| effects of t4 lysozyme release from transgenic potato roots on bacterial rhizosphere communities are negligible relative to natural factors. | rhizosphere bacterial communities of two transgenic potato lines which produce t4 lysozyme for protection against bacterial infections were analyzed in comparison to communities of wild-type plants and transgenic controls not harboring the lysozyme gene. rhizosphere samples were taken from young, flowering, and senescent plants at two field sites in three consecutive years. the communities were characterized in a polyphasic approach. cultivation-dependent methods included heterotrophic plate cou ... | 2002 | 11872484 |
| genetic differentiation between sympatric populations of bacillus cereus and bacillus thuringiensis. | little is known about genetic exchanges in natural populations of bacteria of the spore-forming bacillus cereus group, because no population genetics studies have been performed with local sympatric populations. we isolated strains of bacillus thuringiensis and b. cereus from small samples of soil collected at the same time from two separate geographical sites, one within the forest and the other at the edge of the forest. a total of 100 b. cereus and 98 b. thuringiensis strains were isolated an ... | 2002 | 11872495 |
| raiir genes are part of a quorum-sensing network controlled by cini and cinr in rhizobium leguminosarum. | analysis of n-acyl-l-homoserine lactones (ahls) produced by rhizobium leguminosarum bv. viciae indicated that there may be a network of quorum-sensing regulatory systems producing multiple ahls in this species. using a strain lacking a symbiosis plasmid, which carries some of the quorum-sensing genes, we isolated mutations in two genes (raii and rair) that are required for production of ahls. the raiir genes are located adjacent to dad genes (involved in d-alanine catabolism) on a large indigeno ... | 2002 | 11872711 |
| rubredoxins involved in alkane oxidation. | rubredoxins (rds) are essential electron transfer components of bacterial membrane-bound alkane hydroxylase systems. several rd genes associated with alkane hydroxylase or rd reductase genes were cloned from gram-positive and gram-negative organisms able to grow on n-alkanes (alk-rds). complementation tests in an escherichia coli recombinant containing all pseudomonas putida gpo1 genes necessary for growth on alkanes except rd 2 (alkg) and sequence comparisons showed that the alk-rds can be divi ... | 2002 | 11872724 |
| expression of a crown gall biological control phenotype in an avirulent strain of agrobacterium vitis by addition of the trifolitoxin production and resistance genes. | agrobacterium vitis is a causal agent of crown-gall disease. trifolitoxin (tfx) is a peptide antibiotic active only against members of a specific group of alpha-proteobacteria that includes agrobacterium and its close relatives. the ability of tfx production by an avirulent strain of agrobacterium to reduce crown gall disease is examined here. | 2002 | 11882255 |
| characterization of the urease gene cluster from rhizobium leguminosarum bv. viciae. | moderate levels of urease activity (ca. 300 mu mg(-1)) were detected in rhizobium leguminosarum bv. viciae upm791 vegetative cells. this activity did not require urea for induction and was partially repressed by the addition of ammonium into the medium. lower levels of urease activity (ca. 100 mu mg(-1)) were detected also in pea bacteroids. a dna region of ca. 9 kb containing the urease structural genes ( urea, ureb and urec), accessory genes ( ured, uree, uref, and ureg), and five additional o ... | 2002 | 11889482 |
| an agrobacterium gene involved in tumorigenesis encodes an outer membrane protein exposed on the bacterial cell surface. | a gene designated as aopb was identified which was involved in tumorigenesis of agrobacterium tumefaciens. aopb is located on the circular chromosome as a single copy. this gene shares high homology with ropb, a rhizobium leguminosarum gene encoding an outer membrane protein. a transposon mutant cgi1 containing a gfp-tagged transposon insertion at aopb caused attenuated tumors on plants when inoculated at a low cell concentration (5x10(7) cells/ml). the mutation did not affect the bacterial grow ... | 2002 | 11891052 |
| copper amine oxidase expression in defense responses to wounding and ascochyta rabiei invasion. | wounding chickpea (cicer arietinum) internodes or cotyledons resulted in an increase in the steady-state level of copper amine oxidase (cuao) expression both locally and systemically. dissection of the molecular mechanisms controlling cuao expression indicated that jasmonic acid worked as a potent inducer of the basal and wound-inducible cuao expression, whereas salicylic acid and abscisic acid caused a strong reduction of the wound-induced cuao expression, without having any effect on the basal ... | 2002 | 11891243 |
| the cytochrome c maturation locus of legionella pneumophila promotes iron assimilation and intracellular infection and contains a strain-specific insertion sequence element. | previously, we obtained a legionella pneumophila mutant, nu208, that is hypersensitive to iron chelators when grown on standard legionella media. here, we demonstrate that nu208 is also impaired for growth in media that simply lack their iron supplement. the mutant was not, however, impaired for the production of legiobactin, the only known l. pneumophila siderophore. importantly, nu208 was also highly defective for intracellular growth in human u937 cell macrophages and hartmannella and acantha ... | 2002 | 11895946 |
| the rhizobium leguminosarum prsde genes are required for secretion of several proteins, some of which influence nodulation, symbiotic nitrogen fixation and exopolysaccharide modification. | nodo is a secreted protein from rhizobium leguminosarum bv. viciae with a role in signalling during legume nodulation. a tn5-induced mutant was identified that was defective in nodo secretion. as predicted, the secretion defect decreased pea and vetch nodulation but only when the node gene was also mutated. this confirms earlier observations that nodo plays a particularly important role in nodulation when nod factors carrying c18:1 (but not c18:4) acyl groups are the primary signalling molecules ... | 1997 | 11902716 |
| chronic intracellular infection of alfalfa nodules by sinorhizobium meliloti requires correct lipopolysaccharide core. | our analyses of lipopolysaccharide mutants of sinorhizobium meliloti offer insights into how this bacterium establishes the chronic intracellular infection of plant cells that is necessary for its nitrogen-fixing symbiosis with alfalfa. derivatives of s. meliloti strain rm1021 carrying an lpsb mutation are capable of colonizing curled root hairs and forming infection threads in alfalfa in a manner similar to a wild-type strain. however, developmental abnormalities occur in the bacterium and the ... | 2002 | 11904442 |
| actp controls copper homeostasis in rhizobium leguminosarum bv. viciae and sinorhizobium meliloti preventing low ph-induced copper toxicity. | two 'calcium-irreparable' acid-sensitive mutants were identified after mutagenizing rhizobium leguminosarum bv. viciae and sinorhizobium meliloti with tn5. each mutant contains a single copy of the transposon which, inserted within the actp gene, prevents expression of a p-type atpase that belongs to the cpx heavy metal-transporting subfamily. here, we show that both actp-knockout mutants show sensitivity to copper; omission of this heavy metal from low ph-buffered media restores acid tolerance ... | 2002 | 11936079 |
| ocatin. a novel tuber storage protein from the andean tuber crop oca with antibacterial and antifungal activities. | the most abundant soluble tuber protein from the andean crop oca (oxalis tuberosa mol.), named ocatin, has been purified and characterized. ocatin accounts for 40% to 60% of the total soluble oca tuber proteins, has an apparent molecular mass of 18 kd and an isoelectric point of 4.8. this protein appears to be found only in tubers and is accumulated only within the cells of the pith and peridermis layers (peel) of the tuber as it develops. ocatin inhibits the growth of several phytopathogenic ba ... | 2002 | 11950978 |
| genetic manipulation of the metabolism of polyamines in poplar cells. the regulation of putrescine catabolism. | we investigated the catabolism of putrescine (put) in a non-transgenic (nt) and a transgenic cell line of poplar (populus nigra x maximowiczii) expressing a mouse (mus musculus) ornithine (orn) decarboxylase (odc) cdna. the transgenic cells produce 3- to 4-fold higher amounts of put than the nt cells. the rate of loss of put from the cells and the initial half-life of cellular put were determined by feeding the cells with [u-(14)c]orn and [1,4-(14)c]put as precursors and following the loss of [( ... | 2002 | 11950994 |
| novel plant-microbe rhizosphere interaction involving streptomyces lydicus wyec108 and the pea plant (pisum sativum). | a previously undescribed plant-microbe interaction between a root-colonizing streptomyces species, s. lydicus wyec108, and the legume pisum sativum is described. the interaction is potentially of great importance to the health and growth in nature of this nodulating legume. the root-colonizing soil actinomycete s. lydicus wyec108 influences pea root nodulation by increasing root nodulation frequency, possibly at the level of infection by rhizobium spp. s. lydicus also colonizes and then sporulat ... | 2002 | 11976085 |
| engineering the rhizobium leguminosarum bv. viciae hydrogenase system for expression in free-living microaerobic cells and increased symbiotic hydrogenase activity. | rhizobium leguminosarum bv. viciae upm791 induces hydrogenase activity in pea (pisum sativum l.) bacteroids but not in free-living cells. the symbiotic induction of hydrogenase structural genes (hupsl) is mediated by nifa, the general regulator of the nitrogen fixation process. so far, no culture conditions have been found to induce nifa-dependent promoters in vegetative cells of this bacterium. this hampers the study of the r. leguminosarum hydrogenase system. we have replaced the native nifa-d ... | 2002 | 11976122 |
| conservation of plasmid-encoded traits among bean-nodulating rhizobium species. | rhizobium etli type strain cfn42 contains six plasmids. we analyzed the distribution of genetic markers from some of these plasmids in bean-nodulating strains belonging to different species (rhizobium etli, rhizobium gallicum, rhizobium giardinii, rhizobium leguminosarum, and sinorhizobium fredii). our results indicate that independent of geographic origin, r. etli strains usually share not only the psym plasmid but also other plasmids containing symbiosis-related genes, with a similar organizat ... | 2002 | 11976134 |
| early activation of quorum sensing. | | 2002 | 11976283 |
| the structure of saccharomyces cerevisiae met8p, a bifunctional dehydrogenase and ferrochelatase. | sirohaem is a tetrapyrrole-derived prosthetic group that is required for the essential assimilation of sulfur and nitrogen into all living systems as part of the sulfite and nitrite reductase systems. the final two steps in the biosynthesis of sirohaem involve a beta-nad(+)-dependent dehydrogenation of precorrin-2 to generate sirohydrochlorin followed by ferrochelation to yield sirohaem. in saccharomyces cerevisiae, met8p is a bifunctional enzyme that carries out both of these reactions. here, w ... | 2002 | 11980703 |
| comparative sequence analysis of the symbiosis island of mesorhizobium loti strain r7a. | the mesorhizobium loti strain r7a symbiosis island is a 502-kb chromosomally integrated element which transfers to nonsymbiotic mesorhizobia in the environment, converting them to lotus symbionts. it integrates into a phenylalanine trna gene in a process mediated by a p4-type integrase encoded at the left end of the element. we have determined the nucleotide sequence of the island and compared its deduced genetic complement with that reported for the 611-kb putative symbiosis island of m. loti s ... | 2002 | 12003951 |
| characterization of fro1, a pea ferric-chelate reductase involved in root iron acquisition. | to acquire iron, many plant species reduce soil fe(iii) to fe(ii) by fe(iii)-chelate reductases embedded in the plasma membrane of root epidermal cells. the reduced product is then taken up by fe(ii) transporter proteins. these activities are induced under fe deficiency. we describe here the fro1 gene from pea (pisum sativum), which encodes an fe(iii)-chelate reductase. consistent with this proposed role, fro1 shows similarity to other oxidoreductase proteins, and expression of fro1 in yeast con ... | 2002 | 12011340 |
| structure-function analysis of nod factor-induced root hair calcium spiking in rhizobium-legume symbiosis. | in the rhizobium-legume symbiosis, compatible bacteria and host plants interact through an exchange of signals: host compounds promote the expression of bacterial biosynthetic nod (nodulation) genes leading to the production of a lipochito-oligosaccharide signal, the nod factor (nf). the particular array of nod genes carried by a given species of rhizobium determines the nf structure synthesized and defines the range of legume hosts by which the bacterium is recognized. purified nf can induce ea ... | 2002 | 12011352 |
| genetics of thermotolerance in ciprofloxacin resistant mutant of rhizobium leguminosarum bv phaseoli. | a ciprofloxacin resistant mutant (cf(r)) of rhizobium leguminossarum bv phaseoli usda 2695 which nodulates common bean plants (phaseolus vulgaris l) was isolated after nitrous acid mutagenesis. another mutant resistant to nalidixic acid (nal(r)) was isolated spontaneously. both mutants showed thermotolerance as evident by their ability to grow at elevated (40 degrees c) temperature, although the wild type (usda 2695) failed to grow at this temperature. transformation and plasmid curing experimen ... | 2001 | 12018588 |
| expression cloning and characterization of the c28 acyltransferase of lipid a biosynthesis in rhizobium leguminosarum. | an unusual feature of lipid a from plant endosymbionts of the rhizobiaceae family is the presence of a 27-hydroxyoctacosanoic acid (c28) moiety. an enzyme that incorporates this acyl chain is present in extracts of rhizobium leguminosarum, rhizobium etli, and sinorhizobium meliloti but not escherichia coli. the enzyme transfers 27-hydroxyoctacosanate from a specialized acyl carrier protein (acpxl) to the precursor kdo2 ((3-deoxy-d-manno-octulosonic acid)2)-lipid iv(a). we now report the identifi ... | 2002 | 12019272 |
| autoregulation of root nodule formation: signals of both symbiotic partners studied in a split-root system of vicia sativa subsp. nigra. | inhibition of root nodule formation on leguminous plants by already induced or existing root nodules is called autoregulation of root nodule formation (aut). optimal conditions for aut were determined using a split-root technique newly developed for vicia sativa subsp. nigra. infection of a root a with nodulating rhizobium leguminosarum bv. viciae bacteria systemically inhibited nodulation of a spatially separated root b inoculated 2 days later with the same bacteria. this treatment gives comple ... | 2002 | 12026172 |
| identification of a family of extensin-like glycoproteins in the lumen of rhizobium-induced infection threads in pea root nodules. | rhizobium leguminosarum bv. viciae normally gains access to pea host cells through tubular cell wall ingrowths termed infection threads. matrix glycoprotein (mgp), a major component of the infection thread lumen, is also secreted from the tips of uninoculated roots and can be released into solution under reducing conditions. monoclonal antibody mac265, which recognizes mgp through a carbohydrate epitope, was used for immunoaffinity purification of the glycoprotein from pea roots. following treat ... | 2002 | 12026173 |
| rhizobium leguminosarum bv. trifolii pssp protein is required for exopolysaccharide biosynthesis and polymerization. | rhizobium leguminosarum bv. trifolii produces an acidic exopolysaccharide (eps) that is important for the induction of nitrogen-fixing nodules on clover. recently, three genes, pssn, psso, and pssp, possibly involved in eps biosynthesis and polymerization were identified. the predicted protein product of the pssp gene shows a significant sequence similarity to other proteins belonging to the pcp2a family that are involved in the synthesis of high-molecular-weight eps. an r. leguminosarum bv. tri ... | 2002 | 12026178 |
| the vbs genes that direct synthesis of the siderophore vicibactin in rhizobium leguminosarum: their expression in other genera requires ecf sigma factor rpoi. | a cluster of eight genes, vbsgso, vbsadl, vbsc and vbsp, are involved in the synthesis of vicibactin, a cyclic, trihydroxamate siderophore made by the symbiotic bacterium rhizobium leguminosarum. none of these vbs genes was required for symbiotic n2 fixation on peas or vicia. transcription of vbsc, vbsgso and vbsadl (but not vbsp) was enhanced by growth in low levels of fe. transcription of vbsgso and vbsadl, but not vbsp or vbsc, required the closely linked gene rpoi, which encodes an ecf sigma ... | 2002 | 12028377 |
| atypical processing in domain iii of 23s rrna of rhizobium leguminosarum atcc 10004(t) at a position homologous to an rrna fragmentation site in protozoa. | for still unknown reasons, the 23s rrna of many alpha-proteobacteria shows a unique fragmentation pattern compared to other bacteria. the 23s rrna processing involves rnase iii and additional, yet unidentified enzymes. the alpha-proteobacterium rhizobium leguminosarum atcc 10004(t) possesses two fragmentation sites in its 23s rrna. the first one harbors an intervening sequence in helix 9 which is cleaved by rnase iii. we demonstrate that the mature 5' end of the resulting 2.6-kb rrna fragment is ... | 2002 | 12029033 |
| aspects of marker/reporter stability and selectivity in soil microbiology. | based on several experiences of microbial release using genetically modified rhizobium leguminosarum, we have highlighted a number of aspects related to the suitability of introduced markers such as resistance to mercury and b-galactosidase activity, the latter serving the function of high-expression level reporter gene obtained by the introduction of a synthetic promoter conferring strong inducible expression in gram-negative bacteria. in vitro expression and in vivo performances of the chosen ... | 2001 | 12032607 |
| functional analysis of sinorhizobium meliloti genes involved in biotin synthesis and transport. | external biotin greatly stimulates bacterial growth and alfalfa root colonization by sinorhizobium meliloti strain 1021. several genes involved in responses to plant-derived biotin have been identified in this bacterium, but no genes required for biotin transport are known, and not all loci required for biotin synthesis have been assigned. searches of the s. meliloti genome database in combination with complementation tests of escherichia coli biotin auxotrophs indicate that biotin synthesis pro ... | 2002 | 12039741 |
| key role of bacterial nh(4)(+) metabolism in rhizobium-plant symbiosis. | symbiotic nitrogen fixation is carried out in specialized organs, the nodules, whose formation is induced on leguminous host plants by bacteria belonging to the family rhizobiaceae: nodule development is a complex multistep process, which requires continued interaction between the two partners and thus the exchange of different signals and metabolites. nh(4)(+) is not only the primary product but also the main regulator of the symbiosis: either as ammonium and after conversion into organic compo ... | 2002 | 12040124 |
| rhizobium nod factor perception and signalling. | | 2002 | 12045280 |
| identification of two quorum-sensing systems in sinorhizobium meliloti. | sinorhizobium meliloti is a free-living soil bacterium which is capable of establishing a symbiotic relationship with the alfalfa plant (medicago sativa). this symbiosis involves a network of bacterium-host signaling, as well as the potential for bacterium-bacterium communication, such as quorum sensing. in this study, we characterized the production of n-acyl homoserine lactones (ahls) by two commonly used s. meliloti strains, ak631 and rm1021. we found that ak631 produces at least nine differe ... | 2002 | 12057940 |
| roles for sigma factors in global circadian regulation of the cyanobacterial genome. | the circadian clock of the unicellular cyanobacterium synechococcus elongatus pcc 7942 imposes a global rhythm of transcription on promoters throughout the genome. inactivation of any of the four known group 2 sigma factor genes (rpod2, rpod3, rpod4, and sigc), singly or pairwise, altered circadian expression from the psbai promoter, changing amplitude, phase angle, waveform, or period. however, only the rpod2 mutation and the rpod3 rpod4 and rpod2 rpod3 double mutations affected expression from ... | 2002 | 12057947 |
| genetic locus encoding functions involved in biosynthesis and outer membrane localization of xanthomonadin in xanthomonas oryzae pv. oryzae. | xanthomonadins are membrane-bound, brominated, aryl-polyene pigments specific to the genus xanthomonas. we have characterized a genetic locus (pig) from xanthomonas oryzae pv. oryzae which contains four open reading frames (orfs) that are essential for xanthomonadin production. three of these orfs are homologous to acyl carrier proteins, dehydratases, and acyl transferases, suggesting a type ii polyketide synthase pathway for xanthomonadin biosynthesis. the fourth orf has no homologue in the dat ... | 2002 | 12057948 |
| a promoter overlapping with that of nodf is responsible for a new rna molecule transcription in rhizobium leguminosarum. | the expression of nod genes of rhizobia is controlled at the transcriptional level in a complicated way. in this work, a new promoter, which is responsible for an rna molecule transcription in the opposite direction to that of nodf, was identified in rhizobium leguminosarum. this new promoter was characterized to overlap with that of nodf, and the size of px(2), the rna molecule initiated from this promoter was determined to be of approximately 0.72 kb in length. the study on px2 showed that its ... | 2000 | 12058163 |
| in vitro studies on the effects of herbicides on the growth of rhizobia. | to study the possible adverse effect of herbicides on nodulation and nitrogen fixation in legumes by affecting the nitrogen-fixing rhizobia. | 2002 | 12081542 |
| seasonal fluctuations and long-term persistence of pathogenic populations of agrobacterium spp. in soils. | short- and long-term persistence of pathogenic (i.e., tumor forming) agrobacteria in soil was investigated in six nursery plots with a history of high crown gall incidence. no pathogenic agrobacterium strains were isolated in soil samples taken in fall and winter in any plots, but such strains were isolated from both bulk soils and weed rhizospheres (over 0.5 x 10(5) pathogenic cfu/g of bulk soil or rhizosphere) in three out of six plots in spring and summer. pcr amplifications of a vir sequence ... | 2002 | 12089015 |
| altering plant-microbe interaction through artificially manipulating bacterial quorum sensing. | many bacteria regulate diverse physiological processes in concert with their population size. bacterial cell-to-cell communication utilizes small diffusible signal molecules, which the bacteria both produce and perceive. the bacteria couple gene expression to cell density by eliciting a response only when the signalling molecules reach a critical threshold (a point at which the population is said to be 'quorate'). the population as a whole is thus able to modify its behaviour as a single unit. a ... | 2002 | 12096736 |
| genetic dissection of the initiation of the infection process and nodule tissue development in the rhizobium-pea (pisum sativum l.) symbiosis. | twelve non-nodulating pea (pisum sativum l.) mutants were studied to identify the blocks in nodule tissue development. in nine, the reason for the lack of infection thread (it) development was studied; this had been characterized previously in the other three mutants. with respect to it development, mutants in gene sym7 are interrupted at the stage of colonization of the pocket in the curled root hair (crh- phenotype), mutants in genes sym37 and sym38 are blocked at the stage of it growth in the ... | 2002 | 12096795 |
| rhizobium leguminosarum has a second general amino acid permease with unusually broad substrate specificity and high similarity to branched-chain amino acid transporters (bra/liv) of the abc family. | amino acid uptake by rhizobium leguminosarum is dominated by two abc transporters, the general amino acid permease (aap) and the branched-chain amino acid permease (bra(rl)). characterization of the solute specificity of bra(rl) shows it to be the second general amino acid permease of r. leguminosarum. although bra(rl) has high sequence identity to members of the family of hydrophobic amino acid transporters (haat), it transports a broad range of solutes, including acidic and basic polar amino a ... | 2002 | 12107123 |
| the white clover enod40 gene family. expression patterns of two types of genes indicate a role in vascular function. | enod40 is one of the genes associated with legume nodule development and has a putative role in general plant organogenesis. we have isolated a small enod40 gene family from white clover (trifolium repens), with three genes designated trenod40-1, trenod40-2, and trenod40-3, all containing the conserved enod40 regions i and ii. trenod40-1 and trenod40-2 share over 90% homology in the transcribed regions and high levels of similarity in their upstream regulatory sequences. trenod40-1 and trenod40- ... | 2002 | 12114565 |
| vibrio cholerae cytr is a repressor of biofilm development. | vibrio cholerae is both a human pathogen and a natural inhabitant of aquatic environments. in the aquatic environment, microorganisms are found attached to surfaces in structures known as biofilms. we have identified a transcriptional repressor in v. cholerae that inhibits exopolysaccharide synthesis and biofilm development. our studies show that this repressor is the v. cholerae homologue of escherichia coli cytr, a protein that represses nucleoside uptake and catabolism when nucleosides are sc ... | 2002 | 12123457 |
| n-acyl-homoserine lactone inhibition of rhizobial growth is mediated by two quorum-sensing genes that regulate plasmid transfer. | the growth of some strains of rhizobium leguminosarum bv. viciae is inhibited by n-(3-hydroxy-7-cis tetradecenoyl)-l-homoserine lactone (3oh-c(14:1)-hsl), which was previously known as the small bacteriocin before its characterization as an n-acyl homoserine lactone (ahl). tn5-induced mutants of r. leguminosarum bv. viciae resistant to 3oh-c(14:1)-hsl were isolated, and mutations in two genes were identified. these genes, bisr and trir, which both encode luxr-type regulators required for plasmid ... | 2002 | 12142421 |
| biodiversity of denitrifying and dinitrogen-fixing bacteria in an acid forest soil. | isolated soil dna from an oak-hornbeam forest close to cologne, germany, was suitable for pcr amplification of gene segments coding for the 16s rrna and nitrogenase reductase (nifh), nitrous oxide reductase (nosz), cytochrome cd(1)-containing nitrite reductase (nirs), and cu-containing nitrite reductase (nirk) of denitrification. for each gene segment, diverse pcr products were characterized by cloning and sequencing. none of the 16s rrna gene sequences was identical to any deposited in the data ... | 2002 | 12147477 |
| the diversity of phaseolus-nodulating rhizobial populations is altered by liming of acid soils planted with phaseolus vulgaris l. in brazil. | pcr-mediated restriction fragment length polymorphism (rflp) analysis of the 16s-23s rrna internally transcribed spacer (its) region and the 16s rrna gene indicated that the rhizobial populations isolated from common bean (phaseolus vulgaris l.) nodules in the unlimed soil from a series of five lime rates applied 6 years previously to plots of an acidic oxisol had less diversity than those from plots with higher rates of liming. isolates affiliated with rhizobium tropici iib and rhizobium legumi ... | 2002 | 12147504 |
| possible quorum sensing in marine snow bacteria: production of acylated homoserine lactones by roseobacter strains isolated from marine snow. | we report here, for the first time, that bacteria associated with marine snow produce communication signals involved in quorum sensing in gram-negative bacteria. four of 43 marine microorganisms isolated from marine snow were found to produce acylated homoserine lactones (ahls) in well diffusion and thin-layer chromatographic assays based on the agrobacterium tumefaciens reporter system. three of the ahl-producing strains were identified by 16s ribosomal dna gene sequence analysis as roseobacter ... | 2002 | 12147515 |
| effect of exogenous flavonoids on nodulation of pea (pisum sativum l.). | selected flavonoids that are known as inducers and a suppressor of nodulation (nod) genes of the symbiotic bacterium rhizobium leguminosarum bv. viciae were tested for their effect on symbiosis formation with garden pea as the host. a solid substrate was omitted from the hydroponic growing system in order to prevent losses of flavonoids due to adsorption and degradation. the presumed interaction of the tested flavonoids with nod genes has been verified for the genetic background of strain 128c30 ... | 2002 | 12147723 |
| identification of a dtxr-regulated operon that is essential for siderophore-dependent iron uptake in corynebacterium diphtheriae. | the diphtheria toxin repressor (dtxr) uses fe(2+) as a corepressor and inhibits transcription from iron-regulated promoters (irps) in corynebacterium diphtheriae. a new irp, designated irp6, was cloned from c. diphtheriae by a selex-like procedure. dtxr bound to irp6 in vitro only in the presence of appropriate divalent metal ions, and repression of irp6 by dtxr in an escherichia coli system was iron dependent. the open reading frames (orfs) downstream from irp6 and previously described promoter ... | 2002 | 12169610 |
| transcription of matr gene in rhizobium leguminosarum bv. trifolii. | a transcriptional regulator, matr, encoded on rhizobium leguminosarum bv. trifolii matr gene was reported to repress mat operon gene expression by binding the upstream operator site. also, matr activated its own gene expression by binding the same site that caused the transcriptional repression of the mat operon. this report suggests that matr plays a dual role in the transcription of matr and matabc with malonate as a positive effector. | 2002 | 12186746 |
| [the study of bacterial glycopolymers using laser spectroscopy]. | a possibility has been demonstrated to use laser spectroscopy of bacterial glycopolymers by means of measurement of their water solutions fluorescence. comparative investigations of native lipopolysaccharide (lps) ralstonia solanacearum and its structure components permits a supposition to be made that the lps total spectrum is a result of superposition of the spectrum of o-specific polysaccharide and core oligosaccharide as well as core oligosaccharide and lipid a. the lps spectrum maximum shif ... | 2002 | 12190019 |
| mycobacterium smegmatis l-alanine dehydrogenase (ald) is required for proficient utilization of alanine as a sole nitrogen source and sustained anaerobic growth. | nad(h)-dependent l-alanine dehydrogenase (ec 1.4.1.1) (ald) catalyzes the oxidative deamination of l-alanine and the reductive amination of pyruvate. to assess the physiological role of ald in mycobacterium smegmatis, we cloned the ald gene, identified its promoter, determined the protein expression levels, and analyzed the combined effects of nutrient supplementation, oxygen availability, and growth stage on enzyme activity. high ald activities were observed in cells grown in the presence of l- ... | 2002 | 12193615 |
| a luxr homolog controls production of symbiotically active extracellular polysaccharide ii by sinorhizobium meliloti. | production of complex extracellular polysaccharides (epss) by the nitrogen-fixing soil bacterium sinorhizobium meliloti is required for efficient invasion of root nodules on the host plant alfalfa. any one of three s. meliloti polysaccharides, succinoglycan, eps ii, or k antigen, can mediate infection thread initiation and extension (root nodule invasion) on alfalfa. of these three polysaccharides, the only symbiotically active polysaccharide produced by s. meliloti wild-type strain rm1021 is su ... | 2002 | 12193623 |
| structural studies of the fur protein from rhizobium leguminosarum. | the x-ray crystal structure of the apo-form of the fur protein from rhizobium leguminosarum has been solved at 2.7 a resolution. small-angle x-ray scattering was used to give information on the solution conformation of the protein. the fur homodimer folds into two domains. the n-terminal domain is formed from the packing of two helix-turn-helix motifs while the c-terminal domain appears primarily to stabilize the dimeric state of the protein. | 2002 | 12196192 |
| effect of a sinorhizobium meliloti strain with a modified puta gene on the rhizosphere microbial community of alfalfa. | the success of a rhizobial inoculant in the soil depends to a large extent on its capacity to compete against indigenous strains. m403, a sinorhizobium meliloti strain with enhanced competitiveness for nodule occupancy, was recently constructed by introducing a plasmid containing an extra copy of a modified puta (proline dehydrogenase) gene. this strain and m401, a control strain carrying the same plasmid without the modified gene, were used as soil inoculants for alfalfa in a contained field re ... | 2002 | 12200266 |
| role of tfxe, but not tfxg, in trifolitoxin resistance. | eight genes, tfxabcdefg and tfua, confer production of trifolitoxin (tfx), a ribosomally synthesized, posttranslationally modified peptide antibiotic, in tfx-sensitive alpha-proteobacteria. an in-frame deletion in tfxe significantly reduced a strain's resistance to tfx in comparison to that of an otherwise identical construct containing wild-type tfxe. the deletion of tfxg had no effect on tfx resistance. nevertheless, rnase protection assays showed that tfxe and tfxg are transcribed, showing th ... | 2002 | 12200284 |
| molecular characterization of functional modules of plasmid pwks1 of paracoccus pantotrophus dsm 11072. | the complete nucleotide sequence of the small, cryptic plasmid pwks1 (2697 bp) of paracoccus pantotrophus dsm 11072 was determined. the g+c content of the sequence of this plasmid was 62 mol%. analysis revealed that over 80% of the plasmid genome was covered by two orfs, orf1 and orf2, which were capable of encoding putative peptides of 44.1 and 37.8 kda, respectively. mutational analysis showed that orf2 was crucial for plasmid replication. the translational product of orf2 shared local homolog ... | 2002 | 12213930 |
| a monocarboxylate permease of rhizobium leguminosarum is the first member of a new subfamily of transporters. | amino acid transport by rhizobium leguminosarum is dominated by two abc transporters, the general amino acid permease (aap) and the branched-chain amino acid permease (bra). however, mutation of these transporters does not prevent this organism from utilizing alanine for growth. an r. leguminosarum permease (mctp) has been identified which is required for optimal growth on alanine as a sole carbon and nitrogen source. characterization of mctp confirmed that it transports alanine (k(m) = 0.56 mm) ... | 2002 | 12218032 |
| the two-component system bvrr/bvrs essential for brucella abortus virulence regulates the expression of outer membrane proteins with counterparts in members of the rhizobiaceae. | the brucella bvrr/bvrs two-component regulatory system is homologous to the chvi/chvg systems of sinorhizobium meliloti and agrobacterium tumefaciens necessary for endosymbiosis and pathogenicity in plants. bvrr/bvrs controls cell invasion and intracellular survival. probing the surface of bvrr and bvrs transposon mutants with monoclonal antibodies showed all described major outer membrane proteins (omps) but omp25, a protein known to be involved in brucella virulence. absence of omp25 expressio ... | 2002 | 12218183 |
| sym2 of pea is involved in a nodulation factor-perception mechanism that controls the infection process in the epidermis. | in pea (pisum sativum) up to 50 nodulation mutants are known, several of which are affected in the early steps of the symbiotic interaction with rhizobium sp. bacteria. here we describe the role of the sym2 gene in nodulation (nod) factor perception. our experiments show that the sym2a allele from the wild pea variety afghanistan confers an arrest in infection-thread growth if the rhizobium leguminosarum bv viciae strain does not produce nod factors with a nodx-mediated acetylation at their redu ... | 1997 | 12223813 |
| effects of boron on rhizobium-legume cell-surface interactions and nodule development. | boron (b) is an essential micronutrient for the development of nitrogen-fixing root nodules in pea (pisum sativum). by using monoclonal antibodies that recognize specific glycoconjugate components implicated in legume root-nodule development, we investigated the effects of low b on the formation of infection threads and the colonization of pea nodules by rhizobium leguminosarum bv viciae. in b-deficient nodules the proportion of infected host cells was much lower than in nodules from plants supp ... | 1996 | 12226256 |
| n-acylhomoserine lactones undergo lactonolysis in a ph-, temperature-, and acyl chain length-dependent manner during growth of yersinia pseudotuberculosis and pseudomonas aeruginosa. | in gram-negative bacterial pathogens, such as pseudomonas aeruginosa and yersinia pseudotuberculosis, cell-to-cell communication via the n-acylhomoserine lactone (ahl) signal molecules is involved in the cell population density-dependent control of genes associated with virulence. this phenomenon, termed quorum sensing, relies upon the accumulation of ahls to a threshold concentration at which target structural genes are activated. by using biosensors capable of detecting a range of ahls we obse ... | 2002 | 12228292 |
| two predicted chemoreceptors of helicobacter pylori promote stomach infection. | helicobacter pylori must be motile or display chemotaxis to be able to fully infect mammals, but it is not known how this chemotaxis is directed. we disrupted two genes encoding predicted chemoreceptors, tlpa and tlpc. h. pylori mutants lacking either of these genes are fully motile and chemotactic in vitro and are as able as the wild type to infect mice when they are the sole infecting strains. in contrast, when mice are coinfected with the h. pylori ss1 tlpa or tlpc mutant and the wild type, w ... | 2002 | 12228322 |
| sugar-binding activity of pea lectin expressed in white clover hairy roots. | introduction of the pea (pisum sativum l.) lectin (psl) gene into white clover (trifolium repens l.) hairy roots facilitates nodulation by the nitrogen-fixing bacterium rhizobium leguminosarum biovar viciae, which normally nodulates pea and not white clover (c.l. diaz, l.s. melchers, p.j.j. hooykaas, b.j.j. lugtenberg, and j.w. kijne [1989] nature 338: 579-581). here, we show that psl is functionally expressed in transgenic white clover hairy roots transformed with the psl gene. psl could be iso ... | 1995 | 12228660 |
| root hair deformation activity of nodulation factors and their fate on vicia sativa. | we used a semiquantitative root hair deformation assay for vicia sativa (vetch) to study the activity of rhizobium leguminosarum bv viciae nodulation (nod) factors. five to 10 min of nod factor-root interaction appears to be sufficient to induce root hair deformation. the first deformation is visible within 1 h, and after 3 h about 80% of the root hairs in a small susceptible zone of the root are deformed. this zone encompasses root hairs that have almost reached their maximal size. the nod fact ... | 1994 | 12232242 |
| deficiency of a sinorhizobium meliloti baca mutant in alfalfa symbiosis correlates with alteration of the cell envelope. | the baca protein is essential for the long-term survival of sinorhizobium meliloti and brucella abortus within acidic compartments in plant and animal cells, respectively. since both the s. meliloti and b. abortus baca mutants have an increased resistance to bleomycin, it was hypothesized that baca was a transporter of bleomycin and bleomycin-like compounds into the bacterial cell. however, our finding that the s. meliloti baca mutant also has an increased sensitivity to detergents, a hydrophobi ... | 2002 | 12270820 |
| characterization of the sinorhizobium meliloti sinr/sini locus and the production of novel n-acyl homoserine lactones. | sinorhizobium meliloti is a soil bacterium which can establish a nitrogen-fixing symbiosis with the legume medicago sativa. recent work has identified a pair of genes, sinr and sini, which represent a potential quorum-sensing system and are responsible for the production of n-acyl homoserine lactones (ahls) in two s. meliloti strains, rm1021 and rm41. in this work, we characterize the sinri locus and show that these genes are responsible for the synthesis of several long-chain ahls ranging from ... | 2002 | 12270827 |
| diversity and evolution of hydrogenase systems in rhizobia. | uptake hydrogenases allow rhizobia to recycle the hydrogen generated in the nitrogen fixation process within the legume nodule. hydrogenase (hup) systems in bradyrhizobium japonicum and rhizobium leguminosarum bv. viciae show highly conserved sequence and gene organization, but important differences exist in regulation and in the presence of specific genes. we have undertaken the characterization of hup gene clusters from bradyrhizobium sp. (lupinus), bradyrhizobium sp. (vigna), and rhizobium tr ... | 2002 | 12324339 |
| a polysaccharide deacetylase gene (pdaa) is required for germination and for production of muramic delta-lactam residues in the spore cortex of bacillus subtilis. | the predicted amino acid sequence of bacillus subtilis yfjs (renamed pdaa) exhibits high similarity to those of several polysaccharide deacetylases. beta-galactosidase fusion experiments and results of northern hybridization with sporulation sigma mutants indicated that the pdaa gene is transcribed by e(sigma)(g) rna polymerase. pdaa-deficient spores were bright by phase-contrast microscopy, and the spores were induced to germination on the addition of l-alanine. germination-associated spore dar ... | 2002 | 12374835 |
| rhizobium leguminosarum chaperonin 60.3, but not chaperonin 60.1, induces cytokine production by human monocytes: activity is dependent on interaction with cell surface cd14. | as part of a program of work to understand the interaction of bacterial chaperonins with human leukocytes, we have examined 2 of the 3 chaperonin 60 (cpn 60) gene products of the nonpathogenic plant symbiotic bacterium, rhizobium leguminosarum, for their capacity to induce the production of pro- and antiinflammatory cytokines by human cells. recombinant r. leguminosarum cpn 60.1 and 60.3 proteins were added to human monocytes at a range of concentrations, and cytokine production was measured by ... | 2002 | 12380680 |
| expression and purification of rhizobium leguminosarum nodd. | a rhizobium expression system was constructed via introducing strong transcriptional elements to an incp broad host range plasmid pkt230. using this system, the nodd gene of rhizobium leguminosarum biovar viciae was overexpressed in its own in vivo environment. western blot showed that the nodd yield of the newly constructed expression vector pkndt was much higher than that of a reported vector pij1518. based on the result from quantitative gel retardation assay, the specific dna-binding activit ... | 2002 | 12406687 |
| a new species of devosia that forms a unique nitrogen-fixing root-nodule symbiosis with the aquatic legume neptunia natans (l.f.) druce. | rhizobia are the common bacterial symbionts that form nitrogen-fixing root nodules in legumes. however, recently other bacteria have been shown to nodulate and fix nitrogen symbiotically with these plants. neptunia natans is an aquatic legume indigenous to tropical and subtropical regions and in african soils is nodulated by allorhizobium undicola. this legume develops an unusual root-nodule symbiosis on floating stems in aquatic environments through a unique infection process. here, we analyzed ... | 2002 | 12406707 |
| a sinorhizobium meliloti lipopolysaccharide mutant altered in cell surface sulfation. | the rhizobium-legume symbiosis involves the formation of a novel plant organ, the nodule, in which intracellular bacteria reduce molecular dinitrogen in exchange for plant photosynthates. nodule development requires a bacterial signal referred to as nod factor, which in sinorhizobium meliloti is a beta-(1,4)-linked tetramer of n-acetylglucosamine containing n-acyl and o-acetyl modifications at the nonreducing end and a critical 6-o-sulfate at the reducing end. this sulfate modification requires ... | 2002 | 12426356 |
| symbiotic effects of deltamatb rhizobium leguminosarum bv. trifolii mutant on clovers. | the role of malonate in symbiotic nitrogen metabolism has long been controversial, although it is known to occur in legume roots, especially in the nodules. here we report that malonate metabolism plays a key role in the differentiation of bacteroids rhizobium leguminosarum bv. trifolii in clover nodules. an operon, mat, that consists of three consecutive genes (matabc) has been discovered. mat encodes enzymes that catalyze the uptake and conversion of malonate to acetyl-coa through malonyl-coa. ... | 2002 | 12442899 |
| the escherichia coli gabdtpc operon: specific gamma-aminobutyrate catabolism and nonspecific induction. | nitrogen limitation induces the nitrogen-regulated (ntr) response, which includes proteins that assimilate ammonia and scavenge nitrogen. nitrogen limitation also induces catabolic pathways that degrade four metabolically related compounds: putrescine, arginine, ornithine, and gamma-aminobutyrate (gaba). we analyzed the structure, function, and regulation of the gab operon, whose products degrade gaba, a proposed intermediate in putrescine catabolism. we showed that the gabdtpc gene cluster cons ... | 2002 | 12446648 |
| the influence of the symbiotic plasmid prl1ji on the distribution of gm rhizobia in soil and crop rhizospheres, and implications for gene flow. | the distribution of two genetically modified rhizobium leguminosarum strains was investigated in the field. one, rsm2004, released in 1987, carries a tns marker on its conjugative symbiotic plasmid (psym). the second, ct0370, released at the same site in 1994, has a gusa gene integrated into its chromosome but no psym. plate counts indicated that the ct0370 population became established at a higher level than rsm2004. however, when peas, alfalfa and barley were grown, rsm2004 was found to outnum ... | 2002 | 12448756 |
| identification of an iron-regulated, hemin-binding outer membrane protein in sinorhizobium meliloti. | rhizobia are soil bacteria that are able to establish symbiotic associations with leguminous hosts. in iron-limited environments these bacteria can use iron present in heme or heme compounds (hemoglobin, leghemoglobin). here we report the presence in sinorhizobium meliloti of an iron-regulated outer membrane protein that is able to bind hemin but not hemoglobin. protein assignment was done by matrix-assisted laser desorption ionization-time of flight mass spectrometry. tryptic peptides correlate ... | 2002 | 12450806 |
| xylanase and acetyl xylan esterase activities of xyna, a key subunit of the clostridium cellulovorans cellulosome for xylan degradation. | the clostridium cellulovorans xyna gene encodes the cellulosomal endo-1,4-beta-xylanase xyna, which consists of a family 11 glycoside hydrolase catalytic domain (cd), a dockerin domain, and a nodb domain. the recombinant acetyl xylan esterase (rnodb) encoded by the nodb domain exhibited broad substrate specificity and released acetate not only from acetylated xylan but also from other acetylated substrates. rnodb acted synergistically with the xylanase cd of xyna for hydrolysis of acetylated xyl ... | 2002 | 12450866 |
| structural characterization of the lipid a component of sinorhizobium sp. ngr234 rough and smooth form lipopolysaccharide. demonstration that the distal amide-linked acyloxyacyl residue containing the long chain fatty acid is conserved in rhizobium and sinorhizobium sp. | a broad-host-range endosymbiont, sinorhizobium sp. ngr234 is a component of several legume-symbiont model systems; however, there is little structural information on the cell surface glycoconjugates. ngr234 cells in free-living culture produce a major rough lipopolysaccharide (lps, lacking o-chain) and a minor smooth lps (containing o-chain), and the structure of the lipid a components was investigated by chemical analyses, mass spectrometry, and nmr spectroscopy of the underivatized lipids a. t ... | 2003 | 12456672 |
| rnase e is involved in 5'-end 23s rrna processing in alpha-proteobacteria. | in rhodobacter capsulatus and rhizobium leguminosarum, an internal transcribed spacer consisting of helices 9 and 10 is removed during 23s rrna processing, which leads to the occurrence of a 5.8s-like rrna. the particular rrna maturation steps are not known, with exception of the initial rnase iii cleavage in helix 9. we found that gc-rich stem-loop structures of helix 9, which are released by rnase iii, are immediately degraded. the degradation of helix 10 is slower and its kinetics differs in ... | 2002 | 12470646 |
| rira, an iron-responsive regulator in the symbiotic bacterium rhizobium leguminosarum. | mutations in a rhizobium leguminosarum gene, rira (rhizobial iron regulator), caused high-level, constitutive expression of at least eight operons whose transcription is normally fe-responsive and whose products are involved in the synthesis or uptake of siderophores, or in the uptake of haem or of other iron sources. close homologues of rira exist in other rhizobia and in the pathogen brucella; many other bacteria have deduced proteins with more limited sequence similarity. none of these homolo ... | 2002 | 12480909 |
| the glcb locus of rhizobium leguminosarum vf39 encodes an arabinose-inducible malate synthase. | in the course of a study conducted to isolate genes upregulated by plant cell wall sugars, we identified an arabinose-inducible locus from a transcriptional fusion library of rhizobium leguminosarum vf39, carrying random insertions of the lacz transposon tn5b22. sequence analysis of the locus disrupted by the transposon revealed a high similarity to uncharacterized malate synthase g genes from sinorhizobium meliloti, agrobacterium tumefaciens, and mesorhizobium loti. this enzyme catalyzes the co ... | 2002 | 12489782 |
| crystallization and preliminary x-ray crystallographic analysis of malonyl-coa decarboxylase from rhizobium leguminosarum bv. trifolii. | malonyl-coa decarboxylase (mcd), which catalyzes the conversion of malonyl-coa to acetyl-coa, is an evolutionarily distinct and highly conserved enzyme. mcd does not share sequence homology with other known decarboxylases, while the enzymes from different species exhibit at least >30% sequence identity to each other. in order to provide a canonical structure of the enzyme for detailed study of its structure-function relationship, the mcd of rhizobium leguminosarum bv. trifolii was overexpressed ... | 2003 | 12499559 |
| transfer of the symbiotic plasmid from rhizobium leguminosarum biovar trifolii to agrobacterium tumefaciens. | this study examined the symbiotic properties of agrobacterium transconjugants isolated by transferring a tn5-mob-marked derivative of the 315 kb megaplasmid prt4sa from rhizobium leguminosarum bv. trifolii 4s (wild-type strain) to agrobacterium tumefaciens a136 as the recipient. the genetic characteristics of the at4s transconjugant strains were ascertained by random amplified polymorphic dna (rapd) analyses and southern hybridization using tn5-mob and nod genes as probes. several of these at4s ... | 1998 | 12501295 |
| integration of the temperate phage phiu into the putative trna gene on the chromosome of its host rhizobium leguminosarum biovar trifolii. | the plasmid pci6, carrying the attp site of the temperate phage phiu, integrates into the attb site on the chromosome of rhizobium leguminosarum biovar trifolii strain 4s. the 4 kb ecori-hindiii region of pci6 involved in site-specific integration was subcloned as the attp fragment of phage phiu and sequenced. the attl fragment, one of the new dna junctions generated from the insertion of pci6 into the chromosome of the host rhizobium, was used as a hybridization probe for isolation of the attb ... | 1998 | 12501298 |
| nodulation gene regulation in bradyrhizobium japonicum: a unique integration of global regulatory circuits. | | 2003 | 12513971 |
| an outer membrane enzyme that generates the 2-amino-2-deoxy-gluconate moiety of rhizobium leguminosarum lipid a. | the structures of rhizobium leguminosarum and rhizobium etli lipid a are distinct from those found in other gram-negative bacteria. whereas the more typical escherichia coli lipid a is a hexa-acylated disaccharide of glucosamine that is phosphorylated at positions 1 and 4', r. etli and r. leguminosarum lipid a consists of a mixture of structurally related species (designated a-e) that lack phosphate. a conserved distal unit, comprised of a diacylated glucosamine moiety with galacturonic acid res ... | 2003 | 12531907 |
| origin of the 2-amino-2-deoxy-gluconate unit in rhizobium leguminosarum lipid a. expression cloning of the outer membrane oxidase lpxq. | an unusual feature of the lipid a from the plant endosymbionts rhizobium etli and rhizobium leguminosarum is the presence of a proximal sugar unit consisting of a 2-amino-2-deoxy-gluconate moiety in place of glucosamine. an outer membrane oxidase that generates the 2-amino-2-deoxy-gluconate unit from a glucosamine-containing precursor is present in membranes of r. leguminosarum and r. etli but not in s. meliloti or escherichia coli. we now report the identification of a hybrid cosmid that direct ... | 2003 | 12531908 |
| characterization of helicobacter pylori nickel metabolism accessory proteins needed for maturation of both urease and hydrogenase. | previous studies demonstrated that two accessory proteins, hypa and hypb, play a role in nickel-dependent maturation of both hydrogenase and urease in helicobacter pylori. here, the two proteins were purified and characterized. hypa bound two ni(2+) ions per dimer with positive cooperativity (hill coefficient, approximately 2.0). the dissociation constants k(1) and k(2) for ni(2+) were 58 and 1.3 microm, respectively. studies on purified site-directed mutant proteins in each of the five histidin ... | 2003 | 12533448 |
| quorum sensing in rhizobium sp. strain ngr234 regulates conjugal transfer (tra) gene expression and influences growth rate. | rhizobium sp. strain ngr234 forms symbiotic, nitrogen-fixing nodules on a wide range of legumes via functions largely encoded by the plasmid pngr234a. the pngr234a sequence revealed a region encoding plasmid replication (rep) and conjugal transfer (tra) functions similar to those encoded by the rep and tra genes from the tumor-inducing (ti) plasmids of agrobacterium tumefaciens, including homologues of the ti plasmid quorum-sensing regulators trai, trar, and tram. in a. tumefaciens, trai, a luxi ... | 2003 | 12533456 |
| prediction and overview of the rpon-regulon in closely related species of the rhizobiales. | in the rhizobia, a group of symbiotic gram-negative soil bacteria, rpon (sigma54, sigman, ntra) is best known as the sigma factor enabling transcription of the nitrogen fixation genes. recent reports, however, demonstrate the involvement of rpon in other symbiotic functions, although no large-scale effort has yet been undertaken to unravel the rpon-regulon in rhizobia. we screened two complete rhizobial genomes (mesorhizobium loti, sinorhizobium meliloti) and four symbiotic regions (rhizobium et ... | 2002 | 12537565 |
| cloning and characterization of edwardsiella ictaluri proteins expressed and recognized by the channel catfish ictalurus punctatus immune response during infection. | an edwardsiella ictaluri expression library was screened for clones expressing antigenic e. ictaluri proteins using anti-e. ictaluri serum, which resulted in the isolation of 32 clones. the clones were partially characterized and 4 were selected for complete analysis. sodium dodecyl sulfate polyacrylamide gel electrophoresis (sds-page), 2-dimensional page, western blotting, and dna sequencing were used to analyze expressed antigenic proteins and encoded genes. sequence analysis identified 4 puta ... | 2002 | 12542086 |
| biosynthesis of phosphatidylcholine in bacteria. | phosphatidylcholine (pc) is the major membrane-forming phospholipid in eukaryotes and can be synthesized by either of two pathways, the methylation pathway or the cdp-choline pathway. many prokaryotes lack pc, but it can be found in significant amounts in membranes of rather diverse bacteria and based on genomic data, we estimate that more than 10% of all bacteria possess pc. enzymatic methylation of phosphatidylethanolamine via the methylation pathway was thought to be the only biosynthetic pat ... | 2003 | 12547654 |
| characterization of the nodulation plasmid encoded chemoreceptor gene mcpg from rhizobium leguminosarum. | in general, chemotaxis in rhizobium has not been well characterized. methyl accepting chemotaxis proteins are sensory proteins important in chemotaxis of numerous bacteria, but their involvement in rhizobium chemotaxis is unclear and merits further investigation. | 2003 | 12553885 |
| identification and characterization of a vibrio cholerae gene, mbaa, involved in maintenance of biofilm architecture. | the formation of biofilms is thought to play a key role in the environmental survival of the marine bacterium vibrio cholerae. although the factors involved in v. cholerae attachment to abiotic surfaces have been extensively studied, relatively little is known about the mechanisms involved in the subsequent maturation of the biofilms. here we report the identification of a novel gene, which we have named mbaa (for maintenance of biofilm architecture), that plays a role in the formation and maint ... | 2003 | 12562809 |
| rhizobium etli and rhizobium gallicum nodulate common bean (phaseolus vulgaris) in a traditionally managed milpa plot in mexico: population genetics and biogeographic implications. | the stability of the genetic structure of rhizobial populations nodulating phaseolus vulgaris cultivated in a traditionally managed milpa plot in mexico was studied over three consecutive years. the set of molecular markers analyzed (including partial rrs, glnii, nifh, and nodb sequences), along with host range experiments, placed the isolates examined in rhizobium etli bv. phaseoli and rhizobium gallicum bv. gallicum. cluster analysis of multilocus enzyme electrophoresis and plasmid profile dat ... | 2003 | 12571008 |
| biotin limitation in sinorhizobium meliloti strain 1021 alters transcription and translation. | most sinorhizobium meliloti strains lack several key genes involved in microbial biotin biosynthesis, and it is assumed that this may be a special adaptation which allows the microbe to down-regulate metabolic activities in the absence of a host plant. to further explore this hypothesis, we employed two different strategies. (i) searches of the s. meliloti genome database in combination with the construction of nine different gusa reporter fusions identified three genes involved in a biotin star ... | 2003 | 12571048 |
| purification and characterisation of two gst's forms from rhizobium leguminosarum with a high affinity to herbicides. | cytosolic glutathione transferases are a family of multifunctional proteins that catalyse the conjugation of gsh to a large variety of endogenous and exogenous compounds. these enzymes have been widely studied in mammals and, to a lesser extent, in plants. in plants, gsts can detoxify herbicides; they are also induced by pathogenic infection and are likely to be involved in defence responses. gsts are found in pathogenic and not pathogenic prokaryotes but the functional role played by these enzy ... | 2003 | 12578732 |
| a white clover nodulin gene, dd23b, encoding a cysteine cluster protein, is expressed in roots during the very early stages of interaction with rhizobium leguminosarumbiovar trifolii and after treatment with chitolipooligosaccharide nod factors. | an early nodulin cdna, dd23b, was isolated from white clover root tissue by differential display rt-pcr. its full-length sequence of 340 nucleotides encodes a predicted 72-amino-acid protein of molecular mass 8.3 kda, with a polypeptide region containing cysteine pairs spaced in the manner of a cysteine cluster protein. this feature, which is shared by some other late and early nodulins from pea and broad bean, suggests a role in metal ion binding and membrane transport. temporal and spatial exp ... | 2002 | 12579447 |