| lipopolysaccharide core structures in rhizobium etli and mutants deficient in o-antigen. | lipopolysaccharide (lps) is a major component of the bacterial outer membrane, and for rhizobium spp. has been shown to play a critical role in the establishment of an effective nitrogen-fixing symbiosis with a legume host. many genes required for o-chain polysaccharide synthesis are in the lps alpha region of the ce3 genome; this region may also carry lps genes required for core oligosaccharide synthesis. the lpss from several strains mutated in the alpha region were isolated, and their mild ac ... | 1995 | 7538123 |
| fragmentations of the large-subunit rrna in the family rhizobiaceae. | a 130-nucleotide-long rrna species corresponding to the 5' end of the 23s rrna gene was found in 96 strains belonging to different rhizobium, bradyrhizobium, and agrobacterium species. additional fragmentation in the central region of the large-subunit rrna occurred in all agrobacteria, except agrobacterium vitis, and in most rhizobium leguminosarum and rhizobium etli strains but did not occur in any of the other rhizobia and bradyrhizobia studied. | 1995 | 7592497 |
| phylogenetic relationships and host range of rhizobium spp. that nodulate phaseolus vulgaris l. | we determined the nucleotide sequences of 16s rrna gene segments from five rhizobium strains that have been isolated from tropical legume species. all share the capacity to nodulate phaseolus vulgaris l., the common bean. phylogenetic analysis confirmed that these strains are of two different chromosomal lineages. we defined the host ranges of two strains of rhizobium etli and three strains of r. tropici, comparing them with those of the two most divergently related new strains. twenty-two of th ... | 1995 | 7618891 |
| fermentative and aerobic metabolism in rhizobium etli. | strains of rhizobium etli, rhizobium meliloti, and rhizobium tropici decreased their capacity to grow after successive subcultures in minimal medium, with a pattern characteristic for each species. during the growth of r. etli ce 3 in minimal medium (mm), a fermentation-like response was apparent: the o2 content was reduced and, simultaneously, organic acids and amino acids were excreted and poly-beta-hydroxybutyrate (phb) was accumulated. some of the organic acids excreted into the medium were ... | 1995 | 7768801 |
| discrete amplifiable regions (amplicons) in the symbiotic plasmid of rhizobium etli cfn42. | frequent tandem amplification of defined regions of the genome, called amplicons, is a common characteristic in the genomes of some rhizobium species, such as rhizobium etli. in order to map these zones in a model rhizobium replicon, we undertook an analysis of the plasticity patterns fostered by amplicons in the psym (390 kb) of r. etli cfn42. data presented in this article indicate the presence of four amplicons in psym, used for the generation of tandem amplifications and deletions. the ampli ... | 1995 | 7860608 |
| wild type rhizobium etli, a bean symbiont, produces acetyl-fucosylated, n-methylated, and carbamoylated nodulation factors. | phaseolus vulgaris (common bean) can be nodulated by different rhizobium species. a new species has been recently proposed: rhizobium etli. following transcriptional activation of the bacterial nodulation genes using naringenin or bean seed exudate, we have isolated, purified, and characterized r. etli extracellular nodulation factors. they are chitopentameric compounds that are n-methyl-n-vaccenoylated at their non-reducing end. at position 6 of the reducing n-acetyl-d-glucosamine, they are 4-o ... | 1995 | 7890737 |
| dna binding activity of ntrc from rhizobium grown on different nitrogen sources. | the dna-binding activity of the ntrc protein can be demonstrated in gel retardation assays with concentrated protein extracts of rhizobium etli. using extracts from either the wild type or a ntrc mutant strain and an antiserum raised against the ntrc protein, we demonstrate specific binding of ntrc to the upstream regulatory region of the glnii gene, where two putative ntrc-binding sites are present. kno3-grown bacteria contain less ntrc protein and more ntrc-binding activity than nh4cl-grown ba ... | 1994 | 7957908 |
| nucleotide sequence of the rhizobium etli nods gene. | the complete nucleotide sequence of the nods gene from the bean-nodulating rhizobium etli, presumably encoding a methyltransferase, was determined. a phylogenetic analysis of five different nods proteins from three genera of gram- soil bacteria, azorhizobium, bradyrhizobium and rhizobium, was performed. | 1994 | 7959055 |
| genetic characterization of rhizobium sp. strain tal1145 that nodulates tree legumes. | rhizobium sp. strain tal1145 nodulates leucaena leucocephala and phaseolus vulgaris, in addition to a wide range of tropical tree legumes. six overlapping clones that complemented nodulation defects in leucaena and bean rhizobia were isolated and a 40-kb map of the symbiosis region was constructed. the common nod and nifa genes were situated approximately 17 kb apart, with the nodij genes in between. these clones enabled a derivative of tal1145 carrying a partially deleted psym to form ineffecti ... | 1994 | 8012908 |
| infection of soybean and pea nodules by rhizobium spp. purine auxotrophs in the presence of 5-aminoimidazole-4-carboxamide riboside. | purine auxotrophs of various rhizobium species are symbiotically defective, usually unable to initiate or complete the infection process. earlier studies demonstrated that, in the rhizobium etli-bean symbiosis, infection by purine auxotrophs is partially restored by supplementation of the plant medium with 5-amino-imidazole-4-carboxamide (aica) riboside, the unphosphorylated form of the purine biosynthetic intermediate aicar. the addition of purine to the root environment does not have this effe ... | 1994 | 8195084 |
| genomic heterogeneity among french rhizobium strains isolated from phaseolus vulgaris l. | levels of dna relatedness between strains isolated from root nodules of phaseolus vulgaris and reference strains of different rhizobium species were determined by performing dna-dna hybridization experiments (s1 nuclease method). the nine strains examined were members of three genomic groups previously delineated by a restriction fragment length polymorphism analysis among strains isolated from p. vulgaris at different sites in france. in agreement with the results of the restriction fragment le ... | 1993 | 8240956 |
| reclassification of american rhizobium leguminosarum biovar phaseoli type i strains as rhizobium etli sp. nov. | a new rhizobium species that nodulates phaseolus vulgaris l. is proposed on the basis of a sequence analysis of 16s ribosomal dna. this taxon, rhizobium etli sp. nov., was previously named rhizobium leguminosarum biovar phaseoli (type i strains) and is characterized by the capacity to establish an effective symbiosis with bean plants, the reiteration of the nitrogenase structural genes, the organization of the common nodulation genes into two separate transcriptional units bearing noda and nodbc ... | 1993 | 8494746 |
| isolation, chemical structures and biological activity of the lipo-chitin oligosaccharide nodulation signals from rhizobium etli. | rhizobium etli is a microsymbiont of plants of the genus phaseolus. using mass spectrometry we have identified the lipo-chitin oligosaccharides (lcos) that are produced by r. etli strain ce3. they are n-acetylglucosamine pentasaccharides of which the non-reducing residue is n-methylated and n-acylated with cis-vaccenic acid (c18:1) or stearic acid (c18:0) and carries a carbamoyl group at c4. the reducing residue is substituted at the c6 position with o-acetylfucose. analysis of their biological ... | 1995 | 8534845 |
| the role of glutaminase in rhizobium etli: studies with a new mutant. | in order to examine the role of glutaminase in rhizobium etli, we isolated and characterized a r. etli glutaminase mutant (lm16). this mutant was selected for its impaired ability to grow on glutamine as nitrogen and carbon source while retaining the ability to grow on other nitrogen and carbon sources. the mutant showed very low levels of glutaminase activity under various growth conditions in comparison with the wild-type strain. with glutamine as the only nitrogen and carbon source, lm16 show ... | 1995 | 8535516 |
| 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 ... | 1996 | 8573502 |
| the enhancement of ammonium assimilation in rhizobium etli prevents nodulation of phaseolus vulgaris. | the modification of the ammonium assimilation pathway of rhizobium etli (gs-gogat) by adding an additional ammonium assimilation enzyme, gdh, strongly affects its symbiotic interaction with beans. the plasmid pam1a, based in the stable vector ptr101 (m. weinstein, r. c. roberts, and d. r. helsinki, j. bacteriol. 174,7486-7489, 1992), containing the escherichia coli gdha gene flanked by two transcription-translation terminators was constructed. the expression of gdh in both, the wild type (cfn42/ ... | 1995 | 8589413 |
| genetic and physiological characterization of a rhizobium etli mutant strain unable to synthesize poly-beta-hydroxybutyrate. | rhizobium etli accumulates poly-beta-hydroxybutyrate (phb) in symbiosis and in free life. phb is a reserve material that serves as a carbon and/or electron sink when optimal growth conditions are not met. it has been suggested that in symbiosis phb can prolong nitrogen fixation until the last stages of seed development, but experiments to test this proposition have not been done until now. to address these questions in a direct way, we constructed an r. etli phb-negative mutant by the insertion ... | 1996 | 8626293 |
| isolation of monoclonal antibodies reacting with the core component of lipopolysaccharide from rhizobium leguminosarum strain 3841 and mutant derivatives. | monoclonal antibodies reacting with the core oligosaccharide or lipid a component of rhizobium lipopolysaccharide (lps) could be useful for the elucidation of the structure and biosynthesis of this group of macromolecules. mutant derivatives of rhizobium leguminosarum 3841 with lps structures lacking the major o-antigen moiety were used as immunogens, and eight antibodies were selected for further study. all the antibodies reacted with the fast-migrating species known as lps-2 following gel elec ... | 1996 | 8631658 |
| in vitro characterization of the orf1-ntrbc promoter of rhizobium etli. | rhizobium sigma vegetative-dependent promoters are different from those of enteric bacteria and have never been characterized before. we report here the biochemical characterization of the orf1-ntrbc promoter of rhizobium etli. the minimal promoter region was located by means of a transcriptional fusion and further characterized by in vitro transcription and gel retardation experiments. oligonucleotides used as dna competitors in runoff transcription experiments allowed the precise localisation ... | 1996 | 8654590 |
| regulatory proteins and cis-acting elements involved in the transcriptional control of rhizobium etli reiterated nifh genes. | in rhizobium etli the nitrogenase reductase genes are reiterated. strain ce3 has three copies; nifha and nifhb form part of nifhdk operons with the nitrogenase structural genes, while nifhc is linked to a truncated nifd homolog. their sequences are identical up to 6 residues upstream from a sigma54-dependent promoter. a remarkable difference among them is the absence of canonical nifa binding sites upstream of nifhc while a canonical binding site is located 200 bp upstream of nifha and nifhb. to ... | 1996 | 8655489 |
| conservation of pcaq, a transcriptional activator of pca genes for catabolism of phenolic compounds, in agrobacterium tumefaciens and rhizobium species. | in agrobacterium tumefaciens a348, control of five genes for catabolism of the phenolic compound protocatechuate to beta-ketoadipate is exerted by the gene pcaq. the product of pcaq is a transcriptional activator which is distinct from regulators of the beta-ketoadipate pathway characterized in other bacterial groups. an investigation of whether pcaq is present and conserved in related rhizobium species employed southern hybridization and an agrobacterial pcad::lacz promoter probe plasmid. these ... | 1996 | 8655573 |
| typing of rhizobia by pcr dna fingerprinting and pcr-restriction fragment length polymorphism analysis of chromosomal and symbiotic gene regions: application to rhizobium leguminosarum and its different biovars. | characterization of 43 strains of rhizobium leguminosarum biovars viciae, trifolii, and phaseoli was performed by two methodologies based on pcr amplification, i.e., pcr dna fingerprinting of interrepeat sequences and restriction fragment length polymorphism (rflp) analysis of pcr -amplified chromosomal and symbiotic gene regions. groupings generated by pcr dna fingerprinting with either extragenic palindromic repetitive primers or two different single random primers were correlated with similar ... | 1996 | 8787401 |
| bacillus polymyxa stimulates increased rhizobium etli populations and nodulation when co-resident in the rhizosphere of phaseolus vulgaris. | microbial competition for carbon sources is a primary determinant of rhizosphere ecology. we employed the pcr to examine the population fluctuations of a symbiotic nitrogen-fixing bacterium (rhizobium etli) during the first 11 days following inoculation of phaseolus vulgaris seedlings grown in the presence or absence of a common asymbiotic rhizosphere resident (bacillus polymyxa). when b. polymyxa was applied as a co-inoculant, increases in both early rhizobial root populations and final root po ... | 1996 | 8810510 |
| pyruvate carboxylase from rhizobium etli: mutant characterization, nucleotide sequence, and physiological role. | pyruvate carboxylase (pyc), a biotin-dependent enzyme which catalyzes the conversion of pyruvate to oxaloacetate, was hypothesized to play an important anaplerotic role in the growth of rhizobium etli during serial subcultivation in minimal media containing succinate (s. encarnación, m. dunn, k. willms, and j. mora, j. bacteriol. 177:3058-3066, 1995). r. etli and r. tropici pyc::tn5-mob mutants were selected for their inability to grow in minimal medium with pyruvate as a sole carbon source. dur ... | 1996 | 8830693 |
| a 150-megadalton plasmid in rhizobium etli strain tal182 contains genes for nodulation competitiveness on phaseolus vulgaris l. | rhizobium etli tal182, a competitive strain for the nodulation of phaseolus beans, occupied more than 99% of the nodules when co-inoculated in various proportions with rhizobium tal1145 or rhizobium tropici ciat899. two overlapping cosmid clones, puhr68 and puhr69, containing genes for nodulation competitiveness from tal182, were isolated by functional complementation of strain tal1145. using one of these cosmid clones, we constructed two tn5-insertion mutants of tal182 defective in nodulation c ... | 1996 | 8864213 |
| cloning of the rpod analog from rhizobium etli: siga of r. etli is growth phase regulated. | rhizobium bacteria fix atmospheric nitrogen during symbiosis with legume plants only after bacterial division is arrested. the role of the major vegetative sigma factor, siga, utilized by rhizobium bacteria during symbiosis is unknown. by using pcr technology, a portion of the siga gene corresponding to domain ii was directly amplified from rhizobium etli total dna by using two primers designed in accordance with the published sequence of siga from agrobacterium tumefaciens. the amplified fragme ... | 1996 | 8955394 |
| the role of the nodi and nodj genes in the transport of nod metabolites in rhizobium etli. | a kinetic analysis of secretion of lipo-chitin oligosaccharides (lco) produced by rhizobium etli (re) wild-type (wt) strain and derivatives carrying disrupted nodi or nodj genes was performed. lco were detected in the growth media of the wt strain as early as 1 h after nod gene induction. in contrast, strains carrying nodi or nodj mutations secreted less lco, and accumulated lco metabolites intracellularly after 4 h of induction. these re mutants presented a delayed nodulation phenotype and a re ... | 1996 | 8964496 |
| cloning and sequence analysis of the rhizobium etli ccma and ccmb genes involved in c-type cytochrome biogenesis. | in this paper we describe the sequence analysis of two rhizobium etli genes (ccma and ccmb) which are believed to participate in the transport of the haem moiety to the periplasm in other bacterial species. the characterized dna region was isolated by complementation of a r. etli tn5mob induced mutant (cfn4201) which was affected in the production of c-type cytochromes. sequence analysis of this region identified three open reading frames, two were identified as the ccma and ccmb genes. the pred ... | 1996 | 8982078 |
| evidence that eukaryotic triosephosphate isomerase is of alpha-proteobacterial origin. | we have cloned and sequenced genes for triosephosphate isomerase (tpi) from the gamma-proteobacterium francisella tularensis, the green non-sulfur bacterium chloroflexus aurantiacus, and the alpha-proteobacterium rhizobium etli and used these in phylogenetic analysis with tpi sequences from other members of the bacteria, archaea, and eukarya. these analyses show that eukaryotic tpi genes are most closely related to the homologue from the alpha-proteobacterium and most distantly related to archae ... | 1997 | 9037042 |
| characterization of the promoter of the rhizobium etli reca gene. | the promoter of the rhizobium etli reca gene has been identified by primer extension and by making deletions affecting several regions located upstream of its coding region. a gel mobility shift assay carried out with crude extracts of cells of r. etli has been used to show that a dna-protein complex is formed in the r. etli reca promoter region in vitro. analysis of the minimal region of the reca promoter giving rise to this dna-protein complex revealed the presence of an imperfect palindrome c ... | 1997 | 9045815 |
| rosr, a determinant of nodulation competitiveness in rhizobium etli. | we previously described a tn5 mutant of rhizobium etli strain ce3, designated ce3003, that is decreased in nodulation competitiveness, reduced in competitive growth in the rhizosphere, and has a hydrophobic cell surface (r. s. araujo, e. a. robleto, and j. handelsman, appl. environ. microbiol., 60:1430-1436, 1994). to determine the molecular basis for the mutant phenotypes, we identified a 1.2-kb fragment of dna derived from the parent that restored the wild-type phenotypes to the mutant. dna se ... | 1997 | 9057324 |
| isolation and characterization of rhizobium etli mutants altered in degradation of asparagine. | rhizobium etli mutants unable to grow on asparagine as the nitrogen and carbon source were isolated. two kinds of mutants were obtained: ahz1, with very low levels of aspartase activity, and ahz7, with low levels of asparaginase and very low levels of aspartase compared to the wild-type strain. r. etli had two asparaginases differentiated by their thermostabilities, electrophoretic mobilities, and modes of regulation. the ahz mutants nodulated as did the wild-type strain and had nitrogenase leve ... | 1997 | 9068657 |
| identification of soil bacteria expressing a symbiotic plasmid from rhizobium leguminosarum bv. trofolii. | a hundred strains of non-nodulating, gram-negative, rod-shaped bacteria were isolated from clover-ryegrass pastures on three different soil types and from a sandy loam under lupins. when crossed with escherichia coli pn200 containing the cointegrate plasmid ppn1, 11 transconjugants gained the ability to form nodules on the roots of white clover (trifolium repens cv. grasslands huia). a noda probe indicated that they had gained nodulation genes. the identities of these 11 strains and 4 others der ... | 1997 | 9090106 |
| cloning and characterization of the reca of paracoccus denitrificans and construction of a reca-deficient mutant. | the reca gene of paracoccus denitrificans has been isolated from a genomic library by hybridization with the rhodobacter sphaeroides reca gene. its complete nucleotide sequence consists of 1071 bp encoding a polypeptide of 356 amino acids. nucleotide sequence analysis of the p. denitrificans reca gene revealed the closest identities with the r. sphaeroides and the rhodobacter capsulatus reca genes. nevertheless, and surprisingly, reca genes of these two phototrophic bacteria are not dna damage-i ... | 1997 | 9119195 |
| identification of two glutaminases in rhizobium etli. | we present evidence that rhizobium etli has two glutaminases differentiated by their thermostability and electrophoretic mobility. the thermostable glutaminase (b) is constitutive, in contrast with the thermolabile glutaminase (a), which is positively regulated by glutamine and negatively regulated by ammonium and by the carbon source. in distinction to glutaminase a, glutaminase b plays a minor role in the utilization of glutamine as a carbon source, but it may play a role in maintaining the ba ... | 1996 | 9126674 |
| cloning and transcriptional analysis of the lipa (lipoic acid synthetase) gene from rhizobium etli. | we report here the isolation of a rhizobium etli gene involved in lipoic acid metabolism, the lipa gene, which complements a lipa mutant strain of escherichia coli. a promoter region (lipap) was mapped immediately upstream of lipa and two in vivo transcription initiation sites were identified, preceded by sequences showing some homology to the -10/-35 promoter consensus sequences. the activity of the lipap was found not to be regulated either by the carbon source or by the addition of lipoic aci ... | 1997 | 9141657 |
| genetic evidence for 5-aminoimidazole-4-carboxamide ribonucleotide (aicar) as a negative effector of cytochrome terminal oxidase cbb3 production in rhizobium etli. | a rhizobium etli tn5mob-induced mutant (cfn035) exhibits an enhanced capacity to oxidize n,n,n',n', tetramethyl-p -phenylenediamine (tmpd), a presumptive indicator of elevated cytochrome c terminal oxidase activity. sequencing of the mutated gene in cfn035 revealed that it codes for the amidophosphoribosyl transferase enzyme (purf) that catalyzes the first step in the purine biosynthetic pathway. two c-type cytochromes with molecular weights of 32 and 27 kda were produced in strain cfn035, which ... | 1997 | 9202382 |
| sequence, localization and characteristics of the replicator region of the symbiotic plasmid of rhizobium etli. | the replicator region of the symbiotic plasmid of rhizobium etli cfn42 was cloned and sequenced. a plasmid derivative (ph3) harbouring a 5-6 kb hindiii fragment from the symbiotic plasmid was found to be capable of independent replication and eliminated the symbiotic plasmid when introduced into a r. etli cfnx101 strain (a reca derivative). the stability and the copy number of ph3 were the same as that of the symbiotic plasmid, indicating that the information required for stable replication and ... | 1997 | 9274036 |
| characterization of two plasmid-borne lps beta loci of rhizobium etli required for lipopolysaccharide synthesis and for optimal interaction with plants. | in rhizobium etli cfn42, both the symbiotic plasmid (pd) and plasmid b (pb) are required for effective bean nodulation. this is due to the presence on pb of a region (lps beta) involved in lipopolysaccharide (lps) biosynthesis. we report here the genetic array and functional features of this plasmid-borne region. the sequence analysis of a 3,595-bp fragment revealed the presence of a transcriptional unit integrated by two open reading frames (lps beta 1 and lps beta 2) essential for lps biosynth ... | 1997 | 9304861 |
| evaluation of the role of reca protein in plant virulence with reca mutants of xanthomonas campestris pv. campestris. | xanthomonas campestris pv. campestris nrrl b1459 reca mutants were isolated by recombination with an interrupted rhizobium etli reca gene and selection of double recombinants. the mutants were impaired in homologous genetic recombination and in dna repair as judged by their sensitivity to methyl-methane-sulfonate and to uv irradiation; these defects are complemented in trans by the r. etli reca gene. virulence of x. campestris pv. campestris nrrl b1459 to cabbage is considerably diminished by th ... | 1997 | 9304862 |
| rhizobium gallicum sp. nov. and rhizobium giardinii sp. nov., from phaseolus vulgaris nodules. | thirty-one strains of two new genomic species (genomic species 1 and 2) of rhizobia isolated from root nodules of phaseolus vulgaris and originating from various locations in france were compared with reference strains of rhizobia by performing a numerical analysis of 64 phenotypic features. each genomic species formed a distinct phenon and was separated from the other rhizobial species. a comparison of the complete 16s rrna gene sequences of a representative of genomic species 1 (strain r602spt ... | 1997 | 9336898 |
| classification of austrian rhizobia and the mexican isolate fl27 obtained from phaseolus vulgaris l. as rhizobium gallicum. | the phylogenetic positions of four rhizobial strains obtained from nodules of common bean plants (phaseolus vulgaris l.) grown in an austrian soil and of the mexican bean isolate fl27 are described. analysis of the 16s rrna genes revealed sequences almost identical to that of the rhizobium gallicum type strain, r602sp, with a maximum of two nucleotide substitutions. comparison of the 16s rrna gene sequences with those from other bacteria indicated highest similarity to rhizobium sp. strain ok-50 ... | 1997 | 9336913 |
| expression of thiamin biosynthetic genes (thicoge) and production of symbiotic terminal oxidase cbb3 in rhizobium etli. | in this paper we report the cloning and sequence analysis of four genes, located on plasmid pb, which are involved in the synthesis of thiamin in rhizobium etli (thic, thio, thig, and thie). two precursors, 4-methyl-5-(beta-hydroxyethyl)thiazole monophosphate and 4-amino-5-hydroxymethylpyrimidine pyrophosphate, are coupled to form thiamin monophosphate, which is then phosphorylated to make thiamin pyrophosphate. the first open reading frame (orf) product, of 610 residues, has significant homolog ... | 1997 | 9371431 |
| a cysg mutant strain of rhizobium etli pleiotropically defective in sulfate and nitrate assimilation. | by its inability to grow on sulfate as the sole sulfur source, a mutant strain (ctnux8) of rhizobium etli carrying tn5 was isolated and characterized. sequence analysis showed that tn5 is inserted into a cysg (siroheme synthetase)-homologous gene. by rnase protection assays, it was established that the cysg-like gene had a basal level of expression in thiosulfate- or cysteine-grown cells, which was induced when sulfate or methionine was used. unlike its wild-type parent (strain ce3), the mutant ... | 1997 | 9393698 |
| the arginine deiminase pathway in rhizobium etli: dna sequence analysis and functional study of the arcabc genes. | sequence analysis upstream of the rhizobium etli fixlj homologous genes revealed the presence of three open reading frames homologous to the arcabc genes of pseudomonas aeruginosa. the p. aeruginosa arcabc genes code for the enzymes of the arginine deiminase pathway: arginine deiminase, catabolic ornithine carbamoyltransferase (cotcase), and carbamate kinase. otcase activities were measured in free-living r. etli cells and in bacteroids isolated from bean nodules. otcase activity in free-living ... | 1997 | 9393705 |
| regulation of pyruvate carboxylase in rhizobium etli. | pyruvate carboxylase (pyc) is a biotin-dependent enzyme catalyzing the anaplerotic conversion of pyruvate to oxaloacetate in rhizobium etli strain ce3. a pyc::tn5 mutant had severely reduced growth, or failed to grow on sugars, three-carbon organic acids or glycerol, consistent with these substrates being metabolized via pyruvate. transconjugants expressing a pyc::beta-glucuronidase gene fusion had slightly increased apparent pyc transcription during growth on pyruvate as compared to succinate, ... | 1997 | 9435112 |
| the structures of the lipopolysaccharides from rhizobium etli strains ce358 and ce359. the complete structure of the core region of r. etli lipopolysaccharides. | the structural arrangement of oligosaccharides comprising the core region of rhizobium etli ce3 lipopolysaccharide (lps) has been elucidated through the characterization of the lpss from two r. etli mutants. one mutant, ce358, completely lacks the o-chain polysaccharide, while the second mutant, ce359, contains a truncated portion of this polysaccharide. this structural arrangement of the core oligosaccharides in these lpss was determined using electrospray ionization mass spectrometry, tandem m ... | 1998 | 9446581 |
| nifa-dependent expression of glutamate dehydrogenase in rhizobium etli modifies nitrogen partitioning during symbiosis. | constitutive expression of foreign glutamate dehydrogenase in rhizobium etli inhibits bean plant nodulation (a. mendoza, a. leija, e. martínez-romero, g. hernández, and j. mora. mol. plant-microbe interact. 8:584-592, 1995). here we report that this inhibition is overcome when controlling gdha expression by nifa, thus delaying the gdh activity onset after nodule establishment. expression of gdha modifies the nitrogen partitioning inside the bacteroid, where newly synthesized ammonia is preferent ... | 1998 | 9450332 |
| luxi- and luxr-homologous genes of rhizobium etli cnpaf512 contribute to synthesis of autoinducer molecules and nodulation of phaseolus vulgaris. | autoinduction plays an important role in intercellular communication among symbiotic and pathogenic gram-negative bacteria. we report here that a nitrogen-fixing symbiont of phaseolus vulgaris, rhizobium etli cnpaf512, produces at least seven different autoinducer molecules. one of them exhibits a growth-inhibitory effect like that of the bacteriocin small [n-(3r-hydroxy-7-cis-tetradecanoyl)-l-homoserine lactone]. at least two of the other autoinducers are synthesized by a luxi-homologous autoin ... | 1998 | 9473034 |
| the rhizobium etli amtb gene coding for an nh4+ transporter is down-regulated early during bacteroid differentiation. | during development of root nodules, rhizobium bacteria differentiate inside the invaded plant cells into n2-fixing bacteroids. terminally differentiated bacteroids are unable to grow using the ammonia (nh3) produced therein by the nitrogenase complex. therefore, the nitrogen assimilation activities of bacteroids, including the ammonium (nh4+) uptake activity, are expected to be repressed during symbiosis. by sequence homology the r. etli amtb (ammonium transport) gene was cloned and sequenced. a ... | 1998 | 9487694 |
| rearrangement of actin microfilaments in plant root hairs responding to rhizobium etli nodulation signals | the response of the actin cytoskeleton to nodulation (nod) factors secreted by rhizobium etli has been studied in living root hairs of bean (phaseolus vulgaris) that were microinjected with fluorescein isothiocyanate-phalloidin. in untreated control cells or cells treated with the inactive chitin oligomer, the actin cytoskeleton was organized into long bundles that were oriented parallel to the long axis of the root hair and extended into the apical zone. upon exposure to r. etli nod factors, th ... | 1998 | 9501120 |
| rhizobium etli cychjkl gene locus involved in c-type cytochrome biogenesis: sequence analysis and characterization of two cych mutants. | the cychjkl gene locus was cloned from rhizobium etli by the rescue of a tn5mob insertion of a mutant (ifc01) which was affected in the production of c-type cytochromes. the cych, cycj, cyck and cycl genes are proposed to code for different subunits of a haem lyase complex involved in the attachment of haem to cytochrome c apoproteins. cych of 365 aa shared 27, 36, 47 and 63% identity with cych from paracoccus denitrificans, bradyrhizobium japonicum, r. meliloti, and r. leguminosarum, respective ... | 1998 | 9524269 |
| the rhizobium etli rpon locus: dna sequence analysis and phenotypical characterization of rpon, ptsn, and ptsa mutants. | the rpon region of rhizobium etli was isolated by using the bradyrhizobium japonicum rpon1 gene as a probe. nucleotide sequence analysis of a 5,600-bp dna fragment of this region revealed the presence of four complete open reading frames (orfs), orf258, rpon, orf191, and ptsn, coding for proteins of 258, 520, 191, and 154 amino acids, respectively. the gene product of orf258 is homologous to members of the atp-binding cassette-type permeases. orf191 and ptsn are homologous to conserved orfs foun ... | 1998 | 9537369 |
| covasiam: an image analysis method that allows detection of confluent microbial colonies and colonies of various sizes for automated counting. | in this work we introduce the confluent and various sizes image analysis method (covasiam), an automated colony count technique that uses digital imaging technology for detection and separation of confluent microbial colonies and colonies of various sizes growing on petri dishes. the proposed method takes advantage of the optical properties of the surfaces of most microbial colonies. colonies in the petri dish are epi-illuminated in order to direct the reflection of concentrated light coming fro ... | 1998 | 9546177 |
| the rhizobium etli fixl protein differs in structure from other known fixl proteins. | the central heme-binding domain in the fixl proteins of sinorhizobium meliloti, bradyrhizobium japonicum, rhizobium leguminosarum biovar viciae and azorhizobium caulinodans, is highly conserved. the similarity with the corresponding domain in the rhizobium etli fixl protein is considerably less. this observation prompted us to analyze the heme-binding capacities of the r. etli fixl protein. the r. etli fixl gene was overexpressed in escherichia coli. in the presence of s. meliloti fixj, the over ... | 1998 | 9563844 |
| genes essential for nod factor production and nodulation are located on a symbiotic amplicon (amprtrcfn299pc60) in rhizobium tropici. | amplifiable dna regions (amplicons) have been identified in the genome of rhizobium etli. here we report the isolation and molecular characterization of a symbiotic amplicon of rhizobium tropici. to search for symbiotic amplicons, a cartridge containing a kanamycin resistance marker that responds to gene dosage and conditional origins of replication and transfer was inserted in the nodulation region of the symbiotic plasmid (psym) of r. tropici cfn299. derivatives harboring amplifications were s ... | 1998 | 9603874 |
| multiple recombination events maintain sequence identity among members of the nitrogenase multigene family in rhizobium etli. | a distinctive characteristic of the rhizobium genome is the frequent finding of reiterated sequences, which often constitute multigene families. interestingly, these families usually maintain a high degree of nucleotide sequence identity. it is commonly assumed that apparent gene conversion between reiterated elements might lead to concerted variation among members of a multigene family. however, the operation of this mechanism has not yet been demonstrated in the rhizobiaceae. in this work, we ... | 1998 | 9611191 |
| trifolitoxin production increases nodulation competitiveness of rhizobium etli ce3 under agricultural conditions. | a major barrier to the use of nitrogen-fixing inoculum strains for the enhancement of legume productivity is the inability of commercially available strains to compete with indigenous rhizobia for nodule formation. despite extensive research on nodulation competitiveness, there are no examples of field efficacy studies of strains that have been genetically improved for nodulation competitiveness. we have shown previously that production of the peptide antibiotic trifolitoxin (tfx) by rhizobium e ... | 1998 | 9647840 |
| differential regulation of rhizobium etli rpon2 gene expression during symbiosis and free-living growth. | the rhizobium etli rpon1 gene, encoding the alternative sigma factor sigma54 (rpon), was recently characterized and shown to be involved in the assimilation of several nitrogen and carbon sources during free-living aerobic growth (j. michiels, t. van soom, i. d'hooghe, b. dombrecht, t. benhassine, p. de wilde, and j. vanderleyden, j. bacteriol. 180:1729-1740, 1998). we identified a second rpon gene copy in r. etli, rpon2, encoding a 54.0-kda protein which displays 59% amino acid identity with th ... | 1998 | 9658006 |
| prevalence of the rhizobium etli-like allele in genes coding for 16s rrna among the indigenous rhizobial populations found associated with wild beans from the southern andes in argentina. | a collection of rhizobial isolates from nodules of wild beans, phaseolus vulgaris var. aborigineus, found growing in virgin lands in 17 geographically separate sites in northwest argentina was characterized on the basis of host range, growth, hybridization to a nifh probe, analysis of genes coding for 16s rrna (16s rdna), dna fingerprinting, and plasmid profiles. nodules in field-collected wild bean plants were largely dominated by rhizobia carrying the 16s rdna allele of rhizobium etli. a simil ... | 1998 | 9726909 |
| a stomatin-like protein encoded by the slp gene of rhizobium etli is required for nodulation competitiveness on the common bean. | rhizobium etli strain tal182 is a competitive strain for effective nodulation of beans. from this strain, a novel gene was isolated, slp, which is 669 bp in size and required for nodulation competition on the common bean. the slp knockout mutant of tal182 is defective in nodulation competition, shows reduced growth in the presence of 200 mm nacl, kcl or licl and is complemented by the cloned slp gene. the deduced amino acid sequence of slp shows 66-72% similarity to stomatin proteins of homo sap ... | 1998 | 9782511 |
| glutamine biosynthesis and the utilization of succinate and glutamine by rhizobium etli and sinorhizobium meliloti. | sinorhizobium meliloti 1021 and rhizobium etli ce3 turn over nitrogen and carbon from glutamine to ammonium and co2, respectively. some of the ammonium released is assimilated back into glutamine, indicating that a glutamine cycle similar to that in neurospora operates in rhizobium. in addition, a previously unrecognized metabolic pathway in rhizobium was discovered--namely, conversion of glutamine-carbon to gamma-hydroxybutyric acid and beta-hydroxybutyric acid. additionally, some of the 2-oxog ... | 1998 | 9782512 |
| mutational analysis of the rhizobium etli reca operator. | based upon our earlier studies (a. tapias, a. r. fernández de henestrosa, and j. barbé, j. bacteriol. 179:1573-1579, 1997) we hypothesized that the regulatory sequence of the rhizobium etli reca gene was ttgn11caa. however, further detailed analysis of the r. etli reca operator described in the present work suggests that it may in fact be gaacn7gtac. this new conclusion is based upon pcr mutagenesis analysis carried out in the r. etli reca operator, which indicates that the gaac and gtac submoti ... | 1998 | 9829943 |
| effects of bacterial antibiotic production on rhizosphere microbial communities from a culture-independent perspective | the effects of antibiotic production on rhizosphere microbial communities of field-grown phaseolus vulgaris were assessed by using ribosomal intergenic spacer analysis. inoculum strains of rhizobium etli ce3 differing only in trifolitoxin production were used. trifolitoxin production dramatically reduced the diversity of trifolitoxin-sensitive members of the alpha subdivision of the class proteobacteria with little apparent effect on most microbes. | 1998 | 9835600 |
| the rhizobium etli metz gene is essential for methionine biosynthesis and nodulation of phaseolus vulgaris. | a mutant strain (ctnux23) of rhizobium etli carrying tn5 unable to grow with sulfate as the sole sulfur source was isolated and characterized. sequence analysis showed that tn5 is inserted into a metz (o-succinylhomoserine sulfhydrylase)-homologous gene. the ctnux23 mutant strain had a growth dependency for methionine, although cystathionine or homocysteine, but not homoserine or o-succinylhomoserine, allowed growth of the mutant. rnase protection assays showed that the metz-like gene had a basa ... | 1999 | 9885190 |
| genes involved in the formation and assembly of rhizobial cytochromes and their role in symbiotic nitrogen fixation. | rhizobia fix nitrogen in a symbiotic association with leguminous plants and this occurs in nodules. a low-oxygen environment is needed for nitrogen fixation, which paradoxically has a requirement for rapid respiration to produce atp. these conflicting demands are met by control of oxygen flux and production of leghaemoglobin (an oxygen carrier) by the plant, coupled with the expression of a high-affinity oxidase by the nodule bacteria (bacteroids). many of the bacterial genes encoding cytochrome ... | 1998 | 9889979 |
| group-specific differentiation of rhizobium from clover species by pcr amplification of 23s rdna sequences. | two 20-bp primers that provide group-specific detection of rhizobium spp. by polymerase chain reaction (pcr) have been used to differentiate strains that belong to different effectiveness groups within the rhizobium-trifolium cross-inoculation group. the target for dna amplification was a 370-bp fragment of the 23s rdna region. analysis of additional root-nodule forming, as well as root-associated bacterial species by pcr-primer assay revealed that variability within this 20-bp segment of the 23 ... | 1998 | 10030005 |
| the noll gene from rhizobium etli determines nodulation efficiency by mediating the acetylation of the fucosyl residue in the nodulation factor. | the nodulation factors (nod factors) of rhizobium etli and r. loti carry a 4-o-acetyl-l-fucosyl group at the reducing end. it has been claimed, based on sequence analysis, that noll from r. loti participates in the 4-o-acetylation of the fucosyl residue of the nod factors, as an acetyl-transferase (d. b. scott, c. a. young, j. m. collins-emerson, e. a. terzaghi, e. s. rockman, p. a. lewis, and c. e. pankhurst. mol. plant-microbe interact. 9:187-197, 1996). further support for this hypothesis was ... | 1999 | 10065560 |
| bi-functional gfp- and gusa-containing mini-tn5 transposon derivatives for combined gene expression and bacterial localization studies. | the gfp gene, encoding the green fluorescent protein, was combined with the gusa gene, coding for the beta-glucuronidase enzyme, in mini-tn5 transposon derivatives for use in gram-negative bacteria. these mini-tn5 elements allow simultaneously monitoring of gene expression and localization of the marked bacteria. introduction of the resultant mini-tn5 transposons into rhizobium etli, azospirillum brasilense and pseudomonas stutzeri allowed us to visualise the interaction of these bacteria with t ... | 1999 | 10076635 |
| sequence and molecular analysis of the rhizobium etli glsa gene, encoding a thermolabile glutaminase. | we sequenced a 2.1 kb fragment of dna carrying the structural glsa gene, which codes for the rhizobium etli thermolabile glutaminase (a). the glsa gene complements the r. etli lm16 mutant that lacks glutaminase a activity, and is expressed in the heterologous host sinorhizobium meliloti. the deduced amino acid sequence consists of 309 residues, with a calculated molecular mass of 33 kda. the amino acid sequence shares 53% and 43% identity with two hypothetical glutaminases of e. coli; 42% identi ... | 1999 | 10095071 |
| enhanced nitrogen fixation in a rhizobium etli ntrc mutant that overproduces the bradyrhizobium japonicum symbiotic terminal oxidase cbb3 | the ntrc gene codes for a transcriptional activator protein that modulates gene expression in response to nitrogen. the cytochrome production pattern of a rhizobium etli ntrc mutant (cfn2012) was studied. co difference spectral analysis of membranes showed that cfn2012 produced a terminal oxidase similar to the symbiotic terminal oxidase of bacteroids in free-living cells under aerobic conditions, with a characteristic trough at 553 nm. cfn2012 produced two c-type cytochromes with molecular mass ... | 1999 | 10223993 |
| occurrence of choline and glycine betaine uptake and metabolism in the family rhizobiaceae and their roles in osmoprotection | the role of glycine betaine and choline in osmoprotection of various rhizobium, sinorhizobium, mesorhizobium, agrobacterium, and bradyrhizobium reference strains which display a large variation in salt tolerance was investigated. when externally provided, both compounds enhanced the growth of rhizobium tropici, sinorhizobium meliloti, sinorhizobium fredii, rhizobium galegae, agrobacterium tumefaciens, mesorhizobium loti, and mesorhizobium huakuii, demonstrating their utilization as osmoprotectan ... | 1999 | 10224003 |
| identification of a plasmid-borne locus in rhizobium etli kim5s involved in lipopolysaccharide o-chain biosynthesis and nodulation of phaseolus vulgaris. | screening of derivatives of rhizobium etli kim5s randomly mutagenized with mtn5ssgusa30 resulted in the identification of strain kim-g1. its rough colony appearance, flocculation in liquid culture, and ndv(-) fix(-) phenotype were indicative of a lipopolysaccharide (lps) defect. electrophoretic analysis of cell-associated polysaccharides showed that kim-g1 produces only rough lps. composition analysis of purified lps oligosaccharides from kim-g1 indicated that it produces an intact lps core tris ... | 1999 | 10482500 |
| the rhizobium etli trpb gene is essential for an effective symbiotic interaction with phaseolus vulgaris. | a mutant strain (ctnux4) of rhizobium etli carrying tn5 unable to grow with ammonium as the sole nitrogen source was isolated and characterized. sequence analysis showed that tn5 is inserted into a trpb (tryptophan synthase)-homologous gene. when tested on the roots of phaseolus vulgaris, strain ctnux4 was able to induce only small, slightly pink, ineffective (fix-) nodules. however, under free-living conditions, strain ctnux4 was unable to produce flavonoid-inducible lipo-chitin oligosaccharide ... | 1999 | 10517032 |
| sequence analysis of the rhizobium etli ribose kinase gene rbsk and its phylogenetic position. | dna sequence analysis of a 1878-bp dna fragment located downstream from the rhizobium etli ptsn gene revealed the presence of an open reading frame coding for a protein of 300 amino acids. this protein is homologous to members of the pfkb subfamily of carbohydrate and carbohydrate phosphate kinases. since the highest homology is observed with the ribokinases of escherichia coli, haemophilus influenzae and bacillus subtilis, the isolated gene was named the r. etli rbsk gene. the eubacterial ribok ... | 1998 | 10524758 |
| rhizobium etli bv. mimosae, a novel biovar isolated from mimosa affinis. | fifty rhizobial isolates from root nodules of mimosa affinis, a small leguminous plant native to mexico, were identified as rhizobium etli on the basis of the results of pcr-rflp and rflp analyses of small-subunit rrna genes, multilocus enzyme electrophoresis and dna-dna homology. they are, however, a restricted group of lineages with low genetic diversity within the species. the isolates from m. affinis differed-from the r. etli strains that orginated from bean plants (phaseolus vulgaris) in th ... | 1999 | 10555329 |
| role of the ruvb gene in homologous and homeologous recombination in rhizobium etli. | the rhizobium etli ruva and ruvb genes were cloned through a pcr-based approach, using degenerate primers matching conserved sectors in the amino acid sequences of ruvb from eight bacterial species. comparative analysis of the predicted polypeptides for ruva and ruvb of r. etli showed highly conserved blocks with the corresponding homologs in other bacteria; ruvb depicts characteristic motifs for dna helicases (atp-binding and dexh-box motifs). an r. etli ruvb::loxp sp mutant was constructed by ... | 2000 | 10675620 |
| identification of genes in the rosr regulon of rhizobium etli. | rosr is a determinant of nodulation competitiveness and cell surface characteristics of rhizobium etli and has sequence similarity to a family of transcriptional repressors. to understand how rosr affects these phenotypes, we mutagenized a rosr mutant derivative of r. etli strain ce3 with a mini-tn5 that contains a promoterless gusa gene at one end, which acts as a transcriptional reporter. using a mass-mating technique, we introduced rosr into each mutant in trans and screened for mutants that ... | 2000 | 10692377 |
| nickel availability and hupsl activation by heterologous regulators limit symbiotic expression of the rhizobium leguminosarum bv. viciae hydrogenase system in hup(-) rhizobia. | a limited number of rhizobium and bradyrhizobium strains possess a hydrogen uptake (hup) system that recycles the hydrogen released from the nitrogen fixation process in legume nodules. to extend this ability to rhizobia that nodulate agronomically important crops, we investigated factors that affect the expression of a cosmid-borne hup system from rhizobium leguminosarum bv. viciae upm791 in r. leguminosarum bv. viciae, rhizobium etli, mesorhizobium loti, and sinorhizobium meliloti hup(-) strai ... | 2000 | 10698755 |
| differentiation of o-acetyl and o-carbamoyl esters of n-acetyl-glucosamine by decomposition of their oxonium ions. application to the structure of the nonreducing terminal residue of nod factors. | nod factors are substituted n-acyl chito-oligomers secreted by plant symbiotic bacteria of the rhizobium family. substitutions on the oligosaccharide core specify their recognition by host plants. a method using tandem mass spectrometry is proposed to locate the o-acetyl and o-carbamoyl substituents on the nonreducing terminal residue of the chito-oligomers. as model compounds, all the positional isomers of monoacetyl and monocarbamoyl esters of 1-o-methyl-n-acetyl-alpha-d-glucosamine were synth ... | 2000 | 10757166 |
| recombination enhancement by replication (rer) in rhizobium etli. | studies in several organisms show that recombination and replication interact closely. recombinational repair usually requires associated replication at some stage; moreover, additional replication can induce recombination through either homologous or illegitimate events. in prokaryotes, stimulation of recombination by replication is more dramatic when rolling circle replication is employed. in contrast, theta-type replication induces only a modest increase in recombination frequency. in this ar ... | 2000 | 10757747 |
| analysis of cellular fatty acids and phenotypic relationships of agrobacterium, bradyrhizobium, mesorhizobium, rhizobium and sinorhizobium species using the sherlock microbial identification system. | previous studies have demonstrated that cellular fatty acid analysis is a useful tool for identifying unknown strains of rhizobia and establishing taxonomic relationships between the species. in this study, the fatty acid profiles of over 600 strains belonging to the genera agrobacterium, bradyrhizobium, mesorhizobium, rhizobium and sinorhizobium were evaluated using the gaschromatography-based sherlock microbial identification system (mis). data collected with the mis showed that the three phyl ... | 2000 | 10758890 |
| metabolic analysis of escherichia coli in the presence and absence of the carboxylating enzymes phosphoenolpyruvate carboxylase and pyruvate carboxylase. | fermentation patterns of escherichia coli with and without the phosphoenolpyruvate carboxylase (ppc) and pyruvate carboxylase (pyc) enzymes were compared under anaerobic conditions with glucose as a carbon source. time profiles of glucose and fermentation product concentrations were determined and used to calculate metabolic fluxes through central carbon pathways during exponential cell growth. the presence of the rhizobium etli pyc gene in e. coli (jcl1242/ptrc99a-pyc) restored the succinate pr ... | 2000 | 10788348 |
| multiresistance genes of rhizobium etli cfn42. | multidrug efflux pumps of bacteria are involved in the resistance to various antibiotics and toxic compounds. in rhizobium etli, a mutualistic symbiont of phaseolus vulgaris (bean), genes resembling multidrug efflux pump genes were identified and designated rmra and rmrb. rmra was obtained after the screening of transposon-generated fusions that are inducible by bean-root released flavonoids. the predicted gene products of rmrab shared significant homology to membrane fusion and major facilitato ... | 2000 | 10796024 |
| structural elements required for replication and incompatibility of the rhizobium etli symbiotic plasmid. | the symbiotic plasmid of rhizobium etli ce3 belongs to the repabc family of plasmid replicons. this family is characterized by the presence of three conserved genes, repa, repb, and repc, encoded by the same dna strand. a long intergenic sequence (igs) between repb and repc is also conserved in all members of the plasmid family. in this paper we demonstrate that (i) the repabc genes are organized in an operon; (ii) the repc product is essential for replication; (iii) repa and repb products parti ... | 2000 | 10809690 |
| polyphasic characterization of rhizobia that nodulate phaseolus vulgaris in west africa (senegal and gambia). | fifty-eight new isolates were obtained from root nodules of common bean (phaseolus vulgaris) cultivated in soils originating from different agroecological areas in senegal and gambia (west africa). a polyphasic approach including both phenotypic and genotypic techniques was used to study the diversity of the 58 rhizobium isolates and to determine their taxonomic relationships with reference strains. all the techniques performed, analysis of multilocus enzyme electrophoretic patterns, sds-page pr ... | 2000 | 10826800 |
| expression pattern of rhizobium etli ccmiefh genes involved in c-type cytochrome maturation. | in different bacterial species, ccmiefh genes have been suggested to code for subunits of a bacterial haem-lyase catalyzing the covalent attachment of haem to c-type apoproteins. in rhizobium etli ce3 there are two copies of ccmiefh: one in the chromosome and the other located in plasmid pf. however, the null phenotype of chromosomal ccmf mutant indicates that the gene locus of plasmid pf is not functional. two ccmi chromosomal mutants, previously isolated, produced detectable levels of c-type c ... | 2000 | 10854788 |
| purification and mass spectrometry of six lipid a species from the bacterial endosymbiont rhizobium etli. demonstration of a conserved distal unit and a variable proximal portion. | lipid a of rhizobium etli ce3 differs dramatically from that of other gram-negative bacteria. key features include the presence of an unusual c28 acyl chain, a galacturonic acid moiety at position 4', and an acylated aminogluconate unit in place of the proximal glucosamine. in addition, r. etli lipid a is reported to lack phosphate and acyloxyacyl residues. most of these remarkable structural claims are consistent with our recent enzymatic studies. however, the proposed r. etli lipid a structure ... | 2000 | 10856303 |
| two-dimensional nmr spectroscopy and structures of six lipid a species from rhizobium etli ce3. detection of an acyloxyacyl residue in each component and origin of the aminogluconate moiety. | the chemical structures of six lipid a species (a, b, c, d-1, d-2, and e) purified from rhizobium etli ce3 were investigated by one- and two-dimensional nmr spectroscopy. the r. etli lipid a subtypes each contain an unusual acyloxyacyl residue at position 2' as part of a conserved distal glucosamine moiety but differ in their proximal units. all r. etli lipid a species lack phosphate groups. however, they are derivatized with an alpha-linked galacturonic acid group at position 4', as shown by nu ... | 2000 | 10856304 |
| structural characterization of the o-antigenic polysaccharide of the lipopolysaccharide from rhizobium etli strain ce3. a unique o-acetylated glycan of discrete size, containing 3-o-methyl-6-deoxy-l-talose and 2,3,4-tri-o-,methyl-l fucose. | the o-antigenic polysaccharide of the rhizobium etli ce3 lipopolysaccharide (lps) was structurally characterized using chemical degradations (smith degradation and beta-elimination of uronosyl residues) in combination with alkylation analysis, electrospray, and matrix-assisted laser desorption ionization-time of flight mass spectrometry, tandem mass spectrometry, and (1)h cosy and tocsy nuclear magnetic resonance spectroscopy analyses of the native polysaccharide and the derived oligosaccharides ... | 2000 | 10858446 |
| in rhizobium etli symbiotic plasmid transfer, nodulation competitivity and cellular growth require interaction among different replicons. | bacteria belonging to the genus rhizobium are able to develop two different lifestyles, in symbiotic association with plant roots or through saprophytic growth. the genome of rhizobium strains is constituted by a chromosome and several large plasmids, one of them containing most of the genes involved in symbiosis (symbiotic plasmid or psym). our model strain rhizobium etli cfn42 contains six plasmids. we have constructed multiple plasmid-cured derivatives of this strain and used them to analyze ... | 2000 | 10873525 |
| nodule invasion and symbiosome differentiation during rhizobium etli-phaseolus vulgaris symbiosis. | by means of a detailed ultrastructural analysis of nodules induced by rhizobium etli on the roots of phaseolus vulgaris, we observe that the development of host-invaded cells is not synchronous. an accumulation of mitochondria was found in freshly invaded host cells, containing only a few symbiosomes (sbs) that are released from highly branched intracellular ramification of the infection threads. moreover, besides the fusion between the sb membrane with host secretory vesicles, we observe also a ... | 2000 | 10875334 |
| role of gogat in carbon and nitrogen partitioning in rhizobium etli. | the isolation and characterization of a rhizobium etli glutamate auxotroph, tad12, harbouring a single tn5 insertion, is reported. this mutant produced no detectable glutamate synthase (gogat) activity. the cloning and physical characterization of a 7.2 kb fragment of r. etli dna harbouring the structural genes gltb and gltd encoding the two gogat subunits gltb and gltd is also reported. in comparison with the wild-type strain (cfn42), the gogat mutant strain utilized less succinate and glutamat ... | 2000 | 10878127 |
| lipopolysaccharides of rhizobium etli strain g12 act in potato roots as an inducing agent of systemic resistance to infection by the cyst nematode globodera pallida. | recent studies have shown that living and heat-killed cells of the rhizobacterium rhizobium etli strain g12 induce in potato roots systemic resistance to infection by the potato cyst nematode globodera pallida. to better understand the mechanisms of induced resistance, we focused on identifying the inducing agent. since heat-stable bacterial surface carbohydrates such as exopolysaccharides (eps) and lipopolysaccharides (lps) are essential for recognition in the symbiotic interaction between rhiz ... | 2000 | 10919815 |
| the l-asparagine operon of rhizobium etli contains a gene encoding an atypical asparaginase. | the l-asparagine operon of rhizobium etli was cloned and sequenced. sequence analysis showed four adjacent open reading frames which were designated as ansr, ansp, ansa and ansb. the ansr and ansp genes encoded proteins similar to a transcriptional repressor and an l-asparagine permease, respectively. by tn5 mutagenesis and complementation analysis we identified the ansa product as a thermolabile asparaginase, and the ansb product as an aspartase. an asparagine-inducible transcript covering ansp ... | 2000 | 10930734 |
| rhizobium etli ce3 carries vir gene homologs on a self-transmissible plasmid. | rosr is a transcriptional regulator important for determining cell-surface characteristics and nodulation competitiveness in rhizobium etli ce3. we identified a 15-kb region that contains genes with similarity to members of the virb, virc, virg, and vire operons of agrobacterium tumefaciens and demonstrated that rosr directly regulates one operon in this region. these genes were located on plasmid pa of r. etli ce3, which is self-transmissible between r. etli and a. tumefaciens. | 2000 | 10975659 |
| varying the abundance of o antigen in rhizobium etli and its effect on symbiosis with phaseolus vulgaris. | judged by migration of its lipopolysaccharide (lps) in gel electrophoresis, the o antigen of rhizobium etli mutant strain ce166 was apparently of normal size. however, its lps sugar composition and staining of the lps bands after electrophoresis indicated that the proportion of its lps molecules that possessed o antigen was only 40% of the wild-type value. its lps also differed from the wild type by lacking quinovosamine (2-amino-2,6-dideoxyglucose). both of these defects were due to a single ge ... | 2000 | 10986232 |
| symbiosis-specific expression of rhizobium etli casa encoding a secreted calmodulin-related protein. | symbiosis between rhizobium and its leguminous host requires elaborate communication between the partners throughout the interaction process. a calmodulin-like protein, termed calsymin, was identified in rhizobium etli; a calmodulin-related protein in a gram-negative bacterium had not been described previously. calsymin possesses three repeated homologous domains. each domain contains two predicted ef-hand ca(2+)-binding motifs. ca(2+)-binding activity of calsymin was demonstrated on purified pr ... | 2000 | 10995485 |
| differential regulation of fixn-reiterated genes in rhizobium etli by a novel fixl-fixk cascade. | among the complexities in the regulation of nitrogen fixation in the rhizobiaceae are reiteration of regulatory components as well as variant roles for each component between species. for rhizobium etli cfn42, we reported that the symbiotic plasmid (pcfn42d) contains a key regulatory gene (fixkd) and genes for a symbiotic cytochrome oxidase (fixnoqpd). here we discuss the occurrence of reiteration of these genes (fixkf and fixnoqpf) and the finding of an unusual fixl homolog on a plasmid previou ... | 2000 | 11106020 |
| characterization of rhizobial isolates of phaseolus vulgaris by staircase electrophoresis of low-molecular-weight rna. | low-molecular-weight (lmw) rna molecules were analyzed to characterize rhizobial isolates that nodulate the common bean growing in spain. since lmw rna profiles, determined by staircase electrophoresis, varied across the rhizobial species nodulating beans, we demonstrated that bean isolates recovered from spanish soils presumptively could be characterized as rhizobium etli, rhizobium gallicum, rhizobium giardinii, rhizobium leguminosarum bv. viciae and bv. trifolii, and sinorhizobium fredii. | 2001 | 11157280 |