| the bradyrhizobium japonicum phob gene is required for phosphate-limited growth but not for symbiotic nitrogen fixation. | we identified by cloning and dna sequence analysis the phosphate regulatory gene phob of bradyrhizobium japonicum. the deduced gene product displayed pronounced similarity to the phob protein of sinorhizobium meliloti (71.4% identical amino acids). escherichia coli (50.2%) and other bacterial species. insertion of a kanamycin resistance cassette into phob led to impaired growth of the b. japonicum mutant in media containing approximately 25 microm phosphate or less. a standard plant infection te ... | 1998 | 9561731 |
| 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 |
| new bradyrhizobium japonicum strains that possess high copy numbers of the repeated sequence rs alpha. | in a survey of dna fingerprints of indigenous bradyrhizobium japonicum with the species-specific repeated sequences rs alpha and rs beta, 21 isolates from three field sites showed numerous rs-specific hybridization bands. the isolates were designated highly reiterated sequence-possessing (hrs) isolates, and their dna hybridization profiles were easily distinguished from the normal patterns. some hrs isolates from two field sites possessed extremely high numbers of rs alpha copies, ranging from 8 ... | 1998 | 9572961 |
| regulation of lipid synthesis in bradyrhizobium japonicum: low oxygen concentrations trigger phosphatidylinositol biosynthesis. | lowering oxygen tension in free-living bradyrhizobium japonicum resulted in a dramatic switch of membrane chemistry in which phosphatidylcholine, the predominant lipid in aerated cultures, was no longer synthesized and phosphatidylethanolamine became the major lipid. besides this change, phosphatidylinositol, a typical plant lipid rarely found in bacteria, was also synthesized. | 1998 | 9572982 |
| promoter selectivity of the bradyrhizobium japonicum rpoh transcription factors in vivo and in vitro. | expression of the dnakj and groesl1 heat shock operons of bradyrhizobium japonicum depends on a sigma32-like transcription factor. three such factors (rpoh1, rpoh2, and rpoh3) have previously been identified in this organism. we report here that they direct transcription from some but not all sigma32-type promoters when the respective rpoh genes are expressed in escherichia coli. all three rpoh factors were purified as soluble c-terminally histidine-tagged proteins, although the bulk of overprod ... | 1998 | 9573191 |
| purification and characterization of the nadp-malic enzyme from bradyrhizobium japonicum a1017. | an nadp-malic enzyme [ec 1.1.1.40] was purified to homogeneity from bradyrhizobium japonicum a1017, and the molecular and physiological characteristics were surveyed. the molecular mass of one subunit of the purified enzyme was evaluated to be 77,600 da by sds-page, and the native enzyme was a tetramer in ph 7.0 and dimer in ph 8.0 conditions, showing complex oligomeric characteristics corresponding to ph value. | 1997 | 9058984 |
| characterization of bradyrhizobium japonicum pcabdc genes involved in 4-hydroxybenzoate degradation. | the pca structural genes encode enzymes that participate in the conversion of protocatechuate to succinate and acetylcoenzyme a. a 3. 05-kb region of the bradyrhizobium japonicum strain usda110 genome has been characterized, which contains the pcab, pcad and pcac genes. the predicted protein sequences of the three genes have extensive homologies with beta-carboxy-cis,cis-muconate cycloisomerase (pcab), beta-ketodiapate enol-lactone hydrolase (pcad), and gamma-carboxymuconolactone decarboxylase ( ... | 1998 | 9582432 |
| molecular studies on a new genetic locus linked to the common nodulation genes in bradyrhizobium japonicum. | orfa, an actively transcribed genetic locus linked to the common nodulation genes in bradyrhizobium japonicum usda110, was sequenced and analysed. the expression of orfa is neither dependent on the regulatory proteins nifa, ntrc, ntrb and nodd1 nor on either copy of sigma 54, rpon1 and rpon2. the transcriptional start site of orfa was determined and found to overlap the oppositely transcribed nodz gene by 224 nucleotides. an appropriately located -10 sequence identical to the consensus proposed ... | 1997 | 9084141 |
| replacement of pro109 by his in tlpa, a thioredoxin-like protein from bradyrhizobium japonicum, alters its redox properties but not its in vivo functions. | tlpa, the membrane-anchored, thioredoxin-like protein from bradyrhizobium japonicum, is essential for cytochrome aa3 biogenesis. the periplasmic domain of tlpa was previously shown to have protein thiol:disulfide oxidoreductase activity and reducing properties similar to those of cytoplasmic thioredoxins. here, we replaced the proline-109 in its active-site sequence c107 v108 p109 c110 by a histidine residue. the resulting active-site motif (cvhc) resembles that of oxidizing thiol:disulfide oxid ... | 1997 | 9136895 |
| in vivo studies on the positive control function of nifa: a conserved hydrophobic amino acid patch at the central domain involved in transcriptional activation. | the eubacterial enhancer-binding proteins activate transcription by binding to distant sites and, simultaneously, contacting the rna polymerase r54 promoter complex (esigma54). the positive control function is located at the central domain of these proteins, but it is not know which specific region has the determinants for the interaction with esigma54. here, we present genetic evidence that a small region of hydrophobic amino acids, previously denominated c3, at the central domain of bradyrhizo ... | 1998 | 9593296 |
| transcriptional regulation of delta-aminolevulinic acid dehydratase synthesis by oxygen in bradyrhizobium japonicum and evidence for developmental control of the hemb gene. | an increased demand for cytochromes is associated with symbiotic development and microaerobic metabolism in the bacterium bradyrhizobium japonicum, and evidence suggests that hemb, rather than hema, is the first essential bacterial heme synthesis gene in symbiosis with soybean. steady-state levels of mrna and protein encoded by hemb were strongly and rapidly induced by o2 deprivation as determined by rnase protection and immunoblot analyses, but hemh message was not induced. oxygen limitation re ... | 1997 | 9171420 |
| cloning and sequence analysis of a novel insertion element from plasmids harbored by the carbofuran-degrading bacterium, sphingomonas sp. cfo6. | sphingomonas sp. cfo6 (a member of the alpha group of proteobacteria) was isolated from a washington soil by enrichment on the insecticide carbofuran as a sole source of carbon and energy. this strain has been shown to harbor five plasmids, at least some of which are required for catabolism of carbofuran. rearrangements, deletions, and loss of individual plasmids resulting in the loss of the carbofuran-degrading phenotype were observed following treatment with heat or introduction of tn5. severa ... | 1997 | 9200220 |
| the fixk2 protein is involved in regulation of symbiotic hydrogenase expression in bradyrhizobium japonicum. | the roles of the nitrogen fixation regulatory proteins nifa, fixk1, and fixk2 in the symbiotic regulation of hydrogenase structural gene expression in bradyrhizobium japonicum have been investigated. bacteroids from fixj and fixk2 mutants have little or no hydrogenase activity, and extracts from these mutant bacteroids contain no hydrogenase protein. bacteroids from a fixk1 mutant exhibit wild-type levels of hydrogenase activity. in beta-galactosidase transcriptional assays with nifa and fixk2 e ... | 1998 | 9620982 |
| a novel dna element that controls bacterial heat shock gene expression. | the hsparpoh1 and hspbcdegp heat shock operons of bradyrhizobium japonicum are preceded by a novel, conserved dna element of approximately 100 bp, which is responsible for the temperature-regulated transcription of their sigma70-type promoters. we designated this motif rose for repression of heat shock gene expression and found additional rose elements upstream of two newly identified heat shock operons. a critical core region in the hspa-associated rose1 was defined by introducing insertions or ... | 1998 | 9622356 |
| in vitro sulfotransferase activity of noee, a nodulation protein of rhizobium sp. ngr234. | soil bacteria of the genera azorhizobium, bradyrhizobium, and rhizobium liberate morphogenetic lipochitin-oligosaccharides (nod factors) into legume rhizospheres. nod factors, which are synthesized by the products of rhizobial nodulation (nod) genes, vary in core length as well as in the number and type of substitutions. in rhizobium sp. ngr234, the n-acylated pentamers of n-acetyl-d-glucosamine carry an o-methylfucose group on the reducing terminus that is substituted, on a mutually exclusive b ... | 1998 | 9650293 |
| identification and sequencing of a cytochrome p450 gene cluster from bradyrhizobium japonicum. | sequencing of a region from bradyrhizobium japonicum previously shown to encode for cytochromes p450 revealed a cluster of three complete p450 genes (cyp112, cyp114, and cyp117) plus a partial p450 gene fragment (cyp115p). present also are five additional open reading frames. the close positioning of the genes suggests that they comprise an operon. although the biochemical function of the gene products is uncertain, the similarities to other genes suggests an operon involved in terpenoid synthes ... | 1998 | 9655913 |
| 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 |
| cloning and sequencing of the nitrogenase structural genes nifhdk of herbaspirillum seropedicae. | the nitrogenase structural genes (nifhdk) of the endophytic diazotroph herbaspirillum seropedicae were isolated from a genomic bank by plate hybridization. sequence analysis of the dna showed a consensus promoter region upstream for the nifh gene containing a -24/-12 type promoter together with nifa- and integration host factor (ihf)- binding sites. the derived protein sequences of nifh, nifd and nifk contained conserved cysteine residues for binding iron-sulfur clusters and the iron-molybdenum ... | 1996 | 9222418 |
| biodiversity of rhizobia isolated from a wide range of forest legumes in brazil. | tropical forests have a high diversity of plant species; are they associated with a correspondingly rich microbial flora? we addressed this question by examining the symbiotic rhizobium bacteria that nodulate a diverse pool of forest legume species in brazil. the 44 strains studied had been isolated from 29 legume tree species representing 13 tribes including all three subfamilies of the leguminosae, and were chosen to represent major groups from a larger sample that had previously been characte ... | 1998 | 9691490 |
| the bacterial irr protein is required for coordination of heme biosynthesis with iron availability. | heme is a ubiquitous macromolecule that serves as the active group of proteins involved in many cellular processes. the multienzyme pathway for heme formation culminates with the insertion of iron into a protoporphyrin ring. the cytotoxicity of porphyrins suggests the need for coordination of its biosynthesis with iron availability. we isolated a mutant strain of the bacterium bradyrhizobium japonicum that, under iron limitation, accumulated protoporphyrin and showed aberrantly high expression o ... | 1998 | 9705301 |
| lotus corniculatus nodulation specificity is changed by the presence of a soybean lectin gene | plant lectins have been implicated as playing an important role in mediating recognition and specificity in the rhizobium-legume nitrogen-fixing symbiosis. to test this hypothesis, we introduced the soybean lectin gene le1 either behind its own promoter or behind the cauliflower mosaic virus 35s promoter into lotus corniculatus, which is nodulated by r. loti. we found that nodulelike outgrowths developed on transgenic l. corniculatus plant roots in response to bradyrhizobium japonicum, which nod ... | 1998 | 9707526 |
| isolation of sinorhizobium meliloti tn5 mutants with altered cytochrome terminal oxidase expression and improved symbiotic performance. | the relationship between whole-cell redox potential, cytochrome composition in free-living culture and symbiotic activity of sinorhizobium meliloti was studied. three tn5-induced mutants with increased cellular redox potential were generated. stationary cultures of mutants tb9 and tb16 in contrast to the parental strain produced the b-type terminal oxidase that may be similar to the symbiotically essential cytochrome oxidase cbb3 of bradyrhizobium japonicum. increase in the symbiotic effectivene ... | 1998 | 9711854 |
| cloning of conserved genes from zymomonas mobilis and bradyrhizobium japonicum that function in the biosynthesis of hopanoid lipids. | the squalene-hopene cyclase (shc) is the only enzyme involved in the biosynthesis of hopanoid lipids that has been characterized on the genetic level. to investigate if additional genes involved in hopanoid biosynthesis are clustered with the shc gene, we cloned and analyzed the nucleotide sequences located immediately upstream of the shc genes from zymomonas mobilis and bradyrhizobium japonicum. in z. mobilis, five open reading frames (orfs, designated as hpna-e) were detected in a close arrang ... | 1998 | 9714766 |
| an important developmental role for oligosaccharides during early embryogenesis of cyprinid fish. | derivatives of chitin oligosaccharides have been shown to play a role in plant organogenesis at nanomolar concentrations. here we present data which indicate that chitin oligosaccharides are important for embryogenesis in vertebrates. we characterize chitin oligosaccharides synthesized in vitro by zebrafish and carp embryos in the late gastrulation stage by incorporation of radiolabeled n-acetyl-d-[u14c]glucosamine and by hplc in combination with enzymatic conversion using the bradyrhizobium nod ... | 1997 | 9223299 |
| exopolysaccharide (eps) synthesis in bradyrhizobium japonicum: sequence, operon structure and mutational analysis of an exo gene cluster. | the nucleotide sequence of a 8330-bp dna fragment from bradyrhizobium japonicum 110spc4 was determined. sequence analysis revealed that six orfs were present and the deduced amino acid sequences were homologous to enzymes involved in exopolysaccharide (eps) biosynthesis. the genes appear to be organized into at least four different operons. one gene was found to be homologous to exob, which encodes a udp-galactose 4'-epimerase. other orfs were homologous to udp-hexose transferases and one orf sh ... | 1998 | 9747707 |
| bradyrhizobium japonicum fixk2, a crucial distributor in the fixlj-dependent regulatory cascade for control of genes inducible by low oxygen levels. | bradyrhizobium japonicum possesses a second fixk-like gene, fixk2, in addition to the previously identified fixk1 gene. the expression of both genes depends in a hierarchical fashion on the low-oxygen-responsive two-component regulatory system fixlj, whereby fixj first activates fixk2, whose product then activates fixk1. while the target genes for control by fixk1 are unknown, there is evidence for activation of the fixnoqp, fixghis, and rpon1 genes and some heme biosynthesis and nitrate respira ... | 1998 | 9748464 |
| molecular diversity of rhizobia occurring on native shrubby legumes in southeastern australia | the structure of rhizobial communities nodulating native shrubby legumes in open eucalypt forest of southeastern australia was investigated by a molecular approach. twenty-one genomic species were characterized by small-subunit ribosomal dna pcr-restriction fragment length polymorphism and phylogenetic analyses, among 745 rhizobial strains isolated from nodules sampled on 32 different legume host species at 12 sites. among these rhizobial genomic species, 16 belonged to the bradyrhizobium subgro ... | 1998 | 9758831 |
| purification and characterization of an nad-malic enzyme from bradyrhizobium japonicum a1017. | an nad-malic enzyme was purified to homogeneity from bradyrhizobium japonicum a1017, and its molecular characteristics were surveyed. the enzyme exhibited native and subunit molecular masses of 388 and 85 kda, respectively, suggesting that it exists as a homotetramer, and was activated by metabolic intermediates in glycolysis. the role of the enzyme in bacteroids' carbon metabolism is discussed. | 1998 | 9758846 |
| 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 |
| overproduction of the bradyrhizobium japonicum c-type cytochrome subunits of the cbb3 oxidase in escherichia coli. | we report on a system to improve expression of mature c-type cytochromes in escherichia coli. it is based on the use of plasmid pec86 that expresses the e. coli cytochrome c maturation genes ccmabcdefgh constitutively, whereby the production of both endogenous and foreign c-type cytochromes was increased substantially. the periplasmic soluble domains of the c-type cytochrome subunits fixo and fixp of the bradyrhizobium japonicum cbb3 oxidase could be expressed in e. coli only when pec86 was prov ... | 1998 | 9790980 |
| isolation and classification of a family of cyclin gene homologues in lupinus luteus. | the lupine (lupinus luteus cv. ventus) cdna clones encoding homologues of cyclin (cycb1;2, cycb1;3, cycb1;4) have been isolated from cdna library prepared from roots inoculated with bradyrhizobium lupini. comparison of the deduced amino-acid sequences of cycb1;2, cycb1;3, cycb1;4 and previously described cycb1;1 (deckert et al. 1996, biochimie 78, 90-94) showed that they share 46-65% of identical amino acids. the presence of conserved residues (renaudin et. al., in the plant cell cycle, in the p ... | 1997 | 9241352 |
| heme c incorporation into the c-type cytochromes fixo and fixp is essential for assembly of the bradyrhizobium japonicum cbb3-type oxidase. | the monoheme and diheme c-type cytochromes fixo and fixp are two of the subunits of the respiratory cbb3-type oxidase of bradyrhizobium japonicum. the cysteines of the respective heme c binding motifs cxxch were changed to serines by site-directed mutagenesis, which led to inactive oxidases in all mutants. western blot analyses showed that an intact heme binding site in the fixo polypeptide is a prerequisite not only for the synthesis of holo-fixo protein but also for the formation of the entire ... | 1997 | 9257693 |
| detecting linkage disequilibrium in bacterial populations. | the distribution of the number of pairwise differences calculated from comparisons between n haploid genomes has frequently been used as a starting point for testing the hypothesis of linkage equilibrium. for this purpose the variance of the pairwise differences, vd, is used as a test statistic to evaluate the null hypothesis that all loci are in linkage equilibrium. the problem is to determine the critical value of the distribution of vd. this critical value can be estimated either by monte car ... | 1998 | 9832514 |
| biodiversity of bradyrhizobia nodulating lupinus spp. | the genetic structure of bradyrhizobium isolates recovered from three lupinus species (lupinus campestris, lupinus montanus, and lupinus exaltatus) grown in mexico was examined. among 41 bradyrhizobium isolates, 18 electrophoretic types (ets) were distinguished by multilocus enzyme electrophoresis of five metabolic enzymes. the mean genetic diversity, 0.64, indicated that there was great genetic diversity in the population sampled. most isolates (63%) fell into two closely related clusters (clus ... | 1997 | 9336911 |
| purification and characterization of the membrane-bound nitrate reductase isoenzymes of bradyrhizobium japonicum. | two respiratory membrane-bound nitrate reductase (nr) isoenzymes, nri and nrii, have been purified for the first time from one single microorganism. triton x-100-solubilized nrs were purified by a three-step procedure of differential centrifugation, q-sepharose chromatography, and gel filtration on sephacryl s-300. both isoenzymes were purified to homogeneity by the criteria of nr activity staining in polyacrylamide gels run under non-denaturating conditions and coincident staining of the protei ... | 1996 | 8769303 |
| multiple small heat shock proteins in rhizobia. | seven genes coding for small heat shock proteins (shsps) in bradyrhizobium japonicum have been identified. they are organized in five operons that are coordinately regulated by rose, a negatively cis-acting dna element. the deduced shsps can be divided into two separate classes: class a, consisting of proteins that show similarity to escherichia coli ibpa and ibpb, and class b, whose members display significant similarity to other shsps from prokaryotes and eukaryotes. two-dimensional gel electr ... | 1999 | 9864316 |
| nodule development induced by mutants of bradyrhizobium japonicum defective in cyclic b-glucan synthesis. | the soybean response to inoculation with b. japonicum mutants defective in cyclic beta-(1-->3), beta-(1-->6) glucan synthesis was examined by electron microscopy and by monitoring the expression of early and late nodulin genes. two mutants were examined. strain ab-14 is an ndvb mutant and is unable to synthesize beta-glucans. strain ab-1 is an ndvc mutant and produces cyclic glucans containing 95 to 100% beta-(1-->3) glycosidic linkages. nodules formed by either mutant were defective in nitrogen ... | 1996 | 8810069 |
| phenotypic characterization and regulation of the nola gene of bradyrhizobium japonicum. | two bradyrhizobium japonicum nola mutants were constructed and used to test the functional role of nola in nodulation. contrary to the previous hypothesis that nola acts as a repressor of nod gene transcription, the expression of a nodd1-lacz or nody-lacz fusion in the nola mutant strains was similar to that found in the wild type. however, nola does appear to act as a transcriptional regulatory protein since it is required for its own expression, as well as that of nodd2. expression of nodd2 fr ... | 1996 | 8810078 |
| closely related form i ribulose bisphosphate carboxylase/oxygenase molecules that possess different co2/o2 substrate specificities. | the deduced primary sequence (cbbl and cbbs) of form i ribulose 1, 5-bisphosphate carboxylase/oxygenase (rubisco) from bradyrhizobium japonicum places this enzyme within the type ic subgroup of red-like rubisco enzymes. in addition, b. japonicum appears to organize most of the structural genes of the calvin-benson-bassham (cbb) pathway in at least one major operon. functional expression and characterization of the b. japonicum and xanthobacter flavus enzymes from this group revealed that these m ... | 1999 | 9882445 |
| histidine 131, not histidine 43, of the bradyrhizobium japonicum fixn protein is exposed towards the periplasm and essential for the function of the cbb3-type cytochrome oxidase. | in subunit i (fixn) of the bradyrhizobium japonicum cbb3-type oxidase, only five instead of the normal six strictly conserved histidines (h) could be unambiguously assigned as the putative heme or copper ligands. the ambiguity concerned h43 or h131 as the presumptive n-terminal ligands of the low-spin heme b. we report here that a h43a replacement had a wild-type phenotype, whereas the h131a mutant was defective in oxidase function and subunit assembly or stability, suggesting that h131 serves a ... | 1996 | 8830672 |
| purification and functional reconstitution of soybean nodulin 26. an aquaporin with water and glycerol transport properties. | infection of soybean roots by nitrogen-fixing bradyrhizobium japonicum leads to expression of plant nodule-specific genes known as nodulins. nodulin 26, a member of the major intrinsic protein/aquaporin (aqp) channel family, is a major component of the soybean symbiosome membrane (sm) that encloses the rhizobium bacteroid. to investigate the water and solute transport characteristics of nodulin 26, we purified the protein from sms and reconstituted it into carboxyfluorescein-loaded liposomes for ... | 1999 | 9890916 |
| characterization of the escherichia coli ccmh protein reveals new insights into the redox pathway required for cytochrome c maturation. | the ccmh protein of escherichia coli is encoded by the last gene of the ccm gene cluster required for cytochrome c maturation. a mutant in which the entire ccmh gene was deleted failed to synthesize both indigenous and foreign c-type cytochromes. however, deletion of the c-terminal hydrophilic domain homologous to cych of other gram-negative bacteria affected neither the biogenesis of indigenous c-type cytochromes nor that of the bradyrhizobium japonicum cytochrome c550. this confirmed that only ... | 1999 | 9914305 |
| genetic diversity of rhizobial symbionts isolated from legume species within the genera astragalus, oxytropis, and onobrychis. | the genetic diversity of 44 rhizobial isolates from astragalus, oxytropis, and onobrychis spp. originating from different geographic locations was evaluated by mapped restriction site polymorphism (mrsp) analysis of 16s rrna genes and by pcr dna fingerprinting with repetitive sequences (rep-pcr). a comparison of tree topologies of reference strains constructed with data obtained by mrsp and by 16s rrna gene sequence analyses showed that the topologies were in good agreement, indicating that the ... | 1997 | 9406393 |
| new assay for rhizobitoxine based on inhibition of 1-aminocyclopropane-1-carboxylate synthase. | rhizobitoxine is synthesized by the legume symbiont bradyrhizobium elkanii and the plant pathogen burkholderia andropogonis. rhizobitoxine competitively inhibited 1-aminocyclopropane-1-carboxylate (acc) synthase ble-acs2 from the tomato, a key enzyme in the pathway of ethylene biosynthesis. based on this inhibition of acc synthase, we have developed a new assay for rhizobitoxine. | 1999 | 9925628 |
| the bradyrhizobium japonicum nola gene encodes three functionally distinct proteins. | examination of nola revealed that nola can be uniquely translated from three atg start codons. translation from the first atg (atg1) predicts a protein (nola1) having an n-terminal, helix-turn-helix dna-binding motif similar to the dna-binding domains of the merr-type regulatory proteins. translation from atg2 and atg3 would give the n-terminally truncated proteins nola2 and nola3, respectively, lacking the dna-binding domain. consistent with this, immunoblot analyses of bradyrhizobium japonicum ... | 1999 | 10049387 |
| characterization of the common bean uricase ii and its expression in organs other than nodules. | uricase ii is a purine metabolic enzyme highly induced in root nodules during the symbiosis established between legumes and bacteria of the genera rhizobium and bradyrhizobium. here we describe the characterization of bean (phaseolus vulgaris) nodule uricase ii cdna and show that uricase ii is encoded by a single gene in the bean genome. this gene is also expressed in cotyledons, roots, and hypocotyls during bean seedling establishment, and an anti-uricase antibody recognizes the protein in diff ... | 1997 | 9414545 |
| in vivo genomic footprinting analysis reveals that the complex bradyrhizobium japonicum fixrnifa promoter region is differently occupied by two distinct rna polymerase holoenzymes. | the bradyrhizobium japonicum fixrnifa operon is transcribed from two promoters: fixrp1, a -24/-12 promoter recognized by the sigma54-holoenzyme form of the rna polymerase, and fixrp2, a -35/-10 promoter that is transcribed by a second, unidentified, form of rna polymerase holoenzyme. the fixrp1 promoter is autoregulated during microaerobiosis by nifa, whereas fixrp2 is also activated, but by a different regulatory protein. the main transcription start sites for these promoters are just two nucle ... | 1998 | 9448277 |
| studies on the structure and the solution conformation of an acidic extracellular polysaccharide isolated from bradyrhizobium. | the structure of an acidic extracellular polysaccharide isolated from bradyrhizobium (chamaecytisus proliferus) has been elucidated by hydrolysis, methylation analysis, and 1d and 2d 1h- and 13c-nmr spectroscopy of the complete polysaccharide. the nmr spectrum showed that microheterogeneity was present due to the minor existence of a variety of o-acetyl groups. thus, a deacetylated sample was prepared by alkaline treatment which was then fully analysed. the deacetylated polysaccharide has the fo ... | 1997 | 9468626 |
| cuma, a gene encoding a multicopper oxidase, is involved in mn2+ oxidation in pseudomonas putida gb-1. | pseudomonas putida gb-1-002 catalyzes the oxidation of mn2+. nucleotide sequence analysis of the transposon insertion site of a nonoxidizing mutant revealed a gene (designated cuma) encoding a protein homologous to multicopper oxidases. addition of cu2+ increased the mn2+-oxidizing activity of the p. putida wild type by a factor of approximately 5. the growth rates of the wild type and the mutant were not affected by added cu2+. a second open reading frame (designated cumb) is located downstream ... | 1999 | 10103278 |
| acid tolerance in root nodule bacteria. | biological nitrogen fixation, especially via the legume rhizobium symbiosis, is important for world agriculture. the productivity of legume crops and pastures is significantly affected by soil acidity; in some cases it is the prokaryotic partner that is ph sensitive. growth of rhizobium is adversely affected by low ph, especially in the 'acid stress zone'. rhizobia exhibit an adaptive acid tolerance response (atr) that is influenced by calcium concentration. using tn5-mutagenesis, gusa fusions a ... | 1999 | 10207916 |
| solution conformation and dynamics of an extracellular polysaccharide isolated from bradyrhyzobium as deduced from 1h-nmr off resonance roesy and 13c-nmr relaxation measurements. | the conformational and dynamical features of an extracellular branched deacetylated polysaccharide isolated from bradyrhizobium (chamaecytisus proliferus) have been investigated by homo and heteronuclear nmr methods. 1h-nmr cross relaxation rates have been obtained for this polysaccharide through regular noesy and roesy spectra as well as by modern off resonance roesy techniques. local proton-proton correlation times as well as interproton distances have been obtained. 13c-nmr relaxation paramet ... | 1997 | 9468627 |
| 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 |
| heme-based sensors in biological systems. | the past several years have been witness to a staggering rate of advancement in the understanding of how organisms respond to changes in the availability of diatomic molecules that are toxic and/or crucial to survival. heme-based sensors presently constitute the majority of the proteins known to sense no, o2 and co and to initiate the chemistry required to adapt to changes in their availabilities. knowledge of the three characterized members of this class, soluble guanylate cyclase, fixl and coo ... | 1999 | 10226051 |
| susceptibility to hydrogen peroxide and catalase activity of root nodule bacteria. | the root nodule bacteria (free-living cells) tested had higher susceptibility to hydrogen peroxide (h2o2) than the other genera of aerobic or facultative anaerobic bacteria tested. the catalase activities tended to have a positive correlation with h2o2 resistance among all bacteria tested. addition of a catalase inhibitor such as 3-amino-1, 2, 4-triazole increased the susceptibility to h2o2. these results suggest that the lower catalase activity brings about the higher susceptibility of root nod ... | 1999 | 10227131 |
| how replacements of the 12 conserved histidines of subunit i affect assembly, cofactor binding, and enzymatic activity of the bradyrhizobium japonicum cbb3-type oxidase. | alignments of the amino acid sequences of subunit i (fixn or ccon) of the cbb3-type oxidases show 12 conserved histidines. six of them are diagnostic of heme-copper oxidases and are thought to bind the following cofactors: the low spin heme b and the binuclear high spin heme b-cub center. the other six are fixn(ccon)-specific and their function is unknown. to analyze the contribution of these 12 invariant histidines of fixn in cofactor binding and function of the bradyrhizobium japonicum cbb3-ty ... | 1998 | 9497378 |
| phosphorylation, dephosphorylation and dna-binding of the bradyrhizobium japonicum regsr two-component regulatory proteins. | under low oxygen conditions, induction of many genes required for nitrogen fixation in bradyrhizobium japonicum depends on the redox-responsive transcriptional activator nifa which is encoded in the fixr-nifa operon. basal expression of this operon depends on the response regulator regr and a dna element located around position -68 in the fixr-nifa promoter region. to investigate the functional properties of regr and the interaction with its putative cognate kinase, regs, we overproduced and aff ... | 1999 | 10406954 |
| succinate dehydrogenase (sdh) from bradyrhizobium japonicum is closely related to mitochondrial sdh. | the sdhcdab operon, encoding succinate dehydrogenase, was cloned from the soybean symbiont bradyrhizobium japonicum. sdh from b. japonicum is phylogenetically related to sdh from mitochondria. this is the first example of a mitochondrion-like sdh functionally expressed in escherichia coli. | 1999 | 10419971 |
| roles of the bradyrhizobium japonicum terminal oxidase complexes in microaerobic h2-dependent growth | spectral, inhibitor, and o2-consumption studies on membranes from free-living and bacteroid forms of bradyrhizobium japonicum have revealed the existence of a number of terminal oxidases, and four terminal oxidase gene clusters within the heme-copper cytochrome family have been cloned. here the complexes encoded by coxmnop and coxwxyz, genes with homology to cua-containing cytochrome c oxidases and b-type ubiquinol oxidases respectively, are studied by analysis of mutants in each of the two oxid ... | 1998 | 9554944 |
| nolo and noei (hsniii) of rhizobium sp. ngr234 are involved in 3-o-carbamoylation and 2-o-methylation of nod factors. | loci unique to specific rhizobia direct the adjunction of special groups to the core lipo-oligosaccharide nod factors. host-specificity of nodulation (hsn) genes are thus essential for interaction with certain legumes. rhizobium sp. ngr234, which can nodulate >110 genera of legumes, possesses three hsn loci and secretes a large family of nod factors carrying specific substituents. among them are 3-o (or 4-o)- and 6-o-carbamoyl groups, an n-methyl group, and a 2-o-methylfucose residue which may b ... | 1998 | 9575146 |
| partial characterization of the lipopolysaccharides of peanut specific bradyrhizobium strains. | hexoses, heptose, hexuronic acids, 2-keto-3-deoxyoctonic acid (kdo) contents of the lipopolysaccharides (lps) isolated from peanut (a. hypogaea) specific bradyrhizobium strains nc 92, igr 92, igr 40 and igr 6 were found to vary considerably. sodium dodecyl sulphate polyacrylamide gel electrophoresis showed a heterogeneous lps population and distinct heterogeneity was observed in nc and igr strains. sepharose gel filtration chromatography removed the hexose contaminants from nc 92 lps. polysaccha ... | 1998 | 9584991 |
| iron coordination structures of oxygen sensor fixl characterized by fe k-edge extended x-ray absorption fine structure and resonance raman spectroscopy. | fixl is a heme-based o(2) sensor protein involved in a two-component system of a symbiotic bacterium. in the present study, the iron coordination structure in the heme domain of rhizobium meliloti fixlt (rmfixlt, a soluble truncated fixl) was examined using fe k-edge extended x-ray absorption fine structure (exafs) and resonance raman spectroscopic techniques. in the exafs analyses, the interatomic distances and angles of the fe-ligand bond and the iron displacement from the heme plane were obta ... | 1999 | 10438488 |
| identification and characterization of hupt, a gene involved in negative regulation of hydrogen oxidation in bradyrhizobium japonicum. | the bradyrhizobium japonicum hupt gene was sequenced, and its gene product was found to be homologous to ntrb-like histidine kinases. a hupt mutant expresses higher levels of hydrogenase activity than the wild-type strain under hydrogenase-inducing conditions (i.e., microaerobiosis plus hydrogen, or symbiosis), whereas in noninduced hupt cells, hupsl expression is derepressed but does not lead to hydrogenase activity. we conclude that hupt is involved in the repression of hupsl synthesis at the ... | 1999 | 10438783 |
| purification of two lectins from a nopalin agrobacterium tumefaciens strain. | lectins were evidenced on the surface of one agrobacterium tumefaciens wild strain (82,139) by agglutination test and neoglycoprotein labelling. bacteria were incubated in the presence of various fluorescein-labelled neoglycoproteins and the binding was assessed by a fluorimetric method. among the fluorescein-labelled neoglycoproteins tested, the one bearing alpha-d-galactosyl residues was the most efficient. the labelling was optimal at ph 5.0 and naught at ph above 7. the binding was specifica ... | 1998 | 9587666 |
| structural characterisation of lipo-chitin oligosaccharides isolated from bradyrhizobium aspalati, microsymbionts of commercially important south african legumes. | the shoots of the south african legume aspalathus linearis spp. linearis (a. linearis) are used in the manufacture of an increasingly popular beverage that has acclaimed beneficial effects on health; this important export product is known as rooibos (or redbush) tea. three strains of bradyrhizobium aspalati, which are the nitrogen-fixing symbionts of aspalathus carnosa, a. hispida and a. linearis, were tested for the production of lipo-chitin oligosaccharide signal molecules using thin-layer chr ... | 1999 | 10466212 |
| identification of a functional fur gene in bradyrhizobium japonicum. | the recent identification of the iron response regulator (irr) in bradyrhizobium japonicum raised the question of whether the global regulator fur is present in that organism. a fur gene homolog was isolated by the functional complementation of an escherichia coli fur mutant. the b. japonicum fur bound to a fur box dna element in vitro, and a fur mutant grown in iron-replete medium was derepressed for iron uptake activity. thus, b. japonicum expresses at least two regulators of iron metabolism. | 1999 | 10482529 |
| genotypic characterization of bradyrhizobium strains nodulating endemic woody legumes of the canary islands by pcr-restriction fragment length polymorphism analysis of genes encoding 16s rrna (16s rdna) and 16s-23s rdna intergenic spacers, repetitive extragenic palindromic pcr genomic fingerprinting, and partial 16s rdna sequencing. | we present a phylogenetic analysis of nine strains of symbiotic nitrogen-fixing bacteria isolated from nodules of tagasaste (chamaecytisus proliferus) and other endemic woody legumes of the canary islands, spain. these and several reference strains were characterized genotypically at different levels of taxonomic resolution by computer-assisted analysis of 16s ribosomal dna (rdna) pcr-restriction fragment length polymorphisms (pcr-rflps), 16s-23s rdna intergenic spacer (igs) rflps, and repetitiv ... | 1998 | 9603820 |
| the bradyrhizobium japonicum noed gene: a negatively acting, genotype-specific nodulation gene for soybean. | bradyrhizobium japonicum strain usda 110 is restricted for nodulation by soybean genotype pi 417566. we previously reported the identification of a usda 110 tn5 mutant, strain d4.2-5, that had the ability to overcome nodulation restriction conditioned by pi 417566 (s. m. lohrke, j. h. orf, e. martínez-romero, and m. j. sadowsky, appl. environ. microbiol. 61:2378-2383, 1995). in this study, we report the cloning and characterization of the negatively acting dna region mutated in strain d4.2-5 tha ... | 1998 | 9612946 |
| expression of a soybean nodule-enhanced phosphoenolpyruvate carboxylase gene that shows striking similarity to another gene for a house-keeping isoform. | three different cdnas for phosphoenolpyruvate carboxylase (pepc) were isolated from soybean root nodules. the full-length cdna of the most abundant isoform (gmpepc7) was very similar to another one (gmpepc15), the nucleotide sequence of which is identical to that of a reported clone (gmppc1) (vazquez-tello, a., whittier, r.f., kawasaki, t., sugimoto, t., kawamura, y. and shibata, d. (1993) plant physiol. 103, 1025-1026). in the coding region, the newly isolated gmpepc7 and the previously reporte ... | 1998 | 9680982 |
| expression of the fixr-nifa operon in bradyrhizobium japonicum depends on a new response regulator, regr. | many nitrogen fixation-associated genes in the soybean symbiont bradyrhizobium japonicum are regulated by the transcriptional activator nifa, whose activity is inhibited by aerobiosis. nifa is encoded in the fixr-nifa operon, which is expressed at a low level under aerobic conditions and induced approximately fivefold under low-oxygen tension. this induction depends on a -24/-12-type promoter (fixrp1) that is recognized by the sigma54 rna polymerase and activated by nifa. low-level aerobic expre ... | 1998 | 9683482 |
| biosynthesis of trehalose from maltooligosaccharides in rhizobia. | previously, the enzymes for trehalose synthesis that are present in escherichia coli were demonstrated in bradyrhizobium japonicum and b. elkanii. an alternative mechanism recently reported for the synthesis of trehalose from maltooligosaccharides was considered based on the fact that high concentrations of sugars in liquid culture stimulated the accumulation of trehalose. an assay for the synthesis of trehalose from maltooligosaccharides using crude, gel-filtered protein preparations was develo ... | 1999 | 10528404 |
| relationships of bradyrhizobia from the legumes apios americana and desmodium glutinosum. | multilocus enzyme electrophoresis, partial 23s rrna sequences, and nearly full-length 16s rrna sequences all indicated high genetic similarity among root-nodule bacteria associated with apios americana, desmodium glutinosum, and amphicarpaea bracteata, three common herbaceous legumes whose native geographic ranges in eastern north america overlap extensively. a total of 19 distinct multilocus genotypes (electrophoretic types [ets]) were found among the 35 a. americana and 33 d. glutinosum isolat ... | 1999 | 10543803 |
| glyphosate effects on phenolic metabolism of nodulated soybean (glycine max l. merr.). | glyphosate is a herbicide that blocks the shikimic acid pathway. three bradyrhizobium japonicum strains with different sensitivities to glyphosate were used to test the effect of this herbicide on the phenolic metabolism of nodulated soybeans and on the bacteroid nitrogenase activity. glyphosate caused an inhibition in the bacteroid nitrogenase activity that was related with the sensitivity of the nodule-forming strains. both leaves and nodules accumulated huge amounts of shikimate and phenolic ... | 1999 | 10552587 |
| tricarboxylic acid cycle and anaplerotic enzymes in rhizobia. | rhizobia are a diverse group of gram-negative bacteria comprised of the genera rhizobium, bradyrhizobium, mesorhizobium, sinorhizobium and azorhizobium. a unifying characteristic of the rhizobia is their capacity to reduce (fix) atmospheric nitrogen in symbiotic association with a compatible plant host. symbiotic nitrogen fixation requires a substantial input of energy from the rhizobial symbiont. this review focuses on recent studies of rhizobial carbon metabolism which have demonstrated the im ... | 1998 | 9729766 |
| biochemical alterations in bradyrhizobium sp usda 3187 induced by the fungicide mancozeb. | we have previously shown that fungicide mancozeb causes a 50% decrease in bradyhizobium sp usda 3187 growth rate and affects the bacteria-root symbiotic interaction. in order to elucidate the fungicide toxicity mechanism we determined the effects of mancozeb on cell chemical composition, glutathione (gsh) content (molecule involved in the detoxification process), glutathione s-transferase (gst) activity and on polyamine, exopolysaccharides, capsular polysaccharides and lipopolysaccharides. manco ... | 1998 | 9801766 |
| characterization of the bradyrhizobium japonicum ftsh gene and its product. | the bradyrhizobium japonicum ftsh gene was cloned by using a set of widely applicable degenerated oligonucleotides. western blot experiments indicated that the ftsh protein was produced under standard growth conditions and that it was not heat inducible. attempts to delete the ftsh gene in b. japonicum failed, suggesting a pivotal cellular function of this gene. the expression of b. japonicum ftsh in an ftsh-negative escherichia coli strain significantly enhanced the fitness of this mutant and r ... | 1999 | 10572147 |
| allorhizobium undicola gen. nov., sp. nov., nitrogen-fixing bacteria that efficiently nodulate neptunia natans in senegal. | a group of nodule isolates from neptunia natans, an indigenous stemnodulated tropical legume found in waterlogged areas of senegal, was studied. polyphasic taxonomy was performed, including sds-page of total proteins, auxanography using api galleries, host-plant specificity, pcr-rflp of the internal transcribed spacer region between the 16s and the 23s rrna coding genes, 16s rrna gene sequencing and dna-dna hybridization. it was demonstrated that this group is phenotypically and phylogenetically ... | 1998 | 9828428 |
| electrophoretic behavior and size distribution of the acidic polysaccharides produced by the bacteria bradyrhizobium (chamaecytisus) strain bga-1 and bradyrhizobium japonicum usda 110. | the electrophoretic behavior in polyacrylamide gels of the acidic polysaccharides produced by the soil bacteria bradyrhizobium (chamaecytisus) strain bga1 and bradyrhizobiumjaponicum usda1 10 has been studied. both polysaccharides were polydisperse, producing a ladder-like pattern after fixation with alcian blue and silver staining of the gel. the polysaccharide molecules were separated according to their size, and they behaved as a collection of flexible random coils of different size and simil ... | 1998 | 9848669 |
| role of hrca and circe in the heat shock regulatory network of bradyrhizobium japonicum. | a large number of bacteria regulate chaperone gene expression by the circe-hrca system in which a dna element called circe serves as binding site for the repressor protein hrca under non-heat-shock conditions. we have cloned the two consecutive genes hrca and grpe of bradyrhizobium japonicum by using a complementation approach that screened for grpe function. in vivo and in vitro transcript mapping demonstrated that both genes are transcribed separately from rpoh (sigma(32))-dependent promoters. ... | 2000 | 10613857 |
| 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 |
| effectiveness of ascorbate and ascorbate peroxidase in promoting nitrogen fixation in model systems. | ascorbate and ascorbate peroxidase are important antioxidants that are abundant in n2-fixing legume root nodules. antioxidants are especially critical in root nodules because leghemoglobin, which is present at high concentrations in nodules, is prone to autoxidation and production of activated oxygen species such as o2.- and h2o2. the merits of ascorbate and ascorbate peroxidase for maintaining conditions favorable for n2 fixation were examined in two model systems containing oxygen-binding prot ... | 1999 | 10647213 |
| characterization of an azospirillum brasilense tn5 mutant with enhanced n(2) fixation: the effect of orf280 on nifh expression. | disruption of an open reading frame (orf) of 840 bp (280 amino acids; orf280) in an azospirillum brasilense tn5 mutant resulted in a pleiotrophic phenotype. besides an enhanced n(2)-fixing capacity and altered expression pattern of a nifh-gusa fusion, growth on the charged polar amino acids glutamate and arginine was severely affected. orf280, similar to previously identified orfs present in bradyrhizobium japonicum (orf277), paracoccus denitrificans (orf278) and rhodobacter capsulatus (orf277), ... | 2000 | 10650197 |
| structure of a biological oxygen sensor: a new mechanism for heme-driven signal transduction. | the fixl proteins are biological oxygen sensors that restrict the expression of specific genes to hypoxic conditions. fixl's oxygen-detecting domain is a heme binding region that controls the activity of an attached histidine kinase. the fixl switch is regulated by binding of oxygen and other strong-field ligands. in the absence of bound ligand, the heme domain permits kinase activity. in the presence of bound ligand, this domain turns off kinase activity. comparison of the structures of two for ... | 1998 | 9860942 |
| the glutamine synthetases of rhizobia: phylogenetics and evolutionary implications. | glutamine synthetase exists in at least two related forms, gsi and gsii, the sequences of which have been used in evolutionary molecular clock studies. gsi has so far been found exclusively in bacteria, and gsii has been found predominantly in eukaryotes. to date, only a minority of bacteria, including rhizobia, have been shown to express both forms of gs. the sequences of equivalent internal fragments of the gsi and gsii genes for the type strains of 16 species of rhizobia have been determined ... | 2000 | 10677854 |
| magnetic resonance studies on the active site and metal centers of bradyrhizobium japonicum porphobilinogen synthase. | porphobilinogen synthase (pbgs) is a metalloenzyme which catalyzes the asymmetric condensation of two molecules of 5-aminolevulinic acid (ala) to form porphobilinogen. there are at least four types of pbgs, categorized according to metal ion usage. the pbgs from bradyrhizobium japonicum requires mg(ii) in catalytic metal site a, has an allosteric mg(ii) in metal site c, and also contains an activating monovalent cation binding site [petrovich et al. (1996) j. biol. chem. 271, 8692-8699]. 13c nmr ... | 1997 | 9341235 |
| digalactosyl diacylglycerols, plant glycolipids rarely found in bacteria, are major membrane components of bacteroid forms of bradyrhizobium japonicum. | the membrane lipids of free living and bacteroid forms of bradyrhizobium japonicum, obtained from nodules occupied by both typed and untyped bacteria, were isolated and characterized by a combination of nmr spectroscopy, mass spectrometry, and other chemical and physical methods. these studies indicated that both the free living and bacteroid forms of this organism contain glycolipids almost exclusively of the type found in plant cells. in the bacteroid forms, there was a dramatic shift towards ... | 1997 | 9363436 |
| a second gene for type i signal peptidase in bradyrhizobium japonicum, sipf, is located near genes involved in rna processing and cell division. | the tnphoa-induced bradyrhizobium japonicum mutant 184 shows slow growth and aberrant colonization of soybean nodules. using a dna fragment adjacent to the transposon insertion site as a probe, a 3.4-kb bglii fragment of b. japonicum 110spc4 dna was identified and cloned. sequence analysis indicated that two truncated orfs and three complete orfs were encoded on this fragment. a database search revealed homologies to several other prokaryotic proteins: pdxj (an enzyme involved in vitamin b6 bios ... | 1998 | 9870699 |
| 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 |
| 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 |
| symbiotic deficiencies associated with a coxwxyz mutant of bradyrhizobium japonicum | the terminal oxidase complexes encoded by coxmnop and coxwxyz were studied by analysis of mutations in each of the two oxidases. carbon monoxide difference spectra obtained from membranes of coxmnop mutant bacteroids were like those obtained for the wild type, whereas bacteroid membranes of a coxwxyz mutant were deficient in co-reactive cytochrome b. experiments involving cyanide inhibition of oxidase activity were consistent with the conclusion that the coxx mutant is deficient in a membrane-as ... | 1999 | 9872805 |
| 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 |
| bradyrhizobium japonicum isocitrate dehydrogenase exhibits calcium-dependent hysteresis. | bradyrhizobium japonicum nadp(+)-dependent isocitrate dehydrogenase was purified both from cultured cells and from the symbiotic form of the bacteria and was found to be identical in terms of n-terminal amino acid sequence, kinetics, and physicochemical properties. magnesium and glycerol were absolute requirements for maintaining enzyme activity. the n-terminal amino acid sequence of the enzyme was more similar to the sequences from soybean and yeast than to other bacterial sequences. there was ... | 2000 | 10729195 |
| a novel 53-kda nodulin of the symbiosome membrane of soybean nodules, controlled by bradyrhizobium japonicum. | a nodule-specific 53-kda protein (gmnod53b) of the symbiosome membrane from soybean was isolated and its lysc digestion products were microsequenced. cdna clones of this novel nodulin, obtained from cdna library screening with an rt-pcr (reverse-transcriptase polymerase chain reaction)-generated hybridization probe exhibited no homology to proteins identified so far. the expression of gmnod53b coincides with the onset of nitrogen fixation. therefore, it is a late nodulin. among other changes, th ... | 1999 | 10065559 |
| regulation of soybean nodulation independent of ethylene signaling | leguminous plants regulate the number of bradyrhizobium- or rhizobium-infected sites that develop into nitrogen-fixing root nodules. ethylene has been implicated in the regulation of nodule formation in some species, but this role has remained in question for soybean (glycine max). the present study used soybean mutants with decreased responsiveness to ethylene, soybean mutants with defective regulation of nodule number, and ag+ inhibition of ethylene perception to examine the role of ethylene i ... | 1999 | 10069833 |
| 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 |
| further studies of the role of cyclic beta-glucans in symbiosis. an ndvc mutant of bradyrhizobium japonicum synthesizes cyclodecakis-(1-->3)-beta-glucosyl. | the cyclic beta-(1-->3),beta-(1-->6)-d-glucan synthesis locus of bradyrhizobium japonicum is composed of at least two genes, ndvb and ndvc. mutation in either gene affects glucan synthesis, as well as the ability of the bacterium to establish a successful symbiotic interaction with the legume host soybean (glycine max). b. japonicum strain ab-14 (ndvb::tn5) does not synthesize beta-glucans, and strain ab-1 (ndvc::tn5) synthesizes a cyclic beta-glucan lacking beta-(1-->6)-glycosidic bonds. we det ... | 1999 | 10069844 |
| 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 |
| photosynthetic bradyrhizobia from aeschynomene spp. are specific to stem-nodulated species and form a separate 16s ribosomal dna restriction fragment length polymorphism group. | we obtained nine bacterial isolates from root or collar nodules of the non-stem-nodulated aeschynomene species a. elaphroxylon, a. uniflora, or a. schimperi and 69 root or stem nodule isolates from the stem-nodulated aeschynomene species a. afraspera, a. ciliata, a. indica, a. nilotica, a. sensitiva, and a. tambacoundensis from various places in senegal. these isolates, together with 45 previous isolates from various aeschynomene species, were studied for host-specific nodulation within the genu ... | 1999 | 10388707 |
| [effect of pesticides on bacillus thuringiensis strains under controlled conditions]. | little is known about native populations of bacillus thuringiensis (bt) isolated from soils of argentina. we undertook this study to determine the resistance to different pesticides of two commercial and fourteen native strains of bt under in vitro conditions. an agar plate bioassay test conducted with ten pesticides and sixteen strains of bt showed that basagran, scepter, fungoxan and decis were not toxic for the bioinsecticide bacteria at recommended application rates (rar). in contrast, low c ... | 1999 | 10425660 |
| is1631 occurrence in bradyrhizobium japonicum highly reiterated sequence-possessing strains with high copy numbers of repeated sequences rsalpha and rsbeta. | from bradyrhizobium japonicum highly reiterated sequence-possessing (hrs) strains indigenous to niigata and tokachi in japan with high copy numbers of the repeated sequences rsalpha and rsbeta (k. minamisawa, t. isawa, y. nakatsuka, and n. ichikawa, appl. environ. microbiol. 64:1845-1851, 1998), several insertion sequence (is)-like elements were isolated by using the formation of dna duplexes by denaturation and renaturation of total dna, followed by treatment with s1 nuclease. most of these seq ... | 1999 | 10427040 |