| o-acetylation of the terminal n-acetylglucosamine of the lipooligosaccharide inner core in neisseria meningitidis. influence on inner core structure and assembly. | o-acetylation is a common decoration on endotoxins derived from many gram-negative bacterial species, and it has been shown to be instrumental (e.g. in salmonella typhimurium) in determining the final tertiary structure of the endotoxin and the immunogenicity of the molecule. structural heterogeneity of endotoxins produced by mucosal pathogens such as neisseria meningitidis is determined by decorations on the heptose inner core, including o-acetylation of the terminal n-acetylglucosamine (glcnac ... | 2006 | 16687398 |
| antioxidative enzymes from chloroplasts, mitochondria, and peroxisomes during leaf senescence of nodulated pea plants. | in this work the influence of the nodulation of pea (pisum sativum l.) plants on the oxidative metabolism of different leaf organelles from young and senescent plants was studied. chloroplasts, mitochondria, and peroxisomes were purified from leaves of nitrate-fed and rhizobium leguminosarum-nodulated pea plants at two developmental stages (young and senescent plants). in these cell organelles, the activity of the ascorbate-glutathione cycle enzymes ascorbate peroxidase (apx), monodehydroascorba ... | 2006 | 16698815 |
| [temperature impact on localization of "free" phenolic compounds in the root tissues and deformation of root hairs in pea seedlings inoculated by rhizobium]. | the study was focused on localization of "free" phenolic compounds in pea pisum sativum l. seedling roots grown at 22 and 8 degrees c 24 h after their inoculation with rhizobium leguminosarum bv. viceae bacteria. a comparison of phenolic compound distribution along the root in root tissues, and results of observation of root hair development on the root surface, response of root hairs to inoculation, manifesting itself in various deformation degree (bends, twists, ect.) enabled us to reveal diff ... | 2005 | 16708844 |
| transposon mutations in the 5' end of glnd, the gene for a nitrogen regulatory sensor, that suppress the osmosensitive phenotype caused by otsba lesions in escherichia coli. | glnd of escherichia coli is a bifunctional signal-transducing enzyme (102.4 kda) which uridylylates the allosteric regulatory protein pii and deuridylylates pii-ump in response to growth with nitrogen excess or limitation, respectively. glnd catalyzes these reactions in response to high or low levels of cytoplasmic glutamine, respectively, and indirectly directs the expression of nitrogen-regulated genes, e.g., the glnk-amtb operon. we report that chromosomal mini-tn10 insertions situated after ... | 2006 | 16740928 |
| proteins exported via the prsd-prse type i secretion system and the acidic exopolysaccharide are involved in biofilm formation by rhizobium leguminosarum. | the type i protein secretion system of rhizobium leguminosarum bv. viciae encoded by the prsd and prse genes is responsible for secretion of the exopolysaccharide (eps)-glycanases plya and plyb. the formation of a ring of biofilm on the surface of the glass in shaken cultures by both the prsd and prse secretion mutants was greatly affected. confocal laser scanning microscopy analysis of green-fluorescent-protein-labeled bacteria showed that during growth in minimal medium, r. leguminosarum wild ... | 2006 | 16740954 |
| the lipid a 1-phosphatase of helicobacter pylori is required for resistance to the antimicrobial peptide polymyxin. | modification of the phosphate groups of lipid a with amine-containing substituents, such as phosphoethanolamine, reduces the overall net negative charge of gram-negative bacterial lipopolysaccharide, thereby lowering its affinity to cationic antimicrobial peptides. modification of the 1 position of helicobacter pylori lipid a is a two-step process involving the removal of the 1-phosphate group by a lipid a phosphatase, lpxehp (hp0021), followed by the addition of a phosphoethanolamine residue ca ... | 2006 | 16740959 |
| characterization of 'schizokinen'; a dihydroxamate-type siderophore produced by rhizobium leguminosarum iari 917. | the rhizobia comprise one of the most important groups of beneficial bacteria, which form nodules on the roots (rarely on the stems) of leguminous plants. they live within the nodules and reduce atmospheric nitrogen to ammonia, which is further assimilated by plants into required nitrogenous compounds. the rhizobia in return obtain nutrition from the plant. rhizobia are free-living soil bacteria and have to compete with other microorganisms for the limited available iron in the rhizosphere. in o ... | 2006 | 16758117 |
| roles for redox regulation in leaf senescence of pea plants grown on different sources of nitrogen nutrition. | leaf senescence and associated changes in redox components were monitored in commercial pea (pisum sativum l. cv. phoenix) plants grown under different nitrogen regimes for 12 weeks until both nodules and leaves had fully senesced. one group of plants was inoculated with rhizobium leguminosarum and grown with nutrient solution without nitrogen. a second group was not inoculated and these were grown on complete nutrient solution containing nitrogen. leaf senescence was evident at 11 weeks in both ... | 2006 | 16760420 |
| fixj: a major regulator of the oxygen limitation response and late symbiotic functions of sinorhizobium meliloti. | sinorhizobium meliloti exists either in a free-living state in the soil or in symbiosis within legume nodules, where the bacteria differentiate into nitrogen-fixing bacteroids. expression of genes involved in nitrogen fixation and associated respiration is governed by two intermediate regulators, nifa and fixk, respectively, which are controlled by a two-component regulatory system fixlj in response to low-oxygen conditions. in order to identify the fixlj regulon, gene expression profiles were d ... | 2006 | 16788198 |
| effects of endogenous salicylic acid on nodulation in the model legumes lotus japonicus and medicago truncatula. | the exogenous addition of salicylic acid (sa) was previously shown to inhibit indeterminate but not determinate-type nodulation. we sought to extend these results by modulating endogenous levels of sa through the transgenic expression of salicylate hydroxylase (nahg) in both stably transformed lotus japonicus and composite medicago truncatula plants. nahg expression in l. japonicus resulted in a marked reduction of sa levels. this reduction correlated with an increase in the number of infections ... | 2006 | 16798946 |
| characterization of genes involved in erythritol catabolism in rhizobium leguminosarum bv. viciae. | a genetic locus encoding erythritol uptake and catabolism genes was identified in rhizobium leguminosarum bv. viciae, and shown to be plasmid encoded in a wide range of r. leguminosarum strains. a tn5-b22 mutant (19b-3) unable to grow on erythritol was isolated from a mutant library of r. leguminosarum strain vf39sm. the mutated gene eryf was cloned and partially sequenced, and determined to have a high homology to permease genes of abc transporters. a cosmid complementing the mutation (pcos42) ... | 2006 | 16804181 |
| the brucella abortus cyclic beta-1,2-glucan virulence factor is substituted with o-ester-linked succinyl residues. | brucella periplasmic cyclic beta-1,2-glucan plays an important role during bacterium-host interaction. nuclear magnetic resonance spectrometry analysis, thin-layer chromatography, and deae-sephadex chromatography were used to characterize brucella abortus cyclic glucan. in the present study, we report that a fraction of b. abortus cyclic beta-1,2-glucan is substituted with succinyl residues, which confer anionic character on the cyclic beta-1,2-glucan. the oligosaccharide backbone is substituted ... | 2006 | 16816173 |
| osmotic upshift transiently inhibits uptake via abc transporters in gram-negative bacteria. | atp-binding cassette transporters from several rhizobia and salmonella enterica serovar typhimurium, but not secondarily coupled systems, were inhibited by high concentrations (100 to 500 mm) of various osmolytes, an effect reversed by the removal of the osmolyte. abc systems were also inactivated in isolated pea bacteroids, probably due to the obligatory use of high-osmolarity isolation media. measurement of nutrient cycling in isolated pea bacteroids is impeded by this effect. | 2006 | 16816205 |
| expression of the 1-aminocyclopropane-1-carboxylic acid deaminase gene requires symbiotic nitrogen-fixing regulator gene nifa2 in mesorhizobium loti maff303099. | many soil bacteria contain 1-aminocyclopropane-1-carboxylic acid (acc) deaminase, which degrades acc, a precursor of the phytohormone ethylene. in order to examine the regulation of the acds gene encoding acc deaminase in mesorhizobium loti maff303099 during symbiosis with the host legume lotus japonicus, we introduced the beta-glucuronidase (gus) gene into acds so that gus was expressed under control of the acds promoter, and we also generated disruption mutants with mutations in a nitrogen fix ... | 2006 | 16820494 |
| diverse flavonoids stimulate nodd1 binding to nod gene promoters in sinorhizobium meliloti. | nodd1 is a member of the nodd family of lysr-type transcriptional regulators that mediates the expression of nodulation (nod) genes in the soil bacterium sinorhizobium meliloti. each species of rhizobia establishes a symbiosis with a limited set of leguminous plants. this host specificity results in part from a nodd-dependent upregulation of nod genes in response to a cocktail of flavonoids in the host plant's root exudates. to demonstrate that nodd is a key determinant of host specificity, we e ... | 2006 | 16855231 |
| characterization of the beta-ketoadipate pathway in sinorhizobium meliloti. | aromatic compounds represent an important source of energy for soil-dwelling organisms. the beta-ketoadipate pathway is a key metabolic pathway involved in the catabolism of the aromatic compounds protocatechuate and catechol, and here we show through enzymatic analysis and mutant analysis that genes required for growth and catabolism of protocatechuate in the soil-dwelling bacterium sinorhizobium meliloti are organized on the psymb megaplasmid in two transcriptional units designated pcadchgb an ... | 2006 | 16885292 |
| the nitric oxide-responsive regulator nsrr controls resde-dependent gene expression. | the resd-rese signal transduction system is essential for aerobic and anaerobic respiration in bacillus subtilis. resde-dependent gene expression is induced by oxygen limitation, but full induction under anaerobic conditions requires nitrite or nitric oxide (no). here we report that nsrr (formerly yhde) is responsible for the no-dependent up-regulation of the resde regulon. the null mutation of nsrr led to aerobic derepression of hmp (flavohemoglobin gene) partly in a resde-independent manner. i ... | 2006 | 16885456 |
| the chemical synthesis of the gsti protein by ncl on a x-met site. | the small gsti protein (63 amino acids) of rhizobium leguminosarum is the endogenous inhibitor of the glnii (glutamine synthetase ii) gene expression. it has been suggested that gsti has a predominantly beta-structure and mediates the block of translation and stabilization of glnii mrna through direct binding to its 5' untranslated region. because of the unavailability of adequate amounts of purified recombinant protein, the mechanism as well as the protein tridimensional structure remain very p ... | 2006 | 16888773 |
| response of rhizobial populations to moderate copper stress applied to an agricultural soil. | the use of pesticides in agricultural soils may affect the soil microbiota. the effect of repeated application of copper sulfate in soil on indigenous populations of rhizobia was assessed in a medium-term field experiment. copper sulfate was applied over 8 years at two different rates, 12.5 and 50 kg of cuso4 ha(-1) year(-1), in the field. the concentrations of total copper in soil varied between 14.0 (control plots that did not receive copper sulfate) and 91.0 mg kg(-1) (the most contaminated p ... | 2006 | 16897301 |
| screening possible mechanisms mediating cadmium resistance in rhizobium leguminosarum bv. viciae isolated from contaminated portuguese soils. | environment heavy-metal contamination is now widespread. soils may become contaminated from a variety of anthropogenic sources, such as smelters, mining, industry, and application of metal-containing pesticides and fertilizers. soil microorganisms are very sensitive to moderate heavy-metal concentrations. therefore, the present work was designed to screen possible mechanisms involved in rhizobium's cd resistance; with this purpose, we determined the tolerance levels of several isolates originate ... | 2006 | 16897308 |
| the relaxase of the rhizobium etli symbiotic plasmid shows nic site cis-acting preference. | genetic and biochemical characterization of traa, the relaxase of symbiotic plasmid pretcfn42d from rhizobium etli, is described. after purifying the relaxase domain (n265traa), we demonstrated nic binding and cleavage activity in vitro and thus characterized for the first time the nick site (nic) of a plasmid in the family rhizobiaceae. we studied the range of n265traa relaxase specificity in vitro by testing different oligonucleotides in binding and nicking assays. in addition, the ability of ... | 2006 | 16916896 |
| exo-oligosaccharides of rhizobium sp. strain ngr234 are required for symbiosis with various legumes. | rhizobia are nitrogen-fixing bacteria that establish endosymbiotic associations with legumes. nodule formation depends on various bacterial carbohydrates, including lipopolysaccharides, k-antigens, and exopolysaccharides (eps). an acidic eps from rhizobium sp. strain ngr234 consists of glucosyl (glc), galactosyl (gal), glucuronosyl (glca), and 4,6-pyruvylated galactosyl (pvgal) residues with beta-1,3, beta-1,4, beta-1,6, alpha-1,3, and alpha-1,4 glycoside linkages. here we examined the role of n ... | 2006 | 16923883 |
| proline betaine uptake in sinorhizobium meliloti: characterization of prb, an opp-like abc transporter regulated by both proline betaine and salinity stress. | sinorhizobium meliloti uses proline betaine (pb) as an osmoprotectant when osmotically stressed and as an energy source in low-osmolarity environments. to fulfill this dual function, two separate pb transporters, bets and hut, that contribute to pb uptake at high and low osmolarity, respectively, have been previously identified. here, we characterized a novel transport system that mediates the uptake of pb at both high and low osmolarities. sequence analysis of tn5-luxab chromosomal insertions f ... | 2006 | 16923898 |
| rapid in situ evolution of nodulating strains for biserrula pelecinus l. through lateral transfer of a symbiosis island from the original mesorhizobial inoculant. | diverse rhizobia able to nodulate biserrula pelecinus evolved following in situ transfer of noda and nifh from an inoculant to soil bacteria. transfer of these chromosomal genes and the presence of an identical integrase gene adjacent to a phe trna gene in both the inoculant and recipients indicate that there was lateral transfer of a symbiosis island. | 2006 | 16936054 |
| distinct mechanisms regulate expression of the two major groel homologues in rhizobium leguminosarum. | we investigated the regulation of the two of the three groe operons (cpn.1 and cpn.2) of the root-nodulating bacterium r. leguminosarum strain a34. both are heat inducible, and both have a circe sequence in their upstream regions, suggesting regulation by an hrca repressor. mutagenesis of the circe sequence upstream of cpn.1 led to an increase in the levels of cpn.1 mrna, and knock-out of the hrca gene increased the level of cpn60.1 protein (the groel homologue encoded by the cpn.1 operon). inac ... | 2007 | 16944097 |
| the hmuq and hmud genes from bradyrhizobium japonicum encode heme-degrading enzymes. | utilization of heme by bacteria as a nutritional iron source involves the transport of exogenous heme, followed by cleavage of the heme macrocycle to release iron. bradyrhizobium japonicum can use heme as an iron source, but no heme-degrading oxygenase has been described. here, bioinformatics analyses of the b. japonicum genome identified two paralogous genes renamed hmuq (bll7075) and hmud (bll7423) that encode proteins with weak similarity to the heme-degrading monooxygenase isdg from staphylo ... | 2006 | 16952937 |
| thiamine is synthesized by a salvage pathway in rhizobium leguminosarum bv. viciae strain 3841. | in the absence of added thiamine, rhizobium leguminosarum bv. viciae strain 3841 does not grow in liquid medium and forms only "pin" colonies on agar plates, which contrasts with the good growth of sinorhizobium meliloti 1021, mesorhizobium loti 303099, and rhizobium etli cfn42. these last three organisms have thicoge genes, which are essential for de novo thiamine synthesis. while r. leguminosarum bv. viciae 3841 lacks thicoge, it does have thimed. mutation of thim prevented formation of pin co ... | 2006 | 16952958 |
| comparative and functional genomic analyses of iron transport and regulation in leptospira spp. | the spirochetes of the leptospira genus contain saprophytic and pathogenic members, the latter being responsible for leptospirosis. despite the recent sequencing of the genome of the pathogen l. interrogans, the slow growth of these bacteria, their virulence in humans, and a lack of genetic tools make it difficult to work with these pathogens. in contrast, the development of numerous genetic tools for the saprophyte l. biflexa enables its use as a model bacterium. leptospira spp. require iron fo ... | 2006 | 16980464 |
| lipoprotein pssn of rhizobium leguminosarum bv. trifolii: subcellular localization and possible involvement in exopolysaccharide export. | surface expression of exopolysaccharides (eps) in gram-negative bacteria depends on the activity of proteins found in the cytoplasmic membrane, the periplasmic space, and the outer membrane. psstnop genes identified in rhizobium leguminosarum bv. trifolii strain ta1 encode proteins that might be components of the eps polymerization and secretion system. in this study, we have characterized pssn protein. employing pssn-phoa and pssn-lacz gene fusions and in vivo acylation with [3h]palmitate, we d ... | 2006 | 16980497 |
| expression of the lipopolysaccharide-modifying enzymes pagp and pagl modulates the endotoxic activity of bordetella pertussis. | lipopolysaccharide (lps) is one of the major constituents of the gram-negative bacterial cell envelope. its endotoxic activity causes the relatively high reactogenicity of whole-cell vaccines. several bacteria harbor lps-modifying enzymes that modulate the endotoxic activity of the lps. here we evaluated whether two such enzymes, i.e., pagp and pagl, could be useful tools for the development of an improved and less reactogenic whole-cell pertussis vaccine. we showed that expression of pagp and p ... | 2006 | 16988232 |
| characterization of myo-inositol utilization by corynebacterium glutamicum: the stimulon, identification of transporters, and influence on l-lysine formation. | although numerous bacteria possess genes annotated iol in their genomes, there have been very few studies on the possibly associated myo-inositol metabolism and its significance for the cell. we found that corynebacterium glutamicum utilizes myo-inositol as a carbon and energy source, enabling proliferation with a high maximum rate of 0.35 h-1. whole-genome dna microarray analysis revealed that 31 genes respond to myo-inositol utilization, with 21 of them being localized in two clusters of >14 k ... | 2006 | 16997948 |
| a member of the second carbohydrate uptake subfamily of atp-binding cassette transporters is responsible for ribonucleoside uptake in streptococcus mutans. | streptococcus mutans has a significant number of transporters of the atp-binding cassette (abc) superfamily. members of this superfamily are involved in the translocation of a diverse range of molecules across membranes. however, the functions of many of these members remain unknown. we have investigated the role of the single s. mutans representative of the second subfamily of carbohydrate uptake transporters (cut2) of the abc superfamily. the genetic context of genes encoding this transporter ... | 2006 | 16997965 |
| crystal structure and mechanism of tram2, a second quorum-sensing antiactivator of agrobacterium tumefaciens strain a6. | quorum sensing is a community behavior that bacteria utilize to coordinate a variety of population density-dependent biological functions. in agrobacterium tumefaciens, quorum sensing regulates the replication and conjugative transfer of the tumor-inducing (ti) plasmid from pathogenic strains to nonpathogenic derivatives. most of the quorum-sensing regulatory proteins are encoded within the ti plasmid. among these, trar is a luxr-type transcription factor playing a key role as the quorum-sensing ... | 2006 | 16997969 |
| syntenic arrangements of the surface polysaccharide biosynthesis genes in rhizobium leguminosarum. | we applied a genomic approach in the identification of genes required for the biosynthesis of different polysaccharides in rhizobium leguminosarum bv. trifolii ta1 (rtta1). pulsed-field gel electrophoresis analyses of undigested genomic dna revealed that the rtta1 genome is partitioned into a chromosome and four large plasmids. the combination of sequencing of rtta1 library bac clones and pcr amplification of polysaccharide genes from the rtta1 genome led to the identification of five large regi ... | 2007 | 17014983 |
| the aaur-aaus two-component system regulates uptake and metabolism of acidic amino acids in pseudomonas putida. | pseudomonas putida kt2440 metabolizes a wide range of carbon and nitrogen sources, including many amino acids. in this study, a sigma54-dependent two-component system that controls the uptake and metabolism of acidic amino acids was identified. the system (designated aau, for acidic amino acid utilization) involves a sensor histidine kinase, aaus, encoded by pp1067, and a response regulator, aaur, encoded by pp1066. aaur and aaus deletion mutants were unable to efficiently utilize aspartate (asp ... | 2006 | 17021207 |
| occurrence of sep insecticidal toxin complex genes in serratia spp. and yersinia frederiksenii. | some strains of serratia entomophila and s. proteamaculans cause amber disease of the grass grub costelytra zealandica (coleoptera: scarabaeidae). three genes required for virulence, sepabc, are located on a large plasmid, padap. sequence analysis suggests that the sepabc gene cluster may be part of a horizontally mobile region. this study presents evidence for the putative mobility of the sep genes of padap. southern blot analysis showed that orthologues of the sep genes reside on plasmids with ... | 2006 | 17021209 |
| contribution of ethylamine degrading bacteria to atrazine degradation in soils. | bacterial communities that cooperatively degrade atrazine commonly consist of diverse species in which the genes for atrazine dechlorination and dealkylation are variously distributed among different species. normally, the first step in degradation of atrazine involves dechlorination mediated by atza, followed by stepwise dealkylation to yield either n-ethylammelide or n-isopropylammelide. as the liberated alkylamine moieties are constituents of many organic molecules other than atrazine, it is ... | 2006 | 17064268 |
| the tolc homologue of brucella suis is involved in resistance to antimicrobial compounds and virulence. | brucella spp., like other pathogens, must cope with the environment of diverse host niches during the infection process. in doing this, pathogens evolved different type of transport systems to help them survive and disseminate within the host. members of the tolc family have been shown to be involved in the export of chemically diverse molecules ranging from large protein toxins to small toxic compounds. the role of proteins from the tolc family in brucella and other alpha-2-proteobacteria has b ... | 2007 | 17088356 |
| the tolc homologue of brucella suis is involved in resistance to antimicrobial compounds and virulence. | brucella spp., like other pathogens, must cope with the environment of diverse host niches during the infection process. in doing this, pathogens evolved different type of transport systems to help them survive and disseminate within the host. members of the tolc family have been shown to be involved in the export of chemically diverse molecules ranging from large protein toxins to small toxic compounds. the role of proteins from the tolc family in brucella and other alpha-2-proteobacteria has b ... | 2007 | 17088356 |
| systems approach to refining genome annotation. | genome-scale models of escherichia coli k-12 mg1655 metabolism have been able to predict growth phenotypes in most, but not all, defined growth environments. here we introduce the use of an optimization-based algorithm that predicts the missing reactions that are required to reconcile computation and experiment when they disagree. the computer-generated hypotheses for missing reactions were verified experimentally in five cases, leading to the functional assignment of eight orfs (yjjlmn, yeatu, ... | 2006 | 17088549 |
| nod factor enhances calcium uptake by soybean. | inoculation with rhizobia or application of nod factors (lipo-chitooligosaccharides, lcos) causes transient increases in cytosolic calcium concentration in root hairs of legume plants. we conducted experiments to evaluate whether application of lco and inoculation with rhizobia improved (45)cacl(2) uptake into soybean (glycine max [l.] merr.) leaves. roots of soybean seedlings with one developing trifoliolate were immersed in murashige and skoog (ms) basal liquid medium containing treatment solu ... | 2006 | 17092733 |
| structure and biosynthesis of free lipid a molecules that replace lipopolysaccharide in francisella tularensis subsp. novicida. | francisella tularensis subsp. novicida u112 phospholipids, extracted without hydrolysis, consist mainly of phosphatidylethanolamine, phosphatidylglycerol, phosphatidylcholine, and two lipid a species, designated a1 and a2. these lipid a species, present in a ratio of 7:1, comprise 15% of the total phospholipids, as judged by 32pi labeling. although lipopolysaccharide is detectable in f. tularensis subsp. novicida u112, less than 5% of the total lipid a is covalently linked to it. a1 and a2 were ... | 2006 | 17128982 |
| increased susceptibility to repeated freeze-thaw cycles in escherichia coli following long-term evolution in a benign environment. | in order to study the dynamics of evolutionary change, 12 populations of e. coli b were serially propagated for 20,000 generations in minimal glucose medium at constant 37 degrees c. correlated changes in various other traits have been previously associated with the improvement in competitive fitness in the selective environment. this study examines whether these evolved lines changed in their ability to tolerate the stresses of prolonged freezing and repeated freeze-thaw cycles during adaptatio ... | 2006 | 17147797 |
| only one of five groel genes is required for viability and successful symbiosis in sinorhizobium meliloti. | many bacterial species contain multiple copies of the genes that encode the chaperone groel and its cochaperone, groes, including all of the fully sequenced root-nodulating bacteria that interact symbiotically with legumes to generate fixed nitrogen. in particular, in sinorhizobium meliloti there are four groesl operons and one groel gene. to uncover functional redundancies of these genes during growth and symbiosis, we attempted to construct strains containing all combinations of groel mutation ... | 2007 | 17158666 |
| only one of five groel genes is required for viability and successful symbiosis in sinorhizobium meliloti. | many bacterial species contain multiple copies of the genes that encode the chaperone groel and its cochaperone, groes, including all of the fully sequenced root-nodulating bacteria that interact symbiotically with legumes to generate fixed nitrogen. in particular, in sinorhizobium meliloti there are four groesl operons and one groel gene. to uncover functional redundancies of these genes during growth and symbiosis, we attempted to construct strains containing all combinations of groel mutation ... | 2007 | 17158666 |
| the sxt conjugative element and linear prophage n15 encode toxin-antitoxin-stabilizing systems homologous to the tad-ata module of the paracoccus aminophilus plasmid pami2. | a group of proteic toxin-antitoxin (ta) cassettes whose representatives are widely distributed among bacterial genomes has been identified. these cassettes occur in chromosomes, plasmids, bacteriophages, and noncomposite transposons, as well as in the sxt conjugative element of vibrio cholerae. the following four homologous loci were subjected to detailed comparative studies: (i) tad-ata from plasmid pami2 of paracoccus aminophilus (the prototype of this group), (ii) gp49-gp48 from the linear ba ... | 2007 | 17158670 |
| the sxt conjugative element and linear prophage n15 encode toxin-antitoxin-stabilizing systems homologous to the tad-ata module of the paracoccus aminophilus plasmid pami2. | a group of proteic toxin-antitoxin (ta) cassettes whose representatives are widely distributed among bacterial genomes has been identified. these cassettes occur in chromosomes, plasmids, bacteriophages, and noncomposite transposons, as well as in the sxt conjugative element of vibrio cholerae. the following four homologous loci were subjected to detailed comparative studies: (i) tad-ata from plasmid pami2 of paracoccus aminophilus (the prototype of this group), (ii) gp49-gp48 from the linear ba ... | 2007 | 17158670 |
| lengsin is a survivor of an ancient family of class i glutamine synthetases re-engineered by evolution for a role in the vertebrate lens. | lengsin is a major protein of the vertebrate eye lens. it belongs to the hitherto purely prokaryotic gs i branch of the glutamine synthetase (gs) superfamily, but has no enzyme activity. like the taxon-specific crystallins, lengsin is the result of the recruitment of an ancient enzyme to a noncatalytic role in the vertebrate lens. cryo-em and modeling studies of lengsin show a dodecamer structure with important similarities and differences with prokaryotic gs i structures. gs homology regions of ... | 2006 | 17161372 |
| the major chemotaxis gene cluster of rhizobium leguminosarum bv. viciae is essential for competitive nodulation. | rhizobium leguminosarum biovar viciae strain 3841 is a motile alpha-proteobacterium that can establish a nitrogen-fixing symbiosis within the roots of pea plants. in order to determine the contribution of chemotaxis to the lifestyle of r. leguminosarum, we have characterized the function of two chemotaxis gene clusters (che1 and che2) in controlling motility behaviour. we have found that both chemotaxis gene clusters modulate the motility swimming bias of r. leguminosarum cells and that the che1 ... | 2007 | 17163982 |
| mariner mutagenesis of brucella melitensis reveals genes with previously uncharacterized roles in virulence and survival. | random gene inactivation used to identify cellular functions associated with virulence and survival of brucella spp has relied heavily upon the use of the transposon tn5 that integrates at g/c base pairs. transposons of the mariner family do not require species-specific host factors for efficient transposition, integrate nonspecifically at t/a base pairs, and, at a minimum, provide an alternative approach for gene discovery. in this study, plasmid vector psc189, containing both the hyperactive t ... | 2006 | 17176467 |
| a plasmid sequence from rhizobium leguminosarum 300 contains homology to sequences near the octopine tl-dna right border. | the dna sequence from a rhizobium leguminosarum 300 (rl300) plasmid that contains homology to the tc-dna of agrobacterium tumefaciens is described. the rl300 sequence has 78% homology to a 359 bp sequence in the tc-dna of pti15955. the rl300 homology starts approximately 100 bp from the 24 bp border sequence of the tl-dna and ends approximately 3 bp from an is66 homolog in the tc-dna. an unusual feature of the rl300 homology is the presence of 81 bp direct repeats with tc-dna homology, separated ... | 1987 | 17193713 |
| the lipopolysaccharide of sinorhizobium meliloti suppresses defense-associated gene expression in cell cultures of the host plant medicago truncatula. | in the establishment of symbiosis between medicago truncatula and the nitrogen-fixing bacterium sinorhizobium meliloti, the lipopolysaccharide (lps) of the microsymbiont plays an important role as a signal molecule. it has been shown in cell cultures that the lps is able to suppress an elicitor-induced oxidative burst. to investigate the effect of s. meliloti lps on defense-associated gene expression, a microarray experiment was performed. for evaluation of the m. truncatula microarray datasets, ... | 2007 | 17220366 |
| the francisella pathogenicity island protein igla localizes to the bacterial cytoplasm and is needed for intracellular growth. | francisella tularensis is a gram negative, facultative intracellular bacterium that is the etiological agent of tularemia. f. novicida is closely related to f. tularensis but has low virulence for humans while being highly virulent in mice. igla is a 21 kda protein encoded by a gene that is part of an iglabcd operon located on the francisella pathogenicity island (fpi). | 2007 | 17233889 |
| the symbiosis regulator cbra modulates a complex regulatory network affecting the flagellar apparatus and cell envelope proteins. | sinorhizobium meliloti participates in a nitrogen-fixing symbiosis with legume plant host species of the genera medicago, melilotus, and trigonella. we recently identified an s. meliloti two-component sensory histidine kinase, cbra, which is absolutely required to establish a successful symbiosis with medicago sativa (k. e. gibson, g. r. campbell, j. lloret, and g. c. walker, j. bacteriol. 188:4508-4521, 2006). in addition to having a symbiotic defect, the cbra::tn5 mutant also has free-living p ... | 2007 | 17237174 |
| pleiotropic effects of mutations that alter the sinorhizobium meliloti cytochrome c respiratory system. | using transposon mutagenesis, mutations have been isolated in several genes (ccda, cycm, ccmc, ccmb and senc) that play a role in sinorhizobium meliloti cytochrome metabolism. as in other bacteria, mutations in the s. meliloti ccda, ccmb and ccmc genes resulted in the absence of all c-type cytochromes. however, the s. meliloti ccda mutant also lacked cytochrome oxidase aa(3), a defect that does not appear to have been reported for other bacteria. the aa(3)-type cytochromes were also missing from ... | 2007 | 17259611 |
| a complete set of flagellar genes acquired by horizontal transfer coexists with the endogenous flagellar system in rhodobacter sphaeroides. | bacteria swim in liquid environments by means of a complex rotating structure known as the flagellum. approximately 40 proteins are required for the assembly and functionality of this structure. rhodobacter sphaeroides has two flagellar systems. one of these systems has been shown to be functional and is required for the synthesis of the well-characterized single subpolar flagellum, while the other was found only after the genome sequence of this bacterium was completed. in this work we found th ... | 2007 | 17293429 |
| meningococcal genetic variation mechanisms viewed through comparative analysis of serogroup c strain fam18. | the bacterium neisseria meningitidis is commonly found harmlessly colonising the mucosal surfaces of the human nasopharynx. occasionally strains can invade host tissues causing septicaemia and meningitis, making the bacterium a major cause of morbidity and mortality in both the developed and developing world. the species is known to be diverse in many ways, as a product of its natural transformability and of a range of recombination and mutation-based systems. previous work on pathogenic neisser ... | 2007 | 17305430 |
| living without fur: the subtlety and complexity of iron-responsive gene regulation in the symbiotic bacterium rhizobium and other alpha-proteobacteria. | the alpha-proteobacteria include several important genera, including the symbiotic n(2)-fixing "rhizobia", the plant pathogen agrobacterium, the mammalian pathogens brucella, bartonella as well as many others that are of environmental or other interest--including rhodobacter, caulobacter and the hugely abundant marine genus pelagibacter. only a few species--mainly different members of the rhizobia--have been analyzed directly for their ability to use and to respond to iron. these studies, howeve ... | 2007 | 17310401 |
| role of soil rhizobacteria in phytoremediation of heavy metal contaminated soils. | heavy metal pollution of soil is a significant environmental problem and has its negative impact on human health and agriculture. rhizosphere, as an important interface of soil and plant, plays a significant role in phytoremediation of contaminated soil by heavy metals, in which, microbial populations are known to affect heavy metal mobility and availability to the plant through release of chelating agents, acidification, phosphate solubilization and redox changes, and therefore, have potential ... | 2007 | 17323432 |
| inhibition of lipid a biosynthesis as the primary mechanism of chir-090 antibiotic activity in escherichia coli. | the deacetylation of udp-3-o-[(r)-3-hydroxymyristoyl]-n-acetylglucosamine (udp-3-o-acyl-glcnac) by lpxc is the committed reaction of lipid a biosynthesis. chir-090, a novel n-aroyl-l-threonine hydroxamic acid, is a potent, slow, tight-binding inhibitor of the lpxc deacetylase from the hyperthermophile aquifex aeolicus, and it has excellent antibiotic activity against pseudomonas aeruginosa and escherichia coli, as judged by disk diffusion assays. we now report that chir-090 is also a two-step sl ... | 2007 | 17335290 |
| characterization of sinorhizobium meliloti triose phosphate isomerase genes. | a tn5 mutant strain of sinorhizobium meliloti with an insertion in tpia (systematic identifier smc01023), a putative triose phosphate isomerase (tpi)-encoding gene, was isolated. the tpia mutant grew more slowly than the wild type on rhamnose and did not grow with glycerol as a sole carbon source. the genome of s. meliloti wild-type rm1021 contains a second predicted tpi-encoding gene, tpib (smc01614). we have constructed mutations and confirmed that both genes encode functional tpi enzymes. tpi ... | 2007 | 17337584 |
| quorum-sensing regulation in rhizobia and its role in symbiotic interactions with legumes. | legume-nodulating bacteria (rhizobia) usually produce n-acyl homoserine lactones, which regulate the induction of gene expression in a quorum-sensing (or population-density)-dependent manner. there is significant diversity in the types of quorum-sensing regulatory systems that are present in different rhizobia and no two independent isolates worked on in detail have the same complement of quorum-sensing genes. the genes regulated by quorum sensing appear to be rather diverse and many are associa ... | 2007 | 17360278 |
| attenuated virulence of a francisella mutant lacking the lipid a 4'-phosphatase. | francisella tularensis causes tularemia, a highly contagious disease of animals and humans, but the virulence features of f. tularensis are poorly defined. f. tularensis and the related mouse pathogen francisella novicida synthesize unusual lipid a molecules lacking the 4'-monophosphate group typically found in the lipid a of gram-negative bacteria. lpxf, a selective phosphatase located on the periplasmic surface of the inner membrane, removes the 4'-phosphate moiety in the late stages of f. nov ... | 2007 | 17360489 |
| lipid a modification systems in gram-negative bacteria. | the lipid a moiety of lipopolysaccharide forms the outer monolayer of the outer membrane of most gram-negative bacteria. escherichia coli lipid a is synthesized on the cytoplasmic surface of the inner membrane by a conserved pathway of nine constitutive enzymes. following attachment of the core oligosaccharide, nascent core-lipid a is flipped to the outer surface of the inner membrane by the abc transporter msba, where the o-antigen polymer is attached. diverse covalent modifications of the lipi ... | 2007 | 17362200 |
| [the pssa gene encodes udp-glucose: polyprenyl phosphate-glucosyl phosphotransferase initiating biosynthesis of rhizobium leguminosarum exopolysaccharide]. | symbiotic nitrogen-fixing bacteria rhizobium leguminosarum by. viciae vf39 secrete an acidic heteropolysaccharide, the biosynthesis of which involves the stage of polyprenyl diphosphate octasaccharide formation, with its carbohydrate fragment corresponding to the repeating polymer unit. the amino acid analysis of the product of the pssa gene, we have earlier identified, showed its homology to bacterial polyisoprenyl phosphate hexose 1-phosphate transferases catalyzing the formation of phosphodie ... | 2007 | 17375671 |
| symbiosis-induced cascade regulation of the mesorhizobium loti r7a virb/d4 type iv secretion system. | the mesorhizobium loti r7a symbiosis island contains genes encoding a virb/d4 type iv secretion system (t4ss) similar to that of agrobacterium tumefaciens. this system has host-dependent effects on symbiosis that probably are due to translocation of two effector proteins, msi059 and msi061, into host cells. here we report that, as in a. tumefaciens, the m. loti vir genes are transcriptionally regulated by a vira/virg two-component regulatory system. a virgn54d mutant gene of m. loti caused const ... | 2007 | 17378428 |
| rhizobium-initiated rice growth inhibition caused by nitric oxide accumulation. | isolates of rhizobium leguminosarum bv. trifolii (the clover root-nodule endosymbiont) from the nile river delta have been found to infect rice roots and colonize the intercellular spaces of the rice roots. some of these isolates inhibit rice seedling growth but one in particular, r4, has been found in rice roots which develop and grow normally. we present evidence that the induced growth inhibition is due to a toxic accumulation of nitric oxide (no), from the reduction of nitrate, and suggest t ... | 2007 | 17378431 |
| effector-stimulated single molecule protein-dna interactions of a quorum-sensing system in sinorhizobium meliloti. | intercellular communication by means of small signal molecules coordinates gene expression among bacteria. this population density-dependent regulation is known as quorum sensing. the symbiotic nitrogen-fixing bacterium sinorhizobium meliloti rm1021 possesses the sin quorum sensing system based on n-acyl homoserine lactones (ahl) as signal molecules. here, we demonstrate that the luxr-type regulator expr binds specifically to a target sequence in the sinri locus in the presence of different ahls ... | 2007 | 17384071 |
| response of inoculated foliar fed pea plants (pisum sativum l.) to reduced mo supply. | the application of nutrients to the roots and leaves of inoculated pea plants grown under conditions of reduced mo supply was studied. pea plants (pisum sativum l.) were grown on liquid nutrient solution excluding mo from the media until the 35th day under glasshouse conditions. plants were inoculated with the bacterial suspension of rhizobium leguminosarum bv. vicae, strain d293 at approximately 10(8) cells per cm3. the foliar fertilizer agroleaf was applied at 0.3% concentration. changes in th ... | 2007 | 17385546 |
| an extracytoplasmic function sigma factor acts as a general stress response regulator in sinorhizobium meliloti. | sinorhizobium meliloti genes transcriptionally up-regulated after heat stress, as well as upon entry into stationary phase, were identified by microarray analyses. sixty stress response genes were thus found to be up-regulated under both conditions. one of them, rpoe2 (smc01506), encodes a putative extracytoplasmic function (ecf) sigma factor. we showed that this sigma factor controls its own transcription and is activated by various stress conditions, including heat and salt, as well as entry i ... | 2007 | 17400745 |
| a marine mesorhizobium sp. produces structurally novel long-chain n-acyl-l-homoserine lactones. | our study focused on a mesorhizobium sp. that is phylogenetically affiliated by 16s rrna gene sequence to other marine and saline bacteria of this genus. liquid chromatography-mass spectrometry investigations of the extract obtained from solid-phase extraction of cultures of this bacterium indicated the presence of several n-acyl homoserine lactones (ahls), with chain lengths of c(10) to c(16). chromatographic separation of the active bacterial extract yielded extraordinarily large amounts of tw ... | 2007 | 17400774 |
| nitrogen fixation control under drought stress. localized or systemic? | legume-rhizobium nitrogen fixation is dramatically affected under drought and other environmental constraints. however, it has yet to be established as to whether such regulation of nitrogen fixation is only exerted at the whole-plant level (e.g. by a systemic nitrogen feedback mechanism) or can also occur at a local nodule level. to address this question, nodulated pea (pisum sativum) plants were grown in a split-root system, which allowed for half of the root system to be irrigated at field ca ... | 2007 | 17416644 |
| rhizavidin from rhizobium etli: the first natural dimer in the avidin protein family. | rhizobium etli cfn42 is a symbiotic nitrogen-fixing bacterium of the common bean phaseolus vulgaris. the symbiotic plasmid p42d of r. etli comprises a gene encoding a putative (strept)avidin-like protein, named rhizavidin. the amino acid sequence identity of rhizavidin in relation to other known avidin-like proteins is 20-30%. the amino acid residues involved in the (strept)avidin-biotin interaction are well conserved in rhizavidin. the structural and functional properties of rhizavidin were car ... | 2007 | 17447892 |
| identification of a gene cluster enabling lactobacillus casei bl23 to utilize myo-inositol. | genome analysis of lactobacillus casei bl23 revealed that, compared to l. casei atcc 334, it carries a 12.8-kb dna insertion containing genes involved in the catabolism of the cyclic polyol myo-inositol (mi). indeed, l. casei atcc 334 does not ferment mi, whereas strain bl23 is able to utilize this carbon source. the inserted dna consists of an iolr gene encoding a deor family transcriptional repressor and a divergently transcribed ioltabcdg1g2ejk operon, encoding a complete mi catabolic pathway ... | 2007 | 17449687 |
| trehalose biosynthesis in rhizobium leguminosarum bv. trifolii and its role in desiccation tolerance. | rhizobium leguminosarum bv. trifolii forms nitrogen-fixing root nodules on the pasture legume trifolium repens, and t. repens seed is often coated with a compatible r. leguminosarum bv. trifolii strain prior to sowing. however, significant losses in bacterial viability occur during the seed-coating process and during storage of the coated seeds, most likely due to desiccation stress. the disaccharide trehalose is known to function as an osmoprotectant, and trehalose accumulation due to de novo b ... | 2007 | 17449695 |
| mutagenesis of the carboxy terminal protease ctpa decreases desiccation tolerance in rhizobium leguminosarum. | to better understand the role of proteases in rhizobium leguminosarum biovar viciae, a gene with homology to the carboxy-terminal protease (ctpa), which belongs to a novel group of serine proteases, was studied. the ctpa gene was cloned and mutated using allelic exchange and a gusa reporter gene was used to study ctpa expression. mutational analysis shows that ctpa is critical for the viability of r. leguminosarum when cells are grown on complex semi-solid media but is dispensable when cells are ... | 2007 | 17456188 |
| using the ralstonia solanacearum tat secretome to identify bacterial wilt virulence factors. | to identify secreted virulence factors involved in bacterial wilt disease caused by the phytopathogen ralstonia solanacearum, we mutated tatc, a key component of the twin-arginine translocation (tat) secretion system. the r. solanacearum tatc mutation was pleiotropic; its phenotypes included defects in cell division, nitrate utilization, polygalacturonase activity, membrane stability, and growth in plant tissue. bioinformatic analysis of the r. solanacearum strain gmi1000 genome predicted that t ... | 2007 | 17468289 |
| [a study of the competitive properties of the aluminum-tolerant strain rhizobium leguminosarum bv. trifolii 9-4a by the antibiotic resistance method]. | the virulence, competitive ability, and symbiotic efficiency of 2 rhizobium leguminosarum bv. trifolii strains--the wild aluminum tolerant strain 9-4a and the commercial strain 348a-were compared when introducing their variants marked with antibiotic resistance into the rhizosphere of red clover (trifolium pratense l.) plants. high virulence and competitive ability of the strain tolerant to aluminum was demonstrated by a concurrent inoculation of the seeds with these two strains. the resistance ... | 2007 | 17476807 |
| [active oxygen species in pea seedlings during the interactions with symbiotic and pathogenic microorganisms]. | the level of active oxygen species (aos)--superoxide anion radical (o2*-) and hydrogen peroxide (h2o2)--in pea (pisum sativum l.) cultivar marat seedlings was studied upon their inoculation with symbiotic (rhizobium leguminosarum bv. viceae strain ciam 1026) and pathogenic (pseudomonas syringae pv. pisi sackett) microorganisms. different patterns of the changes in aos in pea seedlings during the interactions with the symbiont and the phytopathogen were recorded. it is assumed that o2*- and h2o2 ... | 2007 | 17476814 |
| genetic diversity of rhizobia associated with vicia faba in three ecological regions of china. | great genetic diversity was revealed among 75 rhizobal isolates associated with vicia faba grown in chinese fields with aflp, ardra, 16s rdna sequencing, dna-dna hybridization, box-pcr and rflp of pcr-amplified nodd and nodc. most of the isolates were rhizobium leguminosarum, and six isolates belonged to an unnamed rhizobium species. in the homogeneity analysis, the isolates were grouped into three clusters corresponding to (1) autumn sowing (subtropical) region where the winter ecotype of v. fa ... | 2007 | 17479251 |
| auxin and nitric oxide control indeterminate nodule formation. | rhizobia symbionts elicit root nodule formation in leguminous plants. nodule development requires local accumulation of auxin. both plants and rhizobia synthesise auxin. we have addressed the effects of bacterial auxin (iaa) on nodulation by using sinorhizobium meliloti and rhizobium leguminosarum bacteria genetically engineered for increased auxin synthesis. | 2007 | 17488509 |
| horizontal gene transfer and homologous recombination drive the evolution of the nitrogen-fixing symbionts of medicago species. | using nitrogen-fixing sinorhizobium species that interact with medicago plants as a model system, we aimed at clarifying how sex has shaped the diversity of bacteria associated with the genus medicago on the interspecific and intraspecific scales. to gain insights into the diversification of these symbionts, we inferred a topology that includes the different specificity groups which interact with medicago species, based on sequences of the nodulation gene cluster. furthermore, 126 bacterial isol ... | 2007 | 17496100 |
| bioformulation of burkholderia sp. mssp with a multispecies consortium for growth promotion of cajanus cajan. | the present work was undertaken to formulate an effective bioformulation using burkholderia sp. strain mssp, a known plant-growth-promoting rhizobacterium. mssp was tagged with the reporter gene of green fluorescent protein (gfp) to monitor its population in cost-effective solid carriers, including sugarcane-bagasse, sawdust, cocoa peat, rice husk, wheat bran, charcoal, and rock phosphate, and paneer-whey as liquid carrier. physical and chemical properties of different low-cost carrier materials ... | 2007 | 17496969 |
| functional characterization of the sinorhizobium meliloti acetate metabolism genes acea, smc00767, and glcb. | the genes encoding malate synthase (glcb) and isocitrate lyase (acea) and a 240-bp open reading frame (smc00767) located downstream of acea were isolated and functionally characterized in sinorhizobium meliloti. independent and double interposon mutants of each gene were constructed, and the corresponding phenotypes were analyzed. acea mutants failed to grow on acetate, and mutants deficient in smc00767 were also affected in acetate utilization. in contrast, mutants deficient in glcb grew on ace ... | 2007 | 17526694 |
| context dependence in the coevolution of plant and rhizobial mutualists. | several mechanisms are expected to rapidly rid mutualisms of genetic variation in partner quality. variation for mutualist quality, however, appears to be widespread. we used a model legume-rhizobium mutualism to test for evidence that context-dependent selection may maintain variation in partner quality. in a greenhouse experiment using 10 natural populations of medicago truncatula and two strains of sinorhizobium medicae, we detected significant genotype x genotype (g x g) interactions for pla ... | 2007 | 17535796 |
| aspartate-444 is essential for productive substrate interactions in a neuronal glutamate transporter. | in the central nervous system, electrogenic sodium- and potassium-coupled glutamate transporters terminate the synaptic actions of this neurotransmitter. in contrast to acidic amino acids, dicarboxylic acids are not recognized by glutamate transporters, but the related bacterial dcta transporters are capable of transporting succinate and other dicarboxylic acids. transmembrane domain 8 contains several residues that differ between these two types of transporters. one of these, aspartate-444 of t ... | 2007 | 17535962 |
| characterization of symbiotic and endophytic bacteria isolated from root nodules of herbaceous legumes grown in qinghai-tibet plateau and in other zones of china. | qinghai-tibet plateau is the highest place in the world and the environment in that plateau is hard for animals and plants, with low temperature, low concentration of oxygen and high solar radiation. in this study, 61 root nodule isolates from vicia, oxytropis, medicago, melilotus and onobrychis species grown in qinghai-tibet plateau and in loess plateau were comparatively characterized. based upon the results of numerical taxonomy, ardra, aflp, dna-dna hybridization and 16s rdna sequencing, the ... | 2007 | 17541555 |
| agrobacterium tumefaciens fur has important physiological roles in iron and manganese homeostasis, the oxidative stress response, and full virulence. | in agrobacterium tumefaciens, the balance between acquiring enough iron and avoiding iron-induced toxicity is regulated in part by fur (ferric uptake regulator). a fur mutant was constructed to address the physiological role of the regulator. atypically, the mutant did not show alterations in the levels of siderophore biosynthesis and the expression of iron transport genes. however, the fur mutant was more sensitive than the wild type to an iron chelator, 2,2'-dipyridyl, and was also more resist ... | 2007 | 17545320 |
| isolation and characterization of a novel haloacid permease from burkholderia cepacia mba4. | burkholderia cepacia mba4 is a bacterium that can utilize 2-haloacids as carbon and energy sources for growth. it has been proposed that dehalogenase-associated permease mediates the uptake of haloacid. in this paper, we report the first cloning and characterization of such a haloacid permease. the structural gene, designated deh4p, was found 353 bases downstream of the dehalogenase gene deh4a. quantitative analysis of the expression of deh4p showed that it was induced by monochloroacetate (mca) ... | 2007 | 17545323 |
| copper induction of lactate oxidase of lactococcus lactis: a novel metal stress response. | lactococcus lactis il1403, a lactic acid bacterium widely used for food fermentation, is often exposed to stress conditions. one such condition is exposure to copper, such as in cheese making in copper vats. copper is an essential micronutrient in prokaryotes and eukaryotes but can be toxic if in excess. thus, copper homeostatic mechanisms, consisting chiefly of copper transporters and their regulators, have evolved in all organisms to control cytoplasmic copper levels. using proteomics to ident ... | 2007 | 17557814 |
| mutations of the quorum sensing-dependent regulator vjbr lead to drastic surface modifications in brucella melitensis. | successful establishment of infection by bacterial pathogens requires fine-tuning of virulence-related genes. quorum sensing (qs) is a global regulation process based on the synthesis of, detection of, and response to small diffusible molecules, called n-acyl-homoserine lactones (ahl), in gram-negative bacteria. in numerous species, qs has been shown to regulate genes involved in the establishment of pathogenic interactions with the host. brucella melitensis produces n-dodecanoyl homoserine lact ... | 2007 | 17557825 |
| sinorhizobium meliloti fur-like (mur) protein binds a fur box-like sequence present in the mnta promoter in a manganese-responsive manner. | in sinorhizobium meliloti, the mur(sm) protein, a homologue of the ferric uptake regulator (fur), mediates manganese-dependent regulation of the mntabcd manganese uptake system. in this study, we analyzed mur(sm) binding to the promoter region of the s. meliloti mnta gene. we demonstrated that mur(sm) protein binds with high affinity to the promoter region of mnta gene in a manganese-responsive manner. moreover, the results presented here indicate that two monomers, or one dimer, of mur(sm) bind ... | 2007 | 17557847 |
| the novel alkali tolerance function of tfxg in sinorhizobium meliloti. | tfxg, one of the tfxabcdefg cluster genes that code for trifolitoxin (tfx) production, was initially described in rhizobium leguminosarum bv. trifolii t24. although several genes in the tfx family have functions related to tfx production or resistance to tfx, the function of tfxg is largely unknown. using cdna-amplified fragment length polymorphism (cdna-aflp) analysis, we found that expression of the tfxg gene dramatically increased under alkaline culture conditions in sinorhizobium meliloti cc ... | 2007 | 17566711 |
| transcriptional regulation of the heme binding protein gene family of bartonella quintana is accomplished by a novel promoter element and iron response regulator. | we previously identified a five-member family of hemin-binding proteins (hbp's) of bartonella quintana that bind hemin on the outer surface but share no homology with known bacterial heme receptors. subsequently, we demonstrated that expression of the hbp family is significantly influenced by oxygen, heme, and temperature conditions encountered by the pathogen in the human host and the body louse vector; e.g., we observed a dramatic (>100-fold) increase in hbpc transcript levels in response to t ... | 2007 | 17576755 |
| large genotypic variation but small variation in n2 fixation among rhizobia nodulating red clover in soils of northern scandinavia. | to analyse the symbiotic variations within indigenous populations of rhizobia nodulating red clover (trifolium pratense l.) in soils of northern norway and sweden at different times of the growing season. | 2007 | 17578428 |
| brucella suis urease encoded by ure1 but not ure2 is necessary for intestinal infection of balb/c mice. | in prokaryotes, the ureases are multi-subunit, nickel-containing enzymes that catalyze the hydrolysis of urea to carbon dioxide and ammonia. the brucella genomes contain two urease operons designated as ure1 and ure2. we investigated the role of the two brucella suis urease operons on the infection, intracellular persistence, growth, and resistance to low-ph killing. | 2007 | 17578575 |
| bigr, a transcriptional repressor from plant-associated bacteria, regulates an operon implicated in biofilm growth. | xylella fastidiosa is a plant pathogen that colonizes the xylem vessels, causing vascular occlusion due to bacterial biofilm growth. however, little is known about the molecular mechanisms driving biofilm formation in xylella-plant interactions. here we show that bigr (for "biofilm growth-associated repressor") is a novel helix-turn-helix repressor that controls the transcription of an operon implicated in biofilm growth. this operon, which encodes bigr, membrane proteins, and an unusual beta-la ... | 2007 | 17586627 |
| quorum-sensing-regulated transcriptional initiation of plasmid transfer and replication genes in rhizobium leguminosarum biovar viciae. | transfer of the rhizobium leguminosarum biovar viciae symbiosis plasmid prl1ji is regulated by a cascade of gene induction involving three luxr-type quorum-sensing regulators, trar, bisr and cinr. trar induces the plasmid transfer trai-trb operon in a population-density-dependent manner in response to n-acylhomoserine lactones (ahls) made by trai. expression of the trar gene is primarily induced by bisr in response to ahls made by cini, and expression of cini is induced by cinr and repressed by ... | 2007 | 17600052 |
| the rhizobium leguminosarum bv. trifolii rosr: transcriptional regulator involved in exopolysaccharide production. | the acidic exopolysaccharide is required for the establishment of symbiosis between the nitrogen-fixing bacterium rhizobium leguminosarum bv. trifolii and clover. here, we describe rosr protein from r. leguminosarum bv. trifolii 24.2, a homolog of transcriptional regulators belonging to the family of ros/mucr proteins. r. leguminosarum bv. trifolii rosr possesses a characteristic cys2his2 type zinc-finger motif in its c-terminal domain. recombinant (his)6rosr binds to an rosr-box sequence locate ... | 2007 | 17601173 |
| [the effect of inoculation with rhizobium leguminosarum on the contents of cytoplasmic protein and free amino acids in the roots of pea seedlings]. | the changes in the contents of protein and free amino acids in pea plants inoculated with rhizobium leguminosarum were studied taking into account the susceptibility of roots to root nodule bacteria. the content of cytoplasmic protein during infection increased in the actively growing root region (0-5 mm) and decreased in the root regions susceptible to rhizobia (5-20 mm from the root tip). the quantitative composition of free amino acids changed essentially upon inoculation of pea seedlings wit ... | 2007 | 17619576 |