Publications

the hydrogenase cytochrome b heme ligands of azotobacter vinelandii are required for full h(2) oxidation capability.	the hydrogenase in azotobacter vinelandii, like other membrane-bound [nife] hydrogenases, consists of a catalytic heterodimer and an integral membrane cytochrome b. the histidines ligating the hemes in this cytochrome b were identified by h(2) oxidation properties of altered proteins produced by site-directed mutagenesis. four fully conserved and four partially conserved histidines in hoxz were substituted with alanine or tyrosine. the roles of these histidines in hoxz heme binding and hydrogena ...	2000	10852874
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
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
rhizobitoxine production by bradyrhizobium elkanii enhances nodulation and competitiveness on macroptilium atropurpureum.	application of 1-aminoocyclopropane-1-carboxylic acid, an ethylene precursor, decreased nodulation of macroptilium atropurpureum by bradyrhizobium elkanii. b. elkanii produces rhizobitoxine, an ethylene synthesis inhibitor. elimination of rhizobitoxine production in b. elkanii increased ethylene evolution and decreased nodulation and competitiveness on m. atropurpureum. these results suggest that rhizobitoxine enhances nodulation and competitiveness of b. elkanii on m. atropurpureum.	2000	10831453
higher diversity of rhizobium leguminosarum biovar viciae populations in arable soils than in grass soils.	the bacterial genetic diversity after long-term arable cultivation was compared with that under permanent grassland using replicated paired contrasts. pea-nodulating rhizobium leguminosarum populations were sampled from pairs of arable and grass sites at four locations in yorkshire, united kingdom. isolates were characterized using both chromosomal (16s-23s ribosomal dna internal transcribed spacer pcr-restriction fragment length polymorphism) and plasmid (group-specific repc pcr amplification) ...	2000	10831423
temporal and spatial order of events during the induction of cortical cell divisions in white clover by rhizobium leguminosarum bv. trifolii inoculation or localized cytokinin addition.	we examined the timing and location of several early root responses to rhizobium leguminosarum bv. trifolii infection, compared with a localized addition of cytokinin in white clover, to study the role of cytokinin in early signaling during nodule initiation. induction of enod40 expression by either rhizobia or cytokinin was similar in timing and location and occurred in nodule progenitor cells in the inner cortex. inoculation of rhizobia in the mature root failed to induce enod40 expression and ...	2000	10830261
chemical characterization of effective and ineffective strains of rhizobium leguminosarum bv. viciae.	chemical composition of lipopolysaccharide (lps) isolated from an effective (97) and ineffective (87) strains of r. l. viciae has been determined. lps preparations from the two strains contained: glucose, galactose, mannose, fucose, arabinose, heptose, glucosamine, galactosamine, quinovosamine, and 3-n-methyl-3,6-dideoxyhexose, as well as glucuronic, galacturonic and 3-deoxyoctulosonic acid. the following fatty acids were identified: 3-oh 14:0, 3-oh 15:0, 3-oh 16:0, 3-oh 18:0 and 27-oh 28:0. the ...	1999	10824871
physiological adaptation to low temperatures of strains of rhizobium leguminosarum bv. viciae associated with lathyrus spp.(1).	strains of rhizobium leguminosarum bv. viciae, isolated from the legume species lathyrus japonicus and lathyrus pratensis in northern quebec (canada), showed different capacities for growing at low temperature. in the present study, we investigated some mechanisms related to cold adaptation. two cold-adapted strains (psychrotrophs) were compared to a poorly adapted strain and to a cold-sensitive strain (reference strain) for freezing survival, protein induction and fatty acid composition under l ...	2000	10817864
intercellular communication in helicobacter pylori: luxs is essential for the production of an extracellular signaling molecule.	individual bacteria of numerous species can communicate and coordinate their actions via the production, release, and detection of extracellular signaling molecules. in this study, we used the vibrio harveyi luminescence bioassay to determine whether helicobacter pylori produces such a factor. cell-free conditioned media from h. pylori strains 60190 and 26695 each induced >100-fold-greater luminescence in v. harveyi than did sterile culture medium. the h. pylori signaling molecule had a molecula ...	2000	10816463
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
a novel autoregulation mechanism of fnrn expression in rhizobium leguminosarum bv viciae.	the fnrn gene from rhizobium leguminosarum upm791 controls microaerobic expression of both nitrogen fixation and hydrogenase activities in symbiotic cells. two copies of fnrn are present in this strain, one chromosomal (fnrn1) and the other located in the symbiotic plasmid (fnrn2). their expression was studied by cloning the regulatory regions in lacz promoter-probe vectors. the fnrn genes were found to be autoregulated: they are expressed only at basal levels under aerobic conditions; they are ...	2000	10792733
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
analysis of the rhizobium leguminosarum siderophore-uptake gene fhua: differential expression in free-living bacteria and nitrogen-fixing bacteroids and distribution of an fhua pseudogene in different strains.	a mutation was isolated in the rhizobium leguminosarum gene fhua, which appears to specify the outer-membrane receptor for the siderophore vicibactin. the mutant was defective in iron uptake and accumulated the siderophore vicibactin in the extracellular medium. expression of fhua was regulated by fe3+, transcription being higher in iron-depleted cells. transcription of fhua was independent of a functional copy of rpol, a neighbouring gene that specifies a putative ecf sigma factor of rna polyme ...	2000	10784041
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
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
identification of a putative lps-associated cation exporter from rhizobium leguminosarum bv. viciae.	a gene, cpaa, with similarity to calcium proton antiporters has been identified adjacent to lpcab in rhizobium leguminosarum. lpca is a galactosyl transferase while lpcb is a 2-keto-3-deoxyoctonate transferase, both of which are required to form the lipopolysaccharide (lps) core in r. leguminosarum. mutations in lpcab result in a rough lps phenotype with a requirement for elevated calcium concentrations to allow growth, suggesting that truncation of the lps core exposes a highly negatively charg ...	2000	10779711
characterization of heat, oxidative, and acid stress responses in brucella melitensis.	brucella melitensis is a facultative intracellular pathogen which is able to survive and replicate within phagocytic cells. therefore, it has to adapt to a range of different hostile environments. in order to understand the mechanisms of intracellular survival employed by virulent b. melitensis 16m, an initial approach consisting of analysis of the differences in patterns of protein synthesis in response to heat, oxidative, and acid ph stresses by two-dimensional (2-d) polyacrylamide gel electro ...	2000	10768994
a novel sphingoglycolipid containing galacturonic acid and 2-hydroxy fatty acid in cellular lipids of sphingomonas yanoikuyae.	a novel sphingoglycolipid was isolated from sphingomonas yanoikuyae, and its structure was identified as a galacturonosyl-beta (1-->1)-ceramide. this was a characteristic sphingoglycolipid present in s. yanoikuyae and certain other species of sphingomonas, such as sphingomonas mali, sphingomonas terrae, and sphingomonas macrogoltabidus, but not in the type species of sphingomonas, sphingomonas paucimobilis.	2000	10762275
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
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
a lotus japonicus nodulation system based on heterologous expression of the fucosyl transferase nodz and the acetyl transferase noil in rhizobium leguminosarum.	heterologous expression of nodz and noll proteins in rhizobium leguminosarum bv. viciae led to the production of acetyl fucosylated lipo-chitin oligosaccharides (lcos), indicating that the noll protein obtained from mesorhizobium loti functions as an acetyl transferase. we show that the noll-dependent acetylation is specific for the fucosyl penta-n-acetylglucosamine species. in addition, the noll protein caused elevated production of lcos. efficient nodulation of lotus japonicus by the nodz/noll ...	2000	10755312
involvement of diamine oxidase and peroxidase in insolubilization of the extracellular matrix: implications for pea nodule initiation by rhizobium leguminosarum.	rhizobium leguminosarum colonizes host cells and tissues through infection threads, which are tubular in-growths of the plant cell wall. monoclonal antibody mac265 recognizes a plant matrix glycoprotein (mgp) associated with the lumen of these infection threads. this glycoprotein is also released in soluble form from the root tips of pea seedlings. in the presence of hydrogen peroxide, release of glycoprotein from root tips was not observed. extractability from root tips was therefore used as th ...	2000	10755304
characterization of the protocatechuic acid catabolic gene cluster from streptomyces sp. strain 2065.	protocatechuate 3,4-dioxygenase (ec 1.13.11.3) catalyzes the ring cleavage step in the catabolism of aromatic compounds through the protocatechuate branch of the beta-ketoadipate pathway. a protocatechuate 3,4-dioxygenase was purified from streptomyces sp. strain 2065 grown in p-hydroxybenzoate, and the n-terminal sequences of the beta- and alpha-subunits were obtained. pcr amplification was used for the cloning of the corresponding genes, and dna sequencing of the flanking regions showed that t ...	2000	10742233
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
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
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
[dna homology in various strains of nitrogen-fixing bacteria].	melting temperature and gc content were evaluated for dna of some nitrogen-fixing bacteria of rhizobium leguminosarum and onobrychis spp. (adans). the degree of homology between strains of the same species was determined. a combination of thermal denaturing and molecular hybridization can serve as a rapid test for evaluating the genome homology of the organisms compared.	2000	10702988
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
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
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
dual roles of bradyrhizobium japonicum nickelin protein in nickel storage and gtp-dependent ni mobilization.	the hydrogenase accessory protein hypb, or nickelin, has two functions in the n(2)-fixing, h(2)-oxidizing bacterium bradyrhizobium japonicum. one function of hypb involves the mobilization of nickel into hydrogenase. hypb also carries out a nickel storage/sequestering function in b. japonicum, binding nine nickel ions per monomer. here we report that the two roles (nickel mobilization and storage) of hypb can be separated in vitro and in vivo using molecular and biochemical approaches. the role ...	2000	10692376
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
components of the rp4 conjugative transfer apparatus form an envelope structure bridging inner and outer membranes of donor cells: implications for related macromolecule transport systems.	during bacterial conjugation, the single-stranded dna molecule is transferred through the cell envelopes of the donor and the recipient cell. a membrane-spanning transfer apparatus encoded by conjugative plasmids has been proposed to facilitate protein and dna transport. for the incpalpha plasmid rp4, a thorough sequence analysis of the gene products of the transfer regions tra1 and tra2 revealed typical features of mainly inner membrane proteins. we localized essential rp4 transfer functions to ...	2000	10692361
a gene cluster involved in metal homeostasis in the cyanobacterium synechocystis sp. strain pcc 6803.	a gene cluster composed of nine open reading frames (orfs) involved in ni(2+), co(2+), and zn(2+) sensing and tolerance in the cyanobacterium synechocystis sp. strain pcc 6803 has been identified. the cluster includes an ni(2+) response operon and a co(2+) response system, as well as a zn(2+) response system previously described. expression of the ni(2+) response operon (nrs) was induced in the presence of ni(2+) and co(2+). reduced ni(2+) tolerance was observed following disruption of two orfs ...	2000	10692354
functional analysis of pvds, an iron starvation sigma factor of pseudomonas aeruginosa.	in pseudomonas aeruginosa, iron modulates gene expression through a cascade of negative and positive regulatory proteins. the master regulator fur is involved in iron-dependent repression of several genes. one of these genes, pvds, was predicted to encode a putative sigma factor responsible for the transcription of a subset of genes of the fur regulon. pvds appears to belong to a structurally and functionally distinct subgroup of the extracytoplasmic function family of alternative sigma factors. ...	2000	10692351
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
signaling components in bacterial locomotion and sensory reception.		2000	10692349
patterns of protein synthesis and tolerance of anoxia in root tips of maize seedlings acclimated to a low-oxygen environment, and identification of proteins by mass spectrometry.	tolerance of anoxia in maize root tips is greatly improved when seedlings are pretreated with 2 to 4 h of hypoxia. we describe the patterns of protein synthesis during hypoxic acclimation and anoxia. we quantified the incorporation of [(35)s]methionine into total protein and 262 individual proteins under different oxygen tensions. proteins synthesized most rapidly under normoxic conditions continued to account for most of the proteins synthesized during hypoxic acclimation, while the production ...	2000	10677424
influence of mutations in the mexr repressor gene on expression of the mexa-mexb-oprm multidrug efflux system of pseudomonas aeruginosa.	several nalb-type multidrug-resistant mutants of pseudomonas aeruginosa overexpressed mexab-oprm and carried mutations in the local regulatory gene, mexr. others, dubbed nalc types, carried mutations elsewhere and overexpressed mexab-oprm less extensively than the nalb strains. available evidence showed that mexr acted solely as repressor. disruption of the mexr gene at various places suggested that the 5' end of mexr may be a part of the mexab-oprm promoter.	2000	10671465
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
the purmn genes of rhizobium leguminosarum and a superficial link with siderophore production.	we isolated a mutant of r. leguminosarum initially on the basis of reduced production of the siderophore vicibactin on chrome azurol sulfonate (cas)/agar indicator plates. the mutation was in the purmn operon and the mutant was shown to be an adenine auxotroph and defective for nodulation of peas. the siderophore defect appears to be trivial, being due to diminished growth of the auxotroph on agar-based minimal medium, which contains unknown contaminant(s) that allow it grow poorly. transcriptio ...	2000	10659713
bacterial activity in the rhizosphere analyzed at the single-cell level by monitoring ribosome contents and synthesis rates.	the growth activity of pseudomonas putida cells colonizing the rhizosphere of barley seedlings was estimated at the single-cell level by monitoring ribosomal contents and synthesis rates. ribosomal synthesis was monitored by using a system comprising a fusion of the ribosomal escherichia coli rrnbp1 promoter to a gene encoding an unstable variant of the green fluorescent protein (gfp). gfp expression in a p. putida strain carrying this system inserted into the chromosome was strongly dependent o ...	2000	10653754
genetic variation among endosymbionts of widely distributed vestimentiferan tubeworms.	vestimentiferan tubeworms thriving in sulfidic deep-sea hydrothermal vents and cold seeps are constrained by their nutritional reliance on chemoautotrophic endosymbionts. in a recent phylogenetic study using 16s ribosomal dna, we found that endosymbionts from vent and seep habitats form two distinct clades with little variation within each clade. in the present study, we used two different approaches to assess the genetic variation among biogeographically distinct vestimentiferan symbionts. dna ...	2000	10653731
mutagenesis and functional characterization of the glnb, glna, and nifa genes from the photosynthetic bacterium rhodospirillum rubrum.	nitrogen fixation is tightly regulated in rhodospirillum rubrum at two different levels: transcriptional regulation of nif expression and posttranslational regulation of dinitrogenase reductase by reversible adp-ribosylation catalyzed by the drat-drag (dinitrogenase reductase adp-ribosyltransferase-dinitrogenase reductase-activating glycohydrolase) system. we report here the characterization of glnb, glna, and nifa mutants and studies of their relationship to the regulation of nitrogen fixation. ...	2000	10648524
visn and visr are global regulators of chemotaxis, flagellar, and motility genes in sinorhizobium (rhizobium) meliloti.	the known 41 flagellar, chemotaxis, and motility genes of sinorhizobium (rhizobium) meliloti contained in the "flagellar regulon" are organized as seven operons and six transcription units that map to a contiguous 45-kb chromosomal region. by probing gene expression on western blots and with lacz fusions, we have identified two master regulatory genes, visn and visr, contained in one operon. the gene products probably form a heterodimer, visnr, acting as a global transcription activator of other ...	2000	10633114
bacteria are not what they eat: that is why they are so diverse.		2000	10629168
identification of cold shock gene loci in sinorhizobium meliloti by using a luxab reporter transposon.	using a luxab reporter transposon, seven mutants of sinorhizobium meliloti were identified as containing insertions in four cold shock loci. luxab activity was strongly induced (25- to 160-fold) after a temperature shift from 30 to 15 degrees c. the transposon and flanking host dna from each mutant was cloned, and the nucleic acid sequence of the insertion site was determined. unexpectedly, five of the seven luxab mutants contained transposon insertions in the 16s and 23s rrna genes of two of th ...	2000	10618254
transcriptional organization and regulation of a polycistronic cold shock operon in sinorhizobium meliloti rm1021 encoding homologs of the escherichia coli major cold shock gene cspa and ribosomal protein gene rpsu.	a homolog of the major eubacterial cold shock gene cspa was identified in sinorhizobium meliloti rm1021 by luxab reporter transposon mutagenesis. here we further characterize the organization and regulation of this locus. dna sequence analysis indicated that the locus includes three open reading frames (orfs) encoding homologs corresponding to cspa, a novel 10.6-kda polypeptide designated orf2, and a homolog of the escherichia coli ribosomal protein s21. transcription analysis indicated that thi ...	2000	10618253
a new chemolithoautotrophic arsenite-oxidizing bacterium isolated from a gold mine: phylogenetic, physiological, and preliminary biochemical studies.	a previously unknown chemolithoautotrophic arsenite-oxidizing bacterium has been isolated from a gold mine in the northern territory of australia. the organism, designated nt-26, was found to be a gram-negative motile rod with two subterminal flagella. in a minimal medium containing only arsenite as the electron donor (5 mm), oxygen as the electron acceptor, and carbon dioxide-bicarbonate as the carbon source, the doubling time for chemolithoautotrophic growth was 7.6 h. arsenite oxidation was f ...	2000	10618208
sequence analysis of the cryptic plasmid pmg101 from rhodopseudomonas palustris and construction of stable cloning vectors.	a 15-kb cryptic plasmid was obtained from a natural isolate of rhodopseudomonas palustris. the plasmid, designated pmg101, was able to replicate in r. palustris and in closely related strains of bradyrhizobium japonicum and phototrophic bradyrhizobium species. however, it was unable to replicate in the purple nonsulfur bacterium rhodobacter sphaeroides and in rhizobium species. the replication region of pmg101 was localized to a 3.0-kb sali-xhoi fragment, and this fragment was stably maintained ...	2000	10618203
the replicator of the nopaline-type ti plasmid ptic58 is a member of the repabc family and is influenced by the trar-dependent quorum-sensing regulatory system.	the replicator (rep) of the nopaline-type ti plasmid ptic58 is located adjacent to the trb operon of this conjugal element. previous genetic studies of this region (d. r. gallie, m. hagiya, and c. i. kado, j. bacteriol. 161:1034-1041, 1985) identified functions involved in partitioning, origin of replication and incompatibility, and copy number control. in this study, we determined the nucleotide sequence of a 6,146-bp segment that encompasses the rep locus of ptic58. the region contained four f ...	2000	10613878
proline catabolism by pseudomonas putida: cloning, characterization, and expression of the put genes in the presence of root exudates.	pseudomonas putida kt2442 is a root-colonizing strain which can use proline, one of the major components in root exudates, as its sole carbon and nitrogen source. a p. putida mutant unable to grow with proline as the sole carbon and nitrogen source was isolated after random mini-tn5-km mutagenesis. the mini-tn5 insertion was located at the puta gene, which is adjacent to and divergent from the putp gene. the puta gene codes for a protein of 1,315 amino acid residues which is homologous to the pu ...	2000	10613867
citrate synthase mutants of sinorhizobium meliloti are ineffective and have altered cell surface polysaccharides.	the glta gene, encoding sinorhizobium meliloti 104a14 citrate synthase, was isolated by complementing an escherichia coli glta mutant. the s. meliloti glta gene was mutated by inserting a kanamycin resistance gene and then using homologous recombination to replace the wild-type glta with the glta::kan allele. the resulting strain, csdx1, was a glutamate auxotroph, and enzyme assays confirmed the absence of a requirement for glutamate. csdx1 did not grow on succinate, malate, aspartate, pyruvate, ...	1999	10601220
rhizobium-legume symbiosis and nitrogen fixation under severe conditions and in an arid climate.	biological n(2) fixation represents the major source of n input in agricultural soils including those in arid regions. the major n(2)-fixing systems are the symbiotic systems, which can play a significant role in improving the fertility and productivity of low-n soils. the rhizobium-legume symbioses have received most attention and have been examined extensively. the behavior of some n(2)-fixing systems under severe environmental conditions such as salt stress, drought stress, acidity, alkalinit ...	1999	10585971
the basis of ammonium release in nifl mutants of azotobacter vinelandii.	in azotobacter vinelandii, nitrogen fixation is regulated at the transcriptional level by an unusual two-component system encoded by nifla. certain mutations in nifl result in the bacterium releasing large quantities of ammonium into the medium, and earlier work suggested that this occurs by a mechanism that does not involve nifa, the activator of nif gene transcription. we have investigated a number of possible alternative mechanisms and find no evidence for their involvement in ammonium releas ...	1999	10572141
a rhizobial homolog of ihf stimulates transcription of dcta in rhizobium leguminosarum but not in sinorhizobium meliloti.	sequence inspection identified several potential ihf binding sites adjacent to the rhizobium leguminosarum dcta promoter. ihf protected the -30 to -76 region from dnase i digestion, but systematic error in quantitative assays suggested that this protein dna interaction is complex. ihf stimulated dctd-mediated transcriptional activation from the r. leguminosarum dcta promoter both in vivo and in vitro. in contrast to r. leguminosarum dcta, the sinorhizobium meliloti dcta promoter region was found ...	1999	10570977
anaerobic growth of paracoccus denitrificans requires cobalamin: characterization of cobk and cobj genes.	a pleiotropic mutant of paracoccus denitrificans, which has a severe defect that affects its anaerobic growth when either nitrate, nitrite, or nitrous oxide is used as the terminal electron acceptor and which is also unable to use ethanolamine as a carbon and energy source for aerobic growth, was isolated. this phenotype of the mutant is expressed only during growth on minimal media and can be reversed by addition of cobalamin (vitamin b(12)) or cobinamide to the media or by growth on rich media ...	1999	10559155
glutathione and homoglutathione synthesis in legume root nodules.	high-performance liquid chromatography (hplc) with fluorescence detection was used to study thiol metabolism in legume nodules. glutathione (gsh) was the major non-protein thiol in all indeterminate nodules examined, as well as in the determinate nodules of cowpea (vigna unguiculata), whereas homoglutathione (hgsh) predominated in soybean (glycine max), bean (phaseolus vulgaris), and mungbean (vigna radiata) nodules. all nodules had greater thiol concentrations than the leaves and roots of the s ...	1999	10557236
a putative ecf sigma factor gene, rpol, regulates siderophore production in rhizobium leguminosarum.	a cloned rhizobium leguminosarum gene, termed rpoi, when transferred to wild-type strains, caused overproduction of the siderophore vicibactin. an rpoi mutant was defective in fe uptake but was unaffected in symbiotic n2 fixation. the rpoi gene product was similar in sequence to extra-cytoplasmic sigma factors of rna polymerase. transcription of rpoi was reduced in cells grown in medium that was replete with fe.	1999	10550895
identification of residues essential for a two-step reaction by malonyl-coa synthetase from rhizobium trifolii.	malonyl-coa synthetase (mcs) catalyses the formation of malonyl-coa in a two-step reaction consisting of the adenylation of malonate with atp followed by malonyl transfer from malonyl-amp to coa. in order to identify amino acid residues essential for each step of the enzyme, catalysis based on chemical modification and database analysis, arg-168, lys-170, and his-206 were selected for site-directed mutagenesis. glutathione-s-transferase-fused enzyme (gst-mcs) was constructed and mutagenized to m ...	1999	10548546
epitope identification for a panel of anti-sinorhizobium meliloti monoclonal antibodies and application to the analysis of k antigens and lipopolysaccharides from bacteroids.	in two published reports using monoclonal antibodies (mabs) generated against whole cells, olsen et al. showed that strain-specific antigens on the surface of cultured cells of sinorhizobium meliloti were diminished or absent in the endophytic cells (bacteroids) recovered from alfalfa nodules, whereas two common antigens were not affected by bacterial differentiation (p. olsen, m. collins, and w. rice, can. j. microbiol. 38:506-509, 1992; p. olsen, s. wright, m. collins, and w. rice, appl. envir ...	1999	10543844
protein-mediated adhesion of the dissimilatory fe(iii)-reducing bacterium shewanella alga bry to hydrous ferric oxide.	the rate and extent of bacterial fe(iii) mineral reduction are governed by molecular-scale interactions between the bacterial cell surface and the mineral surface. these interactions are poorly understood. this study examined the role of surface proteins in the adhesion of shewanella alga bry to hydrous ferric oxide (hfo). enzymatic degradation of cell surface polysaccharides had no effect on cell adhesion to hfo. the proteolytic enzymes streptomyces griseus protease and chymotrypsin inhibited t ...	1999	10543817
biochemical and genetic analyses of ferulic acid catabolism in pseudomonas sp. strain hr199.	the gene loci fcs, encoding feruloyl coenzyme a (feruloyl-coa) synthetase, ech, encoding enoyl-coa hydratase/aldolase, and aat, encoding beta-ketothiolase, which are involved in the catabolism of ferulic acid and eugenol in pseudomonas sp. strain hr199 (dsm7063), were localized on a dna region covered by two ecori fragments (e230 and e94), which were recently cloned from a pseudomonas sp. strain hr199 genomic library in the cosmid pvk100. the nucleotide sequences of parts of fragments e230 and e ...	1999	10543794
structural characterization of the symbiotically important low-molecular-weight succinoglycan of sinorhizobium meliloti.	the production of succinoglycan by sinorhizobium meliloti rm1021 is required for successful nodule invasion by the bacterium of its host plant, alfalfa. rm1021 produces succinoglycan, an acidic exopolysaccharide composed of an octasaccharide repeating unit modified with acetyl, succinyl, and pyruvyl moieties, in both low- and high-molecular-weight forms. low-molecular-weight (lmw) succinoglycan, previously thought to consist of monomers, trimers, and tetramers of the repeating unit, has been rep ...	1999	10542182
molecular characterization of the locus encoding biosynthesis of the lipopolysaccharide o antigen of escherichia coli serotype o113.	shiga toxigenic escherichia coli (stec) strains are a diverse group of organisms capable of causing severe gastrointestinal disease in humans. within the stec family, eae-positive stec strains, particularly those belonging to serogroups o157 and o111, appear to have greater virulence for humans. however, in spite of being eae negative, stec strains belonging to serogroup o113 have frequently been associated with cases of severe stec disease, including hemolytic-uremic syndrome (hus). western blo ...	1999	10531250
genotypic and phenotypic relationships between clinical and environmental isolates of stenotrophomonas maltophilia.	while the gram-negative bacterium stenotrophomonas maltophilia is used in biotechnology (e.g., for biological control of plant pathogens and for bioremediation), the number of s. maltophilia diseases in humans has dramatically increased in recent years. a total of 40 s. maltophilia isolates from clinical and environmental sources (plant associated and water) was investigated to determine the intraspecies diversity of the group and to determine whether or not the strains could be grouped based on ...	1999	10523559
expression of p(ii) and glutamine synthetase is regulated by p(ii), the ntrbc products, and processing of the glnba mrna in rhodospirillum rubrum.	we have studied the transcription of the glnb and glna genes in rhodospirillum rubrum with firefly luciferase as a reporter enzyme. under nh(4)(+) and n(2) conditions, glnba was cotranscribed from a weak and a strong promoter. in nitrogen-fixing cultures, activity of the latter was highly enhanced by ntrc, but transcription from both promoters occurred under both conditions. there is no promoter controlling transcription of glna alone, supporting our proposal that the glna mrna is produced by pr ...	1999	10515946
functional analysis of glycosyltransferase genes from lactococcus lactis and other gram-positive cocci: complementation, expression, and diversity.	sixteen exopolysaccharide (eps)-producing lactococcus lactis strains were analyzed for the chemical compositions of their epss and the locations, sequences, and organization of the eps genes involved in eps biosynthesis. this allowed the grouping of these strains into three major groups, representatives of which were studied in detail. previously, we have characterized the eps gene cluster of strain nizo b40 (group i) and determined the function of three of its glycosyltransferase (gtf) genes. f ...	1999	10515924
characterization of mext, the regulator of the mexe-mexf-oprn multidrug efflux system of pseudomonas aeruginosa.	we investigated the regulation of the mexef-oprn multidrug efflux system of pseudomonas aeruginosa, which is overexpressed in nfxc-type mutants and confers resistance to quinolones, chloramphenicol and trimethoprim. sequencing of the dna region upstream of the mexef-oprn operon revealed the presence of an open reading frame (orf) of 304 amino acids encoding a lysr-type transcriptional activator, termed mext. by using t7-polymerase, a 34-kda protein was expressed in escherichia coli from a plasmi ...	1999	10515918
opening the iron box: transcriptional metalloregulation by the fur protein.		1999	10515908
halomethane:bisulfide/halide ion methyltransferase, an unusual corrinoid enzyme of environmental significance isolated from an aerobic methylotroph using chloromethane as the sole carbon source.	a novel dehalogenating/transhalogenating enzyme, halomethane:bisulfide/halide ion methyltransferase, has been isolated from the facultatively methylotrophic bacterium strain cc495, which uses chloromethane (ch(3)cl) as the sole carbon source. purification of the enzyme to homogeneity was achieved in high yield by anion-exchange chromatography and gel filtration. the methyltransferase was composed of a 67-kda protein with a corrinoid-bound cobalt atom. the purified enzyme was inactive but was act ...	1999	10508052
rsmc of the soft-rotting bacterium erwinia carotovora subsp. carotovora negatively controls extracellular enzyme and harpin(ecc) production and virulence by modulating levels of regulatory rna (rsmb) and rna-binding protein (rsma).	previous studies have shown that the production of extracellular enzymes (pectate lyase [pel], polygalacturonase [peh], cellulase [cel], and protease [prt]) and harpin(ecc) (the elicitor of hypersensitive reaction) in erwinia carotovora subsp. carotovora is regulated by rsma, an rna-binding protein, and rsmb, a regulatory rna (rsm stands for regulator of secondary metabolites) (y. liu et al., mol. microbiol. 29:219-234, 1998). we have cloned and characterized a novel regulatory gene, rsmc, that ...	1999	10498717
effects of calcium and protons on the secondary structure of the nodulation protein nodo from rhizobium leguminosarum biovar viciae.	nodo, a 30-kda nodulation protein secreted by rhizobium leguminosarum biovar viciae, belongs to a family of proteins produced by gram-negative bacteria containing a variable number of glycine/aspartates nonapeptides. in some instances, these are organized into a parallel beta-roll structure and bind ca(2+) (one ion per repeat). to gain insight into nodo's secondary and tertiary structures, and their dependence upon ca(2+) binding, we performed fluorescence experiments and ftir spectroscopy. we f ...	1999	10491324
flavan-containing cells delimit frankia-infected compartments in casuarina glauca nodules.	we investigated the involvement of polyphenols in the casuarina glauca-frankia symbiosis. histological analysis revealed a cell-specific accumulation of phenolics in c. glauca nodule lobes, creating a compartmentation in the cortex. histochemical and biochemical analyses indicated that these phenolic compounds belong to the flavan class of flavonoids. we show that the same compounds were synthesized in nodules and uninfected roots. however, the amount of each flavan was dramatically increased in ...	1999	10482666
stress-induced legume root nodule senescence. physiological, biochemical, and structural alterations.	nitrate-fed and dark-stressed bean (phaseolus vulgaris) and pea (pisum sativum) plants were used to study nodule senescence. in bean, 1 d of nitrate treatment caused a partially reversible decline in nitrogenase activity and an increase in o(2) diffusion resistance, but minimal changes in carbon metabolites, antioxidants, and other biochemical parameters, indicating that the initial decrease in nitrogenase activity was due to o(2) limitation. in pea, 1 d of dark treatment led to a 96% decline in ...	1999	10482665
identification of a functional fur gene in bradyrhizobium japonicum.	the recent identification of the iron response regulator (irr) in bradyrhizobium japonicum raised the question of whether the global regulator fur is present in that organism. a fur gene homolog was isolated by the functional complementation of an escherichia coli fur mutant. the b. japonicum fur bound to a fur box dna element in vitro, and a fur mutant grown in iron-replete medium was derepressed for iron uptake activity. thus, b. japonicum expresses at least two regulators of iron metabolism.	1999	10482529
involvement of the cis/trans isomerase cti in solvent resistance of pseudomonas putida dot-t1e.	pseudomonas putida dot-t1e is a solvent-resistant strain that is able to grow in the presence of high concentrations of toluene. we have cloned and sequenced the cti gene of this strain, which encodes the cis/trans isomerase, termed cti, that catalyzes the cis-trans isomerization of esterified fatty acids in phospholipids, mainly cis-oleic acid (c(16:1,9)) and cis-vaccenic acid (c(18:1,11)), in response to solvents. to determine the importance of this cis/trans isomerase for solvent resistance a ...	1999	10482510
positive transcriptional feedback controls hydrogenase expression in alcaligenes eutrophus h16.	the protein hoxa is the central regulator of the alcaligenes eutrophus h16 hox regulon, which encodes two hydrogenases, a nickel permease and several accessory proteins required for hydrogenase biosynthesis. expression of the regulatory gene hoxa was analyzed. screening of an 8-kb region upstream of hoxa with a promoter probe vector localized four promoter activities. one of these was found in the region immediately 5' of hoxa; the others were correlated with the nickel metabolism genes hypa1, h ...	1999	10482509
inactivation and regulation of the aerobic c(4)-dicarboxylate transport (dcta) gene of escherichia coli.	the gene (dcta) encoding the aerobic c(4)-dicarboxylate transporter (dcta) of escherichia coli was previously mapped to the 79-min region of the linkage map. the nucleotide sequence of this region reveals two candidates for the dcta gene: f428 at 79.3 min and the o157a-o424-o328 (or orfqmp) operon at 79.9 min. the f428 gene encodes a homologue of the sinorhizobium meliloti and rhizobium leguminosarum h(+)/c(4)-dicarboxylate symporter, dcta, whereas the orfqmp operon encodes homologues of the aer ...	1999	10482502
identification of a plasmid-borne locus in rhizobium etli kim5s involved in lipopolysaccharide o-chain biosynthesis and nodulation of phaseolus vulgaris.	screening of derivatives of rhizobium etli kim5s randomly mutagenized with mtn5ssgusa30 resulted in the identification of strain kim-g1. its rough colony appearance, flocculation in liquid culture, and ndv(-) fix(-) phenotype were indicative of a lipopolysaccharide (lps) defect. electrophoretic analysis of cell-associated polysaccharides showed that kim-g1 produces only rough lps. composition analysis of purified lps oligosaccharides from kim-g1 indicated that it produces an intact lps core tris ...	1999	10482500
metabolism and genetics of helicobacter pylori: the genome era.	the publication of the complete sequence of helicobacter pylori 26695 in 1997 and more recently that of strain j99 has provided new insight into the biology of this organism. in this review, we attempt to analyze and interpret the information provided by sequence annotations and to compare these data with those provided by experimental analyses. after a brief description of the general features of the genomes of the two sequenced strains, the principal metabolic pathways are analyzed. in particu ...	1999	10477311
identification of nodulation promoter (nod-box) regions of rhizobium galegae.	a hybridisation analysis of a genomic clone library of rhizobium galegae hambi 1174 located four ecori fragments homologous to the nod-box promoter sequence of sinorhizobium meliloti in two separate gene regions. two of the five nod-boxes detected in the r. galegae genome were carried on a single cosmid clone, prg30, upstream from the nodabcij and nodf genes, whereas the other three nod-boxes were carried on a different cosmid clone, prg10. hybridisations with various nod gene probes from s. mel ...	1999	10474187
characterization of a pseudomonas aeruginosa fatty acid biosynthetic gene cluster: purification of acyl carrier protein (acp) and malonyl-coenzyme a:acp transacylase (fabd).	a dna fragment containing the pseudomonas aeruginosa fabd (encoding malonyl-coenzyme a [coa]:acyl carrier protein [acp] transacylase), fabg (encoding beta-ketoacyl-acp reductase), acpp (encoding acp), and fabf (encoding beta-ketoacyl-acp synthase ii) genes was cloned and sequenced. this fab gene cluster is delimited by the plsx (encoding a poorly understood enzyme of phospholipid metabolism) and pabc (encoding 4-amino-4-deoxychorismate lyase) genes; the fabf and pabc genes seem to be translation ...	1999	10464226
mutations affecting motifs of unknown function in the central domain of nitrogen regulatory protein c.	the positive control function of the bacterial enhancer-binding protein ntrc resides in its central domain, which is highly conserved among activators of sigma54 holoenzyme. previous studies of a small set of mutant forms specifically defective in transcriptional activation, called ntrc repressor [ntrc(rep)] proteins, had enabled us to locate various functional determinants in the central domain. in this more comprehensive survey, the dna encoding a major portion of the central domain was random ...	1999	10464219
reduction of adenosine-5'-phosphosulfate instead of 3'-phosphoadenosine-5'-phosphosulfate in cysteine biosynthesis by rhizobium meliloti and other members of the family rhizobiaceae.	we have cloned and sequenced three genes from rhizobium meliloti (sinorhizobium meliloti) that are involved in sulfate activation for cysteine biosynthesis. two of the genes display homology to the escherichia coli cysdn genes, which code for an atp sulfurylase (ec 2.7.7.4). the third gene has homology to the e. coli cysh gene, a 3'-phosphoadenosine-5'-phosphosulfate (paps) reductase (ec 1.8.99.4), but has greater homology to a set of genes found in arabidopsis thaliana that encode an adenosine- ...	1999	10464198
identification and characterization of hupt, a gene involved in negative regulation of hydrogen oxidation in bradyrhizobium japonicum.	the bradyrhizobium japonicum hupt gene was sequenced, and its gene product was found to be homologous to ntrb-like histidine kinases. a hupt mutant expresses higher levels of hydrogenase activity than the wild-type strain under hydrogenase-inducing conditions (i.e., microaerobiosis plus hydrogen, or symbiosis), whereas in noninduced hupt cells, hupsl expression is derepressed but does not lead to hydrogenase activity. we conclude that hupt is involved in the repression of hupsl synthesis at the ...	1999	10438783
the pseudomonas aeruginosa exotoxin a regulatory gene, ptxs: evidence for negative autoregulation.	we have previously described a pseudomonas aeruginosa gene, ptxr, which enhances exotoxin a production at the transcriptional level. we have also described another gene, ptxs, which is transcribed divergently from ptxr and interferes with the enhancement of exotoxin a synthesis by ptxr. however, the mechanisms through which ptxr and/or ptxs are regulated is not known. in this study, we attempted (by using the dna gel shift assay) to determine if p. aeruginosa contains a potential regulatory prot ...	1999	10438759
genome signature comparisons among prokaryote, plasmid, and mitochondrial dna.	our basic observation is that each genome has a characteristic "signature" defined as the ratios between the observed dinucleotide frequencies and the frequencies expected if neighbors were chosen at random (dinucleotide relative abundances). the remarkable fact is that the signature is relatively constant throughout the genome; i.e. , the patterns and levels of dinucleotide relative abundances of every 50-kb segment of the genome are about the same. comparison of the signatures of different gen ...	1999	10430917
the viable-but-nonculturable condition is induced by copper in agrobacterium tumefaciens and rhizobium leguminosarum.	many bacteria respond to changes in environmental conditions by entering the viable-but-nonculturable state. we have determined that copper can induce nutrient-starved agrobacterium tumefaciens and rhizobium leguminosarum cells to become viable but nonculturable. this is the first report of a chemical inducer of this condition.	1999	10427081
genetic structure of natural populations of escherichia coli in wild hosts on different continents.	current knowledge of genotypic and phenotypic diversity in the species escherichia coli is based almost entirely on strains recovered from humans or zoo animals. in this study, we analyzed a collection of 202 strains obtained from 81 mammalian species representing 39 families and 14 orders in australia and the americas, as well as several reference strains; we also included a strain from a reptile and 10 from different families of birds collected in mexico. the strains were characterized genotyp ...	1999	10427022
abundance and diversity of archaea in heavy-metal-contaminated soils.	the impact of heavy-metal contamination on archaean communities was studied in soils amended with sewage sludge contaminated with heavy metals to varying extents. fluorescent in situ hybridization showed a decrease in the percentage of archaea from 1.3% +/- 0.3% of 4', 6-diamidino-2-phenylindole-stained cells in untreated soil to below the detection limit in soils amended with heavy metals. a comparison of the archaean communities of the different plots by denaturing gradient gel electrophoresis ...	1999	10427009
[effect of the addition of specific lectin on the symbiosis of rhizobium leguminosarum and phaseolus vulgaris].	the effect of specific lectin addition on rhizobium leguminosarum-phaseolus vulgaris symbiosis characteristics was studied. two alternatives were selected for comparison: a) p. vulgaris seedling roots treated with lectin were inoculated with r. leguminosarum and b) p. vulgaris seedling roots were inoculated with r. leguminosarum incubated with lectin for 3 h and 72 h. the following parameters were evaluated: number and dry weight of nodules and dry matter and nitrogen content of shoot. in lectin ...	1999	10425662
mgatp binding and hydrolysis determinants of ntrc, a bacterial enhancer-binding protein.	when phosphorylated, the dimeric form of nitrogen regulatory protein c (ntrc) of salmonella typhimurium forms a larger oligomer(s) that can hydrolyze atp and hence activate transcription by the sigma(54)-holoenzyme form of rna polymerase. studies of mg-nucleoside triphosphate binding using a filter-binding assay indicated that phosphorylation is not required for nucleotide binding but probably controls nucleotide hydrolysis per se. studies of binding by isothermal titration calorimetry indicated ...	1999	10419963
cloning, sequencing, and characterization of the cgmb gene of sinorhizobium meliloti involved in cyclic beta-glucan biosynthesis.	periplasmic cyclic beta-glucans of rhizobium species provide important functions during plant infection and hypo-osmotic adaptation. in sinorhizobium meliloti (also known as rhizobium meliloti), these molecules are highly modified with phosphoglycerol and succinyl substituents. we have previously identified an s. meliloti tn5 insertion mutant, s9, which is specifically impaired in its ability to transfer phosphoglycerol substituents to the cyclic beta-glucan backbone (m. w. breedveld, j. a. hadl ...	1999	10419956
characterization of the serogroup o11 o-antigen locus of pseudomonas aeruginosa pa103.	we previously cloned a genomic dna fragment from the serogroup o11 pseudomonas aeruginosa strain pa103 that contained all genes necessary for o-antigen synthesis and directed the expression of serogroup o11 antigen on recombinant escherichia coli and salmonella. to elucidate the pathway of serogroup o11 antigen synthesis, the nucleotide sequence of the biosynthetic genes was determined. eleven open reading frames likely to be involved in serogroup o11 o-antigen biosynthesis were identified and a ...	1999	10400585
a novel sinorhizobium meliloti operon encodes an alpha-glucosidase and a periplasmic-binding-protein-dependent transport system for alpha-glucosides.	the most abundant carbon source transported into legume root nodules is photosynthetically produced sucrose, yet the importance of its metabolism by rhizobia in planta is not yet known. to identify genes involved in sucrose uptake and hydrolysis, we screened a sinorhizobium meliloti genomic library and discovered a segment of s. meliloti dna which allows ralstonia eutropha to grow on the alpha-glucosides sucrose, maltose, and trehalose. tn5 mutagenesis localized the required genes to a 6.8-kb re ...	1999	10400573
sucrose synthase in legume nodules is essential for nitrogen fixation	the role of sucrose synthase (ss) in the fixation of n was examined in the rug4 mutant of pea (pisum sativum l.) plants in which ss activity was severely reduced. when dependent on nodules for their n supply, the mutant plants were not viable and appeared to be incapable of effective n fixation, although nodule formation was essentially normal. in fact, n and c resources invested in nodules were much greater in mutant plants than in the wild-type (wt) plants. low ss activity in nodules (present ...	1999	10398723
molecular characterization and symbiotic importance of prsd gene of rhizobium leguminosarum bv. trifolii ta1.	the prsd, prse and orf3 genes of rhizobium leguminosarum bv. trifolii strain ta1 encode the proteins which are significantly related to the family of bacterial abc transporters type i secretion systems. the prsd:km(r) mutant of strain ta1 induced non-nitrogen-fixing nodules on trifolium pratense. microscopic analysis of the nodules induced by prsd mutant did not reveal major abberations in the bacteroid appearance. the exopolysaccharide of prsd mutant was produced in increased amount and its lev ...	1998	10397353
occurrence of lipopolysaccharide alterations among tn5 mutants of rhizobium leguminosarum bv. trifolii strain 24.1 with altered colony morphology.	transposon mutants of rhizobium leguminosarum bv. trifolii 24.1 showing less glossy or smaller colonies were screened for properties usually associated with lipopolysaccharide (lps) defects in r. leguminosarum, i.e. motility, growth rate, tendency to agglutination in liquid media and symbiotic efficiency. neither any of the above mutants nor the earlier isolated 24.12 strain, defective in lps, showed all these properties changed simultaneously. according to page/sodium deoxycholate analysis the ...	1998	10397346
brucella outer membrane lipoproteins share antigenic determinants with bacteria of the family rhizobiaceae.	brucellae have been reported to be phylogenetically related to bacteria of the family rhizobiaceae. in the present study, we used a panel of monoclonal antibodies (mabs) to brucella outer membrane proteins (omps) to determine the presence of common omp epitopes in some representative bacteria of this family, i.e., ochrobactrum anthropi, phyllobacterium rubiacearum, rhizobium leguminosarum, and agrobacterium tumefaciens, and also in bacteria reported to serologically cross-react with brucella, i. ...	1999	10391877