| extracellular glycanases of rhizobium leguminosarum are activated on the cell surface by an exopolysaccharide-related component. | rhizobium leguminosarum secretes two extracellular glycanases, plya and plyb, that can degrade exopolysaccharide (eps) and carboxymethyl cellulose (cmc), which is used as a model substrate of plant cell wall cellulose polymers. when grown on agar medium, cmc degradation occurred only directly below colonies of r. leguminosarum, suggesting that the enzymes remain attached to the bacteria. unexpectedly, when a plya-plyb-secreting colony was grown in close proximity to mutants unable to produce or ... | 2000 | 10671451 |
| identification of brucella suis genes affecting intracellular survival in an in vitro human macrophage infection model by signature-tagged transposon mutagenesis. | bacteria of the genus brucella are facultative intracellular pathogens which have developed the capacity to survive and multiply in professional and nonprofessional phagocytes. the genetic basis of this aspect of brucella virulence is still poorly understood. to identify new virulence factors, we have adapted signature-tagged transposon mutagenesis, which has been used essentially in animal models, to an in vitro human macrophage infection model. a library of 1,152 brucella suis 1330 tagged mini ... | 2000 | 10678941 |
| the stachydrine catabolism region in sinorhizobium meliloti encodes a multi-enzyme complex similar to the xenobiotic degrading systems in other bacteria. | stachydrine (proline betaine) can be used by sinorhizobium meliloti as a source of carbon and nitrogen. catabolism depends on an initial n-demethylation, after which the resultant n-methyl proline enters general metabolism. deletion and insertion mutagenesis demonstrated that the information necessary for catabolism is carried on the symbiotic plasmid (psym) distal to nodd2 and the nod-nif cluster. sequencing of an 8.5kb fragment spanning this region revealed four open reading frames with functi ... | 2000 | 10689197 |
| a krüppel-like zinc finger protein is involved in nitrogen-fixing root nodule organogenesis. | mechanisms regulating plant host differentiation of the nitrogen-fixing root nodules remain mostly unknown. sinorhizobium meliloti induces this process in medicago sativa in which the mszpt2-1 gene is expressed in vascular bundles of roots and nodules. this gene codes for a krüppel-like zinc finger protein, a class of transcription factors involved in many animal developmental processes. expression of mszpt2-1 in yeast cells conferred osmotic tolerance. antisense plants grew normally but develop ... | 2000 | 10691739 |
| three new nifa-regulated genes in the bradyrhizobium japonicum symbiotic gene region discovered by competitive dna-rna hybridization. | the so-called symbiotic region of the bradyrhizobium japonicum chromosome (c. kündig, h. hennecke, and m. göttfert, j. bacteriol. 175:613-622, 1993) was screened for the presence of genes controlled by the nitrogen fixation regulatory protein nifa. southern blots of restriction enzyme-digested cosmids that represent an ordered, overlapping library of the symbiotic region were competitively hybridized with in vitro-labeled rna from anaerobically grown wild-type cells and an excess of rna isolated ... | 2000 | 10692350 |
| functionality of purified sigma(n) (sigma(54)) and a nifa-like protein from the hyperthermophile aquifex aeolicus. | the genome sequence of the extremely thermophilic bacterium aquifex aeolicus encodes alternative sigma factor sigma(n) (sigma(54), rpon) and five potential sigma(n)-dependent transcriptional activators. although a. aeolicus possesses no recognizable nitrogenase genes, two of the activators have a high degree of sequence similarity to nifa proteins from nitrogen-fixing proteobacteria. we identified five putative sigma(n)-dependent promoters upstream of operons implicated in functions including su ... | 2000 | 10692367 |
| transcriptional and mutational analysis of the uptake hydrogenase of the filamentous cyanobacterium anabaena variabilis atcc 29413. | a 10-kb dna region of the cyanobacterium anabaena variabilis atcc 29413 containing the structural genes of the uptake hydrogenase (hupsl) was cloned and sequenced. in contrast to the hupl gene of anabaena sp. strain pcc 7120, which is interrupted by a 10.5-kb dna fragment in vegetative cells, there is no programmed rearrangement within the hupl gene during the heterocyst differentiation of a. variabilis. the hupsl genes were transcribed as a 2.7-kb operon and were induced only under nitrogen-fix ... | 2000 | 10692368 |
| identification of genes in the rosr regulon of rhizobium etli. | rosr is a determinant of nodulation competitiveness and cell surface characteristics of rhizobium etli and has sequence similarity to a family of transcriptional repressors. to understand how rosr affects these phenotypes, we mutagenized a rosr mutant derivative of r. etli strain ce3 with a mini-tn5 that contains a promoterless gusa gene at one end, which acts as a transcriptional reporter. using a mass-mating technique, we introduced rosr into each mutant in trans and screened for mutants that ... | 2000 | 10692377 |
| glutathione is involved in environmental stress responses in rhizobium tropici, including acid tolerance. | the isolation of rhizobial strains which exhibit an intrinsic tolerance to acidic conditions has been reported and has facilitated studies on the basic mechanisms underlying acid tolerance. rhizobium tropici strain ciat899 displays a high intrinsic tolerance to acidity and therefore was used in this work to study the molecular basis of bacterial responses to acid conditions and other environmental stresses. we generated a collection of r. tropici ciat899 mutants affected in acid tolerance using ... | 2000 | 10692382 |
| nickel availability and hupsl activation by heterologous regulators limit symbiotic expression of the rhizobium leguminosarum bv. viciae hydrogenase system in hup(-) rhizobia. | a limited number of rhizobium and bradyrhizobium strains possess a hydrogen uptake (hup) system that recycles the hydrogen released from the nitrogen fixation process in legume nodules. to extend this ability to rhizobia that nodulate agronomically important crops, we investigated factors that affect the expression of a cosmid-borne hup system from rhizobium leguminosarum bv. viciae upm791 in r. leguminosarum bv. viciae, rhizobium etli, mesorhizobium loti, and sinorhizobium meliloti hup(-) strai ... | 2000 | 10698755 |
| survival and epiphytic fitness of a nonpathogenic mutant of xanthomonas campestris pv. glycines. | xanthomonas campestris pv. glycines is the causal agent of bacterial pustule disease of soybeans. the objective of this work was to construct a nonpathogenic mutant derived from the pathogenic wild-type strain yr32 and to evaluate its effectiveness in preventing growth of its parent on the soybean phyllosphere. a mini-tn5-derived transposon was used to generate nonpathogenic mutants. southern hybridization and pulsed-field gel electrophoresis confirmed the presence of a single transposon in each ... | 2000 | 10698789 |
| microbial relatives of the seed storage proteins of higher plants: conservation of structure and diversification of function during evolution of the cupin superfamily. | this review summarizes the recent discovery of the cupin superfamily (from the latin term "cupa," a small barrel) of functionally diverse proteins that initially were limited to several higher plant proteins such as seed storage proteins, germin (an oxalate oxidase), germin-like proteins, and auxin-binding protein. knowledge of the three-dimensional structure of two vicilins, seed proteins with a characteristic beta-barrel core, led to the identification of a small number of conserved residues a ... | 2000 | 10704478 |
| molecular basis of symbiotic promiscuity. | eukaryotes often form symbioses with microorganisms. among these, associations between plants and nitrogen-fixing bacteria are responsible for the nitrogen input into various ecological niches. plants of many different families have evolved the capacity to develop root or stem nodules with diverse genera of soil bacteria. of these, symbioses between legumes and rhizobia (azorhizobium, bradyrhizobium, mesorhizobium, and rhizobium) are the most important from an agricultural perspective. nitrogen- ... | 2000 | 10704479 |
| aminoacyl-trna synthetases, the genetic code, and the evolutionary process. | the aminoacyl-trna synthetases (aarss) and their relationship to the genetic code are examined from the evolutionary perspective. despite a loose correlation between codon assignments and aars evolutionary relationships, the code is far too highly structured to have been ordered merely through the evolutionary wanderings of these enzymes. nevertheless, the aarss are very informative about the evolutionary process. examination of the phylogenetic trees for each of the aarss reveals the following. ... | 2000 | 10704480 |
| identification of two novel hrp-associated genes in the hrp gene cluster of xanthomonas oryzae pv. oryzae. | we have cloned a hrp gene cluster from xanthomonas oryzae pv. oryzae. bacteria with mutations in the hrp region have reduced growth in rice leaves and lose the ability to elicit a hypersensitive response (hr) on the appropriate resistant cultivars of rice and the nonhost plant tomato. a 12,165-bp portion of nucleotide sequence from the presumed left end and extending through the hrpb operon was determined. the region was most similar to hrp genes from xanthomonas campestris pv. vesicatoria and r ... | 2000 | 10714988 |
| sinorhizobium meliloti puta gene regulation: a new model within the family rhizobiaceae. | proline dehydrogenase (puta) is a bifunctional enzyme that catalyzes the oxidation of proline to glutamate. in sinorhizobium meliloti, as in other microorganisms, the puta gene is transcriptionally activated in response to proline. in rhodobacter capsulatus, agrobacterium, and most probably in bradyrhizobium, this activation is dependent on an lrp-like protein encoded by the putr gene, located immediately upstream of puta. interestingly, sequence and genetic analysis of the region upstream of th ... | 2000 | 10715000 |
| reciprocal domain evolution within a transactivator in a restricted sequence space. | offhough the concept of domain merging and shuffling as a major force in protein evolution is well established, it has been difficult to demonstrate how domains coadapt. here we show evidence of coevolution of the sinorhizobium meliloti nifa (smnifa) domains. we found that, because of the lack of a conserved glycine in its dna-binding domain, this transactivator protein interacts weakly with the enhancers. this defect, however, was compensated by evolving a highly efficient activation domain tha ... | 2000 | 10716734 |
| requirement for the enzymes acetoacetyl coenzyme a synthetase and poly-3-hydroxybutyrate (phb) synthase for growth of sinorhizobium meliloti on phb cycle intermediates. | we have identified two sinorhizobium meliloti chromosomal loci affecting the poly-3-hydroxybutyrate degradation pathway. one locus was identified as the gene acsa, encoding acetoacetyl coenzyme a (acetoacetyl-coa) synthetase. analysis of the acsa nucleotide sequence revealed that this gene encodes a putative protein with a molecular weight of 72,000 that shows similarity to acetyl-coa synthetase in other organisms. acetyl-coa synthetase activity was not affected in cell extracts of glucose-grown ... | 2000 | 10735852 |
| roles of horizontal gene transfer and gene integration in evolution of 1,3-dichloropropene- and 1,2-dibromoethane-degradative pathways. | the haloalkane-degrading bacteria rhodococcus rhodochrous ncimb13064, pseudomonas pavonaceae 170, and mycobacterium sp. strain gp1 share a highly conserved haloalkane dehalogenase gene (dhaa). here, we describe the extent of the conserved dhaa segments in these three phylogenetically distinct bacteria and an analysis of their flanking sequences. the dhaa gene of the 1-chlorobutane-degrading strain ncimb13064 was found to reside within a 1-chlorobutane catabolic gene cluster, which also encodes a ... | 2000 | 10735862 |
| domain structure, oligomeric state, and mutational analysis of ppsr, the rhodobacter sphaeroides repressor of photosystem gene expression. | the transcription factor ppsr from the facultative photoheterotroph rhodobacter sphaeroides is involved in repression of photosystem gene expression under aerobic growth conditions. we have isolated a number of spontaneous mutations as well as constructed directed mutations and deletions in ppsr. repressor activities and the oligomeric state of the wild-type and mutant proteins were assayed. our results suggest that the wild-type ppsr exists in cell extracts as a tetramer. analysis of the ppsr m ... | 2000 | 10735869 |
| involvement of two plasmids in fenitrothion degradation by burkholderia sp. strain nf100. | a bacterium capable of utilizing fenitrothion (o,o-dimethyl o-4-nitro-m-tolyl phosphorothioate) as a sole carbon source was isolated from fenitrothion-treated soil. this bacterium was characterized taxonomically as being a member of the genus burkholderia and was designated strain nf100. nf100 first hydrolyzed an organophosphate bond of fenitrothion, forming 3-methyl-4-nitrophenol, which was further metabolized to methylhydroquinone. the ability to degrade fenitrothion was found to be encoded on ... | 2000 | 10742273 |
| differentiation of o-acetyl and o-carbamoyl esters of n-acetyl-glucosamine by decomposition of their oxonium ions. application to the structure of the nonreducing terminal residue of nod factors. | nod factors are substituted n-acyl chito-oligomers secreted by plant symbiotic bacteria of the rhizobium family. substitutions on the oligosaccharide core specify their recognition by host plants. a method using tandem mass spectrometry is proposed to locate the o-acetyl and o-carbamoyl substituents on the nonreducing terminal residue of the chito-oligomers. as model compounds, all the positional isomers of monoacetyl and monocarbamoyl esters of 1-o-methyl-n-acetyl-alpha-d-glucosamine were synth ... | 2000 | 10757166 |
| analysis of cellular fatty acids and phenotypic relationships of agrobacterium, bradyrhizobium, mesorhizobium, rhizobium and sinorhizobium species using the sherlock microbial identification system. | previous studies have demonstrated that cellular fatty acid analysis is a useful tool for identifying unknown strains of rhizobia and establishing taxonomic relationships between the species. in this study, the fatty acid profiles of over 600 strains belonging to the genera agrobacterium, bradyrhizobium, mesorhizobium, rhizobium and sinorhizobium were evaluated using the gaschromatography-based sherlock microbial identification system (mis). data collected with the mis showed that the three phyl ... | 2000 | 10758890 |
| ectoine, the compatible solute of halomonas elongata, confers hyperosmotic tolerance in cultured tobacco cells. | 1,4,5,6-tetrahydro-2-methyl-4-pyrimidinecarboxylic acid (ectoine) functions as a compatible osmolyte in the moderate halophile halomonas elongata out30018. ectoine is biosynthesized by three successive enzyme reactions from aspartic beta-semialdehyde. the genes encoding the enzymes involved in the biosynthesis, ecta, ectb, and ectc, encoding l-2,4-diaminobutyric acid acetyltransferase, l-2, 4-diaminobutyric acid transaminase, and l-ectoine synthase, respectively, have been previously cloned. to ... | 2000 | 10759521 |
| homing of a bacterial group ii intron with an intron-encoded protein lacking a recognizable endonuclease domain. | rmint1 is a functional group ii intron found in sinorhizobium meliloti where it interrupts a group of is elements of the is630-tc1 family. in contrast to many other group ii introns, the intron-encoded protein (iep) of rmint1 lacks the characteristic conserved part of the zn domain associated with the iep endonuclease activity. nevertheless, in this study, we show that rmint1 is capable of inserting into a vector containing the dna spanning the rmint1 target site from the genome of s. meliloti. ... | 2000 | 10760141 |
| genetic analysis of functions involved in adhesion of pseudomonas putida to seeds. | many agricultural uses of bacteria require the establishment of efficient bacterial populations in the rhizosphere, for which colonization of plant seeds often constitutes a critical first step. pseudomonas putida kt2440 is a strain that colonizes the rhizosphere of a number of agronomically important plants at high population densities. to identify the functions involved in initial seed colonization by p. putida kt2440, we subjected this strain to transposon mutagenesis and screened for mutants ... | 2000 | 10762233 |
| a sigma(54) activator protein necessary for spore differentiation within the fruiting body of myxococcus xanthus. | insertion of an internal dna fragment into the act1 gene, which encodes one of several sigma(54)-activator proteins in myxococcus xanthus, produced a mutant defective in fruiting body development. while fruiting-body aggregation appears normal in the mutant, it fails to sporulate (<10(-6) the wild-type number of viable spores). the a and c intercellular signals, which are required for sporulation, are produced by the mutant. but, while it produces a-factor at levels as high as that of the wild t ... | 2000 | 10762243 |
| the ++sinorhizobium meliloti lon protease is involved in regulating exopolysaccharide synthesis and is required for nodulation of alfalfa. | while screening for sinorhizobium meliloti pho regulatory mutants, a transposon mutant was isolated that constitutively expressed higher levels of acid and alkaline phosphatase enzymes. this mutant was also found to form pseudonodules on alfalfa that were delayed in appearance relative to those formed by the wild-type strain, it contained few bacteroids, and it did not fix nitrogen. sequence analysis of the transposon insertion site revealed the affected gene to have high homology to lon proteas ... | 2000 | 10762258 |
| rpma is required for nonopsonic phagocytosis of pseudomonas aeruginosa. | pseudomonas aeruginosa causes severe respiratory tract infections in patients with cystic fibrosis (cf). we have been examining nonopsonic phagocytosis of p. aeruginosa by macrophages. to study the p. aeruginosa-macrophage interaction at the molecular level, we have constructed a transposon tn5g bank in a clinical isolate of p. aeruginosa (strain 4020) and identified mutants resistant to nonopsonic phagocytosis. phagocytosis-resistant mutants were enriched by passaging the transposon bank over 1 ... | 2000 | 10768936 |
| the gale gene of campylobacter jejuni is involved in lipopolysaccharide synthesis and virulence. | lipopolysaccharide (lps) is one of the main virulence factors of gram-negative bacteria. the lps from campylobacter spp. has endotoxic properties and has been shown to play a role in adhesion. we previously cloned a gene cluster (wla) which is involved in the synthesis of the campylobacter jejuni 81116 lps molecule. sequence alignment of the first gene in this cluster indicated similarity with gale genes. these genes encode a udp-glucose 4-epimerase, which catalyzes the interconversion of udp-ga ... | 2000 | 10768949 |
| 2-hydroxycyclohexanecarboxyl coenzyme a dehydrogenase, an enzyme characteristic of the anaerobic benzoate degradation pathway used by rhodopseudomonas palustris. | a gene, badh, whose predicted product is a member of the short-chain dehydrogenase/reductase family of enzymes, was recently discovered during studies of anaerobic benzoate degradation by the photoheterotrophic bacterium rhodopseudomonas palustris. purified histidine-tagged badh protein catalyzed the oxidation of 2-hydroxycyclohexanecarboxyl coenzyme a (2-hydroxychc-coa) to 2-ketocyclohexanecarboxyl-coa. these compounds are proposed intermediates of a series of three reactions that are shared by ... | 2000 | 10781543 |
| expression of uptake hydrogenase and molybdenum nitrogenase in rhodobacter capsulatus is coregulated by the regb-rega two-component regulatory system. | purple photosynthetic bacteria are capable of generating cellular energy from several sources, including photosynthesis, respiration, and h(2) oxidation. under nutrient-limiting conditions, cellular energy can be used to assimilate carbon and nitrogen. this study provides the first evidence of a molecular link for the coregulation of nitrogenase and hydrogenase biosynthesis in an anoxygenic photosynthetic bacterium. we demonstrated that molybdenum nitrogenase biosynthesis is under the control of ... | 2000 | 10781552 |
| catabolism of alpha-ketoglutarate by a suca mutant of bradyrhizobium japonicum: evidence for an alternative tricarboxylic acid cycle. | a complete tricarboxylic acid (tca) cycle is generally considered necessary for energy production from the dicarboxylic acid substrates malate, succinate, and fumarate. however, a bradyrhizobium japonicum suca mutant that is missing alpha-ketoglutarate dehydrogenase is able to grow on malate as its sole source of carbon. this mutant also fixes nitrogen in symbiosis with soybean, where dicarboxylic acids are its principal carbon substrate. using a flow chamber system to make direct measurements o ... | 2000 | 10781553 |
| fabg, an nadph-dependent 3-ketoacyl reductase of pseudomonas aeruginosa, provides precursors for medium-chain-length poly-3-hydroxyalkanoate biosynthesis in escherichia coli. | escherichia coli hosts expressing fabg of pseudomonas aeruginosa showed 3-ketoacyl coenzyme a (coa) reductase activity toward r-3-hydroxyoctanoyl-coa. furthermore, e. coli recombinants carrying the poly-3-hydroxyalkanoate (pha) polymerase-encoding gene phac in addition to fabg accumulated medium-chain-length phas (mcl-phas) from alkanoates. when e. coli fadb or fada mutants, which are deficient in steps downstream or upstream of the 3-ketoacyl-coa formation step during beta-oxidation, respective ... | 2000 | 10781572 |
| expression and purification of four different rhizobial acyl carrier proteins. | in rhizobia, besides the constitutive acyl carrier protein (acpp) involved in the biosynthesis and transfer of common fatty acids, there are at least three specialized acyl carrier proteins (acps): (1) the flavonoid-inducible nodulation protein nodf; (2) the rkpf protein, which is required for the biosynthesis of rhizobial capsular polysaccharides; and (3) acpxl, which transfers 27-hydroxyoctacosanoic acid to a sugar backbone during lipid a biosynthesis. whereas the nucleotide sequences encoding ... | 2000 | 10784042 |
| isolation of adherent polycyclic aromatic hydrocarbon (pah)-degrading bacteria using pah-sorbing carriers. | two different procedures were compared to isolate polycyclic aromatic hydrocarbon (pah)-utilizing bacteria from pah-contaminated soil and sludge samples, i.e., (i) shaken enrichment cultures in liquid mineral medium in which pahs were supplied as crystals and (ii) a new method in which pah degraders were enriched on and recovered from hydrophobic membranes containing sorbed pahs. both techniques were successful, but selected from the same source different bacterial strains able to grow on pahs a ... | 2000 | 10788347 |
| coexistence of two different o demethylation systems in lignin metabolism by sphingomonas paucimobilis syk-6: cloning and sequencing of the lignin biphenyl-specific o-demethylase (ligx) gene. | sphingomonas paucimobilis syk-6 can grow on several dimeric model compounds of lignin as a carbon and energy source. it has o demethylation systems on three kinds of substrates: 5, 5'-dehydrodivanillic acid (ddva), syringate, and vanillate. we previously reported the cloning of a gene involved in the tetrahydrofolate-dependent o demethylation of syringate and vanillate. in the study reported here, we cloned the gene responsible for ddva o demethylation. using nitrosoguanidine mutagenesis, a muta ... | 2000 | 10788391 |
| effects of glucosinolates and flavonoids on colonization of the roots of brassica napus by azorhizobium caulinodans ors571. | plants of brassica napus were assessed quantitatively for their susceptibility to lateral root crack colonization by azorhizobium caulinodans ors571(pxlgd4) (a rhizobial strain carrying the lacz reporter gene) and for the concentration of glucosinolates in their roots by high-pressure liquid chromatography (hplc). high- and low-glucosinolate-seed (hgs and lgs) varieties exhibited a relatively low and high percentage of colonized lateral roots, respectively. hplc showed that roots of hgs plants c ... | 2000 | 10788398 |
| increase of the atp-dependent phosphoenolpyruvate carboxykinase activity in sinorhizobium meliloti (rhizobium meliloti) during hypothermic environmental conditions. | sinorhizobium meliloti growth is affected when the incubation temperature is lower than 22 degrees c. in culture media containing glucose or fructose (1%, w/v), the doubling time at 19 degrees c was about 6.25 h during the exponential growth phase, while it was 2.75 h at 30 degrees c; at 17 degrees c it was three-fold higher than at 30 degrees c. modifications in the bacterial metabolism explain the doubling time increase when bacteria are incubated at low temperature. we determine here, the pho ... | 2000 | 10791719 |
| is the accumulation of osmoprotectant the unique mechanism involved in bacterial osmoprotection? | sucrose, trehalose, maltose, cellobiose, gentiobiose, turanose and palatinose are very unusual osmoprotectants for sinorhizobium meliloti, because these compounds, unlike other bacterial osmoprotectants, do not accumulate as cytosolic osmolytes in salt-stressed s. meliloti cells. rather, these compounds were catabolized during early exponential growth, and contributed to enhance the cytosolic levels of the two endogenously-synthesized osmolytes: glutamate and the dipeptide n-acetylglutaminylglut ... | 2000 | 10791739 |
| symbiotic induction of pyruvate dehydrogenase genes from sinorhizobium meliloti. | genes coding for components of the pyruvate dehydrogenase (pdh) multienzyme complex (pdhc) from sinorhizobium meliloti, the alfalfa symbiont, have been isolated on the basis of their high expression in symbiotic bacteria. the elp component, pdh, is encoded by two genes, pdhaalpha (1,047 bp) and pdhabeta (1,383 bp), a situation encountered in the alpha-proteobacteria rickettsia prowazekii and zymomonas mobilis as well as in some gram-positive bacteria and in mitochondria. pdhaalpha and pdhabeta p ... | 2000 | 10796014 |
| a complex insertion sequence cluster at a point of interaction between the linear plasmid scp1 and the linear chromosome of streptomyces coelicolor a3(2). | the giant linear plasmid scp1 can integrate into the central region of the linear chromosome of streptomyces coelicolor a3(2). nucleotide sequence analysis around the target site for scp1 integration in strain m145 identified a total of five copies of four insertion sequences (iss) in a 6.5-kb dna stretch. three of the four (is468, is469, and is470) are new is elements, and the other is is466. all of these elements contain one open reading frame which encodes a transposase-like protein. two copi ... | 2000 | 10809688 |
| structural elements required for replication and incompatibility of the rhizobium etli symbiotic plasmid. | the symbiotic plasmid of rhizobium etli ce3 belongs to the repabc family of plasmid replicons. this family is characterized by the presence of three conserved genes, repa, repb, and repc, encoded by the same dna strand. a long intergenic sequence (igs) between repb and repc is also conserved in all members of the plasmid family. in this paper we demonstrate that (i) the repabc genes are organized in an operon; (ii) the repc product is essential for replication; (iii) repa and repb products parti ... | 2000 | 10809690 |
| overexpression of protective antigen as a novel approach to enhance vaccine efficacy of brucella abortus strain rb51. | brucella abortus strain rb51 is an attenuated rough strain that is currently being used as the official live vaccine for bovine brucellosis in the united states and several other countries. we reasoned that overexpression of a protective antigen(s) of b. abortus in strain rb51 should enhance its vaccine efficacy. to test this hypothesis, we overexpressed cu/zn superoxide dismutase (sod) protein of b. abortus in strain rb51. this was accomplished by transforming strain rb51 with a broad-host-rang ... | 2000 | 10816475 |
| gene expression of medicago sativa inoculated with sinorhizobium meliloti as modulated by the xenobiotics cadmium and fluoranthene. | alfalfa plants (medicago sativa cv. europe) inoculated with sinorhizobium meliloti 2011 (formerly rhizobium meliloti, de lajudie et al., 1994) were cultivated for 14 days under standardized growth conditions in mineral medium with addition of the heavy metal cadmium or the polycyclic aromatic hydrocarbon fluoranthene. these xenobiotics significantly reduced the numbers of root nodules before any visible damage to the plant could be detected. ec10, ec50, and ec90 (effective concentrations reducin ... | 2000 | 10817212 |
| sinorhizobium meliloti nfe (nodulation formation efficiency) genes exhibit temporal and spatial expression patterns similar to those of genes involved in symbiotic nitrogen fixation. | the nfe genes (nfea, nfeb, and nfed) are involved in the nodulation efficiency and competitiveness of the sinorhizobium meliloti strain gr4 on alfalfa roots. the nfea and nfeb genes are preceded by functional nif consensus sequences and nifa binding motifs. here, we determined the temporal and spatial expression patterns of the nfe genes in symbiosis with alfalfa. translational fusions of the nfe promoters with the gusa gene and reverse transcription-polymerase chain reaction analyses indicate t ... | 2000 | 10830257 |
| disruption of a gene essential for sulfoquinovosyldiacylglycerol biosynthesis in sinorhizobium meliloti has no detectable effect on root nodule symbiosis. | the sulfolipid sulfoquinovosyldiacylglycerol is commonly found in the thylakoid membranes of photosynthetic bacteria and plants. while there is a good correlation between the occurrence of sulfolipid and photosynthesis, a number of exceptions are known. most recently, sulfoquinovosyldiacylglycerol was discovered in the non-photosynthetic, root nodule-forming bacterium sinorhizobium meliloti. this discovery raised the questions of the phylogenetic origin of genes essential for the biosynthesis of ... | 2000 | 10830266 |
| osmoprotection by pipecolic acid in sinorhizobium meliloti: specific effects of d and l isomers. | dl-pipecolic acid (dl-pip) promotes growth restoration of sinorhizobium meliloti cells facing inhibitory hyperosmolarity. surprisingly, d and l isomers of this imino acid supplied separately were not effective. the uptake of l-pip was significantly favored in the presence of the d isomer and by a hyperosmotic stress. chromatographic analysis of the intracellular solutes showed that stressed cells did not accumulate radiolabeled l-pip. rather, it participates in the synthesis of the main endogeno ... | 2000 | 10831411 |
| prey range characterization, ribotyping, and diversity of soil and rhizosphere bdellovibrio spp. isolated on phytopathogenic bacteria. | thirty new bdellovibrio strains were isolated from an agricultural soil and from the rhizosphere of plants grown in that soil. using a combined molecular and culture-based approach, we found that the soil bdellovibrios included subpopulations of organisms that differed from rhizosphere bdellovibrios. thirteen soil and seven common bean rhizosphere bdellovibrio strains were isolated when pseudomonas corrugata was used as prey; seven and two soil strains were isolated when erwinia carotovora subsp ... | 2000 | 10831412 |
| differential effects of permeating and nonpermeating solutes on the fatty acid composition of pseudomonas putida. | we examined the effect of reduced water availability on the fatty acid composition of pseudomonas putida strain mt-2 grown in a defined medium in which the water potential was lowered with the permeating solutes nacl or polyethylene glycol (peg) with a molecular weight of 200 (peg 200) or the nonpermeating solute peg 8000. transmission electron microscopy showed that -1.0-mpa peg 8000-treated cells had convoluted outer membranes, whereas -1.0-mpa nacl-treated or control cells did not. at the ran ... | 2000 | 10831419 |
| use of repetitive dna sequences and the pcr to differentiate escherichia coli isolates from human and animal sources. | the rep-pcr dna fingerprint technique, which uses repetitive intergenic dna sequences, was investigated as a way to differentiate between human and animal sources of fecal pollution. box and rep primers were used to generate dna fingerprints from escherichia coli strains isolated from human and animal sources (geese, ducks, cows, pigs, chickens, and sheep). our initial studies revealed that the dna fingerprints obtained with the box primer were more effective for grouping e. coli strains than th ... | 2000 | 10831440 |
| identification of sinorhizobium meliloti genes regulated during symbiosis. | rna fingerprinting by arbitrarily primed pcr was used to isolate sinorhizobium meliloti genes regulated during the symbiotic interaction with alfalfa (medicago sativa). sixteen partial cdnas were isolated whose corresponding genes were differentially expressed between symbiotic and free-living conditions. thirteen sequences corresponded to genes up-regulated during symbiosis, whereas three were instead repressed during establishment of the symbiotic interaction. seven cdnas corresponded to known ... | 2000 | 10850975 |
| characterization of a snorhizobium meliloti atp-binding cassette histidine transporter also involved in betaine and proline uptake. | the symbiotic soil bacterium sinorhizobium meliloti uses the compatible solutes glycine betaine and proline betaine for both protection against osmotic stress and, at low osmolarities, as an energy source. a pcr strategy based on conserved domains in components of the glycine betaine uptake systems from escherichia coli (prou) and bacillus subtilis (opua and opuc) allowed us to identify a highly homologous atp-binding cassette (abc) binding protein-dependent transporter in s. meliloti. this syst ... | 2000 | 10850986 |
| marinomonas mediterranea mmb-1 transposon mutagenesis: isolation of a multipotent polyphenol oxidase mutant. | marinomonas mediterranea is a melanogenic marine bacterium expressing a multifunctional polyphenol oxidase (ppo) able to oxidize substrates characteristic for laccases and tyrosinases, as well as produce a classical tyrosinase. a new and quick method has been developed for screening laccase activity in culture plates to detect mutants differentially affected in this ppo activity. transposon mutagenesis has been applied for the first time to m. mediterranea by using different minitransposons load ... | 2000 | 10850991 |
| synechocystis strain pcc 6803 cya2, a prokaryotic gene that encodes a guanylyl cyclase. | synechocystis strain pcc 6803 exhibits similar levels of cyclic amp (camp) and cyclic gmp (cgmp). a thorough analysis of its genome showed that cya2 (sll0646) has all the sequence determinants required in terms of activity and purine specificity for being a guanylyl cyclase. insertional mutagenesis of cya2 caused a marked reduction in cgmp content without altering the camp content. thus, cya2 represents the first example of a prokaryotic guanylyl cyclase. | 2000 | 10851002 |
| inactivation of gltb abolishes expression of the assimilatory nitrate reductase gene (nasb) in pseudomonas putida kt2442. | by using mini-tn5 transposon mutagenesis, random transcriptional fusions of promoterless bacterial luciferase, luxab, to genes of pseudomonas putida kt2442 were generated. insertion mutants that responded to ammonium deficiency by induction of bioluminescence were selected. the mutant that responded most strongly was genetically analyzed and is demonstrated to bear the transposon within the assimilatory nitrate reductase gene (nasb) of p. putida kt2442. genetic evidence as well as sequence analy ... | 2000 | 10852866 |
| salmonella enterica serovar typhimurium peptidase b is a leucyl aminopeptidase with specificity for acidic amino acids. | peptidase b (pepb) of salmonella enterica serovar typhimurium is one of three broad-specificity aminopeptidases found in this organism. we have sequenced the pepb gene and found that it encodes a 427-amino-acid (46.36-kda) protein, which can be unambiguously assigned to the leucyl aminopeptidase (lap) structural family. pepb has been overexpressed and purified. the active enzyme shows many similarities to other members of the lap family: it is a heat-stable (70 degrees c; 20 min) hexameric ( app ... | 2000 | 10852868 |
| genetic and phenotypic analyses of the rdx locus of rhodobacter sphaeroides 2.4.1. | previously, we reported that rdxb, encoding a likely membrane-bound two [4fe-4s]-containing center, is involved in the aerobic regulation of photosystem gene expression in rhodobacter sphaeroides 2.4.1. to further investigate the role of rdxb as well as other genes of the rdxbhis operon on photosystem gene expression, we constructed a series of nonpolar, in-frame deletion mutations in each of the rdx genes. using both puc and puf operon lacz fusions to monitor photosystem gene expression, under ... | 2000 | 10852880 |
| the brucella abortus ccrm dna methyltransferase is essential for viability, and its overexpression attenuates intracellular replication in murine macrophages. | the ccrm dna methyltransferase of the alpha-proteobacteria catalyzes the methylation of the adenine in the sequence gantc. like dam in the enterobacteria, ccrm plays a regulatory role in caulobacter crescentus and rhizobium meliloti. ccrm is essential for viability in both of these organisms, and we show here that it is also essential in brucella abortus. further, increased copy number of the ccrm gene results in striking changes in b. abortus morphology, dna replication, and growth in murine ma ... | 2000 | 10852881 |
| virulence of the phytopathogen pseudomonas syringae pv. maculicola is rpon dependent. | we cloned the rpon (ntra and glnf) gene encoding sigma(54) from the phytopathogen pseudomonas syringae pv. maculicola strain es4326. the p. syringae es4326 rpon gene complemented pseudomonas aeruginosa, escherichia coli, and klebsiella aerogenes rpon mutants for a variety of rpon mutant phenotypes, including the inability to utilize nitrate as sole nitrogen source. dna sequence analysis of the p. syringae es4326 rpon gene revealed that the deduced amino acid sequence was most similar (86% identi ... | 2000 | 10852883 |
| the alternative sigma factor rpon is required for hrp activity in pseudomonas syringae pv. maculicola and acts at the level of hrpl transcription. | beta-glucuronidase (uida) reporter gene fusions were constructed for the hrpz, hrpl, and hrps genes from the phytopathogen pseudomonas syringae pv. maculicola strain es4326. these reporters, as well as an avrrpt2-uida fusion, were used to measure transcriptional activity in es4326 and a es4326 rpon mutant. rpon was required for the expression of avrrpt2, hrpz, and hrpl in vitro in minimal media and in vivo when infiltrated into arabidopsis thaliana leaves. in contrast, the expression of hrps was ... | 2000 | 10852884 |
| megaplasmid prme2011a of sinorhizobium meliloti is not required for viability. | we report the curing of the 1,360-kb megaplasmid prme2011a from sinorhizobium meliloti strain rm2011. with a positive selection strategy that utilized tn5b12-s containing the sacb gene, we were able to cure this replicon by successive rounds of selecting for deletion formation in vivo. subsequent southern blot, eckhardt gel, and pulsed-field gel electrophoresis analyses were consistent with the hypothesis that the resultant strain was indeed missing prme2011a. the cured derivative grew as well a ... | 2000 | 10852892 |
| purification and mass spectrometry of six lipid a species from the bacterial endosymbiont rhizobium etli. demonstration of a conserved distal unit and a variable proximal portion. | lipid a of rhizobium etli ce3 differs dramatically from that of other gram-negative bacteria. key features include the presence of an unusual c28 acyl chain, a galacturonic acid moiety at position 4', and an acylated aminogluconate unit in place of the proximal glucosamine. in addition, r. etli lipid a is reported to lack phosphate and acyloxyacyl residues. most of these remarkable structural claims are consistent with our recent enzymatic studies. however, the proposed r. etli lipid a structure ... | 2000 | 10856303 |
| high-resolution physical map of the psymb megaplasmid and comparison of the three replicons of sinorhizobium meliloti strain 1021. | a high-resolution physical map of the larger megaplasmid (psymb) of sinorhizobium meliloti strain 1021 has been constructed by using bac libraries and an original two-step pcr screening method. this method, previously used to map both the chromosome and the smaller megaplasmid (psyma), allowed us to position over the genome a total of 842 markers with an average density of one marker every 8.3 kb. in addition, we used blastx and prodom analysis to predict a function for a number of stss. this wo ... | 2000 | 10856376 |
| regulation of brucella abortus catalase. | all aerobic organisms have mechanisms that protect against oxidative compounds. catalase, peroxidase, superoxide dismutase, glutathione, and thioredoxin are widely distributed in many taxa and constitute elements of a nearly ubiquitous antioxidant metabolic strategy. interestingly, the regulatory mechanisms that control these elements are rather different depending on the nature of the oxidative stress and the organism. catalase is well documented to play an important role in protecting cells fr ... | 2000 | 10858195 |
| an arac-like transcriptional activator is required for induction of genes needed for alpha-galactoside utilization in sinorhizobium meliloti. | the nodulating bacterium sinorhizobium meliloti can utilize alpha-galactosides like melibiose and raffinose as sole sources of carbon and energy. we show that this utilization requires an arac-like transcriptional activator, agpt. when agpt was inactivated, rhizobium meliloti could not utilize alpha-galactosides or induce genes required for transport and catabolism of these sugars. the agpt gene was not essential for the establishment of an effective nitrogen-fixing symbiosis. | 2000 | 10867229 |
| a promoter region binding protein and dna gyrase regulate anaerobic transcription of nifla in enterobacter cloacae. | our work provides evidence that a sequence characteristic of fnr binding sites, when interacted with by a trans-acting factor, activates anaerobic transcription of the nifla operon in enterobacter cloacae. dna gyrase activity has been found to be important for the anaerobic transcription of the nifla promoter. our results suggest that anaerobic regulation of the nifla operon is mediated through the control of the promoter region-binding trans-acting factor at the transcriptional level, while dna ... | 2000 | 10869067 |
| genome structure of the genus azospirillum. | azospirillum species are plant-associated diazotrophs of the alpha subclass of proteobacteria. the genomes of five of the six azospirillum species were analyzed by pulsed-field gel electrophoresis. all strains possessed several megareplicons, some probably linear, and 16s ribosomal dna hybridization indicated multiple chromosomes in genomes ranging in size from 4.8 to 9.7 mbp. the nifhdk operon was identified in the largest replicon. | 2000 | 10869094 |
| the role of region ii in the rna polymerase sigma factor sigma(n) (sigma(54)). | bacterial rna polymerase holoenzymes containing the sigma subunit sigma(n) (sigma(54)) can form a stable closed complex with promoter dna but only undergo transition to an open complex and transcription initiation when acted on by an activator protein. proteins of the sigma(n) family have a conserved n-terminal region of 50 amino acids (region i) that is separated from a conserved c-terminal region of around 360 amino acids (region iii) by a much more variable sequence of between 30 and 110 resi ... | 2000 | 10871407 |
| [lps mutants of sinorhizobium meliloti and their nodulation competitiveness]. | four tn5-transposon lps mutants of sinorhizobium meliloti (tb9, tb29, ts22 and ts32) have been studied. each of four mutants has been established to contain a single insertion of tn5-transposon in its genome. all mutations are located on a chromosome. nodulation competitiveness (nc) of mutants towards the parent strain of s. meliloti cxm1-188 was investigated by resistant method using coinoculation of mutant and parent strain in the ratio 1:1. it was shown that nc was only 19-31% and 8-10%, for ... | 2000 | 10872284 |
| genes expressed in pseudomonas putida during colonization of a plant-pathogenic fungus. | in vivo expression technology (ivet) was employed to study colonization of phytophthora parasitica by a biological control bacterium, pseudomonas putida 06909, based on a new selection marker. the pyrb gene, which encodes aspartate transcarbamoylase, an enzyme used for pyrimidine biosynthesis, was cloned from p. putida 06909. a pyrb-disrupted mutant did not grow in pyrimidine-deficient media unless it was complemented with pyrbc' behind an active promoter. thirty clones obtained from p. putida 0 ... | 2000 | 10877766 |
| characterization of an atrazine-degrading pseudaminobacter sp. isolated from canadian and french agricultural soils. | atrazine, a herbicide widely used in corn production, is a frequently detected groundwater contaminant. fourteen bacterial strains able to use this herbicide as a sole source of nitrogen were isolated from soils obtained from two farms in canada and two farms in france. these strains were indistinguishable from each other based on repetitive extragenic palindromic pcr genomic fingerprinting performed with primers eric1r, eric2, and boxa1r. based on 16s rrna sequence analysis of one representativ ... | 2000 | 10877767 |
| the common nodulation genes of astragalus sinicus rhizobia are conserved despite chromosomal diversity. | the nodulation genes of mesorhizobium sp. (astragalus sinicus) strain 7653r were cloned by functional complementation of sinorhizobium meliloti nod mutants. the common nod genes, nodd, noda, and nodbc, were identified by heterologous hybridization and sequence analysis. the noda gene was found to be separated from nodbc by approximately 22 kb and was divergently transcribed. the 2. 0-kb noddbc region was amplified by pcr from 24 rhizobial strains nodulating a. sinicus, which represented differen ... | 2000 | 10877796 |
| genomic variability of haemophilus influenzae isolated from mexican children determined by using enterobacterial repetitive intergenic consensus sequences and pcr. | genomic fingerprints from 92 capsulated and noncapsulated strains of haemophilus influenzae from mexican children with different diseases and healthy carriers were generated by pcr using the enterobacterial repetitive intergenic consensus (eric) sequences. a cluster analysis by the unweighted pair-group method with arithmetic averages based on the overall similarity as estimated from the characteristics of the genomic fingerprints, was conducted to group the strains. a total of 69 fingerprint pa ... | 2000 | 10878033 |
| fluorescent whole-cell hybridization with 16s rrna-targeted oligonucleotide probes to identify brucella spp. by flow cytometry. | a whole-cell hybridization assay with fluorescent oligonucleotide probes derived from the 16s rrna sequence of brucella abortus in combination with flow cytometry has been developed. with the three fluorescent probes selected, a positive signal was observed with all the representative strains of the species and biovars of brucella and with a total of nine different brucella clinical isolates. using the b9 probe in the hybridization assay, it was possible to discriminate between brucella suis bio ... | 2000 | 10878084 |
| crystal structure of cystalysin from treponema denticola: a pyridoxal 5'-phosphate-dependent protein acting as a haemolytic enzyme. | cystalysin is a c(beta)-s(gamma) lyase from the oral pathogen treponema denticola catabolyzing l-cysteine to produce pyruvate, ammonia and h(2)s. with its ability to induce cell lysis, cystalysin represents a new class of pyridoxal 5'-phosphate (plp)-dependent virulence factors. the crystal structure of cystalysin was solved at 1.9 a resolution and revealed a folding and quaternary arrangement similar to aminotransferases. based on the active site architecture, a detailed catalytic mechanism is ... | 2000 | 10880431 |
| the bacterial cell-division protein zipa and its interaction with an ftsz fragment revealed by x-ray crystallography. | in escherichia coli, ftsz, a homologue of eukaryotic tubulins, and zipa, a membrane-anchored protein that binds to ftsz, are two essential components of the septal ring structure that mediates cell division. recent data indicate that zipa is involved in the assembly of the ring by linking ftsz to the cytoplasmic membrane and that the zipa-ftsz interaction is mediated by their c-terminal domains. we present the x-ray crystal structures of the c-terminal ftsz-binding domain of zipa and a complex b ... | 2000 | 10880432 |
| identification and cell cycle control of a novel pilus system in caulobacter crescentus. | pilus assembly in caulobacter: crescentus occurs during a short period of the cell cycle and pili are only present at the flagellar pole of the swarmer cell. here we report a novel assay to visualize pili by light microscopy that led to the purification of caulobacter: pili and the isolation of a cluster of seven genes, including the major pilin subunit gene pila. this gene cluster encodes a novel group of pilus assembly proteins. we have shown that the pila promoter is activated late in the cel ... | 2000 | 10880436 |
| tmrnas that encode proteolysis-inducing tags are found in all known bacterial genomes: a two-piece tmrna functions in caulobacter. | a general mechanism in bacteria to rescue stalled ribosomes and to clear the cell of incomplete polypeptides involves an rna species, tmrna (ssra), which functions as both a trna and an mrna. this rna encodes a peptide tag that is incorporated at the end of the aberrant polypeptide and targets it for proteolysis. we have identified a circularly permuted version of the tmrna gene in alpha-proteobacteria as well as in a lineage of cyanobacteria. the genes in these two groups seem to have arisen fr ... | 2000 | 10884408 |
| mtsym6, a gene conditioning sinorhizobium strain-specific nitrogen fixation in medicago truncatula. | the availability of a wide range of independent lines for the annual medic medicago truncatula led us to search for natural variants in the symbiotic association with sinorhizobium meliloti. two homozygous lines, jemalong 6 and dza315.16, originating from an australian cultivar and a natural algerian population, respectively, were inoculated with two wild-type strains of s. meliloti, rcr2011 and a145. both plant lines formed nitrogen-fixing (effective) nodules with the rcr2011 strain. however, t ... | 2000 | 10889234 |
| characterization of sulfate assimilation in marine algae focusing on the enzyme 5'-adenylylsulfate reductase. | 5'-adenylylsulfate (aps) reductase was characterized in diverse marine algae. a cdna encoding aps reductase from enteromorpha intestinalis (eapr) was cloned by functional complementation of an escherichia coli cysh mutant. the deduced amino acid sequence shows high homology with aps reductase (apr) from flowering plants. based on the probable transit peptide cleavage site the mature protein is 45.7 kd. eapr expressed as a his-tagged recombinant protein catalyzes reduced glutathione-dependent red ... | 2000 | 10889258 |
| biochemical evidence for two novel enzymes in the biosynthesis of 3-dimethylsulfoniopropionate in spartina alterniflora. | 3-dimethylsulfoniopropionate (dmsp) is an osmoprotectant accumulated by the cordgrass spartina alterniflora and other salt-tolerant plants. previous in vivo isotope tracer and metabolic modeling studies demonstrated that s. alterniflora synthesizes dmsp via the route s-methyl-met --> 3-dimethylsulfoniopropylamine (dmsp-amine) --> 3-dimethylsulfoniopropionaldehyde --> dmsp and indicated that the first reaction requires a far higher substrate concentration than the second to attain one-half-maxima ... | 2000 | 10889264 |
| methods to evaluate nodulation competitiveness between sinorhizobium meliloti strains using melanin production as a marker. | three methods to evaluate the relative ability of different strains of sinorhizobium meliloti to occupy nodules formed on alfalfa after co-inoculation were compare in this study. results obtained using the three methods of evaluation together, provided insight into the relative nodulation competitiveness between two given sinorhizobial strains. a simple visual phenotypic marker, i.e., melanin production was used to distinguish individual strains in a given assay. as such, melanin producing strai ... | 2000 | 10889314 |
| new substrates for the dicarboxylate transport system of sinorhizobium meliloti. | the dicarboxylate transport (dct) system of sinorhizobium meliloti, which is essential for a functional nitrogen-fixing symbiosis, has been thought to transport only dicarboxylic acids. we show here that the permease component of the dct system, dcta, can transport orotate, a monocarboxylic acid, with an apparent k(m) of 1.7 mm and a v(max) of 163 nmol min(-1) per mg of protein in induced cells. dcta was not induced by the presence of orotate. the transport of orotate was inhibited by several co ... | 2000 | 10894729 |
| a redox-responsive regulator of photosynthesis gene expression in the cyanobacterium synechocystis sp. strain pcc 6803. | we have identified genes in the unicellular cyanobacterium synechocystis sp. strain pcc 6803 that are involved with redox control of photosynthesis and pigment-related genes. the genes, rppa (sll0797) and rppb (sll0798), represent a two-component regulatory system that controls the synthesis of photosystem ii (psii) and psi genes, in addition to photopigment-related genes. rppa (regulator of photosynthesis- and photopigment-related gene expression) and rppb exhibit strong sequence similarity to ... | 2000 | 10894737 |
| alfalfa root nodule invasion efficiency is dependent on sinorhizobium meliloti polysaccharides. | the soil bacterium sinorhizobium meliloti is capable of entering into a nitrogen-fixing symbiosis with medicago sativa (alfalfa). particular low-molecular-weight forms of certain polysaccharides produced by s. meliloti are crucial for establishing this symbiosis. alfalfa nodule invasion by s. meliloti can be mediated by any one of three symbiotically important polysaccharides: succinoglycan, eps ii, or k antigen (also referred to as kps). using green fluorescent protein-labeled s. meliloti cells ... | 2000 | 10894742 |
| characterization of the sinorhizobium meliloti genes encoding a functional dihydrodipicolinate synthase (dapa) and dihydrodipicolinate reductase (dapb). | in bacteria, the known pathways for diaminopimelate (dap) and lysine biosynthesis share two key enzymes, dihydrodipicolinate synthase and dihydrodipicolinate reductase, encoded by the dapa and dapb genes, respectively. in rhizobia, these genes have not yet been genetically characterized. in this work, by sequence analysis, we identified two divergent open reading frames on the 140-mda plasmid prmegr4b of sinorhizobium meliloti strain gr4. termed dapa and dapb, these encode products which show si ... | 2000 | 10896225 |
| in rhizobium leguminosarum, nodd represses its own transcription by competing with rna polymerase for binding sites. | we isolated rna polymerase (rnap) from rhizobium leguminosarum, the nitrogen-fixing symbiont of peas and vicia: its 91 kda subunit, which is homologous to sigma(70) of escherichia coli rnap, is necessary for transcription of the regulatory nodd gene, which in the presence of certain flavonoids induces transcription of other nod genes that are needed for the early steps of infection. we also show that negative autoregulation of nodd was achieved through competition between rnap and nodd for their ... | 2000 | 10908336 |
| identification of essential amino acid residues in the sinorhizobium meliloti glucosyltransferase exom. | exom is a beta(1-4)-glucosyltransferase involved in the assembly of the repeat unit of the exopolysaccharide succinoglycan from sinorhizobium meliloti. by comparing the sequence of exom to those of other members of the pfam glyco domain 2 family, most notably spsa (bacillus subtilis) for whom the three-dimensional structure has been resolved, three potentially important aspartic acid residues of exom were identified. single substitutions of each of the asp amino acids at positions 44, 96, and 18 ... | 2000 | 10908566 |
| elevated levels of synthesis of over 20 proteins results after mutation of the rhizobium leguminosarum exopolysaccharide synthesis gene pssa. | the protein expression profiles of rhizobium leguminosarum strains in response to specific genetic perturbations in exopolysaccharide (eps) biosynthesis genes were examined using two-dimensional gel electrophoresis. lesions in either pssa, pssd, or psse of r. leguminosarum bv. viciae vf39 or in pssa of r. leguminosarum bv. trifolii anu794 not only abolished the capacity of these strains to synthesize eps but also had a pleiotropic effect on protein synthesis levels. a minimum of 22 protein diffe ... | 2000 | 10913086 |
| developmental regulation of the cell division protein ftsz in anabaena sp. strain pcc 7120, a cyanobacterium capable of terminal differentiation. | heterocysts are terminally differentiated cells devoted to nitrogen fixation in the filamentous cyanobacterium anabaena sp. strain pcc 7120. we show here that the cell division protein ftsz is present in vegetative cells but undetectable in heterocysts. these results provide a first rational explanation for the inability of mature heterocysts to undergo cell division. | 2000 | 10913101 |
| lipopolysaccharides of rhizobium etli strain g12 act in potato roots as an inducing agent of systemic resistance to infection by the cyst nematode globodera pallida. | recent studies have shown that living and heat-killed cells of the rhizobacterium rhizobium etli strain g12 induce in potato roots systemic resistance to infection by the potato cyst nematode globodera pallida. to better understand the mechanisms of induced resistance, we focused on identifying the inducing agent. since heat-stable bacterial surface carbohydrates such as exopolysaccharides (eps) and lipopolysaccharides (lps) are essential for recognition in the symbiotic interaction between rhiz ... | 2000 | 10919815 |
| effect of field inoculation with sinorhizobium meliloti l33 on the composition of bacterial communities in rhizospheres of a target plant (medicago sativa) and a non-target plant (chenopodium album)-linking of 16s rrna gene-based single-strand conformation polymorphism community profiles to the diversity of cultivated bacteria. | fourteen weeks after field release of luciferase gene-tagged sinorhizobium meliloti l33 in field plots seeded with medicago sativa, we found that the inoculant also occurred in bulk soil from noninoculated control plots. in rhizospheres of m. sativa plants, s. meliloti l33 could be detected in noninoculated plots 12 weeks after inoculation, indicating that growth in the rhizosphere preceded spread into bulk soil. to determine whether inoculation affected bacterial diversity, 1,119 bacteria were ... | 2000 | 10919821 |
| pcr use of highly conserved dna regions for identification of sinorhizobium meliloti. | a pcr identification method in which four primers that recognize homologous conserved regions in the sinorhizobium meliloti genome are used was developed and tested. the regions used for identification were the nodbox 4 locus, which is located in one of the symbiotic megaplasmids, and the mucr gene, which is located in the chromosome. the new method was used to establish a collection of s. meliloti strains from polluted soils. | 2000 | 10919829 |
| bacterial type iv secretion: conjugation systems adapted to deliver effector molecules to host cells. | several bacterial pathogens utilize conjugation machines to export effector molecules during infection. such systems are members of the type iv or 'adapted conjugation' secretion family. the prototypical type iv system is the agrobacterium tumefaciens t-dna transfer machine, which delivers oncogenic nucleoprotein particles to plant cells. other pathogens, including bordetella pertussis, legionella pneumophila, brucellaspp. and helicobacter pylori, use type iv machines to export effector proteins ... | 2000 | 10920394 |
| characterization of bartonella clarridgeiae flagellin (flaa) and detection of antiflagellin antibodies in patients with lymphadenopathy. | cat scratch disease (csd) is a frequent clinical outcome of bartonella henselae infection in humans. recently, two case reports indicated bartonella clarridgeiae as an additional causative agent of csd. both pathogens have been isolated from domestic cats, which are considered to be their natural reservoir. b. clarridgeiae and b. henselae can be distinguished phenotypically by the presence or absence of flagella, respectively. separation of the protein content of purified flagella of b. clarridg ... | 2000 | 10921956 |
| phylogenetic analysis of 23s rrna gene sequences of. agrobacterium, rhizobium and sinorhizobium strains. | the phylogenetic relationship among twelve agrobacterium, four rhizobium, and two sinorhizobium strains originating from various host plants and geographical regions was studied by analysis of the 23s rdna sequences. the study included agrobacterium strains belonging to biovars 1, 2 (with tumor- or hairy-root inducing and non-pathogenic strains), a. vitis, a. rubi; representative species of the rhizobium genus: r. galegae, r. leguminosarum and r. tropici and sinorhizobium meliloti strains. the p ... | 2000 | 10930076 |
| the l-asparagine operon of rhizobium etli contains a gene encoding an atypical asparaginase. | the l-asparagine operon of rhizobium etli was cloned and sequenced. sequence analysis showed four adjacent open reading frames which were designated as ansr, ansp, ansa and ansb. the ansr and ansp genes encoded proteins similar to a transcriptional repressor and an l-asparagine permease, respectively. by tn5 mutagenesis and complementation analysis we identified the ansa product as a thermolabile asparaginase, and the ansb product as an aspartase. an asparagine-inducible transcript covering ansp ... | 2000 | 10930734 |
| conservation of a pseudomonad-like hydrocarbon degradative ferredoxin oxygenase complex involved in rhizopine catabolism in sinorhizobium meliloti and rhizobium leguminosarum bv. viciae. | in sinorhizobium meliloti the moccabr genes have previously been shown to be required for rhizopine (3-o-methyl-scyllo-inosamine, 3-o-msi) catabolism. we show that the mocde(f) gene cluster is also needed. mocde(f), which is involved in the catabolism of 3-o-msi to its demethylated form scyllo-inosamine (si) has homology to components that would comprise a ferredoxin-oxygenase system. the moccabrde(f) suite of genes is required for 3-o-msi catabolism in both s. meliloti and r. leguminosarum bv. ... | 2000 | 10937432 |
| nod factors of rhizobium leguminosarum bv. viciae and their fucosylated derivatives stimulate a nod factor cleaving activity in pea roots and are hydrolyzed in vitro by plant chitinases at different rates. | nod factors (nfs) are rhizobial lipo-chitooligosaccharide signals that trigger root nodule development in legumes. modifications of nf structures influence their biological activity and affect their degradation by plant chitinases. nodulation of certain pea cultivars by rhizobium leguminosarum bv. viciae requires modification of nfs at the reducing end by either an o-acetyl or a fucosyl group. fucosylated nfs were produced by an in vitro reaction with nodz fucosyltransferase and purified. their ... | 2000 | 10939251 |