Publications
| Title | Abstract | Year(sorted descending) Filter | PMID Filter |
|---|
| more than one way to sense chemicals. | 2001 | 11466269 | |
| fructose uptake in sinorhizobium meliloti is mediated by a high-affinity atp-binding cassette transport system. | by transposon mutagenesis, we have isolated a mutant of sinorhizobium meliloti which is totally unable to grow on fructose as sole carbon source as a consequence of its inability to transport this sugar. the cloning and sequencing analysis of the chromosomal dna region flanking the tnphoa insertion revealed the presence of six open reading frames (orfs) organized in two loci, frcrs and frcbcak, transcribed divergently. the frcbca genes encode the characteristic components of an atp-binding casse ... | 2001 | 11466273 |
| analysis of the genetic region encoding a novel rhizobiocin from rhizobium leguminosarum bv. viciae strain 306. | cross-testing of a number of strains of rhizobium leguminosarum for bacteriocin production revealed that strain 306 produced at least two distinct bacteriocins. further analysis involving plasmid transfer to agrobacterium and other hosts demonstrated that there were bacteriocin determinants on plasmids prle306b and prle306c, as well as a third bacteriocin. the bacteriocin encoded by prle306b was indistinguishable from the bacteriocin encoded by strain 248, whereas the bacteriocin encoded by plas ... | 2001 | 11467725 |
| comparative strain typing of rhizobium leguminosarum bv. viciae natural populations. | 372 natural isolates of rhizobium leguminosarum bv. viciae, rescued from nodules of pea plants grown in an agricultural field in northern italy, were analyzed by different methods. three dna-based fingerprinting techniques were lined up to compare their relative degree of resolution and possible advantages of each approach. the methods included (i) eckhardt gel plasmid profiles, (ii) pulsed-field gel electrophoresis (pfge) of genomic large fragment digests, and (iii) random amplified polymorphic ... | 2001 | 11467734 |
| [effects of inoculation with rhizobium leguminosarum biovar trifolii on wheat cultivated in clover crop rotation agricultural soil in morocco]. | one hundred strains of rhizobium leguminosarum bv. trifolii were isolated from roots of wheat cultivated in rotation with clover in two different regions of morocco. the isolates were first screened for their effect on the growth of the cultivar rihane of wheat cultivated in an agricultural soil under greenhouse conditions. after 5 weeks of growth, 14 strains stimulating the fresh or dry matter yield of shoots were selected and used in a second pot inoculation trial performed with two different ... | 2001 | 11469254 |
| direct amplification of nodd from community dna reveals the genetic diversity of rhizobium leguminosarum in soil. | sequences of nodd, a gene found only in rhizobia, were amplified from total community dna isolated from a pasture soil. the polymerase chain reaction (pcr) primers used, y5 and y6, match nodd from rhizobium leguminosarum biovar trifolii, r. leguminosarum biovar viciae and sinorhizobium meliloti. the pcr product was cloned and yielded 68 clones that were identified by restriction pattern as derived from biovar trifolii [11 restriction fragment length polymorphism (rflp) types] and 15 clones ident ... | 2001 | 11472501 |
| effect of primers hybridizing to different evolutionarily conserved regions of the small-subunit rrna gene in pcr-based microbial community analyses and genetic profiling. | genetic profiling techniques of microbial communities based on pcr-amplified signature genes, such as denaturing gradient gel electrophoresis or single-strand-conformation polymorphism (sscp) analysis, are normally done with pcr products of less than 500-bp. the most common target for diversity analysis, the small-subunit rrna genes, however, are larger, and thus, only partial sequences can be analyzed. here, we compared the results obtained by pcr targeting different variable (v) regions (v2 an ... | 2001 | 11472932 |
| 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 |
| sinorhizobium meliloti cells require biotin and either cobalt or methionine for growth. | sinorhizobium meliloti is usually cultured in rich media containing yeast extract. it has been suggested that some components of yeast extract are also required for growth in minimal medium. we tested 27 strains of this bacterium and found that none were able to grow in minimal medium when methods to limit carryover of yeast extract were used during inoculation. by fractionation of yeast extract, two required growth factors were identified. biotin was found to be absolutely required for growth, ... | 2001 | 11472965 |
| 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 |
| nucleotide sequence and predicted functions of the entire sinorhizobium meliloti psyma megaplasmid. | the symbiotic nitrogen-fixing soil bacterium sinorhizobium meliloti contains three replicons: psyma, psymb, and the chromosome. we report here the complete 1,354,226-nt sequence of psyma. in addition to a large fraction of the genes known to be specifically involved in symbiosis, psyma contains genes likely to be involved in nitrogen and carbon metabolism, transport, stress, and resistance responses, and other functions that give s. meliloti an advantage in its specialized niche. | 2001 | 11481432 |
| the molecular weight distribution of succinoglycan produced by sinorhizobium meliloti is influenced by specific tyrosine phosphorylation and atpase activity of the cytoplasmic domain of the exop protein. | it is thought that in the gram-negative soil bacterium sinorhizobium meliloti the protein exop is involved in biosynthesis of the acidic exopolysaccharide succinoglycan (eps i). the amounts and compositions of eps i produced by mutants expressing exop proteins characterized by specific amino acid substitutions in the c-terminal cytoplasmic domain were analyzed. the cytoplasmic domain of the exop protein was shown to have atpase activity. mutations in the highly conserved walker a atp-binding mot ... | 2001 | 11489870 |
| investigation of myo-inositol catabolism in rhizobium leguminosarum bv. viciae and its effect on nodulation competitiveness. | three discrete loci required for growth on myo-inositol in rhizobium leguminosarum bv. viciae have been characterized. two of these are catabolic loci that code for malonate semialdehyde dehydrogenase (iola) and malonate semialdehyde dehydrogenase (iold). iold is part of a possible operon, ioldeb, although the functions of iole and iolb are unknown. the third locus, int, codes for an abc transport system that is highly specific for myo-inositol. lacz analysis showed that mutation of iold, which ... | 2001 | 11497462 |
| structural and genetic analyses of o polysaccharide from actinobacillus actinomycetemcomitans serotype f. | the oral bacterium actinobacillus actinomycetemcomitans is implicated as a causative agent of localized juvenile periodontitis (ljp). a. actinomycetemcomitans is classified into five serotypes (a to e) corresponding to five structurally and antigenically distinct o polysaccharide (o-ps) components of their respective lipopolysaccharide molecules. serotype b has been reported to be the dominant serotype isolated from ljp patients. we determined the lipopolysaccharide o-ps structure from a. actino ... | 2001 | 11500407 |
| overexpression of the mexef-oprn multidrug efflux system affects cell-to-cell signaling in pseudomonas aeruginosa. | intrinsic and acquired antibiotic resistance of the nosocomial pathogen pseudomonas aeruginosa is mediated mainly by the expression of several efflux pumps of broad substrate specificity. here we report that nfxc type mutants, overexpressing the mexef-oprn efflux system, produce lower levels of extracellular virulence factors than the susceptible wild type. these include pyocyanin, elastase, and rhamnolipids, three factors controlled by the las and rhl quorum-sensing systems of p. aeruginosa. in ... | 2001 | 11514502 |
| distribution of the ssudat1i restriction-modification system among different serotypes of streptococcus suis. | the ssudat1i restriction-modification (r-m) system, which contains two methyltransferases and two restriction endonucleases with recognition sequence 5'-gatc-3', was first found in a field isolate of streptococcus suis serotype 2. isoschizomers of the r-m system were found in the same locus between purh and purd in a field isolate of serotype 1/2 and the reference strains of serotypes 3, 7, 23, and 26 among 29 strains of different serotypes examined in this study. the r-m gene sequences in serot ... | 2001 | 11514530 |
| characterization of two novel rhizobium leguminosarum bacteriophages from a field release site of genetically-modified rhizobia. | two rhizobium leguminosarum biovar viceae bacteriophages with contrasting properties were isolated from a field site in which the survival of genetically modified r. leguminosarum inoculants had been monitored for several years. inoculant strain rsm2004 was used as the indicator for phage isolation and propagation. one phage, rl1res, was temperate and could not replicate in any of the 42 indigenous r. leguminosarum field isolates tested although nested pcr indicated that phage sequences were pre ... | 2001 | 11520005 |
| construction and environmental release of a sinorhizobium meliloti strain genetically modified to be more competitive for alfalfa nodulation. | highly efficient nitrogen-fixing strains selected in the laboratory often fail to increase legume production in agricultural soils containing indigenous rhizobial populations because they cannot compete against these populations for nodule formation. we have previously demonstrated, with a sinorhizobium meliloti puta- mutant strain, that proline dehydrogenase activity is required for colonization and therefore for the nodulation efficiency and competitiveness of s. meliloti on alfalfa roots (j. ... | 2001 | 11525978 |
| microbial population structures in soil particle size fractions of a long-term fertilizer field experiment. | soil structure depends on the association between mineral soil particles (sand, silt, and clay) and organic matter, in which aggregates of different size and stability are formed. although the chemistry of organic materials, total microbial biomass, and different enzyme activities in different soil particle size fractions have been well studied, little information is available on the structure of microbial populations in microhabitats. in this study, topsoil samples of different fertilizer treat ... | 2001 | 11526026 |
| physiological characterization of pseudomonas putida dot-t1e tolerance to p-hydroxybenzoate. | pseudomonas putida dot-t1e was isolated as a toluene-tolerant strain. we show that it is also able to grow on high concentrations (up to 17 g/liter [123 mm]) of p-hydroxybenzoate (4hba). tolerance to this aromatic carboxylic acid (up to 30 g/liter [217 mm]) is improved by preexposing the cells to low 4hba concentrations; the adaptation process is caused by the substrate itself rather than by products resulting from its metabolism. the mechanisms of 4hba tolerance seem to involve increased rigidi ... | 2001 | 11526042 |
| the rhizobium leguminosarum tonb gene is required for the uptake of siderophore and haem as sources of iron. | in the n2-fixing bacterium rhizobium leguminosarum, mutations in a homologue of tonb (tonb(rl)) block the import of vicibactin and haem as iron sources in free-living bacteria. tonb(rl) mutants were normal for growth with ferric dicitrate and slightly reduced for growth with haemoglobin as sole iron sources. the deduced tonb(rl) product is larger than that of (for example) escherichia coli, on account of an extended n-terminal domain. transcription of tonb(rl) was enhanced in low-fe growth condi ... | 2001 | 11532145 |
| evidence for redundancy in cysteine biosynthesis in rhizobium leguminosarum rl3841: analysis of a cyse gene encoding serine acetyltransferase. | a cyse gene encoding a serine acetyltransferase (sat) potentially involved in the biosynthesis of cysteine was identified approximately 4 kb upstream of the previously described aapjqmp gene cluster that encodes an amino acid permease in rhizobium leguminosarum strain 3841. the gene exhibits >40% identity to the family of sats containing n-terminal extensions that have been described for other bacteria and plants. the orf has three possible translation initiation sites which potentially encode p ... | 2001 | 11535795 |
| direct cloning from enrichment cultures, a reliable strategy for isolation of complete operons and genes from microbial consortia. | enrichment cultures of microbial consortia enable the diverse metabolic and catabolic activities of these populations to be studied on a molecular level and to be explored as potential sources for biotechnology processes. we have used a combined approach of enrichment culture and direct cloning to construct cosmid libraries with large (>30-kb) inserts from microbial consortia. enrichment cultures were inoculated with samples from five environments, and high amounts of avidin were added to the cu ... | 2001 | 11133432 |
| analysis of bacterial communities in the rhizosphere of chrysanthemum via denaturing gradient gel electrophoresis of pcr-amplified 16s rrna as well as dna fragments coding for 16s rrna. | the effect of developing chrysanthemum roots on the presence and activity of bacterial populations in the rhizosphere was examined by using culture-independent methods. nucleic acids were extracted from rhizosphere soil samples associated with the bases of roots or root tips of plants harvested at different stages of development. pcr and reverse transcriptase (rt) pcr were used to amplify 16s ribosomal dna (rdna) and 16s rrna, respectively, and the products were subjected to denaturing gradient ... | 2001 | 11133442 |
| polyhydroxyalkanoate degradation is associated with nucleotide accumulation and enhances stress resistance and survival of pseudomonas oleovorans in natural water microcosms. | pseudomonas oleovorans gpo1 and its polyhydroxyalkanoic acid (pha) depolymerization-minus mutant, gpo500 phaz, residing in natural water microcosms, were utilized to asses the effect of pha availability on survival and resistance to stress agents. the wild-type strain showed increased survival compared to the pha depolymerase-minus strain. the appearance of a round cellular shape, characteristic of bacteria growing under starvation conditions, was delayed in the wild type in comparison to the mu ... | 2001 | 11133449 |
| pigment and virulence deficiencies associated with mutations in the aroe gene of xanthomonas oryzae pv. oryzae. | xanthomonadins are yellow, membrane-bound pigments produced by members of the genus xanthomonas. we identified an ethyl methanesulfonate-induced xanthomonas oryzae pv. oryzae mutant (bxo65) that is deficient for xanthomonadin production and virulence on rice, as well as auxotrophic for aromatic amino acids (pig(-) vir(-) aro(-)). reversion analysis indicated that these multiple phenotypes are due to a single mutation. a genomic library of the wild-type strain was used to isolate a 7.0-kb clone t ... | 2001 | 11133452 |
| small-subunit rrna genotyping of rhizobia nodulating australian acacia spp. | the structure of rhizobial communities nodulating acacia in southeastern australia from south queensland to tasmania was investigated by a molecular approach. a total of 118 isolates from nodule samples from 13 different acacia species collected at 44 sites were characterized by small-subunit (ssu) ribosomal dna (rdna) pcr-restriction fragment length polymorphism analysis. nine rhizobial genomospecies were identified, and these taxa corresponded to previously described genomospecies (b. lafay an ... | 2001 | 11133471 |
| evidence for horizontal transfer of ssudat1i restriction-modification genes to the streptococcus suis genome. | different strains of streptococcus suis serotypes 1 and 2 isolated from pigs either contained a restriction-modification (r-m) system or lacked it. the r-m system was an isoschizomer of streptococcus pneumoniae dpnii, which recognizes nucleotide sequence 5'-gatc-3'. the nucleotide sequencing of the genes encoding the r-m system in s. suis dat1, designated ssudat1i, showed that the ssudat1i gene region contained two methyltransferase genes, designated ssuma and ssumb, as does the dpnii system. th ... | 2001 | 11133943 |
| smcr-dependent regulation of adaptive phenotypes in vibrio vulnificus. | vibrio vulnificus contains homologues of the v. harveyi luxr and luxs genes. a null mutation in smcr (luxr) resulted in a defect in starvation survival, inhibition of starvation-induced maintenance of culturability that occurs when v. vulnificus is starved prior to low-temperature incubation, and increased expression of stationary-phase phenotypes. | 2001 | 11133972 |
| lipid a and o-chain modifications cause rhizobium lipopolysaccharides to become hydrophobic during bacteroid development. | modifications to the lipopolysaccharide (lps) structure caused by three different growth conditions were investigated in the pea-nodulating strain rhizobium leguminosarum 3841. the lpss extracted by hot phenol-water from cultured cells fractionated into hydrophilic water and/or hydrophobic phenol phases. most of the lpss from cells grown under standard conditions extracted into the water phase, but a greater proportion of lpss were extracted into the phenol phase from cells grown under acidic or ... | 2001 | 11136459 |
| limited genetic diversity of brucella spp. | multilocus enzyme electrophoresis (mlee) of 99 brucella isolates, including the type strains from all recognized species, revealed a very limited genetic diversity and supports the proposal of a monospecific genus. in mlee-derived dendrograms, brucella abortus and a marine brucella sp. grouped into a single electrophoretic type related to brucella neotomae and brucella ovis. brucella suis and brucella canis formed another cluster linked to brucella melitensis and related to rhizobium tropici. th ... | 2001 | 11136777 |
| the adna transcriptional factor affects persistence and spread of pseudomonas fluorescens under natural field conditions. | a soil plot was inoculated with a mixture of pseudomonas fluorescens pf0-2, the wild type, and pf0-5a, a tn5 insertion mutant in adna, at 7.84 log cfu/g of soil. over a period of 231 days, culturable populations of both strains were measured at selected times below and away from the point of inoculation. pf0-5a did not spread as fast and attained significantly lower populations than pf0-2. at sample depths below the inoculation site, the adna mutant showed a significant decrease in cfu/g of soil ... | 2001 | 11157254 |
| 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 |
| synthesis of a low-molecular-weight form of exopolysaccharide by bradyrhizobium japonicum usda 110. | a novel extracellular low-molecular-weight polysaccharide was detected as a contaminant within extracellular cyclic beta-1,6-beta-1,3-glucan preparations from bradyrhizobium japonicum usda 110 cultures. compositional analysis, methylation analysis, and nuclear magnetic resonance analysis revealed that this low-molecular-weight polysaccharide was composed of the same pentasaccharide repeating unit previously described for the high-molecular-weight form of the exopolysaccharide (eps) synthesized b ... | 2001 | 11157281 |
| genetic characterization of a sinorhizobium meliloti chromosomal region in lipopolysaccharide biosynthesis. | the genetic characterization of a 5.5-kb chromosomal region of sinorhizobium meliloti 2011 that contains lpsb, a gene required for the normal development of symbiosis with medicago spp., is presented. the nucleotide sequence of this dna fragment revealed the presence of six genes: grea and lpsb, transcribed in the forward direction; and lpse, lpsd, lpsc, and lrp, transcribed in the reverse direction. except for lpsb, none of the lps genes were relevant for nodulation and nitrogen fixation. analy ... | 2001 | 11157937 |
| subset of hybrid eukaryotic proteins is exported by the type i secretion system of erwinia chrysanthemi. | erwinia chrysanthemi exports degradative enzymes by using a type i protein secretion system. the proteases secreted by this system lack an n-terminal signal peptide but contain a c-terminal secretion signal. to explore the substrate specificity of this system, we have expressed the e. chrysanthemi transporter system (prtdef genes) in escherichia coli and tested the ability of this abc transporter to export hybrid proteins carrying c-terminal fragments of e. chrysanthemi protease b. the c terminu ... | 2001 | 11157948 |
| fnr is required for nifl-dependent oxygen control of nif gene expression in klebsiella pneumoniae. | in klebsiella pneumoniae, nifa-dependent transcription of nitrogen fixation (nif) genes is inhibited by nifl in response to molecular oxygen and combined nitrogen. we recently showed that k. pneumoniae nifl is a flavoprotein, which apparently senses oxygen through a redox-sensitive, conformational change. we have now studied the oxygen regulation of nifl activity in escherichia coli and k. pneumoniae strains by monitoring its inhibition of nifa-mediated expression of k. pneumoniae phi (nifh'-'la ... | 2001 | 11157952 |
| potential symbiosis-specific genes uncovered by sequencing a 410-kilobase dna region of the bradyrhizobium japonicum chromosome. | the physical and genetic map of the bradyrhizobium japonicum chromosome revealed that nitrogen fixation and nodulation genes are clustered. because of the complex interactions between the bacterium and the plant, we expected this chromosomal sector to contain additional genes that are involved in the maintenance of an efficient symbiosis. therefore, we determined the nucleotide sequence of a 410-kb region. the overall g+c nucleotide content was 59.1%. using a minimum gene length of 150 nucleotid ... | 2001 | 11157954 |
| control of hema expression in rhodobacter sphaeroides 2.4.1: effect of a transposon insertion in the hbda gene. | the common precursor to all tetrapyrroles is 5-aminolevulinic acid (ala), and in rhodobacter sphaeroides its formation occurs via the shemin pathway. ala synthase activity is encoded by two differentially regulated genes in r. sphaeroides 2.4.1: hema and hemt. in our investigations of hema regulation, we applied transposon mutagenesis under aerobic conditions, followed by a selection that identified transposon insertion mutants in which hema expression is elevated. one of these mutants has been ... | 2001 | 11160087 |
| aspects of marker/reporter stability and selectivity in soil microbiology. | based on several experiences of microbial release using genetically modified rhizobium leguminosarum, we have highlighted a number of aspects related to the suitability of introduced markers such as resistance to mercury and b-galactosidase activity, the latter serving the function of high-expression level reporter gene obtained by the introduction of a synthetic promoter conferring strong inducible expression in gram-negative bacteria. in vitro expression and in vivo performances of the chosen ... | 2001 | 12032607 |
| [a study on growth of rhizobium leguminosarum in air pressure oscillating, solid-state fermenter]. | rhizobium leguminosarum l003, a kind of biofertilizers, was cultured in a periodic air pressure oscillating, solid-state fermenter by using straw of wheat as an inert solid support. effects of air pressure oscillation amplitude, frequency on the viable cells of r. leguminosarum l003 and oxygen transfer rate were investigated. it was found that enhanced oxygen transfer and biochemical reaction occurred in this system. under the optimized conditions, about a 3-fold increase of the viable cells was ... | 2001 | 11797231 |
| root colonization of faba bean (vicia faba l.) and pea (pisum sativum l.) by rhizobium leguminosarum bv. viciae in the presence of nitrate-nitrogen. | there is a lack of knowledge concerning the effect of nitrate-nitrogen (no3(-)-n) at levels known to inhibit nodule formation and functioning on root colonization of dinitrogen-fixing legumes. firstly, this study investigated potential differences between rhizobium leguminosarum bv. viciae 175f9 and its bioluminescent-labeled strain 175f9.lux on root colonization of faba bean (vicia faba l.) and pea (pisum sativum l.). these two strains similarly colonized the roots of both hosts. secondly, this ... | 2001 | 11822831 |
| two types of pea leghemoglobin genes showing different o2-binding affinities and distinct patterns of spatial expression in nodules. | five distinct cdna clones for leghemoglobin (lb) were isolated from pea (pisum sativum) nodules. they were classified into two groups designated pslba and pslbb according to sequence homology, o(2)-binding affinities of the recombinant proteins, and in situ localization of the mrnas. the pslbb group was comprised of four cdna clones: pslb120-1, -8, -29, and -34. they showed a high similarity of deduced amino acid sequences and o(2)-binding affinities of their recombinant proteins. among them, th ... | 2001 | 11161022 |
| patterns of protein synthesis and tolerance of anoxia in root tips of maize seedlings acclimated to a low-oxygen environment, and identification of proteins by mass spectrometry. | tolerance of anoxia in maize root tips is greatly improved when seedlings are pretreated with 2 to 4 h of hypoxia. we describe the patterns of protein synthesis during hypoxic acclimation and anoxia. we quantified the incorporation of [(35)s]methionine into total protein and 262 individual proteins under different oxygen tensions. proteins synthesized most rapidly under normoxic conditions continued to account for most of the proteins synthesized during hypoxic acclimation, while the production ... | 2000 | 10677424 |
| a promoter overlapping with that of nodf is responsible for a new rna molecule transcription in rhizobium leguminosarum. | the expression of nod genes of rhizobia is controlled at the transcriptional level in a complicated way. in this work, a new promoter, which is responsible for an rna molecule transcription in the opposite direction to that of nodf, was identified in rhizobium leguminosarum. this new promoter was characterized to overlap with that of nodf, and the size of px(2), the rna molecule initiated from this promoter was determined to be of approximately 0.72 kb in length. the study on px2 showed that its ... | 2000 | 12058163 |
| the promoter of the vicia faba l. gene vfenod12 encoding an early nodulin is active in cortical cells and nodule primordia of transgenic hairy roots of vicia hirsuta as well as in the prefixing zone ii of mature transgenic v. hirsuta root nodules. | a full-length cdna encoding the vicia faba l. early nodulin vfenod12 was isolated. the deduced protein sequence specified a 90 amino acid protein with a mw of 10206 and contained a putative signal peptide sequence followed by ppx(3) repeats characteristic of enod12 proteins. the vfenod12 gene was found to be expressed specifically in root nodules as early as 3 days post inoculation with rhizobium leguminosarum bv. viciae. in mature nodules, vfenod12 transcripts were confined to the prefixing zon ... | 2000 | 11164578 |
| 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 |
| proline catabolism by pseudomonas putida: cloning, characterization, and expression of the put genes in the presence of root exudates. | pseudomonas putida kt2442 is a root-colonizing strain which can use proline, one of the major components in root exudates, as its sole carbon and nitrogen source. a p. putida mutant unable to grow with proline as the sole carbon and nitrogen source was isolated after random mini-tn5-km mutagenesis. the mini-tn5 insertion was located at the puta gene, which is adjacent to and divergent from the putp gene. the puta gene codes for a protein of 1,315 amino acid residues which is homologous to the pu ... | 2000 | 10613867 |
| the replicator of the nopaline-type ti plasmid ptic58 is a member of the repabc family and is influenced by the trar-dependent quorum-sensing regulatory system. | the replicator (rep) of the nopaline-type ti plasmid ptic58 is located adjacent to the trb operon of this conjugal element. previous genetic studies of this region (d. r. gallie, m. hagiya, and c. i. kado, j. bacteriol. 161:1034-1041, 1985) identified functions involved in partitioning, origin of replication and incompatibility, and copy number control. in this study, we determined the nucleotide sequence of a 6,146-bp segment that encompasses the rep locus of ptic58. the region contained four f ... | 2000 | 10613878 |
| sequence analysis of the cryptic plasmid pmg101 from rhodopseudomonas palustris and construction of stable cloning vectors. | a 15-kb cryptic plasmid was obtained from a natural isolate of rhodopseudomonas palustris. the plasmid, designated pmg101, was able to replicate in r. palustris and in closely related strains of bradyrhizobium japonicum and phototrophic bradyrhizobium species. however, it was unable to replicate in the purple nonsulfur bacterium rhodobacter sphaeroides and in rhizobium species. the replication region of pmg101 was localized to a 3.0-kb sali-xhoi fragment, and this fragment was stably maintained ... | 2000 | 10618203 |
| a new chemolithoautotrophic arsenite-oxidizing bacterium isolated from a gold mine: phylogenetic, physiological, and preliminary biochemical studies. | a previously unknown chemolithoautotrophic arsenite-oxidizing bacterium has been isolated from a gold mine in the northern territory of australia. the organism, designated nt-26, was found to be a gram-negative motile rod with two subterminal flagella. in a minimal medium containing only arsenite as the electron donor (5 mm), oxygen as the electron acceptor, and carbon dioxide-bicarbonate as the carbon source, the doubling time for chemolithoautotrophic growth was 7.6 h. arsenite oxidation was f ... | 2000 | 10618208 |
| transcriptional organization and regulation of a polycistronic cold shock operon in sinorhizobium meliloti rm1021 encoding homologs of the escherichia coli major cold shock gene cspa and ribosomal protein gene rpsu. | a homolog of the major eubacterial cold shock gene cspa was identified in sinorhizobium meliloti rm1021 by luxab reporter transposon mutagenesis. here we further characterize the organization and regulation of this locus. dna sequence analysis indicated that the locus includes three open reading frames (orfs) encoding homologs corresponding to cspa, a novel 10.6-kda polypeptide designated orf2, and a homolog of the escherichia coli ribosomal protein s21. transcription analysis indicated that thi ... | 2000 | 10618253 |
| identification of cold shock gene loci in sinorhizobium meliloti by using a luxab reporter transposon. | using a luxab reporter transposon, seven mutants of sinorhizobium meliloti were identified as containing insertions in four cold shock loci. luxab activity was strongly induced (25- to 160-fold) after a temperature shift from 30 to 15 degrees c. the transposon and flanking host dna from each mutant was cloned, and the nucleic acid sequence of the insertion site was determined. unexpectedly, five of the seven luxab mutants contained transposon insertions in the 16s and 23s rrna genes of two of th ... | 2000 | 10618254 |
| visn and visr are global regulators of chemotaxis, flagellar, and motility genes in sinorhizobium (rhizobium) meliloti. | the known 41 flagellar, chemotaxis, and motility genes of sinorhizobium (rhizobium) meliloti contained in the "flagellar regulon" are organized as seven operons and six transcription units that map to a contiguous 45-kb chromosomal region. by probing gene expression on western blots and with lacz fusions, we have identified two master regulatory genes, visn and visr, contained in one operon. the gene products probably form a heterodimer, visnr, acting as a global transcription activator of other ... | 2000 | 10633114 |
| mutagenesis and functional characterization of the glnb, glna, and nifa genes from the photosynthetic bacterium rhodospirillum rubrum. | nitrogen fixation is tightly regulated in rhodospirillum rubrum at two different levels: transcriptional regulation of nif expression and posttranslational regulation of dinitrogenase reductase by reversible adp-ribosylation catalyzed by the drat-drag (dinitrogenase reductase adp-ribosyltransferase-dinitrogenase reductase-activating glycohydrolase) system. we report here the characterization of glnb, glna, and nifa mutants and studies of their relationship to the regulation of nitrogen fixation. ... | 2000 | 10648524 |
| bacterial activity in the rhizosphere analyzed at the single-cell level by monitoring ribosome contents and synthesis rates. | the growth activity of pseudomonas putida cells colonizing the rhizosphere of barley seedlings was estimated at the single-cell level by monitoring ribosomal contents and synthesis rates. ribosomal synthesis was monitored by using a system comprising a fusion of the ribosomal escherichia coli rrnbp1 promoter to a gene encoding an unstable variant of the green fluorescent protein (gfp). gfp expression in a p. putida strain carrying this system inserted into the chromosome was strongly dependent o ... | 2000 | 10653754 |
| the purmn genes of rhizobium leguminosarum and a superficial link with siderophore production. | we isolated a mutant of r. leguminosarum initially on the basis of reduced production of the siderophore vicibactin on chrome azurol sulfonate (cas)/agar indicator plates. the mutation was in the purmn operon and the mutant was shown to be an adenine auxotroph and defective for nodulation of peas. the siderophore defect appears to be trivial, being due to diminished growth of the auxotroph on agar-based minimal medium, which contains unknown contaminant(s) that allow it grow poorly. transcriptio ... | 2000 | 10659713 |
| extracellular glycanases of rhizobium leguminosarum are activated on the cell surface by an exopolysaccharide-related component. | rhizobium leguminosarum secretes two extracellular glycanases, plya and plyb, that can degrade exopolysaccharide (eps) and carboxymethyl cellulose (cmc), which is used as a model substrate of plant cell wall cellulose polymers. when grown on agar medium, cmc degradation occurred only directly below colonies of r. leguminosarum, suggesting that the enzymes remain attached to the bacteria. unexpectedly, when a plya-plyb-secreting colony was grown in close proximity to mutants unable to produce or ... | 2000 | 10671451 |
| influence of mutations in the mexr repressor gene on expression of the mexa-mexb-oprm multidrug efflux system of pseudomonas aeruginosa. | several nalb-type multidrug-resistant mutants of pseudomonas aeruginosa overexpressed mexab-oprm and carried mutations in the local regulatory gene, mexr. others, dubbed nalc types, carried mutations elsewhere and overexpressed mexab-oprm less extensively than the nalb strains. available evidence showed that mexr acted solely as repressor. disruption of the mexr gene at various places suggested that the 5' end of mexr may be a part of the mexab-oprm promoter. | 2000 | 10671465 |
| three new nifa-regulated genes in the bradyrhizobium japonicum symbiotic gene region discovered by competitive dna-rna hybridization. | the so-called symbiotic region of the bradyrhizobium japonicum chromosome (c. kündig, h. hennecke, and m. göttfert, j. bacteriol. 175:613-622, 1993) was screened for the presence of genes controlled by the nitrogen fixation regulatory protein nifa. southern blots of restriction enzyme-digested cosmids that represent an ordered, overlapping library of the symbiotic region were competitively hybridized with in vitro-labeled rna from anaerobically grown wild-type cells and an excess of rna isolated ... | 2000 | 10692350 |
| functional analysis of pvds, an iron starvation sigma factor of pseudomonas aeruginosa. | in pseudomonas aeruginosa, iron modulates gene expression through a cascade of negative and positive regulatory proteins. the master regulator fur is involved in iron-dependent repression of several genes. one of these genes, pvds, was predicted to encode a putative sigma factor responsible for the transcription of a subset of genes of the fur regulon. pvds appears to belong to a structurally and functionally distinct subgroup of the extracytoplasmic function family of alternative sigma factors. ... | 2000 | 10692351 |
| a gene cluster involved in metal homeostasis in the cyanobacterium synechocystis sp. strain pcc 6803. | a gene cluster composed of nine open reading frames (orfs) involved in ni(2+), co(2+), and zn(2+) sensing and tolerance in the cyanobacterium synechocystis sp. strain pcc 6803 has been identified. the cluster includes an ni(2+) response operon and a co(2+) response system, as well as a zn(2+) response system previously described. expression of the ni(2+) response operon (nrs) was induced in the presence of ni(2+) and co(2+). reduced ni(2+) tolerance was observed following disruption of two orfs ... | 2000 | 10692354 |
| components of the rp4 conjugative transfer apparatus form an envelope structure bridging inner and outer membranes of donor cells: implications for related macromolecule transport systems. | during bacterial conjugation, the single-stranded dna molecule is transferred through the cell envelopes of the donor and the recipient cell. a membrane-spanning transfer apparatus encoded by conjugative plasmids has been proposed to facilitate protein and dna transport. for the incpalpha plasmid rp4, a thorough sequence analysis of the gene products of the transfer regions tra1 and tra2 revealed typical features of mainly inner membrane proteins. we localized essential rp4 transfer functions to ... | 2000 | 10692361 |
| transcriptional and mutational analysis of the uptake hydrogenase of the filamentous cyanobacterium anabaena variabilis atcc 29413. | a 10-kb dna region of the cyanobacterium anabaena variabilis atcc 29413 containing the structural genes of the uptake hydrogenase (hupsl) was cloned and sequenced. in contrast to the hupl gene of anabaena sp. strain pcc 7120, which is interrupted by a 10.5-kb dna fragment in vegetative cells, there is no programmed rearrangement within the hupl gene during the heterocyst differentiation of a. variabilis. the hupsl genes were transcribed as a 2.7-kb operon and were induced only under nitrogen-fix ... | 2000 | 10692368 |
| dual roles of bradyrhizobium japonicum nickelin protein in nickel storage and gtp-dependent ni mobilization. | the hydrogenase accessory protein hypb, or nickelin, has two functions in the n(2)-fixing, h(2)-oxidizing bacterium bradyrhizobium japonicum. one function of hypb involves the mobilization of nickel into hydrogenase. hypb also carries out a nickel storage/sequestering function in b. japonicum, binding nine nickel ions per monomer. here we report that the two roles (nickel mobilization and storage) of hypb can be separated in vitro and in vivo using molecular and biochemical approaches. the role ... | 2000 | 10692376 |
| 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 |
| glutathione is involved in environmental stress responses in rhizobium tropici, including acid tolerance. | the isolation of rhizobial strains which exhibit an intrinsic tolerance to acidic conditions has been reported and has facilitated studies on the basic mechanisms underlying acid tolerance. rhizobium tropici strain ciat899 displays a high intrinsic tolerance to acidity and therefore was used in this work to study the molecular basis of bacterial responses to acid conditions and other environmental stresses. we generated a collection of r. tropici ciat899 mutants affected in acid tolerance using ... | 2000 | 10692382 |
| 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 |
| [dna homology in various strains of nitrogen-fixing bacteria]. | melting temperature and gc content were evaluated for dna of some nitrogen-fixing bacteria of rhizobium leguminosarum and onobrychis spp. (adans). the degree of homology between strains of the same species was determined. a combination of thermal denaturing and molecular hybridization can serve as a rapid test for evaluating the genome homology of the organisms compared. | 2000 | 10702988 |
| microbial relatives of the seed storage proteins of higher plants: conservation of structure and diversification of function during evolution of the cupin superfamily. | this review summarizes the recent discovery of the cupin superfamily (from the latin term "cupa," a small barrel) of functionally diverse proteins that initially were limited to several higher plant proteins such as seed storage proteins, germin (an oxalate oxidase), germin-like proteins, and auxin-binding protein. knowledge of the three-dimensional structure of two vicilins, seed proteins with a characteristic beta-barrel core, led to the identification of a small number of conserved residues a ... | 2000 | 10704478 |
| molecular basis of symbiotic promiscuity. | eukaryotes often form symbioses with microorganisms. among these, associations between plants and nitrogen-fixing bacteria are responsible for the nitrogen input into various ecological niches. plants of many different families have evolved the capacity to develop root or stem nodules with diverse genera of soil bacteria. of these, symbioses between legumes and rhizobia (azorhizobium, bradyrhizobium, mesorhizobium, and rhizobium) are the most important from an agricultural perspective. nitrogen- ... | 2000 | 10704479 |
| sinorhizobium meliloti puta gene regulation: a new model within the family rhizobiaceae. | proline dehydrogenase (puta) is a bifunctional enzyme that catalyzes the oxidation of proline to glutamate. in sinorhizobium meliloti, as in other microorganisms, the puta gene is transcriptionally activated in response to proline. in rhodobacter capsulatus, agrobacterium, and most probably in bradyrhizobium, this activation is dependent on an lrp-like protein encoded by the putr gene, located immediately upstream of puta. interestingly, sequence and genetic analysis of the region upstream of th ... | 2000 | 10715000 |
| characterization of the protocatechuic acid catabolic gene cluster from streptomyces sp. strain 2065. | protocatechuate 3,4-dioxygenase (ec 1.13.11.3) catalyzes the ring cleavage step in the catabolism of aromatic compounds through the protocatechuate branch of the beta-ketoadipate pathway. a protocatechuate 3,4-dioxygenase was purified from streptomyces sp. strain 2065 grown in p-hydroxybenzoate, and the n-terminal sequences of the beta- and alpha-subunits were obtained. pcr amplification was used for the cloning of the corresponding genes, and dna sequencing of the flanking regions showed that t ... | 2000 | 10742233 |
| involvement of diamine oxidase and peroxidase in insolubilization of the extracellular matrix: implications for pea nodule initiation by rhizobium leguminosarum. | rhizobium leguminosarum colonizes host cells and tissues through infection threads, which are tubular in-growths of the plant cell wall. monoclonal antibody mac265 recognizes a plant matrix glycoprotein (mgp) associated with the lumen of these infection threads. this glycoprotein is also released in soluble form from the root tips of pea seedlings. in the presence of hydrogen peroxide, release of glycoprotein from root tips was not observed. extractability from root tips was therefore used as th ... | 2000 | 10755304 |
| a lotus japonicus nodulation system based on heterologous expression of the fucosyl transferase nodz and the acetyl transferase noil in rhizobium leguminosarum. | heterologous expression of nodz and noll proteins in rhizobium leguminosarum bv. viciae led to the production of acetyl fucosylated lipo-chitin oligosaccharides (lcos), indicating that the noll protein obtained from mesorhizobium loti functions as an acetyl transferase. we show that the noll-dependent acetylation is specific for the fucosyl penta-n-acetylglucosamine species. in addition, the noll protein caused elevated production of lcos. efficient nodulation of lotus japonicus by the nodz/noll ... | 2000 | 10755312 |
| 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 |
| the ++sinorhizobium meliloti lon protease is involved in regulating exopolysaccharide synthesis and is required for nodulation of alfalfa. | while screening for sinorhizobium meliloti pho regulatory mutants, a transposon mutant was isolated that constitutively expressed higher levels of acid and alkaline phosphatase enzymes. this mutant was also found to form pseudonodules on alfalfa that were delayed in appearance relative to those formed by the wild-type strain, it contained few bacteroids, and it did not fix nitrogen. sequence analysis of the transposon insertion site revealed the affected gene to have high homology to lon proteas ... | 2000 | 10762258 |
| a novel sphingoglycolipid containing galacturonic acid and 2-hydroxy fatty acid in cellular lipids of sphingomonas yanoikuyae. | a novel sphingoglycolipid was isolated from sphingomonas yanoikuyae, and its structure was identified as a galacturonosyl-beta (1-->1)-ceramide. this was a characteristic sphingoglycolipid present in s. yanoikuyae and certain other species of sphingomonas, such as sphingomonas mali, sphingomonas terrae, and sphingomonas macrogoltabidus, but not in the type species of sphingomonas, sphingomonas paucimobilis. | 2000 | 10762275 |
| characterization of heat, oxidative, and acid stress responses in brucella melitensis. | brucella melitensis is a facultative intracellular pathogen which is able to survive and replicate within phagocytic cells. therefore, it has to adapt to a range of different hostile environments. in order to understand the mechanisms of intracellular survival employed by virulent b. melitensis 16m, an initial approach consisting of analysis of the differences in patterns of protein synthesis in response to heat, oxidative, and acid ph stresses by two-dimensional (2-d) polyacrylamide gel electro ... | 2000 | 10768994 |
| identification of a putative lps-associated cation exporter from rhizobium leguminosarum bv. viciae. | a gene, cpaa, with similarity to calcium proton antiporters has been identified adjacent to lpcab in rhizobium leguminosarum. lpca is a galactosyl transferase while lpcb is a 2-keto-3-deoxyoctonate transferase, both of which are required to form the lipopolysaccharide (lps) core in r. leguminosarum. mutations in lpcab result in a rough lps phenotype with a requirement for elevated calcium concentrations to allow growth, suggesting that truncation of the lps core exposes a highly negatively charg ... | 2000 | 10779711 |
| expression of uptake hydrogenase and molybdenum nitrogenase in rhodobacter capsulatus is coregulated by the regb-rega two-component regulatory system. | purple photosynthetic bacteria are capable of generating cellular energy from several sources, including photosynthesis, respiration, and h(2) oxidation. under nutrient-limiting conditions, cellular energy can be used to assimilate carbon and nitrogen. this study provides the first evidence of a molecular link for the coregulation of nitrogenase and hydrogenase biosynthesis in an anoxygenic photosynthetic bacterium. we demonstrated that molybdenum nitrogenase biosynthesis is under the control of ... | 2000 | 10781552 |
| catabolism of alpha-ketoglutarate by a suca mutant of bradyrhizobium japonicum: evidence for an alternative tricarboxylic acid cycle. | a complete tricarboxylic acid (tca) cycle is generally considered necessary for energy production from the dicarboxylic acid substrates malate, succinate, and fumarate. however, a bradyrhizobium japonicum suca mutant that is missing alpha-ketoglutarate dehydrogenase is able to grow on malate as its sole source of carbon. this mutant also fixes nitrogen in symbiosis with soybean, where dicarboxylic acids are its principal carbon substrate. using a flow chamber system to make direct measurements o ... | 2000 | 10781553 |
| analysis of the rhizobium leguminosarum siderophore-uptake gene fhua: differential expression in free-living bacteria and nitrogen-fixing bacteroids and distribution of an fhua pseudogene in different strains. | a mutation was isolated in the rhizobium leguminosarum gene fhua, which appears to specify the outer-membrane receptor for the siderophore vicibactin. the mutant was defective in iron uptake and accumulated the siderophore vicibactin in the extracellular medium. expression of fhua was regulated by fe3+, transcription being higher in iron-depleted cells. transcription of fhua was independent of a functional copy of rpol, a neighbouring gene that specifies a putative ecf sigma factor of rna polyme ... | 2000 | 10784041 |
| expression and purification of four different rhizobial acyl carrier proteins. | in rhizobia, besides the constitutive acyl carrier protein (acpp) involved in the biosynthesis and transfer of common fatty acids, there are at least three specialized acyl carrier proteins (acps): (1) the flavonoid-inducible nodulation protein nodf; (2) the rkpf protein, which is required for the biosynthesis of rhizobial capsular polysaccharides; and (3) acpxl, which transfers 27-hydroxyoctacosanoic acid to a sugar backbone during lipid a biosynthesis. whereas the nucleotide sequences encoding ... | 2000 | 10784042 |
| a novel autoregulation mechanism of fnrn expression in rhizobium leguminosarum bv viciae. | the fnrn gene from rhizobium leguminosarum upm791 controls microaerobic expression of both nitrogen fixation and hydrogenase activities in symbiotic cells. two copies of fnrn are present in this strain, one chromosomal (fnrn1) and the other located in the symbiotic plasmid (fnrn2). their expression was studied by cloning the regulatory regions in lacz promoter-probe vectors. the fnrn genes were found to be autoregulated: they are expressed only at basal levels under aerobic conditions; they are ... | 2000 | 10792733 |
| 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 |
| intercellular communication in helicobacter pylori: luxs is essential for the production of an extracellular signaling molecule. | individual bacteria of numerous species can communicate and coordinate their actions via the production, release, and detection of extracellular signaling molecules. in this study, we used the vibrio harveyi luminescence bioassay to determine whether helicobacter pylori produces such a factor. cell-free conditioned media from h. pylori strains 60190 and 26695 each induced >100-fold-greater luminescence in v. harveyi than did sterile culture medium. the h. pylori signaling molecule had a molecula ... | 2000 | 10816463 |
| physiological adaptation to low temperatures of strains of rhizobium leguminosarum bv. viciae associated with lathyrus spp.(1). | strains of rhizobium leguminosarum bv. viciae, isolated from the legume species lathyrus japonicus and lathyrus pratensis in northern quebec (canada), showed different capacities for growing at low temperature. in the present study, we investigated some mechanisms related to cold adaptation. two cold-adapted strains (psychrotrophs) were compared to a poorly adapted strain and to a cold-sensitive strain (reference strain) for freezing survival, protein induction and fatty acid composition under l ... | 2000 | 10817864 |
| temporal and spatial order of events during the induction of cortical cell divisions in white clover by rhizobium leguminosarum bv. trifolii inoculation or localized cytokinin addition. | we examined the timing and location of several early root responses to rhizobium leguminosarum bv. trifolii infection, compared with a localized addition of cytokinin in white clover, to study the role of cytokinin in early signaling during nodule initiation. induction of enod40 expression by either rhizobia or cytokinin was similar in timing and location and occurred in nodule progenitor cells in the inner cortex. inoculation of rhizobia in the mature root failed to induce enod40 expression and ... | 2000 | 10830261 |
| higher diversity of rhizobium leguminosarum biovar viciae populations in arable soils than in grass soils. | the bacterial genetic diversity after long-term arable cultivation was compared with that under permanent grassland using replicated paired contrasts. pea-nodulating rhizobium leguminosarum populations were sampled from pairs of arable and grass sites at four locations in yorkshire, united kingdom. isolates were characterized using both chromosomal (16s-23s ribosomal dna internal transcribed spacer pcr-restriction fragment length polymorphism) and plasmid (group-specific repc pcr amplification) ... | 2000 | 10831423 |
| rhizobitoxine production by bradyrhizobium elkanii enhances nodulation and competitiveness on macroptilium atropurpureum. | application of 1-aminoocyclopropane-1-carboxylic acid, an ethylene precursor, decreased nodulation of macroptilium atropurpureum by bradyrhizobium elkanii. b. elkanii produces rhizobitoxine, an ethylene synthesis inhibitor. elimination of rhizobitoxine production in b. elkanii increased ethylene evolution and decreased nodulation and competitiveness on m. atropurpureum. these results suggest that rhizobitoxine enhances nodulation and competitiveness of b. elkanii on m. atropurpureum. | 2000 | 10831453 |
| 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 |
| characterization of a snorhizobium meliloti atp-binding cassette histidine transporter also involved in betaine and proline uptake. | the symbiotic soil bacterium sinorhizobium meliloti uses the compatible solutes glycine betaine and proline betaine for both protection against osmotic stress and, at low osmolarities, as an energy source. a pcr strategy based on conserved domains in components of the glycine betaine uptake systems from escherichia coli (prou) and bacillus subtilis (opua and opuc) allowed us to identify a highly homologous atp-binding cassette (abc) binding protein-dependent transporter in s. meliloti. this syst ... | 2000 | 10850986 |
| the hydrogenase cytochrome b heme ligands of azotobacter vinelandii are required for full h(2) oxidation capability. | the hydrogenase in azotobacter vinelandii, like other membrane-bound [nife] hydrogenases, consists of a catalytic heterodimer and an integral membrane cytochrome b. the histidines ligating the hemes in this cytochrome b were identified by h(2) oxidation properties of altered proteins produced by site-directed mutagenesis. four fully conserved and four partially conserved histidines in hoxz were substituted with alanine or tyrosine. the roles of these histidines in hoxz heme binding and hydrogena ... | 2000 | 10852874 |
| genetic and phenotypic analyses of the rdx locus of rhodobacter sphaeroides 2.4.1. | previously, we reported that rdxb, encoding a likely membrane-bound two [4fe-4s]-containing center, is involved in the aerobic regulation of photosystem gene expression in rhodobacter sphaeroides 2.4.1. to further investigate the role of rdxb as well as other genes of the rdxbhis operon on photosystem gene expression, we constructed a series of nonpolar, in-frame deletion mutations in each of the rdx genes. using both puc and puf operon lacz fusions to monitor photosystem gene expression, under ... | 2000 | 10852880 |
| virulence of the phytopathogen pseudomonas syringae pv. maculicola is rpon dependent. | we cloned the rpon (ntra and glnf) gene encoding sigma(54) from the phytopathogen pseudomonas syringae pv. maculicola strain es4326. the p. syringae es4326 rpon gene complemented pseudomonas aeruginosa, escherichia coli, and klebsiella aerogenes rpon mutants for a variety of rpon mutant phenotypes, including the inability to utilize nitrate as sole nitrogen source. dna sequence analysis of the p. syringae es4326 rpon gene revealed that the deduced amino acid sequence was most similar (86% identi ... | 2000 | 10852883 |
| the alternative sigma factor rpon is required for hrp activity in pseudomonas syringae pv. maculicola and acts at the level of hrpl transcription. | beta-glucuronidase (uida) reporter gene fusions were constructed for the hrpz, hrpl, and hrps genes from the phytopathogen pseudomonas syringae pv. maculicola strain es4326. these reporters, as well as an avrrpt2-uida fusion, were used to measure transcriptional activity in es4326 and a es4326 rpon mutant. rpon was required for the expression of avrrpt2, hrpz, and hrpl in vitro in minimal media and in vivo when infiltrated into arabidopsis thaliana leaves. in contrast, the expression of hrps was ... | 2000 | 10852884 |
| megaplasmid prme2011a of sinorhizobium meliloti is not required for viability. | we report the curing of the 1,360-kb megaplasmid prme2011a from sinorhizobium meliloti strain rm2011. with a positive selection strategy that utilized tn5b12-s containing the sacb gene, we were able to cure this replicon by successive rounds of selecting for deletion formation in vivo. subsequent southern blot, eckhardt gel, and pulsed-field gel electrophoresis analyses were consistent with the hypothesis that the resultant strain was indeed missing prme2011a. the cured derivative grew as well a ... | 2000 | 10852892 |
| 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 |