| the pleiotropic nature of symbiotic regulatory mutants: bradyrhizobium japonicum nifa gene is involved in control of nif gene expression and formation of determinate symbiosis. | in the slow-growing soybean symbiont, bradyrhizobium japonicum (strain 110), a nifa-like regulatory gene was located immediately upstream of the previously mapped fixa gene. by interspecies hybridization and partial dna sequencing the gene was found to be homologous to nifa from klebsiella pneumoniae and rhizobium meliloti, and to a lesser extent, also to ntrc from k. pneumoniae. the b. japonicum nifa gene product was shown to activate b. japonicum and k. pneumoniae nif promoters (using nif::lac ... | 1986 | 15966104 |
| inactivation of the pst system reduces the virulence of an avian pathogenic escherichia coli o78 strain. | escherichia coli o78 strains are frequently associated with extraintestinal diseases, such as airsacculitis and septicemia, in poultry, livestock, and humans. to understand the influence of the pst operon in the virulence of e. coli, we introduced mutations into the pst genes of the avian pathogenic e. coli (apec) o78:k80 strain chi7122 by allelic exchange. the mutation of pst genes led to the constitutive expression of the pho regulon. furthermore, the virulence of apec strain chi7122 in a chic ... | 2005 | 15972503 |
| brigep--the bridge-based genome-transcriptome-proteome browser. | the growing amount of information resulting from the increasing number of publicly available genomes and experimental results thereof necessitates the development of comprehensive systems for data processing and analysis. in this paper, we describe the current state and latest developments of our brigep bioinformatics software system consisting of three web-based applications: gendb, emma and prodb. these applications facilitate the processing and analysis of bacterial genome, transcriptome and ... | 2005 | 15980569 |
| the mrp system: a giant among monovalent cation/proton antiporters? | mrp systems are a novel and broadly distributed type of monovalent cation/proton antiporter of bacteria and archaea. monovalent cation/proton antiporters are membrane transport proteins that catalyze efflux of cytoplasmic sodium, potassium or lithium ions in exchange for external hydrogen ions (protons). other known monovalent cation antiporters are single gene products, whereas mrp systems have been proposed to function as hetero-oligomers. a mrp operon typically has six or seven genes encoding ... | 2005 | 15980940 |
| [the expression of gene related to salt tolerance from sinorhizobium meliloti 042bm in escherichia coli and purification of its fusion protein]. | a 1.9kb dna fragment related to salt tolerance of s. meliloti strain 042bm containing two open reading frames were obtained by pcr amplification and ligated into shuttle vector pbbr1-mcs2. the complementation experiment showed that orf2 is related to salt tolerance and named as rsta gene. then the gene was cloned into the expression vector pthio-hisa, b and c, respectively, and recombinant expression vectors pgsa, pgb and pgc were constructed, and transformed into e. coli top10. inducing by iptg ... | 2005 | 15989246 |
| citrate synthase mutants of agrobacterium are attenuated in virulence and display reduced vir gene induction. | a citrate synthase (cs) deletion mutant of agrobacterium tumefaciens c58 is highly attenuated in virulence. the identity of the mutant was initially determined from its amino acid sequence, which is 68% identical to escherichia coli and 77% identical to brucella melitensis. the mutant lost all cs enzymatic activity, and a cloned cs gene complemented a cs mutation in sinorhizobium. the cs mutation resulted in a 10-fold reduction in vir gene expression, which likely accounts for the attenuated vir ... | 2005 | 15995199 |
| a conserved mechanism for sulfonucleotide reduction. | sulfonucleotide reductases are a diverse family of enzymes that catalyze the first committed step of reductive sulfur assimilation. in this reaction, activated sulfate in the context of adenosine-5'-phosphosulfate (aps) or 3'-phosphoadenosine 5'-phosphosulfate (paps) is converted to sulfite with reducing equivalents from thioredoxin. the sulfite generated in this reaction is utilized in bacteria and plants for the eventual production of essential biomolecules such as cysteine and coenzyme a. hum ... | 2005 | 16008502 |
| soil nematodes mediate positive interactions between legume plants and rhizobium bacteria. | symbiosis between legume species and rhizobia results in the sequestration of atmospheric nitrogen into ammonium, and the early mechanisms involved in this symbiosis have become a model for plant-microbe interactions and thus highly amenable for agricultural applications. the working model for this interaction states that the symbiosis is the outcome of a chemical/molecular dialogue initiated by flavonoids produced by the roots of legumes and released into the soil as exudates, which specificall ... | 2005 | 16025342 |
| unusual group ii introns in bacteria of the bacillus cereus group. | a combination of sequence and structure analysis and reverse transcriptase pcr experiments was used to characterize the group ii introns in the complete genomes of two strains of the pathogen bacillus cereus. while b. cereus atcc 14579 harbors a single intron element in the chromosome, b. cereus atcc 10987 contains three introns in the chromosome and four in its 208-kb pbc10987 plasmid. the most striking finding is the presence in b. cereus atcc 10987 of an intron [b.c.i2(a)] located on the reve ... | 2005 | 16030238 |
| the lipopolysaccharide of brucella abortus bvrs/bvrr mutants contains lipid a modifications and has higher affinity for bactericidal cationic peptides. | the two-component bvrs/bvrr system is essential for brucella abortus virulence. it was shown previously that its dysfunction abrogates expression of some major outer membrane proteins and increases bactericidal peptide sensitivity. here, we report that bvrs/bvrr mutants have increased surface hydrophobicity and susceptibility to killing by nonimmune serum. the bvrs and bvrr mutant lipopolysaccharides (lpss) bound more polymyxin b, chimeras constructed with bvrs mutant cells and parental lps show ... | 2005 | 16077108 |
| flig subunit arrangement in the flagellar rotor probed by targeted cross-linking. | flig is a component of the switch complex on the rotor of the bacterial flagellum. each flagellar motor contains about 25 flig molecules. the protein of escherichia coli has 331 amino acid residues and comprises at least two discrete domains. a c-terminal domain of about 100 residues functions in rotation and includes charged residues that interact with the stator protein mota. other parts of the flig protein are essential for flagellar assembly and interact with the ms ring protein flif and the ... | 2005 | 16077109 |
| carboxyl-terminal protease regulates brucella suis morphology in culture and persistence in macrophages and mice. | the putative carboxyl-terminal processing protease (ctpa) of brucella suis 1330 is a member of a novel family of endoproteases involved in the maturation of proteins destined for the cell envelope. the b. suis ctpa protein shared up to 77% homology with ctpa proteins of other bacteria. a ctpa-deficient brucella strain (1330deltactpa), generated by allelic exchange, produced smaller colonies on enriched agar plates and exhibited a 50% decrease in growth rate in enriched liquid medium and no growt ... | 2005 | 16077124 |
| transcriptome-based identification of the sinorhizobium meliloti nodd1 regulon. | the nodd1 regulon of sinorhizobium meliloti was determined through the analysis of the s. meliloti transcriptome in response to the plant flavone luteolin and the overexpression of nodd1. nine new genes regulated by both nodd1 and luteolin were identified, demonstrating that nodd1 controls few functions behind nodulation in s. meliloti. | 2005 | 16085895 |
| properties of motility in bacillus subtilis powered by the h+-coupled motab flagellar stator, na+-coupled motps or hybrid stators motas or motpb. | bacillus subtilis has a single set of flagellar rotor proteins that interact with two distinct stator-force generators, the h+-coupled motab complex and the na+-coupled motps complex, that energize rotation. here, motility on soft agar plates and in liquid was assayed in wild-type b.subtilis and strains expressing only one stator, either motab, motps or hybrid motas or motpb. the strains expressing motab or motas had an average of 11 flagella/cell while those expressing motps or motpb had an ave ... | 2005 | 16095621 |
| phosphoenolpyruvate carboxykinase is an acid-induced, chromosomally encoded virulence factor in agrobacterium tumefaciens. | the pcka gene, encoding phosphoenolpyruvate carboxykinase, catalyzes the reversible decarboxylation and phosphorylation of oxaloacetate to form phosphoenolpyruvate. located on the circular chromosome of agrobacterium, this locus is adjacent to the loci chvg and chvi, encoding a two-component regulatory system that has been shown to be important in virulence. using a reporter gene fusion, studies showed that the pcka gene is induced by acidic ph but not by acetosyringone. this acid induction is r ... | 2005 | 16109945 |
| individual subunits of the glutamate transporter eaac1 homotrimer function independently of each other. | glutamate transporters are thought to be assembled as trimers of identical subunits that line a central hole, possibly the permeation pathway for anions. here, we have tested the effect of multimerization on the transporter function. to do so, we coexpressed eaac1(wt) with the mutant transporter eaac1(r446q), which transports glutamine but not glutamate. application of 50 microm glutamate or 50 microm glutamine to cells coexpressing similar numbers of both transporters resulted in anion currents ... | 2005 | 16128593 |
| two-component signal transduction pathways regulating growth and cell cycle progression in a bacterium: a system-level analysis. | two-component signal transduction systems, comprised of histidine kinases and their response regulator substrates, are the predominant means by which bacteria sense and respond to extracellular signals. these systems allow cells to adapt to prevailing conditions by modifying cellular physiology, including initiating programs of gene expression, catalyzing reactions, or modifying protein-protein interactions. these signaling pathways have also been demonstrated to play a role in coordinating bact ... | 2005 | 16176121 |
| vira and virg activate the ti plasmid repabc operon, elevating plasmid copy number in response to wound-released chemical signals. | the vir genes of agrobacterium tumefaciens tumor-inducing (ti) plasmids direct the transfer of oncogenic portion of the ti (tumor-inducing) plasmid that is transferred to plant cells (t-dna) into plant cells and are coordinately induced by plant-released phenolic chemical signals. we have used dna microarrays, representing all genes of the octopine- and nopaline-type ti plasmids, to identify all ti-plasmid-encoded genes in the vir regulons of both plasmids. acetosyringone (as) induced the expres ... | 2005 | 16195384 |
| novel pathway for arsenic detoxification in the legume symbiont sinorhizobium meliloti. | we report a novel pathway for arsenic detoxification in the legume symbiont sinorhizobium meliloti. although a majority of ars operons consist of three genes, arsr (transcriptional regulator), arsb [as(oh)3/h+ antiporter], and arsc (arsenate reductase), the s. meliloti ars operon includes an aquaglyceroporin (aqps) in place of arsb. the presence of aqps in an arsenic resistance operon is interesting, since aquaglyceroporin channels have previously been shown to adventitiously facilitate uptake o ... | 2005 | 16199569 |
| replication regions of sinorhizobium meliloti plasmids. | the replication (rep) regions of small plasmids from three sinorhizobium meliloti strains were cloned by marker rescue. two unique replication regions were identified, one of which was common to two different strains. plasmid pbb83 carried a 7.2 kbp rep region from a 42 kbp plasmid, and pbb84 carried a 4.5 kbp rep region from a 36 kbp plasmid. the cloned rep regions were of different compatibility types, and were capable of displacing their parent plasmids from s. meliloti. neither could functio ... | 2006 | 16202450 |
| role of the regulatory gene rira in the transcriptional response of sinorhizobium meliloti to iron limitation. | a regulatory network of sinorhizobium meliloti genes involved in adaptation to iron-limiting conditions and the involvement of the rhizobial iron regulator gene (rira) were analyzed by mutation and microarray analyses. a constructed s. meliloti rira mutant exhibited growth defects and enhanced h2o2 sensitivity in the presence of iron, but symbiotic nitrogen fixation was not affected. to identify iron-responsive and rira-regulated s. meliloti genes, a transcriptome approach using whole-genome mic ... | 2005 | 16204511 |
| single-site mutations on the catalase-peroxidase from sinorhizobium meliloti: role of the distal gly and the three amino acids of the putative intrinsic cofactor. | katb is the only catalase-peroxidase identified so far in sinorhizobium meliloti. it plays a housekeeping role, as it is expressed throughout all the growth phases of the free-living bacterium and also during symbiosis. this paper describes the functional and structural characterization of the katb mutants gly303ser, trp95ala, trp95phe, tyr217leu, tyr217phe and met243val carried out by optical and electron spin resonance spectroscopy. the aim of this work was to investigate the involvement of th ... | 2005 | 16217641 |
| sas solution structures of the apo and mg2+/bef3(-)-bound receiver domain of dctd from sinorhizobium meliloti. | two-component signal transduction is the predominant information processing mechanism in prokaryotes and is also present in single-cell eukaryotes and higher plants. a phosphorylation-based switch is commonly used to activate as many as 40 different types of output domains in more than 6000 two-component response regulators that can be identified in the sequence databases. previous biochemical and crystallographic studies showed that phosphorylation of the two-component receiver domain of dctd c ... | 2005 | 16229485 |
| evolutionary, structural and functional relationships revealed by comparative analysis of syntenic genes in rhizobiales. | comparative genomics has provided valuable insights into the nature of gene sequence variation and chromosomal organization of closely related bacterial species. however, questions about the biological significance of gene order conservation, or synteny, remain open. moreover, few comprehensive studies have been reported for rhizobial genomes. | 2005 | 16229745 |
| plasmid-associated genes in the model micro-symbiont sinorhizobium meliloti 1021 affect the growth and development of young rice seedlings. | sinorhizobium meliloti strain 1021 and its closely related strain rm2011 inhibit rice seedling (oryza sativa l. cv. pelde) growth and development under certain rice-growing conditions. experiments showed that inoculation of seedlings with approximately less than 10 cells of 1021 was sufficient to cause this inhibition. by using a series of plasmid-cured and plasmid-deleted derivatives of rm2011, it was found that interactions between genes encoded on psyma, and possibly psymb, of rm2011, affecte ... | 2005 | 16232297 |
| complete cdna sequence of chitin deacetylase from gongronella butleri and its phylogenetic analysis revealed clusters corresponding to taxonomic classification of fungi. | a cdna library containing a chitin deacetylase (cda) gene from a zygomycete gongronella butleri was constructed and the complete gene was sequenced. the complete gene contains an open reading frame of 1290 nucleotides which encodes a sequence of 430 amino acid residues. the gene sequence consists of nucleotides encoding a polysaccharide deacetylase domain located in the middle, covering 34% of the entire sequence. this domain shares high sequence similarities with cdas of fungi and other deacety ... | 2002 | 16233217 |
| diversification of dna sequences in the symbiotic genome of rhizobium etli. | bacteria of the genus rhizobium and related genera establish nitrogen-fixing symbioses with the roots of leguminous plants. the genetic elements that participate in the symbiotic process are usually compartmentalized in the genome, either as independent replicons (symbiotic plasmids) or as symbiotic regions or islands in the chromosome. the complete nucleotide sequence of the symbiotic plasmid of rhizobium etli model strain cfn42, symbiont of the common bean plant, has been reported. to better u ... | 2005 | 16237002 |
| identification of the rcta gene, which is required for repression of conjugative transfer of rhizobial symbiotic megaplasmids. | an analysis of the conjugative transfer of pretcfn42d, the symbiotic plasmid (psym) of rhizobium etli, has revealed a novel gene, rcta, as an essential element of a regulatory system for silencing the conjugative transfer of r. etli psym by repressing the transcription of conjugal transfer genes in standard laboratory media. the rcta gene product lacks sequence conservation with other proteins of known function but may belong to the winged-helix dna-binding subfamily of transcriptional regulator ... | 2005 | 16237017 |
| cpse from type 2 streptococcus pneumoniae catalyzes the reversible addition of glucose-1-phosphate to a polyprenyl phosphate acceptor, initiating type 2 capsule repeat unit formation. | the majority of the 90 capsule types made by the gram-positive pathogen streptococcus pneumoniae are assembled by a block-type mechanism similar to that utilized by the wzy-dependent o antigens and capsules of gram-negative bacteria. in this mechanism, initiation of repeat unit formation occurs by the transfer of a sugar to a lipid acceptor. in s. pneumoniae, this step is catalyzed by cpse, a protein conserved among the majority of capsule types. membranes from s. pneumoniae type 2 strain d39 an ... | 2005 | 16237026 |
| a lux-like quorum sensing system in the extreme acidophile acidithiobacillus ferrooxidans. | the genome of the acidophilic, proteobacterium acidithiobacillusferrooxidans, contains linked but divergently oriented genes, termed afel and afer, whose predicted protein products are significantly similar to the luxi and luxr families of proteins. a possible promoter and lux box are predicted upstream of afel. a cloned copy of afel, expressed in e. coli, encodes an enzyme that catalyzes the production of a diffusible compound identified by gas chromatography and mass spectrometry as an unsubst ... | 2005 | 16238107 |
| phosphate limitation induces catalase expression in sinorhizobium meliloti, pseudomonas aeruginosa and agrobacterium tumefaciens. | growth of sinorhizobium meliloti under pi-limiting conditions induced expression of the major h2o2-inducible catalase (hpii) gene (kata) in this organism. this transcription required the phob transcriptional regulator and initiated from a promoter that was distinct from the oxyr-dependent promoter which activates kata transcription in response to addition of h2o2. in n2-fixing root nodules, kata was transcribed from the oxyr- and not the phob-dependent promoter. this is consistent with the accum ... | 2005 | 16238634 |
| a study of archaeal enzymes involved in polar lipid synthesis linking amino acid sequence information, genomic contexts and lipid composition. | cellular membrane lipids, of which phospholipids are the major constituents, form one of the characteristic features that distinguish archaea from other organisms. in this study, we focused on the steps in archaeal phospholipid synthetic pathways that generate polar lipids such as archaetidylserine, archaetidylglycerol, and archaetidylinositol. only archaetidylserine synthase (ass), from methanothermobacter thermautotrophicus, has been experimentally identified. other enzymes have not been fully ... | 2005 | 16243780 |
| molecular cloning and biochemical characterization of l-n-carbamoylase from sinorhizobium meliloti cect4114. | an n-carbamoyl-l-amino acid amidohydrolase (l-n-carbamoylase) from sinorhizobium meliloti cect 4114 was cloned and expressed in escherichia coli. the recombinant enzyme catalyzed the hydrolysis of n-carbamoyl alpha-amino acid to the corresponding free amino acid, and its purification has shown it to be strictly l-specific. the enzyme showed broad substrate specificity, and it is the first l-n-carbamoylase that hydrolyses n-carbamoyl-l-tryptophan as well as n-carbamoyl l-amino acids with aliphati ... | 2005 | 16254442 |
| nitrogen reserves, spring regrowth and winter survival of field-grown alfalfa (medicago sativa) defoliated in the autumn. | the objective of the study was to characterize variations in proline, arginine, histidine, vegetative storage proteins, and cold-inducible gene expression in overwintering roots of field-grown alfalfa, in response to autumn defoliation, and in relation to spring regrowth and winter survival. | 2006 | 16260440 |
| gene expression patterns and catalytic properties of udp-d-glucose 4-epimerases from barley (hordeum vulgare l.). | uge (udp-glc 4-epimerase or udp-gal 4-epimerase; ec 5.1.3.2) catalyses the interconversion of udp-gal and udp-glc. both nucleotide sugars act as activated sugar donors for the biosynthesis of cell wall polysaccharides such as cellulose, xyloglucans, (1,3;1,4)-beta-d-glucan and pectins, together with other biologically significant compounds including glycoproteins and glycolipids. three members of the hvuge (barley uge) gene family, designated hvuge1, hvuge2 and hvuge3, have been characterized. q ... | 2006 | 16266295 |
| diversity of "candidatus liberibacter asiaticus," based on the omp gene sequence. | huanglongbing (yellow dragon disease) is a destructive disease of citrus. the etiological agent is a noncultured, phloem-restricted alpha-proteobacterium, "candidatus liberibacter africanus" in africa and "candidatus liberibacter asiaticus" in asia. in this study, we used an omp-based pcr-restriction fragment length polymorphism (rflp) approach to analyze the genetic variability of "ca. liberibacter asiaticus" isolates. by using five different enzymes, each the 10 isolates tested could be associ ... | 2005 | 16269671 |
| bacteria associated with spores of the arbuscular mycorrhizal fungi glomus geosporum and glomus constrictum. | spores of the arbuscular mycorrhizal fungi (amf) glomus geosporum and glomus constrictum were harvested from single-spore-derived pot cultures with either plantago lanceolata or hieracium pilosella as host plants. pcr-denaturing gradient gel electrophoresis analysis revealed that the bacterial communities associated with the spores depended more on amf than host plant identity. the composition of the bacterial populations linked to the spores could be predominantly influenced by a specific spore ... | 2005 | 16269696 |
| polyphenol oxidase activity expression in ralstonia solanacearum. | sequencing of the genome of ralstonia solanacearum revealed several genes that putatively code for polyphenol oxidases (ppos). to study the actual expression of these genes, we looked for and detected all kinds of ppo activities, including laccase, cresolase, and catechol oxidase activities, in cellular extracts of this microorganism. the conditions for the ppo assays were optimized for the phenolic substrate, ph, and sodium dodecyl sulfate concentration used. it was demonstrated that three diff ... | 2005 | 16269713 |
| evidence for a functional quorum-sensing type ai-1 system in the extremophilic bacterium acidithiobacillus ferrooxidans. | acidithiobacillus ferrooxidans is one of the main acidophilic chemolithotrophic bacteria involved in the bioleaching of metal sulfide ores. the bacterium-mineral interaction requires the development of biofilms, whose formation is regulated in many microorganisms by type ai-1 quorum sensing. here, we report the existence and characterization of a functional type ai-1 quorum-sensing system in a. ferrooxidans. this microorganism produced mainly acyl-homoserine lactones (ahl) with medium and large ... | 2005 | 16269739 |
| novel dna sequences from natural strains of the nitrogen-fixing symbiotic bacterium sinorhizobium meliloti. | variation in genome size and content is common among bacterial strains. identifying these naturally occurring differences can accelerate our understanding of bacterial attributes, such as ecological specialization and genome evolution. in this study, we used representational difference analysis to identify potentially novel sequences not present in the sequenced laboratory strain rm1021 of the nitrogen-fixing bacterium sinorhizobium meliloti. using strain rm1021 as the driver and the type strain ... | 2005 | 16269751 |
| methylotrophic metabolism is advantageous for methylobacterium extorquens during colonization of medicago truncatula under competitive conditions. | facultative methylotrophic bacteria of the genus methylobacterium are commonly found in association with plants. inoculation experiments were performed to study the importance of methylotrophic metabolism for colonization of the model legume medicago truncatula. competition experiments with methylobacterium extorquens wild-type strain am1 and methylotrophy mutants revealed that the ability to use methanol as a carbon and energy source provides a selective advantage during colonization of m. trun ... | 2005 | 16269765 |
| ascending migration of endophytic rhizobia, from roots to leaves, inside rice plants and assessment of benefits to rice growth physiology. | rhizobia, the root-nodule endosymbionts of leguminous plants, also form natural endophytic associations with roots of important cereal plants. despite its widespread occurrence, much remains unknown about colonization of cereals by rhizobia. we examined the infection, dissemination, and colonization of healthy rice plant tissues by four species of gfp-tagged rhizobia and their influence on the growth physiology of rice. the results indicated a dynamic infection process beginning with surface col ... | 2005 | 16269768 |
| first genome data from uncultured upland soil cluster alpha methanotrophs provide further evidence for a close phylogenetic relationship to methylocapsa acidiphila b2 and for high-affinity methanotrophy involving particulate methane monooxygenase. | members of upland soil cluster alpha (usc alpha) are assumed to be methanotrophic bacteria (mb) adapted to the trace level of atmospheric methane. so far, these mb have eluded all cultivation attempts. while the 16s rrna phylogeny of usc alpha members is still not known, phylogenies constructed for the active-site polypeptide (encoded by pmoa) of particulate methane monooxygenase (pmmo) placed usc alpha next to the alphaproteobacterial methylocapsa acidiphila b2. to assess whether the pmoa tree ... | 2005 | 16269789 |
| solution structure of the c-terminal transcriptional activator domain of fixj from sinorhizobium meliloti and its recognition of the fixk promoter. | fixj is a response regulator of the two-component signal transduction pathway involved in the transcriptional activation of nitrogen fixation genes of sinorhizobium meliloti. upon phosphorylation, fixj transcriptionally activates the fixk and nifa promoters. we identified a fixj recognition sequence of 16 bp in the high affinity binding site of the fixk promoter by means of a gel shift assay. in addition, the solution structure of the truncated c-terminal dna binding domain of fixj (fixjc) was s ... | 2005 | 16274231 |
| preferential attachment in the evolution of metabolic networks. | many biological networks show some characteristics of scale-free networks. scale-free networks can evolve through preferential attachment where new nodes are preferentially attached to well connected nodes. in networks which have evolved through preferential attachment older nodes should have a higher average connectivity than younger nodes. here we have investigated preferential attachment in the context of metabolic networks. | 2005 | 16281983 |
| large-scale genetic variation of the symbiosis-required megaplasmid psyma revealed by comparative genomic analysis of sinorhizobium meliloti natural strains. | sinorhizobium meliloti is a soil bacterium that forms nitrogen-fixing nodules on the roots of leguminous plants such as alfalfa (medicago sativa). this species occupies different ecological niches, being present as a free-living soil bacterium and as a symbiont of plant root nodules. the genome of the type strain rm 1021 contains one chromosome and two megaplasmids for a total genome size of 6 mb. we applied comparative genomic hybridisation (cgh) on an oligonucleotide microarrays to estimate ge ... | 2005 | 16283928 |
| arbuscular mycorrhizal fungi elicit a novel intracellular apparatus in medicago truncatula root epidermal cells before infection. | the penetration of arbuscular mycorrhizal (am) fungi through the outermost root tissues of the host plant is a critical step in root colonization, ultimately leading to the establishment of this ecologically important endosymbiotic association. to evaluate the role played by the host plant during am infection, we have studied in vivo cellular dynamics within medicago truncatula root epidermal cells using green fluorescent protein labeling of both the plant cytoskeleton and the endoplasmic reticu ... | 2005 | 16284314 |
| oxygen blocks the reaction of the fixl-fixj complex with atp but does not influence binding of fixj or atp to fixl. | the rmfixl-rmfixj oxygen signal transduction system ensures that a cascade of the sinorhizobium meliloti nitrogen fixation genes is induced as the concentration of o2 drops below 50 microm in symbiotic nodules. deoxy-rmfixl is a histidine protein kinase that catalyzes a phosphoryl transfer from atp to the aspartate 54 residue of rmfixj; rmfixj is a response regulator that becomes activated as a transcription factor by phosphorylation. association of o2 with a heme-binding domain in rmfixl trigge ... | 2005 | 16285740 |
| sini- and expr-dependent quorum sensing in sinorhizobium meliloti. | quorum sensing (qs) in sinorhizobium meliloti, the n-fixing bacterial symbiont of medicago host plants, involves at least half a dozen different n-acyl homoserine lactone (ahl) signals and perhaps an equal number of ahl receptors. the accumulation of 55 proteins was found to be dependent on sini, the ahl synthase, and/or on expr, one of the ahl receptors. gas chromatography-mass spectrometry and electrospray ionization tandem mass spectrometry identified 3-oxo-c(14)-homoserine lactone (3-oxo-c(1 ... | 2005 | 16291666 |
| use of artificial genomes in assessing methods for atypical gene detection. | parametric methods for identifying laterally transferred genes exploit the directional mutational biases unique to each genome. yet the development of new, more robust methods--as well as the evaluation and proper implementation of existing methods--relies on an arbitrary assessment of performance using real genomes, where the evolutionary histories of genes are not known. we have used the framework of a generalized hidden markov model to create artificial genomes modeled after genuine genomes. ... | 2005 | 16292353 |
| whole-genome analyses of speciation events in pathogenic brucellae. | despite their high dna identity and a proposal to group classical brucella species as biovars of brucella melitensis, the commonly recognized brucella species can be distinguished by distinct biochemical and fatty acid characters, as well as by a marked host range (e.g., brucella suis for swine, b. melitensis for sheep and goats, and brucella abortus for cattle). here we present the genome of b. abortus 2308, the virulent prototype biovar 1 strain, and its comparison to the two other human patho ... | 2005 | 16299333 |
| transcriptome profiling of bacterial responses to root exudates identifies genes involved in microbe-plant interactions. | molecules exuded by plant roots are thought to act as signals to influence the ability of microbial strains to colonize the roots and to survive in the rhizosphere. differential bacterial responses to signals from different plant species may mediate the selection of specific rhizosphere populations. very little, however, is known about the effects of plant exudates on patterns of bacterial gene expression. here, we have tested the concept that plant root exudates modulate expression of bacterial ... | 2005 | 16301542 |
| production of oligoglucuronans by enzymatic depolymerization of nascent glucuronan. | an original bioreactor process for production of oligoglucuronans was developed using the sinorhizobium meliloti m5n1cs strain that produces glucuronan. this anionic homopolysaccharide was composed of beta-d-(1,4)-glucopyranosyluronic residues variably o-acetylated at c-3 and/or c-2 positions according to culture conditions. it was depolymerized during its biosynthesis by addition of a fungal glucuronan lyase activity in broths. after purification by tangential ultrafiltration and low-pressure l ... | 2005 | 16321066 |
| l-canavanine made by medicago sativa interferes with quorum sensing in sinorhizobium meliloti. | sinorhizobium meliloti is a gram-negative soil bacterium, capable of establishing a nitrogen-fixing symbiosis with its legume host, alfalfa (medicago sativa). quorum sensing plays a crucial role in this symbiosis, where it influences the nodulation process and the synthesis of the symbiotically important exopolysaccharide ii (eps ii). s. meliloti has three quorum-sensing systems (sin, tra, and mel) that use n-acyl homoserine lactones as their quorum-sensing signal molecule. increasing evidence i ... | 2005 | 16321947 |
| purification and preliminary x-ray crystallographic analysis of the ligand-binding domain of sinorhizobium meliloti dctb. | sinorhizobium meliloti dctbd is a well-characterized two-component system. it is believed that dctb senses the concentration of c4-dicarboxylate compounds on the outside of the bacterium and phosphorylates dctd, which in turn activates transcription of the dcta gene, coding for a gene of c4-dicarboxylate permease. the structure and function of the ligand-binding domain of dctb has not been thoroughly investigated. in this study, this domain was produced in e. coli in soluble form, and purified t ... | 2006 | 16332458 |
| characterization of a thermoacidophilic l-arabinose isomerase from alicyclobacillus acidocaldarius: role of lys-269 in ph optimum. | the araa gene encoding l-arabinose isomerase (ai) from the thermoacidophilic bacterium alicyclobacillus acidocaldarius was cloned, sequenced, and expressed in escherichia coli. analysis of the sequence revealed that the open reading frame of the araa gene consists of 1,491 bp that encodes a protein of 497 amino acid residues with a calculated molecular mass of 56,043 da. comparison of the deduced amino acid sequence of a. acidocaldarius ai (aaai) with other ais demonstrated that aaai has 97% and ... | 2005 | 16332764 |
| l-selective amidase with extremely broad substrate specificity from ochrobactrum anthropi ncimb 40321. | an industrially attractive l-specific amidase was purified to homogeneity from ochrobactrum anthropi ncimb 40321 wild-type cells. the purified amidase displayed maximum initial activity between ph 6 and 8.5 and was fully stable for at least 1 h up to 60 degrees c. the purified enzyme was strongly inhibited by the metal-chelating compounds edta and 1,10-phenanthroline. the activity of the edta-treated enzyme could be restored by the addition of zn2+ (to 80%), mn2+ (to 400%), and mg2+ (to 560%). s ... | 2005 | 16332774 |
| microarray-based detection and typing of the rhizobium nodulation gene nodc: potential of dna arrays to diagnose biological functions of interest. | environmental screening of bacteria for the presence of genes of interest is a challenging problem, due to the high variability of the nucleotide sequence of a given gene between species. here, we tackle this general issue using a particularly well-suited model system that consists of the nodulation gene nodc, which is shared by phylogenetically distant rhizobia. 41mer and 50mer oligonucleotides featuring the nucleotide diversity of two highly conserved regions of the nodc protein were spotted o ... | 2005 | 16332784 |
| characterization of a unique chromosomal copper resistance gene cluster from xanthomonas campestris pv. vesicatoria. | we characterized the copper resistance genes in strain xvp26 of xanthomonas campestris pv. vesicatoria, which was originally isolated from a pepper plant in taiwan. the copper resistance genes were localized to a 7,652-bp region which, based on pulsed-field gel electrophoresis and southern hybridization, was determined to be located on the chromosome. these genes hybridized only weakly, as determined by southern analysis, to other copper resistance genes in xanthomonas and pseudomonas strains. w ... | 2005 | 16332814 |
| activity and composition of the denitrifying bacterial community respond differently to long-term fertilization. | the objective of this study was to explore the long-term effects of different organic and inorganic fertilizers on activity and composition of the denitrifying and total bacterial communities in arable soil. soil from the following six treatments was analyzed in an experimental field site established in 1956: cattle manure, sewage sludge, ca(no3)2, (nh4)2so4, and unfertilized and unfertilized bare fallow. all plots but the fallow were planted with corn. the activity was measured in terms of pote ... | 2005 | 16332820 |
| diversity and structure of bacterial chemolithotrophic communities in pine forest and agroecosystem soils. | obligate lithotrophs (e.g., ammonia oxidizers) and facultative lithotrophs (e.g., co and hydrogen oxidizers) collectively comprise a phylogenetically diverse functional group that contributes significantly to carbon and nitrogen cycles in soils and plays important roles in trace gas dynamics (e.g., carbon monoxide and nitrous and nitric oxides) that affect tropospheric chemistry and radiative forcing. in spite of their diverse physiologies, facultative and obligate lithotrophs typically possess ... | 2005 | 16332829 |
| prophage-like elements in bifidobacteria: insights from genomics, transcription, integration, distribution, and phylogenetic analysis. | so far, there is only fragmentary and unconfirmed information on bacteriophages infecting the genus bifidobacterium. in this report we analyzed three prophage-like elements that are present in the genomes of bifidobacterium breve ucc 2003, bifidobacterium longum ncc 2705, and bifidobacterium longum djo10a, designated bbr-1, bl-1, and blj-1, respectively. these prophagelike elements exhibit homology with genes of double-stranded dna bacteriophages spanning a broad phylogenetic range of host bacte ... | 2005 | 16332864 |
| genetic characterization of the bifidobacterium breve ucc 2003 hrca locus. | the bacterial heat shock response is characterized by the elevated expression of a number of chaperone complexes and transcriptional regulators, including the dnaj and the hrca proteins. genome analysis of bifidobacterium breve ucc 2003 revealed a second copy of a dnaj gene, named dnaj2, which is flanked by the hrca gene in a genetic constellation that appears to be unique to the actinobacteria. phylogenetic analysis using 53 bacterial dnaj sequences, including both dnaj1 and dnaj2 sequences, su ... | 2005 | 16332909 |
| use of two-dimensional polyacrylamide gel electrophoresis to identify and classify rhizobium strains. | fifty-seven strains of various rhizobium species were analyzed by two-dimensional gel electrophoresis. since the protein pattern on such gels is a reflection of the genetic background of the tested strains, similarities in pattern allowed us to estimate the relatedness between these strains. all group ii rhizobia (slow growing) were closely related and were very distinct from group i rhizobia (fast growing). rhizobium meliloti strains formed a distinct group. the collection of r. leguminosarum a ... | 1980 | 16345514 |
| method for testing degree of infectivity of rhizobium meliloti strains. | the infectiveness of different strains of rhizobium meliloti was tested with a technique that uses the addition of tetracycline to the root medium. to stop the infection, the antibiotic was added some time after the inoculation of medicago sativa plants. a coefficient of infectivity for each strain was calculated according to the number of nodules that appeared with and without the addition of the antibiotic. this method seems useful in infectivity studies and is simpler and easier to perform th ... | 1980 | 16345574 |
| relative efficacy of different alfalfa cultivar-rhizobium meliloti strain combinations for symbiotic nitrogen fixation. | five rhizobium meliloti isolates known to have different capabilities for expression of nitrogenase activity under symbiotic conditions were used to inoculate four representative medicago sativa cultivars under aseptic conditions. nitrogenase activities and respiratory activity were measured for whole plants and excised nodules. dry weights and nodule numbers were also recorded after 4 weeks of growth in plastic pouches on a nitrogen-free nutrient medium. hydrogen evolution and acetylene reducti ... | 1982 | 16345986 |
| root surface association in relation to nodulation of medicago sativa. | nine strains of rhizobium meliloti, ranging in competitive ability on medicago sativa from excellent to poor in autoclaved soils, were paired in 29 combinations and used to inoculate m. sativa in a liquid rooting medium. a positive correlation (r = 0.545) between strain ratios in nodules after 28 days and root surface cell ratios after 7 days was determined. two cell fractions from the root surface, representing loosely and firmly adhering cells, were investigated. infectivity was linked to the ... | 1982 | 16346071 |
| competitive abilities of rhizobium meliloti strains considered to have potential as inoculants. | twenty four strains of rhizobium meliloti considered to have potential for inoculant production were grouped in pairs and tested for their ability to compete for nodulation on medicago sativa, medicago truncatula, and medicago littoralis. at the outset, each pair of strains, which consisted of a wild type and a selected streptomycin-resistant mutant of another strain, was tested in an autoclaved soil. six strain pairs, each consisting of a good and a poor competitor, reacted consistently when te ... | 1982 | 16346072 |
| interaction of agromyces ramosus with other bacteria in soil. | agromyces ramosus occurs in very high numbers in most soils and, based on studies of laboratory isolates, does not require host cells for growth. nevertheless, it attacked and destroyed most of the gram-positive and gram-negative bacterial species tested as possible host organisms. a. ramosus also attacked and destroyed saccharomyces cerevisiae. the possibility of attack on fungi was unclear. among the bacteria serving as hosts were the important soil species azotobacter vinelandii, rhizobium le ... | 1983 | 16346402 |
| motility and chemotaxis of rhizobium meliloti in soil. | the spreading of rhizobium meliloti strains in various autoclaved soils was measured by using simple modifications of established techniques. behavioral mutants were used to demonstrate that efficient spreading requires active motility and chemotaxis. the rate of spreading was affected by physical or chemical differences among soils and by changes in water content. | 1983 | 16346435 |
| mineral soils as carriers for rhizobium inoculants. | mineral soil-based inoculants of rhizobium meliloti and rhizobium phaseoli survived better at 4 degrees c than at higher temperatures, but ca. 15% of the cells were viable at 37 degrees c after 27 days. soil-based inoculants of r. meliloti, r. phaseoli, rhizobium japonicum, and a cowpea rhizobium sp. applied to seeds of their host legumes also survived better at low temperatures, but the percent survival of such inoculants was higher than peat-based inoculants at 35 degrees c. survival of r. pha ... | 1984 | 16346460 |
| complementary methods for the differentiation of rhizobium meliloti isolates. | because of the scarcity of literature on the successful use of serological methods for differentiation of rhizobium meliloti isolates, the objectives of this study were to provide a rationale for selecting isolates to which antisera could be raised and to appraise the suitability of published methods of preparing r. meliloti antigens for the serological identification of field isolates. we used one-dimensional sodium dodecyl sulfate-polyacrylamide gel electrophoresis to develop protein profiles ... | 1984 | 16346506 |
| effect of plasmid pij1008 from rhizobium leguminosarum on symbiotic function of rhizobium meliloti. | plasmid pij1008, which carries determinants for uptake hydrogenase (hup) activity, was transferred from rhizobium leguminosarum to rhizobium meliloti without impairing the capacity of the latter species to form root nodules on alfalfa. the plasmid was still present in rhizobia reisolated from the root nodules of 12 different alfalfa cultivars, but only low levels of hup activity were detected in alfalfa. | 1984 | 16346527 |
| variation in preference for rhizobium meliloti within and between medicago sativa cultivars grown in soil. | variation in nodulation preferences for rhizobium strains within and between medicago sativa cultivars was assessed in the greenhouse with plants grown in leonard jars and two soils of diverse origin (lanark and ottawa), using inocula consisting of effective individual or paired strains of r. meliloti which could be recognized by high-concentration antibiotic resistance. the results indicated considerable variability in host preferences for r. meliloti among plants within cultivars but not betwe ... | 1984 | 16346682 |
| general method for the identification of plasmid species in fast-growing soil microorganisms. | using a horizontal gel electrophoresis method, we demonstrated reproducibly the presence of indigenous plasmids in different rhizobium, agrobacterium, and pseudomonas strains. the method yields a large amount of plasmid dna and is sensitive in detecting megaplasmids with molecular weights higher than 5 x 10. in two rhizobium meliloti strains, a megaplasmid other than the low-mobility plasmid already known was detected. | 1985 | 16346763 |
| conserved nodulation genes in rhizobium meliloti and rhizobium trifolii. | plasmids which contained wild-type or mutated rhizobium meliloti nodulation (nod) genes were introduced into nodr. trifolii mutants anu453 and anu851 and tested for their ability to nodulate clover. cloned wild-type and mutated r. meliloti nod gene segments restored anu851 to nod, with the exception of nodd mutants. similarly, wild-type and mutant r. meliloti nod genes complemented anu453 to nod, except for nodcii mutants. thus, anu851 identifies the equivalent of the r. meliloti nodd genes, and ... | 1985 | 16346809 |
| rates of drying and survival of rhizobium meliloti strains during storage at different relative humidities. | an investigation was made of the survival of six strains of rhizobium meliloti filtered on membrane filters and held in atmospheres of controlled relative humidities (rh) of from 0 to 100% at 30 degrees c in the presence of air. the rate of water loss in the desiccator was determined by the humidity-controlling solution used. drying was accelerated by a mild evacuation of the desiccator during the drying step. survival rates of r. meliloti strains were much higher after slow drying to 0% rh than ... | 1985 | 16346846 |
| regulation of nodulation by rhizobium meliloti 102f15 on its mutant which forms an unusually high number of nodules on alfalfa. | a mutant (wl3a150) of rhizobium meliloti 102f51 that elicits an unusually high number of nodules on its host, alfalfa (medicago sativa), supports the idea that the host may rely on early bacteroid development in the nodule or on metabolites produced in the infection thread as one of the signals to control further nodulation. this mutant was initially isolated because of its fix phenotype. it consistently formed many more nodules than all the other fix mutants isolated from strain 102f51 (a total ... | 1985 | 16346908 |
| influence of location, host cultivar, and inoculation on the composition of naturalized populations of rhizobium meliloti in medicago sativa nodules. | a phage typing system was used to evaluate the composition of indigenous populations of rhizobium meliloti inhabiting nodules of medicago sativa cultivars grown with and without inoculation at two field sites during 1983 and 1984. soil at both locations contained established populations of r. meliloti at planting. analysis of 1,920 nodule isolates revealed 55 unique phage types of indigenous r. meliloti at one site and 65 indigenous types at the other location. the distributions of phage types d ... | 1986 | 16347054 |
| analysis of rhizobium meliloti sym mutants obtained by heat treatment. | deletions in the psym megaplasmid of rhizobium meliloti were produced at a high frequency, and their lengths varied according to incubation temperature. morphological differentiation into large and small colonies occurred after heat treatment. small colonies elicited pseudonodules on alfalfa roots. | 1986 | 16347063 |
| quantitation of adsorption of rhizobia in low numbers to small legume roots. | bacteria adsorbed in low numbers to alfalfa or clover root surfaces were counted after incubation of seedlings in mineral solution with very dilute inocula (less than 10 bacteria per ml) of an antibiotic-resistant strain under defined conditions. after specified washing, bacteria which remained adsorbed to roots were selectively quantitated by culturing the roots embedded in yeast extract-mannitol-antibiotic agar and counting the microcolonies along the root surface; the range was from about 1 b ... | 1986 | 16347137 |
| host-symbiont specificity expressed during early adsorption of rhizobium meliloti to the root surface of alfalfa. | early (4 h) adsorption of rhizobium meliloti l5-30 in low numbers to alfalfa roots in mineral solution was examined for competition with other bacterial strains. all tested competitor strains decreased the adsorption of l5-30 by extents which depended on the strain and its concentration. the decrease of adsorption by r. meliloti competitors (all of them infective in alfalfa) was nearly complete at saturation (97 to 99% decrease). all other heterologous rhizobia and agrobacterium tumefaciens at s ... | 1986 | 16347138 |
| bacterial growth rates and competition affect nodulation and root colonization by rhizobium meliloti. | the addition of streptomycin to nonsterile soil suppressed the numbers of bacterial cells in the rhizosphere of alfalfa (medicago sativa l.) for several days, resulted in the enhanced growth of a streptomycin-resistant strain of rhizobium meliloti, and increased the numbers of nodules on the alfalfa roots. a bacterial mixture inoculated into sterile soil inhibited the colonization of alfalfa roots by r. meliloti, caused a diminution in the number of nodules, and reduced plant growth. enterobacte ... | 1986 | 16347173 |
| large-scale production of rhizobium meliloti on whey. | whey, a by-product of the cheese industry, can sustain the growth of fast-growing rhizobia. to avoid any latency of growth, rhizobial inoculum must be prepared under inducing conditions. in unsupplemented whey, the number of cells of rhizobium meliloti balsac reached 5 x 10 cfu/ml in 48 h of incubation. this is comparable to the yield obtained with yeast-mannitol broth, the standard medium for the growth of rhizobia. in raw whey supplemented with yeast extract (1.0 g/liter) and phosphate (0.5 g/ ... | 1986 | 16347176 |
| distribution of hydrogen-metabolizing bacteria in alfalfa field soil. | h(2) evolved by alfalfa root nodules during the process of n(2) fixation may be an important factor influencing the distribution of soil bacteria. to test this hypothesis under field conditions, over 700 bacterial isolates were obtained from fallow soil or from the 3-mm layer of soil surrounding alfalfa (medicago sativa l.) root nodules, alfalfa roots, or bindweed (convolvulus arvensis l.) roots. bacteria were isolated under either aerobic or microaerophilic conditions and were tested for their ... | 1986 | 16347207 |
| serological relatedness of rhizobium fredii to other rhizobia and to the bradyrhizobia. | several isolates of rhizobium fredii were examined for their serological relatedness to each other, to bradyrhizobium japonicum, and to other fast- and slow-growing rhizobia. immunofluorescence, agglutination, and immunodiffusion analyses indicated that r. fredii contains at least three separate somatic serogroups, usda 192, usda 194, and usda 205. there was no cross-reaction between any of the r. fredii isolates and 13 of the 14 b. japonicum somatic serogroups tested. cross-reactions were obtai ... | 1987 | 16347404 |
| high survivability of cheese whey-grown rhizobium meliloti cells upon exposure to physical stress. | whey, a by-product of the dairy industry, has been found to protect the rhizobia cells during freezing and thawing. cells of rhizobia grown on whey sustained freezing better at -18 degrees c than did cells grown on mannitol or sucrose. suspensions of cells grown on whey or mannitol that were suspended in whey performed equally well at -18 and -80 degrees c, with 94 and 100% survival, respectively. whey-grown rhizobia in pellets withstood desiccation better than did their mannitol-grown equivalen ... | 1988 | 16347524 |
| a study of 33 bacteriophages of rhizobium meliloti. | a total of 33 rhizobium meliloti bacteriophages were studied. of those, 21 were isolated in northern france from field soil in which medicago sativa l. was grown. the other 12 phages were obtained by uv light and mitomycin c induction from 46 r. meliloti strains. rhizobiophages were characterized by their morphology, host range, serological properties, restriction endonuclease patterns, dna-dna homologies, and dna molecular weights. five morphotypes were observed showing tailed phages with icosa ... | 1988 | 16347525 |
| growth of indigenous rhizobium leguminosarum and rhizobium meliloti in soils amended with organic nutrients. | the ability of indigenous rhizobium leguminosarum and rhizobium meliloti to use organic nutrients as growth substrates in soil was assessed by indirect bacteriophage analysis. a total of 17 organic compounds, including 9 carbohydrates, 3 organic acids, and 5 amino acids, were tested (1,000 mug g) in three soils with different cropping histories. four additional soils were screened with a glucose amendment. nutrient amendments stimulated growth of indigenous rhizobia, allowing subsequent replicat ... | 1988 | 16347530 |
| a positive strain identification method for rhizobium meliloti. | about 80% of rhizobium meliloti strains contain 1 to 11 copies of insertion sequence isrm1 in their genomes (r. wheatcroft and r. j. watson, j. gen. microbiol. 134:113-121, 1988). hybridization to separated genomic dna fragments with an isrm1-specific probe produces patterns of hybridization bands which are distinctive for each strain. these patterns can be compared between strains to prove or disprove common identity. in most cases relatedness can be inferred despite phenotypic differences or m ... | 1988 | 16347567 |
| diversity of plasmid profiles and conservation of symbiotic nitrogen fixation genes in newly isolated rhizobium strains nodulating sulla (hedysarum coronarium l.). | forty-five rhizobium strains nodulating sulla (hedysarum coronarium l.), isolated from plants grown in different sites in menorca island and southern spain, were examined for plasmid content and the location and organization of nif (nitrogen fixation) and nod (nodulation) sequences. a great diversity in both number and size of the plasmids was observed in this native population of strains, which could be distributed among 19 different groups according to their plasmid profiles. no correlation wa ... | 1988 | 16347636 |
| numerical taxonomic analysis of some strains of rhizobium spp. that uses a qualitative coding of immunodiffusion reactions. | antigenic relationships among seven strains of bradyrhizobium japonicum were examined by immunodiffusion reactions, in which cells of each strain were reacted against each of the seven corresponding antisera. similar analyses were performed with rhizobium trifolii (28 strains), rhizobium meliloti (9 strains), and rhizobia of the cowpea miscellany (13 strains). antigens and antisera were reacted within each species only; serological interspecies cross-reactions were not performed. the results, sc ... | 1988 | 16347692 |
| exopolysaccharide-deficient mutants of rhizobium fredii hh303 which are symbiotically effective. | nineteen tn5-induced mutants of rhizobium fredii hh303 defective in acidic exopolysaccharide synthesis were isolated by screening for lack of calcofluor fluorescence. they were grouped by complementation analysis by using rhizobium meliloti cosmids carrying exo genes. all of the 19 mutants were symbiotically effective or partially effective, indicating that the major bacterial acidic exopolysaccharide of this strain of r. fredii may not be required for symbiotic development in the soybean. | 1989 | 16347980 |
| maintenance of intracellular ph and acid tolerance in rhizobium meliloti. | the development and function of the rhizobium meliloti-medicago sp. symbiosis are sensitive to soil acidity. physiological criteria that can be measured in culture which serve to predict acid tolerance in soil would be valuable. the intracellular ph of r. meliloti was measured using either radioactively labeled weak acids (5,5-dimethyloxazolidine-2,4-dione and butyric acid) or ph-sensitive fluorescent compounds; both methods gave similar values. six acid-tolerant strains (wsm419, wsm533, wsm539, ... | 1989 | 16347984 |
| growth and nodulation responses of rhizobium meliloti to water stress induced by permeating and nonpermeating solutes. | isolates of rhizobium meliloti, representing antigenically distinct indigenous serogroups 31 and 17, were grown in yeast extract-mannitol broth (yem) containing nacl or polyethylene glycol (peg) to provide external water potentials ranging from -0.15 to -1.5 mpa. several differences were found between representatives of the two groups in their abilities to adapt to water stress induced by the nonpermeating solute peg. at potentials below -0.5 mpa, strain 31 had a lower specific growth rate than ... | 1989 | 16348021 |
| host restriction and transduction in rhizobium meliloti. | a host restriction difference exists between rhizobium meliloti rm41 and su47 exists as indicated by the reduce plating efficiency of transducing phage phim12h1. restriction can be attenuated by incubating cells at 42 degrees c for 3 h; this procedure overcomes a block to transduction from su47 to rm41. | 1989 | 16348079 |
| osmoregulation in rhizobium meliloti: production of glutamic acid in response to osmotic stress. | rhizobium meliloti, like many other bacteria, accumulates high levels of glutamic acid when osmotically stressed. the effect was found to be proportional to the osmolarity of the growth medium. nacl, kci, sucrose, and polyethylene glycol elicited this response. the intracellular levels of glutamate and k began to increase immediately when cells were shifted to high-osmolarity medium. antibiotics that inhibit protein synthesis did not affect this increase in glutamate production. cells growing in ... | 1990 | 16348124 |
| specificity of octopine uptake by rhizobium and pseudomonas strains. | the octopine-utilizing strain agrobacterium tumefaciens b6s3 and three nonagrobacteria which had the capacity to utilize this opine were compared for octopine uptake. the characteristics of uptake by rhizobium meliloti a3 and strain b6s3 were similar. in both bacteria, uptake activity was inducible by octopine and by the related opine octopinic acid, and competition assays showed that these two opine substrates were accepted by the same uptake system with an equivalent affinity. cells of pseudom ... | 1990 | 16348194 |
| conjugal transfer of megaplasmid 2 between rhizobium meliloti strains in alfalfa nodules. | a dna fragment containing the rp4 mob function, as well as the gentamicin and spectinomycin resistance genes, was inserted by gene replacement onto the megaplasmid 2 (pm2) of rhizobium meliloti 0540 (inf eps), resulting in pg101 (inf eps). the self-transfer of pm2 and the mobilization of pm2 by plasmid rp4-4 were investigated during conjugation between pg101 and r. meliloti 2526 (nod). in filter conjugations, pm2 was readily mobilized by rp4-4. in addition to this, the self-transfer of one megap ... | 1990 | 16348248 |
| carbon metabolism enzymes of rhizobium meliloti cultures and bacteroids and their distribution within alfalfa nodules. | several carbon metabolism enzymes were measured in cultured cells and bacteroids of rhizobium meliloti 102f51 and in alfalfa root nodule cytosol. the enzyme activity levels of the pentose phosphate pathway were much higher than those of the embden-meyerhof-parnas or entner-doudoroff pathways in extracts of cultured cells. the pattern of enzyme activities in the bacteroids was different from that of cultured cells. | 1990 | 16348268 |