| how rhizobial symbionts invade plants: the sinorhizobium-medicago model. | nitrogen-fixing rhizobial bacteria and leguminous plants have evolved complex signal exchange mechanisms that allow a specific bacterial species to induce its host plant to form invasion structures through which the bacteria can enter the plant root. once the bacteria have been endocytosed within a host-membrane-bound compartment by root cells, the bacteria differentiate into a new form that can convert atmospheric nitrogen into ammonia. bacterial differentiation and nitrogen fixation are depend ... | 2007 | 17632573 |
| controlled synthesis of the dsf cell-cell signal is required for biofilm formation and virulence in xanthomonas campestris. | virulence of the black rot pathogen xanthomonas campestris pv. campestris (xcc) is regulated by cell-cell signalling involving the diffusible signal factor dsf. synthesis and perception of dsf require products of genes within the rpf cluster (for regulation of pathogenicity factors). rpff directs dsf synthesis whereas rpfc and rpfg are involved in dsf perception. here we have examined the role of the rpf/dsf system in biofilm formation in minimal medium using confocal laser-scanning microscopy o ... | 2007 | 17635553 |
| the expr/sin quorum-sensing system controls succinoglycan production in sinorhizobium meliloti. | sinorhizobium meliloti is a gram-negative soil bacterium capable of forming a symbiotic nitrogen-fixing relationship with its plant host, medicago sativa. various bacterially produced factors are essential for successful nodulation. for example, at least one of two exopolysaccharides produced by s. meliloti (succinoglycan or eps ii) is required for nodule invasion. both of these polymers are produced in high- and low-molecular-weight (hmw and lmw, respectively) fractions; however, only the lmw f ... | 2007 | 17644606 |
| roles of curli, cellulose and bapa in salmonella biofilm morphology studied by atomic force microscopy. | curli, cellulose and the cell surface protein bapa are matrix components in salmonella biofilms. in this study we have investigated the roles of these components for the morphology of bacteria grown as colonies on agar plates and within a biofilm on submerged mica surfaces by applying atomic force microscopy (afm) and light microscopy. | 2007 | 17650335 |
| transcriptional and physiological responses of bradyrhizobium japonicum to desiccation-induced stress. | the growth and persistence of rhizobia and bradyrhizobia in soils are negatively impacted by drought conditions. in this study, we used genome-wide transcriptional analyses to obtain a comprehensive understanding of the response of bradyrhizobium japonicum to drought. desiccation of cells resulted in the differential expression of 15 to 20% of the 8,453 [corrected] b. japonicum open reading frames, with considerable differentiation between early (after 4 h) and late (after 24 and 72 h) expressed ... | 2007 | 17660288 |
| homologous cpn60 genes in rhizobium leguminosarum are not functionally equivalent. | many bacteria possess 2 or more genes for the chaperonin groel and the cochaperonin groes. in particular, rhizobial species often have multiple groel and groes genes, with a high degree of amino-acid similarity, in their genomes. the rhizobium leguminosarum strain a34 has 3 complete groe operons, which we have named cpn.1, cpn.2 and cpn.3. previously we have shown the cpn. 1 operon to be essential for growth, but the two other cpn operons to be dispensable. here, we have investigated the extent ... | 2007 | 17688191 |
| lysm domains mediate lipochitin-oligosaccharide recognition and nfr genes extend the symbiotic host range. | legume-rhizobium symbiosis is an example of selective cell recognition controlled by host/non-host determinants. individual bacterial strains have a distinct host range enabling nodulation of a limited set of legume species and vice versa. we show here that expression of lotus japonicus nfr1 and nfr5 nod-factor receptor genes in medicago truncatula and l. filicaulis, extends their host range to include bacterial strains, mesorhizobium loti or dzl, normally infecting l. japonicus. as a result, th ... | 2007 | 17690687 |
| diminished redundancy of outer membrane factor proteins in rhizobiales: a nodt homolog is essential for free-living rhizobium etli. | rhizobium etli is a gram-negative soil bacterium that induces nitrogen-fixing nodules on common bean roots (phaseolus vulgaris). r. etli encodes two genes homologous to nodt of rhizobium leguminosarum. nodtch is chromosomal and forms an operon with new genes resembling a multi-drug efflux pump of the resistance-nodulation-cell division (rnd) family. nodtch is the last gene of this operon and can also be independently transcribed; the gene product is located in the bacterial outer membrane. cell ... | 2007 | 17693710 |
| enzymatic synthesis of aromatic polyketides using pks4 from gibberella fujikuroi. | | 2007 | 17696354 |
| gntr family of regulators in mycobacterium smegmatis: a sequence and structure based characterization. | mycobacterium smegmatis is fast growing non-pathogenic mycobacteria. this organism has been widely used as a model organism to study the biology of other virulent and extremely slow growing species like mycobacterium tuberculosis. based on the homology of the n-terminal dna binding domain, the recently sequenced genome of m. smegmatis has been shown to possess several putative gntr regulators. a striking characteristic feature of this family of regulators is that they possess a conserved n-termi ... | 2007 | 17714599 |
| host-specific regulation of symbiotic nitrogen fixation in rhizobium leguminosarum biovar trifolii. | strains of rhizobium leguminosarum bv. trifolii (rlt) able to form effective nodules on trifolium ambiguum (caucasian clover, cc) form ineffective nodules on trifolium repens (white clover, wc), whereas strains that form effective nodules on wc usually do not nodulate cc. here, we investigate the genetic basis of the host-specific nitrogen-fixation phenotype of cc rhizobia. a cosmid library of the symbiotic plasmid from the wc rhizobium strain rlt nzp514 was introduced into the cc rhizobium stra ... | 2007 | 17768261 |
| induction of pre-infection thread structures in the leguminous host plant by mitogenic lipo-oligosaccharides of rhizobium. | root nodules of leguminous plants are symbiotic organs in which rhizobium bacteria fix nitrogen. their formation requires the induction of a nodule meristem and the formation of a tubular structure, the infection thread, through which the rhizobia reach the nodule primordium. in the rhizobium host plants pea and vetch, pre-infection thread structures always preceded the formation of infection threads. these structures consisted of cytoplasmic bridges traversing the central vacuole of outer corti ... | 1992 | 17800714 |
| rhizobium leguminosarum bv. viciae genotypes interact with pea plants in developmental responses of nodules, roots and shoots. | the variability of the developmental responses of two contrasting cultivars of pea (pisum sativum) was studied in relation to the genetic diversity of their nitrogen-fixing symbiont rhizobium leguminosarum bv. viciae. a sample of 42 strains of pea rhizobia was chosen to represent 17 genotypes predominating in indigenous rhizobial populations, the genotypes being defined by the combination of haplotypes characterized with rdna intergenic spacer and nodd gene regions as markers. we found contrasti ... | 2007 | 17822397 |
| the mesorhizobium loti purb gene is involved in infection thread formation and nodule development in lotus japonicus. | the purb and purh mutants of mesorhizobium loti exhibited purine auxotrophy and nodulation deficiency on lotus japonicus. in the presence of adenine, only the purh mutant induced nodule formation and the purb mutant produced few infection threads, suggesting that 5-aminoimidazole-4-carboxamide ribonucleotide biosynthesis catalyzed by purb is required for the establishment of symbiosis. | 2007 | 17827288 |
| genome sequence analysis of the emerging human pathogenic acetic acid bacterium granulibacter bethesdensis. | chronic granulomatous disease (cgd) is an inherited immune deficiency characterized by increased susceptibility to infection with staphylococcus, certain gram-negative bacteria, and fungi. granulibacter bethesdensis, a newly described genus and species within the family acetobacteraceae, was recently isolated from four cgd patients residing in geographically distinct locales who presented with fever and lymphadenitis. we sequenced the genome of the reference strain of granulibacter bethesdensis, ... | 2007 | 17827295 |
| type vi secretion system translocates a phage tail spike-like protein into target cells where it cross-links actin. | genes encoding type vi secretion systems (t6ss) are widely distributed in pathogenic gram-negative bacterial species. in vibrio cholerae, t6ss have been found to secrete three related proteins extracellularly, vgrg-1, vgrg-2, and vgrg-3. vgrg-1 can covalently cross-link actin in vitro, and this activity was used to demonstrate that v. cholerae can translocate vgrg-1 into macrophages by a t6ss-dependent mechanism. protein structure search algorithms predict that vgrg-related proteins likely assem ... | 2007 | 17873062 |
| structural biology of membrane-intrinsic beta-barrel enzymes: sentinels of the bacterial outer membrane. | the outer membranes of gram-negative bacteria are replete with integral membrane proteins that exhibit antiparallel beta-barrel structures, but very few of these proteins function as enzymes. in escherichia coli, only three beta-barrel enzymes are known to exist in the outer membrane; these are the phospholipase ompla, the protease ompt, and the phospholipidcolon, two colonslipid a palmitoyltransferase pagp, all of which have been characterized at the structural level. structural details have al ... | 2008 | 17880914 |
| structural biology of membrane-intrinsic beta-barrel enzymes: sentinels of the bacterial outer membrane. | the outer membranes of gram-negative bacteria are replete with integral membrane proteins that exhibit antiparallel beta-barrel structures, but very few of these proteins function as enzymes. in escherichia coli, only three beta-barrel enzymes are known to exist in the outer membrane; these are the phospholipase ompla, the protease ompt, and the phospholipidcolon, two colonslipid a palmitoyltransferase pagp, all of which have been characterized at the structural level. structural details have al ... | 2008 | 17880914 |
| l-rhamnose transport is sugar kinase (rhak) dependent in rhizobium leguminosarum bv. trifolii. | strains of rhizobium leguminosarum which are unable to catabolize l-rhamnose, a methyl-pentose sugar, are compromised in the ability to compete for nodule occupancy versus wild-type strains. previous characterization of the 11-kb region necessary for the utilization of rhamnose identified a locus carrying catabolic genes and genes encoding the components of an abc transporter. genetic evidence suggested that the putative kinase rhak carried out the first step in the catabolism of rhamnose. chara ... | 2007 | 17890304 |
| increased metabolic potential of rhizobium spp. is associated with bacterial competitiveness. | of 105 rhizobial isolates obtained from nodules of commonly cultivated legumes, we selected 19 strains on the basis of a high rate of symbiotic plant growth promotion. individual strains within the species rhizobium leguminosarum bv. trifolii, r. leguminosarum bv. viciae, and rhizobium etli displayed variation not only in plasmid sizes and numbers but also in the chromosomal 16s-23s internal transcribed spacer. the strains were tagged with gusa gene and their competitiveness was examined in rela ... | 2007 | 17898852 |
| genetic diversity of a natural population of rhizobium leguminosarum bv. viciae nodulating plants of vicia faba in the vesuvian area. | a total of 98 rhizobial strains, isolated during the winter of the years 2003 (35 isolates), 2004 (33 isolates), and 2005 (30 isolates) were analyzed to determine the genetic diversity of the natural population nodulating vicia faba plants and to identify dominant genotypes. all isolates were identified as rhizobium leguminosarum bv. viciae by biovar-specific polymerase chain reaction amplification of the nodc gene. intraspecific dna polymorphism was evaluated through the restriction endonucleas ... | 2007 | 17899266 |
| chromosomal and symbiotic relationships of rhizobia nodulating medicago truncatula and m. laciniata. | multilocus sequence typing (mlst) is a sequence-based method used to characterize bacterial genomes. this method was used to examine the genetic structure of medicago-nodulating rhizobia at the amra site, which is located in an arid region of tunisia. here the annual medics medicago laciniata and m. truncatula are part of the natural flora. the goal of this study was to identify whether distinct chromosomal groups of rhizobia nodulate m. laciniata because of its restricted requirement for specif ... | 2007 | 17921275 |
| orotate phosphoribosyltransferase from corynebacterium ammoniagenes lacking a conserved lysine. | the pyre gene, encoding orotate phosphoribosyltransferase (oprtase), was cloned by nested pcr and colony blotting from corynebacterium ammoniagenes atcc 6872, which is widely used in nucleotide production. sequence analysis shows that there is a lack of an important conserved lysine (lys 73 in salmonella enterica serovar typhimurium oprtase) in the c. ammoniagenes oprtase. this lysine has been considered to contribute to the initiation of catalysis. the enzyme was overexpressed and purified from ... | 2007 | 17921291 |
| influence of the poly-3-hydroxybutyrate (phb) granule-associated proteins (phap1 and phap2) on phb accumulation and symbiotic nitrogen fixation in sinorhizobium meliloti rm1021. | sinorhizobium meliloti cells store excess carbon as intracellular poly-3-hydroxybutyrate (phb) granules that assist survival under fluctuating nutritional conditions. phb granule-associated proteins (phasins) are proposed to regulate phb synthesis and granule formation. although the enzymology and genetics of phb metabolism in s. meliloti have been well characterized, phasins have not yet been described for this organism. comparison of the protein profiles of the wild type and a phb synthesis mu ... | 2007 | 17921298 |
| h2o2 is required for optimal establishment of the medicago sativa/sinorhizobium meliloti symbiosis. | the symbiotic interaction between medicago sativa and sinorhizobium meliloti rmkatb(++) overexpressing the housekeeping catalase katb is delayed, and this delay is combined with an enlargement of infection threads. this result provides evidence that h(2)o(2) is required for optimal progression of infection threads through the root hairs and plant cell layers. | 2007 | 17921312 |
| metabolic reconstruction and modeling of nitrogen fixation in rhizobium etli. | rhizobiaceas are bacteria that fix nitrogen during symbiosis with plants. this symbiotic relationship is crucial for the nitrogen cycle, and understanding symbiotic mechanisms is a scientific challenge with direct applications in agronomy and plant development. rhizobium etli is a bacteria which provides legumes with ammonia (among other chemical compounds), thereby stimulating plant growth. a genome-scale approach, integrating the biochemical information available for r. etli, constitutes an im ... | 2007 | 17922569 |
| human selection and the relaxation of legume defences against ineffective rhizobia. | enforcement mechanisms are thought to be important in maintaining mutualistic cooperation between species. a clear example of an enforcement mechanism is how legumes impose sanctions on rhizobial symbionts that fail to provide sufficient fixed n2. however, with domestication and breeding in high-soil-n environments, humans may have altered these natural legume defences and reduced the agricultural benefits of the symbiosis. using six genotypes of soya beans, representing 60 years of breeding, we ... | 2007 | 17939985 |
| application of physical and genetic map of rhizobium leguminosarum bv. trifolii ta1 to comparison of three closely related rhizobial genomes. | a combined physical and genetic map of rhizobium leguminosarum biovar trifolii ta1 (rtta1) genome was constructed and used in comparison of chromosomal organization with the closely related r. leguminosarum bv. viciae 3841 (rlv) and rhizobium etli cnf42 (rhe). this approach allowed evaluation of chromosome and genome plasticity and provided important insights into r. leguminosarum lineage diversity. mssi, smii, paci, and i-ceui restriction endonucleases were chosen for the analysis, generating f ... | 2008 | 17960422 |
| identification of differentially expressed small non-coding rnas in the legume endosymbiont sinorhizobium meliloti by comparative genomics. | bacterial small non-coding rnas (srnas) are being recognized as novel widespread regulators of gene expression in response to environmental signals. here, we present the first search for srna-encoding genes in the nitrogen-fixing endosymbiont sinorhizobium meliloti, performed by a genome-wide computational analysis of its intergenic regions. comparative sequence data from eight related alpha-proteobacteria were obtained, and the interspecies pairwise alignments were scored with the programs eqrn ... | 2007 | 17971083 |
| phylogenetic diversity based on rrs, atpd, reca genes and 16s-23s intergenic sequence analyses of rhizobial strains isolated from vicia faba and pisum sativum in peru. | in this study 17 isolates from effective nodules of vicia faba and pisum sativum var. macrocarpum growing in different soils from peru were isolated and characterized. the isolates, presenting 11 different rapd profiles, were distributed in three groups on the basis of their 16s-rflp patterns. the 16s rrna gene sequences of strains from 16s-rflp groups i, ii and iii were closely related (identities higher than 99.5%) to rhizobium leguminosarum bv. trifolii dsm 30141 (=atcc 14480), r. leguminosar ... | 2008 | 17985116 |
| multiple phospholipid n-methyltransferases with distinct substrate specificities are encoded in bradyrhizobium japonicum. | phosphatidylcholine (pc) is the major phospholipid in eukaryotic membranes. in contrast, it is found in only a few prokaryotes including members of the family rhizobiaceae. in these bacteria, pc is required for pathogenic and symbiotic plant-microbe interactions, as shown for agrobacterium tumefaciens and bradyrhizobium japonicum. at least two different phospholipid n-methyltransferases (pmta and pmtx) have been postulated to convert phosphatidylethanolamine (pe) to pc in b. japonicum by three c ... | 2008 | 17993534 |
| multiple phospholipid n-methyltransferases with distinct substrate specificities are encoded in bradyrhizobium japonicum. | phosphatidylcholine (pc) is the major phospholipid in eukaryotic membranes. in contrast, it is found in only a few prokaryotes including members of the family rhizobiaceae. in these bacteria, pc is required for pathogenic and symbiotic plant-microbe interactions, as shown for agrobacterium tumefaciens and bradyrhizobium japonicum. at least two different phospholipid n-methyltransferases (pmta and pmtx) have been postulated to convert phosphatidylethanolamine (pe) to pc in b. japonicum by three c ... | 2008 | 17993534 |
| long term evaluation of field-released genetically modified rhizobia. | this is the report of the first open field release of genetically modified microorganisms (gmms) in italy. it covers ten years of monitoring, and follows in-field gmm dynamics from strain release to disappearance below detection limits, as well as assessment of impact on resident microorganisms. the bacteria released belong to the nitrogen fixing legume endosymbiont rhizobium leguminosarum bv. viciae, and were engineered with non-agronomically-proficient traits, in order to assess their behavior ... | 2007 | 18001684 |
| phyr is involved in the general stress response of methylobacterium extorquens am1. | phyr represents a novel alphaproteobacterial family of response regulators having a structure consisting of two domains; a predicted amino-terminal extracytoplasmic function (ecf) sigma factor-like domain and a carboxy-terminal receiver domain. phyr was first described in methylobacterium extorquens am1, in which it has been shown to be essential for plant colonization, probably due to its suggested involvement in the regulation of a number of stress proteins. here we investigated the phyr regul ... | 2008 | 18024517 |
| phyr is involved in the general stress response of methylobacterium extorquens am1. | phyr represents a novel alphaproteobacterial family of response regulators having a structure consisting of two domains; a predicted amino-terminal extracytoplasmic function (ecf) sigma factor-like domain and a carboxy-terminal receiver domain. phyr was first described in methylobacterium extorquens am1, in which it has been shown to be essential for plant colonization, probably due to its suggested involvement in the regulation of a number of stress proteins. here we investigated the phyr regul ... | 2008 | 18024517 |
| molecular characterization of a functional type vi secretion system from a clinical isolate of aeromonas hydrophila. | our laboratory recently molecularly characterized the type ii secretion system (t2ss)-associated cytotoxic enterotoxin (act) and the t3ss-secreted aexu effector from a diarrheal isolate ssu of aeromonas hydrophila. the role of these toxin proteins in the pathogenesis of a. hydrophila infections was subsequently delineated in in vitro and in vivo models. in this study, we characterized the new type vi secretion system (t6ss) from isolate ssu of a. hydrophila and demonstrated its role in bacterial ... | 2008 | 18037263 |
| molecular characterization of a functional type vi secretion system from a clinical isolate of aeromonas hydrophila. | our laboratory recently molecularly characterized the type ii secretion system (t2ss)-associated cytotoxic enterotoxin (act) and the t3ss-secreted aexu effector from a diarrheal isolate ssu of aeromonas hydrophila. the role of these toxin proteins in the pathogenesis of a. hydrophila infections was subsequently delineated in in vitro and in vivo models. in this study, we characterized the new type vi secretion system (t6ss) from isolate ssu of a. hydrophila and demonstrated its role in bacterial ... | 2008 | 18037263 |
| [oxidation processes at initial stages of interaction of root nodule bacteria (rhizobium leguminosarum) and pea (pisum sativum l.): a review]. | a possible physiological mechanism of legume-rhizobium symbiosis, consisting in regulation of the intensity of oxidation processes by the microsymbiont in response to infection with rhizobium, was analyzed using our own and published data. the results used in the analysis included data on the content of reactive oxygen species (o2*-, and h2o2), activity of antioxidant enzymes (superoxide dismutase, catalase, and peroxidase), and intensity of lipid peroxidation proceeding with the involvement of ... | 2007 | 18038678 |
| phylogenomics and signature proteins for the alpha proteobacteria and its main groups. | alpha proteobacteria are one of the largest and most extensively studied groups within bacteria. however, for these bacteria as a whole and for all of its major subgroups (viz. rhizobiales, rhodobacterales, rhodospirillales, rickettsiales, sphingomonadales and caulobacterales), very few or no distinctive molecular or biochemical characteristics are known. | 2007 | 18045498 |
| co-ordinated regulation of gluconate catabolism and glucose uptake in corynebacterium glutamicum by two functionally equivalent transcriptional regulators, gntr1 and gntr2. | corynebacterium glutamicum is a gram-positive soil bacterium that prefers the simultaneous catabolism of different carbon sources rather than their sequential utilization. this type of metabolism requires an adaptation of the utilization rates to the overall metabolic capacity. here we show how two functionally redundant gntr-type transcriptional regulators, designated gntr1 and gntr2, co-ordinately regulate gluconate catabolism and glucose uptake. gntr1 and gntr2 strongly repress the genes enco ... | 2008 | 18047570 |
| co-ordinated regulation of gluconate catabolism and glucose uptake in corynebacterium glutamicum by two functionally equivalent transcriptional regulators, gntr1 and gntr2. | corynebacterium glutamicum is a gram-positive soil bacterium that prefers the simultaneous catabolism of different carbon sources rather than their sequential utilization. this type of metabolism requires an adaptation of the utilization rates to the overall metabolic capacity. here we show how two functionally redundant gntr-type transcriptional regulators, designated gntr1 and gntr2, co-ordinately regulate gluconate catabolism and glucose uptake. gntr1 and gntr2 strongly repress the genes enco ... | 2008 | 18047570 |
| periplasmic phosphorylation of lipid a is linked to the synthesis of undecaprenyl phosphate. | one-third of the lipid a found in the escherichia coli outer membrane contains an unsubstituted diphosphate unit at position 1 (lipid a 1-diphosphate). we now report an inner membrane enzyme, lpxt (yeiu), which specifically transfers a phosphate group to lipid a, forming the 1-diphosphate species. (32)p-labelled lipid a obtained from lpxt mutants do not produce lipid a 1-diphosphate. in vitro assays with kdo(2)-[4'-(32)p]lipid a as the acceptor shows that lpxt uses undecaprenyl pyrophosphate as ... | 2008 | 18047581 |
| periplasmic phosphorylation of lipid a is linked to the synthesis of undecaprenyl phosphate. | one-third of the lipid a found in the escherichia coli outer membrane contains an unsubstituted diphosphate unit at position 1 (lipid a 1-diphosphate). we now report an inner membrane enzyme, lpxt (yeiu), which specifically transfers a phosphate group to lipid a, forming the 1-diphosphate species. (32)p-labelled lipid a obtained from lpxt mutants do not produce lipid a 1-diphosphate. in vitro assays with kdo(2)-[4'-(32)p]lipid a as the acceptor shows that lpxt uses undecaprenyl pyrophosphate as ... | 2008 | 18047581 |
| binding site determinants for the lysr-type transcriptional regulator pcaq in the legume endosymbiont sinorhizobium meliloti. | lysr-type transcriptional regulators represent one of the largest groups of prokaryotic regulators described to date. in the gram-negative legume endosymbiont sinorhizobium meliloti, enzymes involved in the protocatechuate branch of the beta-ketoadipate pathway are encoded within the pcadchgb operon, which is subject to regulation by the lysr-type protein pcaq. in this work, purified pcaq was shown to bind strongly (equilibrium dissociation constant, 0.54 nm) to a region at positions -78 to -45 ... | 2008 | 18055594 |
| binding site determinants for the lysr-type transcriptional regulator pcaq in the legume endosymbiont sinorhizobium meliloti. | lysr-type transcriptional regulators represent one of the largest groups of prokaryotic regulators described to date. in the gram-negative legume endosymbiont sinorhizobium meliloti, enzymes involved in the protocatechuate branch of the beta-ketoadipate pathway are encoded within the pcadchgb operon, which is subject to regulation by the lysr-type protein pcaq. in this work, purified pcaq was shown to bind strongly (equilibrium dissociation constant, 0.54 nm) to a region at positions -78 to -45 ... | 2008 | 18055594 |
| multiple ku orthologues mediate dna non-homologous end-joining in the free-living form and during chronic infection of sinorhizobium meliloti. | the bacterial non-homologous end-joining (nhej) apparatus is a two-component system that uses ku and ligd to repair dna double-strand breaks. although the reaction mechanism has been extensively studied, much less is known about the physiological role of bacterial nhej. recent studies suggest that nhej acts under conditions where dna replication is reduced or absent (such as in a spore or stationary phase). interestingly, genes encoding ku and ligd have been identified in a wide range of bacteri ... | 2008 | 18067541 |
| multiple ku orthologues mediate dna non-homologous end-joining in the free-living form and during chronic infection of sinorhizobium meliloti. | the bacterial non-homologous end-joining (nhej) apparatus is a two-component system that uses ku and ligd to repair dna double-strand breaks. although the reaction mechanism has been extensively studied, much less is known about the physiological role of bacterial nhej. recent studies suggest that nhej acts under conditions where dna replication is reduced or absent (such as in a spore or stationary phase). interestingly, genes encoding ku and ligd have been identified in a wide range of bacteri ... | 2008 | 18067541 |
| identification of chromosomal alpha-proteobacterial small rnas by comparative genome analysis and detection in sinorhizobium meliloti strain 1021. | small untranslated rnas (srnas) seem to be far more abundant than previously believed. the number of srnas confirmed in e. coli through various approaches is above 70, with several hundred more srna candidate genes under biological validation. although the total number of srnas in any one species is still unclear, their importance in cellular processes has been established. however, unlike protein genes, no simple feature enables the prediction of the location of the corresponding sequences in g ... | 2007 | 18093320 |
| rhau of rhizobium leguminosarum is a rhamnose mutarotase. | of the nine genes comprising the l-rhamnose operon of rhizobium leguminosarum, rhau has not been assigned a function. the construction of a delta rhau strain revealed a growth phenotype that was slower than that of the wild-type strain, although the ultimate cell yields were equivalent. the transport of l-rhamnose into the cell and the rate of its phosphorylation were unaffected by the mutation. rhau exhibits weak sequence similarity to the formerly hypothetical protein yiil of escherichia coli ... | 2008 | 18156270 |
| rhau of rhizobium leguminosarum is a rhamnose mutarotase. | of the nine genes comprising the l-rhamnose operon of rhizobium leguminosarum, rhau has not been assigned a function. the construction of a delta rhau strain revealed a growth phenotype that was slower than that of the wild-type strain, although the ultimate cell yields were equivalent. the transport of l-rhamnose into the cell and the rate of its phosphorylation were unaffected by the mutation. rhau exhibits weak sequence similarity to the formerly hypothetical protein yiil of escherichia coli ... | 2008 | 18156270 |
| large-scale transposon mutagenesis of photobacterium profundum ss9 reveals new genetic loci important for growth at low temperature and high pressure. | microorganisms adapted to piezopsychrophilic growth dominate the majority of the biosphere that is at relatively constant low temperatures and high pressures, but the genetic bases for the adaptations are largely unknown. here we report the use of transposon mutagenesis with the deep-sea bacterium photobacterium profundum strain ss9 to isolate dozens of mutant strains whose growth is impaired at low temperature and/or whose growth is altered as a function of hydrostatic pressure. in many cases t ... | 2008 | 18156275 |
| large-scale transposon mutagenesis of photobacterium profundum ss9 reveals new genetic loci important for growth at low temperature and high pressure. | microorganisms adapted to piezopsychrophilic growth dominate the majority of the biosphere that is at relatively constant low temperatures and high pressures, but the genetic bases for the adaptations are largely unknown. here we report the use of transposon mutagenesis with the deep-sea bacterium photobacterium profundum strain ss9 to isolate dozens of mutant strains whose growth is impaired at low temperature and/or whose growth is altered as a function of hydrostatic pressure. in many cases t ... | 2008 | 18156275 |
| a large scale analysis of protein-protein interactions in the nitrogen-fixing bacterium mesorhizobium loti. | global viewing of protein-protein interactions (ppis) is a useful way to assign biological roles to large numbers of proteins predicted by complete genome sequence. here, we systematically analyzed ppis in the nitrogen-fixing soil bacterium mesorhizobium loti using a modified high-throughput yeast two-hybrid system. the aims of this study are primarily on the providing functional clues to m. loti proteins that are relevant to symbiotic nitrogen fixation and conserved in other rhizobium species, ... | 2008 | 18192278 |
| analysis of the campylobacter jejuni flgr response regulator suggests integration of diverse mechanisms to activate an ntrc-like protein. | flagellar motility in campylobacter jejuni mediates optimal interactions with human or animal hosts. sigma(54) and the flgsr two-component system are necessary for the expression of many c. jejuni flagellar genes. the flgr response regulator is homologous to the ntrc family of transcriptional activators. these regulators usually contain an n-terminal receiver domain, a central domain that interacts with sigma(54) and hydrolyzes atp, and a dna-binding c-terminal domain. most often, phosphorylatio ... | 2008 | 18223079 |
| identification of protein secretion systems and novel secreted proteins in rhizobium leguminosarum bv. viciae. | proteins secreted by bacteria play an important role in infection of eukaryotic hosts. rhizobia infect the roots of leguminous plants and establish a mutually beneficial symbiosis. proteins secreted during the infection process by some rhizobial strains can influence infection and modify the plant defence signalling pathways. the aim of this study was to systematically analyse protein secretion in the recently sequenced strain rhizobium leguminosarum bv. viciae 3841. | 2008 | 18230162 |
| hydrocarbon utilization by nodule bacteria and plant growth-promoting rhizobacteria. | standard and locally isolated nodule bacteria and plant growth-promoting rhizobacteria (pgpr) were grown on crude oil and individual pure hydrocarbons as sole sources of carbon and energy. the nodule bacteria included two standard rhizobium leguminosarum strains, two standard bradyrhizobium japonicum strains, and one unknown nodule bacterial strain that was locally isolated from vicia faba nodules. the pgpr included one standard serratia liquefaciens strain and two locally isolated strains of ps ... | 2007 | 18246774 |
| secretome analysis uncovers an hcp-family protein secreted via a type vi secretion system in agrobacterium tumefaciens. | agrobacterium tumefaciens is a plant-pathogenic bacterium capable of secreting several virulence factors into extracellular space or the host cell. in this study, we used shotgun proteomics analysis to investigate the secretome of a. tumefaciens, which resulted in identification of 12 proteins, including 1 known secretory protein (virb1*) and 11 potential secretory proteins. interestingly, one unknown protein, which we designated hemolysin-coregulated protein (hcp), is a predicted soluble protei ... | 2008 | 18263727 |
| an extracellular glycoprotein is implicated in cell-cell contacts in the toxic cyanobacterium microcystis aeruginosa pcc 7806. | microcystins are the most common cyanobacterial toxins found in freshwater lakes and reservoirs throughout the world. they are frequently produced by the unicellular, colonial cyanobacterium microcystis aeruginosa; however, the role of the peptide for the producing organism is poorly understood. differences in the cellular aggregation of m. aeruginosa pcc 7806 and a microcystin-deficient delta mcyb mutant guided the discovery of a surface-exposed protein that shows increased abundance in pcc 780 ... | 2008 | 18281396 |
| novel arrangement of enhancer sequences for nifa-dependent activation of the hydrogenase gene promoter in rhizobium leguminosarum bv. viciae. | the transcriptional activation of the nifa-dependent sigma(54) promoter of the rhizobium leguminosarum hydrogenase structural genes hupsl (p(1)) has been studied through gel retardation analysis and detailed mutagenesis. gel retardation analysis indicated the existence of a physical interaction between nifa and the promoter. extensive mutagenesis followed by in vivo expression analysis showed that three sequences of 4 bases each (-170 acaa -167, -161 acaa -158, and -145 ttgt -142) are required f ... | 2008 | 18310336 |
| influence of the sigmab stress factor and yxab, the gene for a putative exopolysaccharide synthase under sigmab control, on biofilm formation. | bacillus subtilis forms structured communities of biofilms encased in an exopolysaccharide matrix on solid surfaces and at the air-liquid interface. it is postulated that nonoptimal growth conditions induce this multicellular behavior. we showed that under laboratory conditions a strain deleted for sigb was unable to form a floating pellicle on the surface of a liquid medium. however, overexpression of yxab, encoding a putative exopolysaccharide synthase, from a p(spac) promoter in a sigb-delete ... | 2008 | 18326573 |
| functional nodfe genes are present in sinorhizobium sp. strain mus10, a symbiont of the tropical legume sesbania rostrata. | we have cloned the nodfe operon from sinorhizobium sp. strain mus10. mus10 nodf shows sequence homology to acyl carrier protein and enables an s. meliloti nodf mutant to effectively nodulate alfalfa. our results demonstrate the occurrence of nodfe in a symbiont that nodulates a legume host not belonging to the galegoid group. | 2008 | 18326678 |
| genomic insights into mn(ii) oxidation by the marine alphaproteobacterium aurantimonas sp. strain si85-9a1. | microbial mn(ii) oxidation has important biogeochemical consequences in marine, freshwater, and terrestrial environments, but many aspects of the physiology and biochemistry of this process remain obscure. here, we report genomic insights into mn(ii) oxidation by the marine alphaproteobacterium aurantimonas sp. strain si85-9a1, isolated from the oxic/anoxic interface of a stratified fjord. the si85-9a1 genome harbors the genetic potential for metabolic versatility, with genes for organoheterotro ... | 2008 | 18344346 |
| ultrastructural characterization of the prokaryotic symbiosis in "chlorochromatium aggregatum". | the phototrophic consortium "chlorochromatium aggregatum" currently represents the most highly developed interspecific association of bacteria and consists of green sulfur bacteria, so-called epibionts, surrounding a central, motile, chemotrophic bacterium. in order to identify subcellular structures characteristic of this symbiosis, consortia were studied by a combination of high-resolution analytical scanning electron microscopy, transmission electron microscopy, and three-dimensional reconstr ... | 2008 | 18344357 |
| cellulose synthesis in phytophthora infestans is required for normal appressorium formation and successful infection of potato. | cellulose, the important structural compound of cell walls, provides strength and rigidity to cells of numerous organisms. here, we functionally characterize four cellulose synthase genes (cesa) in the oomycete plant pathogen phytophthora infestans, the causal agent of potato (solanum tuberosum) late blight. three members of this new protein family contain pleckstrin homology domains and form a distinct phylogenetic group most closely related to the cellulose synthases of cyanobacteria. expressi ... | 2008 | 18349153 |
| ttsi regulates symbiotic genes in rhizobium species ngr234 by binding to tts boxes. | infection of legumes by rhizobium sp. ngr234 and subsequent development of nitrogen-fixing nodules are dependent on the coordinated actions of nod factors, proteins secreted by a type iii secretion system (t3ss) and modifications to surface polysaccharides. the production of these signal molecules is dependent on plant flavonoids which trigger a regulatory cascade controlled by the transcriptional activators nodd1, nodd2, syrm2 and ttsi. ttsi is known to control the genes responsible for t3ss fu ... | 2008 | 18363648 |
| the function of three indigenous plasmids in mesorhizobium huakuii 2020 and its symbiotic interaction with sym pjb5ji of rhizobium leguminosarum. | a mesorhizobium huakuii strain 2020, isolated from a rice-growing field in southern china, contains three indigenous plasmids named p2020a, p2020b and p2020c, respectively. the plasmids were deleted via tn5-sacb insertion, and two cured derivatives were obtained. interestingly, the mutant 2020d29 curing of p2020c could significantly enhance the capacity of symbiotic nitrogen fixation. but the mutant 2020d8 curing of p2020b lost the ability to nodulate astragalus sinicus. furthermore, the third p ... | 2008 | 18368313 |
| plant phenology and genetic variability in root and nodule development strongly influence genetic structuring of rhizobium leguminosarum biovar viciae populations nodulating pea. | the symbiotic relationships between legumes and their nitrogen (n(2))-fixing bacterial partners (rhizobia) vary in effectiveness to promote plant growth according to both bacterial and legume genotype. to assess the selective effect of host plant on its microsymbionts, the influence of the pea (pisum sativum) genotype on the relative nodulation success of rhizobium leguminosarum biovar viciae (rlv) genotypes from the soil populations during plant development has been investigated. five pea lines ... | 2008 | 18373650 |
| structural characterization of the primary o-antigenic polysaccharide of the rhizobium leguminosarum 3841 lipopolysaccharide and identification of a new 3-acetimidoylamino-3-deoxyhexuronic acid glycosyl component: a unique o-methylated glycan of uniform size, containing 6-deoxy-3-o-methyl-d-talose, n-acetylquinovosamine, and rhizoaminuronic acid (3-acetimidoylamino-3-deoxy-d-gluco-hexuronic acid). | rhizobium are gram-negative bacteria that survive intracellularly, within host membrane-derived plant cell compartments called symbiosomes. within the symbiosomes the bacteria differentiate to bacteroids, the active form that carries out nitrogen fixation. the progression from free-living bacteria to bacteroid is characterized by physiological and morphological changes at the bacterial surface, a phase shift with an altered array of cell surface glycoconjugates. lipopolysaccharides undergo struc ... | 2008 | 18387959 |
| the xenorhabdus nematophila nilabc genes confer the ability of xenorhabdus spp. to colonize steinernema carpocapsae nematodes. | members of the steinernema genus of nematodes are colonized mutualistically by members of the xenorhabdus genus of bacteria. in nature, steinernema carpocapsae nematodes are always found in association with xenorhabdus nematophila bacteria. thus, this interaction, like many microbe-host associations, appears to be species specific. x. nematophila requires the nila, nilb, and nilc genes to colonize s. carpocapsae. in this work, we showed that of all the xenorhabdus species examined, only x. nemat ... | 2008 | 18390667 |
| host-dependent expression of rhizobium leguminosarum bv. viciae hydrogenase is controlled at transcriptional and post-transcriptional levels in legume nodules. | the legume host affects the expression of rhizobium leguminosarum hydrogenase activity in root nodules. high levels of symbiotic hydrogenase activity were detected in r. leguminosarum bacteroids from different hosts, with the exception of lentil (lens culinaris). transcription analysis showed that the nifa-regulated r. leguminosarum hydrogenase structural gene promoter (p(1)) is poorly induced in lentil root nodules. replacement of the p(1) promoter by the fnrn-dependent promoter of the fixn gen ... | 2008 | 18393619 |
| the rhizobial adhesion protein rapa1 is involved in adsorption of rhizobia to plant roots but not in nodulation. | the effect of the rhizobium adhesion protein rapa1 on rhizobium leguminosarum bv. trifolii adsorption to trifolium pratense (red clover) roots was investigated. we altered rapa1 production by cloning its encoding gene under the plac promoter into the stable vector phc60. after introducing this plasmid in r. leguminosarum bv. trifolii, three to four times more rapa1 was produced, and two to five times higher adsorption to red clover roots was obtained, as compared with results for the empty vecto ... | 2008 | 18393991 |
| in vivo expression technology (ivet) selection of genes of rhizobium leguminosarum biovar viciae a34 expressed in the rhizosphere. | ivet was used to identify genes that are specifically expressed in the rhizosphere of the pea-nodulating bacterium rhizobium leguminosarum a34. a library of r. leguminosarum a34 cloned in the integration vector pie1, with inserts upstream of a promoter-less purn:gfp:gusa, was conjugated into purn host ru2249 and recombined into the genome. after removal of colonies that expressed the reporter genes of the vector under laboratory conditions, the library was inoculated into a nonsterile pea rhizos ... | 2008 | 18399996 |
| influence of phosphate and ammonia on the growth, exopolysaccharide production and symbiosis of rhizobium leguminosarum bv. trifolii ta1 with clover (trifolium pratense). | the rhizobium-legume interaction is sensitive to a number of environmental factors, among which phosphate (pi) and ammonium availability are the most important. we investigated the effect of pi and ammonia concentration on exopolysaccharide production and symbiosis trifolium pratense with rhizobium leguminosarum bv. trifolii ta1 (rtta1). the optimal pi concentration in the bacterial growth medium for rtta1 growth and exopolysaccharide production was in the range from 0.9 mm to 8.1 mm. independen ... | 2008 | 18401950 |
| synthesis and stereochemistry-activity relationship of small bacteriocin, an autoinducer of the symbiotic nitrogen-fixing bacterium rhizobium leguminosarum. | the four stereoisomers of small bacteriocin, an autoinducer of the symbiotic nitrogen-fixing bacterium rhizobium leguminosarum, were synthesized via a versatile methodology for 3'-hydroxyacyl homoserine lactones based on the nagao asymmetric aldol reaction. the synthetic isomers were much less effective at inhibiting the growth of r. leguminosarum rbl5523 than the natural isomer, showing the importance of stereochemistry for activity. | 2008 | 18402461 |
| introduction of a novel pathway for iaa biosynthesis to rhizobia alters vetch root nodule development. | we introduced into rhizobium leguminosarum bv. viciae lpr1105 a new pathway for the biosynthesis of the auxin, indole-3-acetic acid (iaa), under the control of a stationary phase-activated promoter active both in free-living bacteria and bacteroids. the newly introduced genes are the iaam gene from pseudomonas savastanoi and the tms2 gene from agrobacterium tumefaciens. free-living bacteria harbouring the promoter-iaamtms2 construct release into the growth medium 14-fold more iaa than the wild-t ... | 2008 | 18415080 |
| the complete genome, comparative and functional analysis of stenotrophomonas maltophilia reveals an organism heavily shielded by drug resistance determinants. | stenotrophomonas maltophilia is a nosocomial opportunistic pathogen of the xanthomonadaceae. the organism has been isolated from both clinical and soil environments in addition to the sputum of cystic fibrosis patients and the immunocompromised. whilst relatively distant phylogenetically, the closest sequenced relatives of s. maltophilia are the plant pathogenic xanthomonads. | 2008 | 18419807 |
| transcriptional interference and repression modulate the conjugative ability of the symbiotic plasmid of rhizobium etli. | bacteria of the order rhizobiales are able to establish nitrogen-fixing symbioses with legumes. commonly, genes for symbiosis are harbored on large symbiotic plasmids. although the transfer of symbiotic plasmids is commonly detected in nature, there are few experimentally characterized examples. in rhizobium etli, the product of rcta inhibits the conjugation of the symbiotic plasmid by reducing the transcription of the virb operon. rcta is transcribed divergently from this operon, and its produc ... | 2008 | 18424522 |
| a polyketide macrolactone synthase from the filamentous fungus gibberella zeae. | resorcylic acid lactones represent a unique class of fungal polyketides and display a wide range of biological activities, such as nanomolar inhibitors of hsp90 and map kinase. the biosynthesis of these compounds is proposed to involve two fungal polyketide synthases (pks) that function collaboratively to yield a 14-membered macrolactone with a resorcylate core. we report here the reconstitution of gibberella zeae pks13, which is the nonreducing pks associated with zearalenone biosynthesis. usin ... | 2008 | 18427109 |
| glucomannan-mediated attachment of rhizobium leguminosarum to pea root hairs is required for competitive nodule infection. | the rhizobium leguminosarum biovar viciae genome contains several genes predicted to determine surface polysaccharides. mutants predicted to affect the initial steps of polysaccharide synthesis were identified and characterized. in addition to the known cellulose (cel) and acidic exopolysaccharide (eps) (pss) genes, we mutated three other loci; one of these loci (gmsa) determines glucomannan synthesis and one (gela) determines a gel-forming polysaccharide, but the role of the other locus (an exo ... | 2008 | 18441060 |
| transcription of the extended hyp-operon in nostoc sp. strain pcc 7120. | the maturation of hydrogenases into active enzymes is a complex process and e.g. a correctly assembled active site requires the involvement of at least seven proteins, encoded by hypabcdef and a hydrogenase specific protease, encoded either by hupw or hoxw. the n2-fixing cyanobacterium nostoc sp. strain pcc 7120 may contain both an uptake and a bidirectional hydrogenase. the present study addresses the presence and expression of hyp-genes in nostoc sp. strain pcc 7120. | 2008 | 18442387 |
| cyanogenic pseudomonads influence multitrophic interactions in the rhizosphere. | in the rhizosphere, plant roots cope with both pathogenic and beneficial bacterial interactions. the exometabolite production in certain bacterial species may regulate root growth and other root-microbe interactions in the rhizosphere. here, we elucidated the role of cyanide production in pseudomonad virulence affecting plant root growth and other rhizospheric processes. exposure of arabidopsis thaliana col-0 seedlings to both direct (with kcn) and indirect forms of cyanide from different pseudo ... | 2008 | 18446201 |
| identification of new genes in sinorhizobium meliloti using the genome sequencer flx system. | sinorhizobium meliloti is an agriculturally important model symbiont. there is an ongoing need to update and improve its genome annotation. in this study, we used a high-throughput pyrosequencing approach to sequence the transcriptome of s. meliloti, and search for new bacterial genes missed in the previous genome annotation. this is the first report of sequencing a bacterial transcriptome using the pyrosequencing technology. | 2008 | 18454850 |
| rhizobium cellulase celc2 is essential for primary symbiotic infection of legume host roots. | the rhizobia-legume, root-nodule symbiosis provides the most efficient source of biologically fixed ammonia fertilizer for agricultural crops. its development involves pathways of specificity, infectivity, and effectivity resulting from expressed traits of the bacterium and host plant. a key event of the infection process required for development of this root-nodule symbiosis is a highly localized, complete erosion of the plant cell wall through which the bacterial symbiont penetrates to establi ... | 2008 | 18458328 |
| genome sequence of brucella abortus vaccine strain s19 compared to virulent strains yields candidate virulence genes. | the brucella abortus strain s19, a spontaneously attenuated strain, has been used as a vaccine strain in vaccination of cattle against brucellosis for six decades. despite many studies, the physiological and molecular mechanisms causing the attenuation are not known. we have applied pyrosequencing technology together with conventional sequencing to rapidly and comprehensively determine the complete genome sequence of the attenuated brucella abortus vaccine strain s19. the main goal of this study ... | 2008 | 18478107 |
| genome sequence of the beta-rhizobium cupriavidus taiwanensis and comparative genomics of rhizobia. | we report the first complete genome sequence of a beta-proteobacterial nitrogen-fixing symbiont of legumes, cupriavidus taiwanensis lmg19424. the genome consists of two chromosomes of size 3.42 mb and 2.50 mb, and a large symbiotic plasmid of 0.56 mb. the c. taiwanensis genome displays an unexpected high similarity with the genome of the saprophytic bacterium c. eutrophus h16, despite being 0.94 mb smaller. both organisms harbor two chromosomes with large regions of synteny interspersed by speci ... | 2008 | 18490699 |
| the effect of chromosome geometry on genetic diversity. | although organisms with linear chromosomes must solve the problem of fully replicating their chromosome ends, this chromosome configuration has emerged repeatedly during bacterial evolution and is evident in three divergent bacterial phyla. the benefit usually ascribed to this topology is the ability to boost genetic variation through increased recombination. but because numerous processes can impact linkage disequilibrium, such an effect is difficult to assess by comparing across bacterial taxa ... | 2008 | 18493068 |
| nitrogen fixation island and rhizosphere competence traits in the genome of root-associated pseudomonas stutzeri a1501. | the capacity to fix nitrogen is widely distributed in phyla of bacteria and archaea but has long been considered to be absent from the pseudomonas genus. we report here the complete genome sequencing of nitrogen-fixing root-associated pseudomonas stutzeri a1501. the genome consists of a single circular chromosome with 4,567,418 bp. comparative genomics revealed that, among 4,146 protein-encoding genes, 1,977 have orthologs in each of the five other pseudomonas representative species sequenced to ... | 2008 | 18495935 |
| transposon mediation allows a symbiotic plasmid of rhizobium leguminosarum bv. trifolii to become a symbiosis island in agrobacterium and rhizobium. | the symbiotic plasmid (psym) of rhizobium leguminosarum bv. trifolii 4s5, which carries tn5-mob, was successfully transferred into agrobacterium tumefaciens a136 by using a conjugation method. the resulting transconjugants induced the development of ineffective nitrogen-fixing nodules on the roots of white clover seedlings. depending on the manner in which the psym was retained, the transconjugants were divided into two groups of strains, afp and afcs. psym was retained as a plasmid in the afp s ... | 2008 | 18497485 |
| visualization of symbiotic tissue in intact root nodules of vicia tetrasperma using gfp-marked rhizobium leguminosarum bv. viciae. | in rhizobial symbiosis with legume plant hosts, the symbiotic tissue in the root nodules of indeterminate type is localized to the basal part of the nodule where the symbiotic zones contain infected cells (ic) interspersed with uninfected cells (uc) that are devoid of rhizobia. although ic are easily distinguished in nodule sections using standard histochemical techniques, their observation in intact nodules is hampered by nodule tissue characteristics. tagging of rhizobium leguminosarum bv. vic ... | 2008 | 18500633 |
| soybean seed extracts preferentially express genomic loci of bradyrhizobium japonicum in the initial interaction with soybean, glycine max (l.) merr. | initial interaction between rhizobia and legumes actually starts via encounters of both partners in the rhizosphere. in this study, the global expression profiles of bradyrhizobium japonicum usda 110 in response to soybean (glycine max) seed extracts (sse) and genistein, a major soybean-released isoflavone for nod genes induction of b. japonicum, were compared. sse induced many genomic loci as compared with genistein (5.0 microm), nevertheless sse-supplemented medium contained 4.7 microm geniste ... | 2008 | 18511436 |
| the genome of the versatile nitrogen fixer azorhizobium caulinodans ors571. | biological nitrogen fixation is a prokaryotic process that plays an essential role in the global nitrogen cycle. azorhizobium caulinodans ors571 has the dual capacity to fix nitrogen both as free-living organism and in a symbiotic interaction with sesbania rostrata. the host is a fast-growing, submergence-tolerant tropical legume on which a. caulinodans can efficiently induce nodule formation on the root system and on adventitious rootlets located on the stem. | 2008 | 18522759 |
| membrane topology and roles of pseudomonas aeruginosa alg8 and alg44 in alginate polymerization. | mucoid strains of pseudomonas aeruginosa that overproduce alginate are associated with chronic pulmonary disease (e.g. cystic fibrosis). mutants defective in one of several periplasmic proteins (algkgx) for alginate secretion release alginate fragments due to the activity of an alginate lyase (algl) in the periplasm, which cleaves the newly formed polymers. however, mutants defective in alg8 or alg44 did not secrete polymer or alginate fragments, suggesting that both these membrane proteins have ... | 2008 | 18524915 |
| highly plastic genome of microcystis aeruginosa pcc 7806, a ubiquitous toxic freshwater cyanobacterium. | the colonial cyanobacterium microcystis proliferates in a wide range of freshwater ecosystems and is exposed to changing environmental factors during its life cycle. microcystis blooms are often toxic, potentially fatal to animals and humans, and may cause environmental problems. there has been little investigation of the genomics of these cyanobacteria. | 2008 | 18534010 |
| the bradyrhizobium japonicum irr protein is a transcriptional repressor with high-affinity dna-binding activity. | the irr protein is a global regulator of iron homeostasis in bradyrhizobium japonicum, and a subset of genes within the irr regulon are negatively controlled under iron limitation. however, repressor function, high-affinity dna binding in vitro, or promoter occupancy in vivo of irr for a negatively regulated gene has not been demonstrated. here, we show that the blr7895 and bll6680 genes are negatively regulated by irr as determined by derepression of transcript levels in iron-limited cells of a ... | 2008 | 18539736 |
| glutathione and transition-metal homeostasis in escherichia coli. | glutathione (gsh) and its derivative phytochelatin are important binding factors in transition-metal homeostasis in many eukaryotes. here, we demonstrate that gsh is also involved in chromate, zn(ii), cd(ii), and cu(ii) homeostasis and resistance in escherichia coli. while the loss of the ability to synthesize gsh influenced metal tolerance in wild-type cells only slightly, gsh was important for residual metal resistance in cells without metal efflux systems. in mutant cells without the p-type a ... | 2008 | 18539744 |
| 1-aminocyclopropane-1-carboxylate (acc) deaminase genes in rhizobia from southern saskatchewan. | a collection of 233 rhizobia strains from 30 different sites across saskatchewan, canada was assayed for 1-aminocyclopropane-1-carboxylate (acc) deaminase activity, with 27 of the strains displaying activity. when all 27 strains were characterized based on 16s rrna gene sequences, it was noted that 26 strains are close to rhizobium leguminosarum and one strain is close to rhizobium gallicum. polymerase chain reaction (pcr) was used to rapidly isolate acc deaminase structural genes from the above ... | 2009 | 18548183 |
| sequencing and expression of two arsenic resistance operons with different functions in the highly arsenic-resistant strain ochrobactrum tritici scii24t. | arsenic (as) is a natural metalloid, widely used in anthropogenic activities, that can exist in different oxidation states. throughout the world, there are several environments contaminated with high amounts of arsenic where many organisms can survive. the most stable arsenical species are arsenate and arsenite that can be subject to chemically and microbiologically oxidation, reduction and methylation reactions. organisms surviving in arsenic contaminated environments can have a diversity of me ... | 2008 | 18554386 |
| bradyrhizobium elkanii, bradyrhizobium yuanmingense and bradyrhizobium japonicum are the main rhizobia associated with vigna unguiculata and vigna radiata in the subtropical region of china. | cowpea (vigna unguiculata) and mung bean (vigna radiata) are important legume crops yet their rhizobia have not been well characterized. in the present study, 62 rhizobial strains isolated from the root nodules of these plants grown in the subtropical region of china were analyzed via a polyphasic approach. the results showed that 90% of the analyzed strains belonged to or were related to bradyrhizobium japonicum, bradyrhizobium liaoningense, bradyrhizobium yuanmingense and bradyrhizobium elkani ... | 2008 | 18564340 |
| a common genomic framework for a diverse assembly of plasmids in the symbiotic nitrogen fixing bacteria. | this work centres on the genomic comparisons of two closely-related nitrogen-fixing symbiotic bacteria, rhizobium leguminosarum biovar viciae 3841 and rhizobium etli cfn42. these strains maintain a stable genomic core that is also common to other rhizobia species plus a very variable and significant accessory component. the chromosomes are highly syntenic, whereas plasmids are related by fewer syntenic blocks and have mosaic structures. the pairs of plasmids p42f-prl12, p42e-prl11 and p42b-prl9 ... | 2008 | 18596979 |
| broad-host-range expression vectors with tightly regulated promoters and their use to examine the influence of trar and tram expression on ti plasmid quorum sensing. | experiments requiring strong repression and precise control of cloned genes can be difficult to conduct because of the relatively high basal level of expression of currently employed promoters. we report the construction of a family of vectors that contain a reengineered laci(q)-lac promoter-operator complex in which cloned genes are strongly repressed in the absence of inducer. the vectors, all based on the broad-host-range plasmid pbbr1, are mobilizable and stably replicate at moderate copy nu ... | 2008 | 18606801 |