j. bacteriol. 128:382-389, 1976) for purifying ribonucleic acid polymerase by polyethylene glycol (peg) precipitation, enabled us to obtain high yields of gs ... | 1980 | 6102984 |
| physiological roles of glutamine synthetases i and ii in ammonium assimilation in rhizobium sp. 32h1. | the two glutamine synthetases of rhizobium sp. 32h1 appear to be structurally and functionally distinct. glutamine synthetase i was reversibly adenylylated, and its synthesis was repressed only twofold by ammonium. when in the unadenylylated configuration, it was the enzyme which allowed the organism to grow, albeit marginally, on ammonium as a nitrogen source. there is no evidence to suggest that the second enzyme, glutamine synthetase ii, is regulated by adenylylation. however, this enzyme was ... | 1980 | 6102559 |
| rhizobium sp. strain ors571 grows synergistically on n2 and nicotinate as n sources. | rhizobium sp. strain ors571 conducts synergistic, free-living n2 fixation and nicotinate oxidation. explicitly, ors571 is able to fix n2 aerobically because 6-oh-nicotinate acts as an intracellular o2 sink. because 6-oh-nicotinate oxidation is mandatory for aerobic, free-living n2 fixation and because the synergistic processes yield ammonium from substrates (as the nitrogen source for growth), ors571 is not a diazotroph. | 1986 | 3753598 |
| a locus encoding host range is linked to the common nodulation genes of bradyrhizobium japonicum. | by using cloned rhizobium meliloti, rhizobium leguminosarum, and rhizobium sp. strain mpik3030 nodulation (nod) genes as hybridization probes, homologous regions were detected in the slow-growing soybean symbiont bradyrhizobium japonicum usda 110. these regions were found to cluster within a 25-kilobase (kb) region. specific nod probes from r. meliloti were used to identify noda-, nodb-, nodc-, and nodd-like sequences clustered on two adjacent hindiii restriction fragments of 3.9 and 5.6 kb. a 7 ... | 1987 | 3584066 |
| nucleotide sequence of the gene encoding the nitrogenase iron protein of thiobacillus ferrooxidans. | the dna sequence was determined for the cloned thiobacillus ferrooxidans nifh and part of the nifd genes. a putative t. ferrooxidans nifh promoter was identified whose sequences showed perfect consensus with those of the klebsiella pneumoniae nif promoter. two putative consensus upstream activator sequences were also identified. the amino acid sequence was deduced from the dna sequence. in a comparison of nifh dna sequences from t. ferrooxidans and eight other nitrogen-fixing microbes, a rhizobi ... | 1987 | 3539923 |
| nitrogen fixation ability of exopolysaccharide synthesis mutants of rhizobium sp. strain ngr234 and rhizobium trifolii is restored by the addition of homologous exopolysaccharides. | several transposon tn5-induced mutants of the broad-host-range rhizobium sp. strain ngr234 produce little or no detectable acidic exopolysaccharide (eps) and are unable to induce nitrogen-fixing nodules on leucaena leucocephala var. peru or siratro plants. the ability of these exo- mutants to induce functioning nodules on leucaena plants was restored by coinoculation with a sym plasmid-cured (nod- exo+) derivative of parent strain ngr234, purified eps from the parent strain, or the oligosacchari ... | 1987 | 3025187 |
| characterization of three genomic loci encoding rhizobium sp. strain ors571 n2 fixation genes. | sixty-five independent, n2 fixation-defective (nif-) vector insertion (vi) mutants were selected, cloned, and mapped to the ors571 genome. the recombinant nif::vi plasmids obtained in this way were used as dna hybridization probes to isolate homologous phages from a genomic library of ors571 constructed in lambda embl3. genomic maps were drawn for three ors571 nif gene loci. forty-five nif::vi mutants in genomic nif locus 1 defined two gene clusters separated by 8 kilobase pairs (kb) of dna. in ... | 1986 | 3001035 |
| vector insertion mutagenesis of rhizobium sp. strain ors571: direct cloning of mutagenized dna sequences. | when the limited-host-range plasmid pvp2021 carrying tn5 was mobilized into rhizobium sp. strain ors571 and stable acquisition of tn5 was selected, ors571 plasmid-genome cointegrates were exclusively obtained; direct tn5 transposition was never observed. in every case, genomic cointegrates exhibited an additional (third) is50 element that bordered vp2021 dna sequences but maintained a single tn5 element. genomic cointegrates containing is50 triplications were stable; neither phenotypic reversion ... | 1985 | 2984177 |
| product of the lactococcus lactis gene required for malolactic fermentation is homologous to a family of positive regulators. | malolactic fermentation is a secondary fermentation that many lactic acid bacteria can carry out when l-malate is present in the medium. the activation of the malolactic system in lactococcus lactis is mediated by a locus we call mler. induction of the genes necessary to perform malolactic fermentation occurs only in bacteria with a functional copy of mler. the mler gene consists of one open reading frame capable of coding for a protein with a calculated molecular mass of 33,813 daltons. the ami ... | 1989 | 2498286 |
| rhizobium meliloti nodd genes mediate host-specific activation of nodabc. | to differentiate among the roles of the three nodd genes of rhizobium meliloti 1021, we studied the activation of a nodc-lacz fusion by each of the three nodd genes in response to root exudates from several r. meliloti host plants and in response to the flavone luteolin. we found (i) that the nodd1 and nodd2 products (nodd1 and nodd2) responded differently to root exudates from a variety of hosts, (ii) that nodd1 but not nodd2 responded to luteolin, (iii) that nodd2 functioned synergistically wi ... | 1990 | 2298703 |
| sequence and analysis of the rpon sigma factor gene of rhizobium sp. strain ngr234, a primary coregulator of symbiosis. | we report the nucleotide sequence of the rpon gene from broad-host-range rhizobium sp. strain ngr234 and analyze the encoded rpon protein, a sigma factor. comparative analysis of the deduced amino acid sequence of rpon from ngr234 with sequences from other gram-negative bacteria identified a perfectly conserved rpon box unique to rpon sigma factors. symbiotic regulatory phenotypes were defined for a site-directed internal deletion within the coding sequence of the rpon gene of rhizobium strain n ... | 1990 | 2211497 |
| functional and evolutionary relatedness of genes for exopolysaccharide synthesis in rhizobium meliloti and rhizobium sp. strain ngr234. | rhizobium meliloti su47 and rhizobium sp. strain ngr234 produce distinct exopolysaccharides that have some similarities in structure. r. meliloti has a narrow host range, whereas rhizobium strain ngr234 has a very broad host range. in cross-species complementation and hybridization experiments, we found that several of the genes required for the production of the two polysaccharides were functionally interchangeable and similar in evolutionary origin. ngr234 exoc and exoy corresponded to r. meli ... | 1990 | 2203745 |
| 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 ... | 1990 | 2152899 |
| two genes that regulate exopolysaccharide production in rhizobium meliloti. | we describe a new rhizobium meliloti gene, exox, that regulates the synthesis of the exopolysaccharide, succinoglycan, exox resembled the psi gene of r. leguminosarum bv. phaseoli and the exox gene of rhizobium sp. strain ngr234 in its ability to inhibit exopolysaccharide synthesis when present in multiple copies, exox did not appear to regulate the expression of exop. the effect of exox was counterbalanced by another r. meliloti gene, exof. exof is equivalent to rhizobium sp. strain ngr234 exoy ... | 1990 | 2118508 |
| heterologous exopolysaccharide production in rhizobium sp. strain ngr234 and consequences for nodule development. | rhizobium sp. strain ngr234 produces large amounts of acidic exopolysaccharide. mutants that fail to synthesize this exopolysaccharide are also unable to nodulate the host plant leucaena leucocephala. a hybrid strain of rhizobium sp. strain ngr234 containing exo genes from rhizobium meliloti was constructed. the background genetics and nod genes of rhizobium sp. strain ngr234 are retained, but the cluster of genes involved in exopolysaccharide biosynthesis was deleted. these exo genes were repla ... | 1991 | 2022612 |
| specific oligosaccharide form of the rhizobium meliloti exopolysaccharide promotes nodule invasion in alfalfa. | rhizobium meliloti strain su47 produces both high molecular weight (hmw) and low molecular weight (lmw) forms of an acidic exopolysaccharide, succinoglycan. genetic studies have shown that succinoglycan is required for alfalfa root nodule invasion. we found that lmw succinoglycan, when applied exogenously to alfalfa roots, restored nodule invasion to exoa, exob, exof, and exoh mutants. nodule initiation signals were not involved, since lmw succinoglycan from r. meliloti nodd1d2d3 and noda mutant ... | 1992 | 1608972 |
| phylogenetic position of rhizobium sp. strain or 191, a symbiont of both medicago sativa and phaseolus vulgaris, based on partial sequences of the 16s rrna and nifh genes. | phenotypic and dna sequence comparisons are presented for eight rhizobium isolates that were cultured from field-grown alfalfa (medicago sativa l.) in oregon. these isolates were previously shown to nodulate both alfalfa and common bean (phaseolus vulgaris (l.) savi.). the objective of the present study was to determine their phylogenetic relationships to the normal symbionts of these plants, rhizobium meliloti and rhizobium leguminosarum biovar phaseoli, respectively. phenotypically, the oregon ... | 1992 | 1377901 |