Articles de revues : « Plasmi freddi »

1

Acosta-Jurado, Sebastián, Cynthia Alías-Villegas, Andrés Almozara, M. Rosario Espuny, José-María Vinardell et Francisco Pérez-Montaño. « Deciphering the Symbiotic Significance of Quorum Sensing Systems of Sinorhizobium fredii HH103 ». Microorganisms 8, n^o 1 (2 janvier 2020) : 68. http://dx.doi.org/10.3390/microorganisms8010068.

Texte intégral

Résumé :

Quorum sensing (QS) is a bacterial cell-to-cell signaling mechanism that collectively regulates and synchronizes behaviors by means of small diffusible chemical molecules. In rhizobia, QS systems usually relies on the synthesis and detection of N-acyl-homoserine lactones (AHLs). In the model bacterium Sinorhizobium meliloti functions regulated by the QS systems TraI-TraR and SinI-SinR(-ExpR) include plasmid transfer, production of surface polysaccharides, motility, growth rate and nodulation. These systems are also present in other bacteria of the Sinorhizobium genus, with variations at the species and strain level. In Sinorhizobium fredii NGR234 phenotypes regulated by QS are plasmid transfer, growth rate, sedimentation, motility, biofilm formation, EPS production and copy number of the symbiotic plasmid (pSym). The analysis of the S. fredii HH103 genomes reveal also the presence of both QS systems. In this manuscript we characterized the QS systems of S. fredii HH103, determining that both TraI and SinI AHL-synthases proteins are responsible of the production of short- and long-chain AHLs, respectively, at very low and not physiological concentrations. Interestingly, the main HH103 luxR-type genes, expR and traR, are split into two ORFs, suggesting that in S. fredii HH103 the corresponding carboxy-terminal proteins, which contain the DNA-binding motives, may control target genes in an AHL-independent manner. The presence of a split traR gene is common in other S. fredii strains.

Styles APA, Harvard, Vancouver, ISO, etc.

2

Vinardell, JoséMaría, Francisco Javier Ollero, Ángeles Hidalgo, Francisco Javier López-Baena, Carlos Medina, Kalojan Ivanov-Vangelov, Maribel Parada et al. « NolR Regulates Diverse Symbiotic Signals of Sinorhizobium fredii HH103 ». Molecular Plant-Microbe Interactions® 17, n^o 6 (juin 2004) : 676–85. http://dx.doi.org/10.1094/mpmi.2004.17.6.676.

Texte intégral

Résumé :

We have investigated in Sinorhizobium fredii HH103-1 (=HH103 Strr) the influence of the nolR gene on the production of three different bacterial symbiotic signals: Nod factors, signal responsive (SR) proteins, and exopolysac-charide (EPS). The presence of multiple copies of nolR (in plasmid pMUS675) repressed the transcription of all the flavonoid-inducible genes analyzed: nodA, nodD1, nolO, nolX, noeL, rhcJ, hesB, and y4pF. Inactivation of nolR (mutant SVQ517) or its overexpression (presence of pMUS675) altered the amount of Nod factors detected. Mutant SVQ517 produced Nod factors carrying N-methyl residues at the nonreducing N-acetyl-glucosamine, which never have been detected in S. fredii HH103. Plasmid pMUS675 increased the amounts of EPS produced by HH103-1 and SVQ517. The flavonoid genistein repressed EPS production of HH103-1 and SVQ517 but the presence of pMUS675 reduced this repression. The presence of plasmid pMUS675 clearly decreased the secretion of SR proteins. Inactivation, or overexpression, of nolR decreased the capacity of HH103 to nodulate Glycine max. However, HH103-1 and SVQ517 carrying plasmid pMUS675 showed enhanced nodulation capacity with Vigna unguiculata. The nolR gene was positively identified in all S. fredii strains investigated, S. xinjiangense CCBAU110, and S. saheli USDA4102. Apparently, S. teranga USDA4101 does not contain this gene.

Styles APA, Harvard, Vancouver, ISO, etc.

3

Dave, Akash, Tanvi Khanna et Pushpa Robin. « Exploiting Rhizobium for Cadmium Sulphide Nanoparticle Synthesis : Heterologous Expression of an Escherichia coli DH10B Enzyme, YbdK [EC : 6.3.2.2] in Sinorhizobium fredii NGR234 ». Journal of Pure and Applied Microbiology 16, n^o 1 (25 février 2022) : 593–605. http://dx.doi.org/10.22207/jpam.16.1.59.

Texte intégral

Résumé :

Escherichia coli DH10B has 1.1 kb ybdK gene which is responsible for encoding YbdK enzyme that possess a Gamma glutamyl cysteine synthetase activity. ybdK gene was ligated downstream of a constitutive derepressed lac promoter of a low copy number plasmid vector pBBR1MCS-2, giving rise to a recombinant plasmid pPAT. Sinorhizobium fredii NGR234 transformed with pPAT showed an augmented production of glutathione which in turn increased the production of cadmium sulphide nanoparticles to some extent. Also, a heterologous expression of YbdK in Sinorhizobium fredii NGR234 improved the oxidation status of bacterial cells which is confirmed by fluorescence microscopy images and fluorometry. Genetically modified (GM) cells stained by DCFDA showed a significant decrease in fluorescence compared to wild type (WT) cells. Physical and chemical properties of the nanoparticles produced by the pPAT transformed Sinorhizobium fredii NGR234 differed significantly compared to wild type (WT) Sinorhizobium fredii NGR234. Comparative analysis of the nanoparticles by FTIR and SEM analysis revealed the functional groups attached to nanoparticles and average nanoparticle size respectively. Nanoparticles synthesized by genetically modified (GM) bacteria were about 3 times smaller in size compared to those produced by wild type (WT) rhizobium. FTIR analysis revealed an augmented presence of peptide with the nanoparticles produced by GM bacteria compared to those produced by the WT bacteria. XRD data revealed that biosynthesized CdS nanoparticles are face centered crystalline particles which was confirmed by comparing the peaks to standard JCPDS data (JCPDS card no. 10-454).

Styles APA, Harvard, Vancouver, ISO, etc.

4

Jiang, Guoqiao, et Hari B. Krishnan. « Sinorhizobium fredii USDA257, a Cultivar-Specific Soybean Symbiont, Carries Two Copies of y4yA and y4yB, Two Open Reading Frames That Are Located in a Region That Encodes the Type III Protein Secretion System ». Molecular Plant-Microbe Interactions® 13, n^o 9 (septembre 2000) : 1010–14. http://dx.doi.org/10.1094/mpmi.2000.13.9.1010.

Texte intégral

Résumé :

Sinorhizobium fredii USDA257 forms nitrogen-fixing nodules on primitive soybean (Glycine max) cultivar Peking but fails to nodulate the improved cultivar McCall. Cultivar specificity is governed by a plasmid-borne locus, nolXBTUV. By DNA sequence analysis, we have identified two open reading frames, y4yA and y4yB, immediately downstream of nolX. Northern (RNA) blot analysis indicated that the expression of both y4yA and y4yB is inducible by isoflavonoids, and an intact copy of nolX is required. Two copies each of y4yA and y4yB are present in S. fredii USDA257, one on the sym plasmid (y4yAsp and y4yBsp), and the other on the chromosome (y4yAc and y4yBc). The cultivar-nonspecific strain USDA191 lacks y4yAc and y4yBc. Introduction of y4yAc plus y4yBc from USDA257 into USDA191 did not influence the ability of the latter strain to nodulate McCall soybean plants. Unlike nolX, the inactivation of y4yAsp and y4yBsp of USDA257 did not extend the host range of this strain. A double mutant, in which both the plasmid and chromosomal copies of y4yA and y4yB were mutated, had no observable effect on symbiotic ability of USDA257. The y4yAsp and y4yBsp mutants did not influence flavonoid-dependent extracellular protein production. Rhizobium sp. strain NGR234 and S. saheli USDA4893 both contain sequences similar to S. fredii USDA257 y4yAsp and y4yBsp; however, Bradyrhizobium spp., the traditional soybean symbionts, lack these genes.

Styles APA, Harvard, Vancouver, ISO, etc.

5

Vinardell, José-María, Sebastián Acosta-Jurado, Susanne Zehner, Michael Göttfert, Anke Becker, Irene Baena, Jochem Blom et al. « The Sinorhizobium fredii HH103 Genome : A Comparative Analysis With S. fredii Strains Differing in Their Symbiotic Behavior With Soybean ». Molecular Plant-Microbe Interactions® 28, n^o 7 (juillet 2015) : 811–24. http://dx.doi.org/10.1094/mpmi-12-14-0397-fi.

Texte intégral

Résumé :

Sinorhizobium fredii HH103 is a fast-growing rhizobial strain infecting a broad range of legumes including both American and Asiatic soybeans. In this work, we present the sequencing and annotation of the HH103 genome (7.25 Mb), consisting of one chromosome and six plasmids and representing the structurally most complex sinorhizobial genome sequenced so far. Comparative genomic analyses of S. fredii HH103 with strains USDA257 and NGR234 showed that the core genome of these three strains contains 4,212 genes (61.7% of the HH103 genes). Synteny plot analysis revealed that the much larger chromosome of USDA257 (6.48 Mb) is colinear to the HH103 (4.3 Mb) and NGR324 chromosomes (3.9 Mb). An additional region of the USDA257 chromosome of about 2 Mb displays similarity to plasmid pSfHH103e. Remarkable differences exist between HH103 and NGR234 concerning nod genes, flavonoid effect on surface polysaccharide production, and quorum-sensing systems. Furthermore a number of protein secretion systems have been found. Two genes coding for putative type III–secreted effectors not previously described in S. fredii, nopI and gunA, have been located on the HH103 genome. These differences could be important to understand the different symbiotic behavior of S. fredii strains HH103, USDA257, and NGR234 with soybean.

Styles APA, Harvard, Vancouver, ISO, etc.

6

Hashem, F. M., L. D. Kuykendall, S. E. Udell et P. M. Thomas. « Phage susceptibility and plasmid profile analysis of Sinorhizobium fredii ». Plant and Soil 186, n^o 1 (septembre 1996) : 127–34. http://dx.doi.org/10.1007/bf00035066.

Texte intégral

Styles APA, Harvard, Vancouver, ISO, etc.

7

Krishnan, Hari B., Won-Seok Kim, Jeong Sun-Hyung, Kil Yong Kim et Guoqiao Jiang. « Citrate Synthase Mutants of Sinorhizobium fredii USDA257 Form Ineffective Nodules with Aberrant Ultrastructure ». Applied and Environmental Microbiology 69, n^o 6 (juin 2003) : 3561–68. http://dx.doi.org/10.1128/aem.69.6.3561-3568.2003.

Texte intégral

Résumé :

ABSTRACT The tricarboxylic acid (TCA) cycle plays an important role in generating the energy required by bacteroids to fix atmospheric nitrogen. Citrate synthase is the first enzyme that controls the entry of carbon into the TCA cycle. We cloned and determined the nucleotide sequence of the gltA gene that encodes citrate synthase in Sinorhizobium fredii USDA257, a symbiont of soybeans (Glycine max [L.] Merr.) and several other legumes. The deduced citrate synthase protein has a molecular weight of 48,198 and exhibits sequence similarity to citrate synthases from several bacterial species, including Sinorhizobium meliloti and Rhizobium tropici. Southern blot analysis revealed that the fast-growing S. fredii strains and Rhizobium sp. strain NGR234 contained a single copy of the gene located in the bacterial chromosome. S. fredii USDA257 gltA mutant HBK-CS1, which had no detectable citrate synthase activity, had diminished nodulation capacity and produced ineffective nodules on soybean. Light and electron microscopy observations revealed that the nodules initiated by HBK-CS1 contained very few bacteroids. The infected cells contained large vacuoles and prominent starch grains. Within the vacuoles, membrane structures that appeared to be reminiscent of disintegrating bacteroids were detected. The citrate synthase mutant had altered cell surface characteristics and produced three times more exopolysaccarides than the wild type produced. A plasmid carrying the USDA257 gltA gene, when introduced into HBK-CS1, was able to restore all of the defects mentioned above. Our results demonstrate that a functional citrate synthase gene of S. fredii USDA257 is essential for efficient soybean nodulation and nitrogen fixation.

Styles APA, Harvard, Vancouver, ISO, etc.

8

Jiao, Jian, Li Juan Wu, Biliang Zhang, Yue Hu, Yan Li, Xing Xing Zhang, Hui Juan Guo et al. « MucR Is Required for Transcriptional Activation of Conserved Ion Transporters to Support Nitrogen Fixation of Sinorhizobium fredii in Soybean Nodules ». Molecular Plant-Microbe Interactions® 29, n^o 5 (mai 2016) : 352–61. http://dx.doi.org/10.1094/mpmi-01-16-0019-r.

Texte intégral

Résumé :

To achieve effective symbiosis with legume, rhizobia should fine-tune their background regulation network in addition to activating key genes involved in nodulation (nod) and nitrogen fixation (nif). Here, we report that an ancestral zinc finger regulator, MucR1, other than its paralog, MucR2, carrying a frameshift mutation, is essential for supporting nitrogen fixation of Sinorhizobium fredii CCBAU45436 within soybean nodules. In contrast to the chromosomal mucR1, mucR2 is located on symbiosis plasmid, indicating its horizontal transfer potential. A MucR2 homolog lacking the frameshift mutation, such as the one from S. fredii NGR234, can complement phenotypic defects of the mucR1 mutant of CCBAU45436. RNA-seq analysis revealed that the MucR1 regulon of CCBAU45436 within nodules exhibits significant difference compared with that of free-living cells. MucR1 is required for active expression of transporters for phosphate, zinc, and elements essential for nitrogenase activity (iron, molybdenum, and sulfur) in nodules but is dispensable for transcription of key genes (nif/fix) involved in nitrogen fixation. Further reverse genetics suggests that S. fredii uses high-affinity transporters to meet the demand for zinc and phosphate within nodules. These findings, together with the horizontal transfer potential of the mucR homolog, imply an intriguing evolutionary role of this ancestral regulator in supporting nitrogen fixation.

Styles APA, Harvard, Vancouver, ISO, etc.

9

Ramakrishnan, Neela, R. K. Prakash et Alan G. Atherly. « Conservation of IS66 homologue of octopine Ti plasmid DNA in Rhizobium fredii plasmid DNA ». Plant Molecular Biology 7, n^o 3 (1986) : 177–88. http://dx.doi.org/10.1007/bf00021329.

Texte intégral

Styles APA, Harvard, Vancouver, ISO, etc.

10

Mathis, James N., W. Mark Barbour et Gerald H. Elkan. « Effect of Sym Plasmid Curing on Symbiotic Effectiveness in Rhizobium fredii† ». Applied and Environmental Microbiology 49, n^o 6 (1985) : 1385–88. http://dx.doi.org/10.1128/aem.49.6.1385-1388.1985.

Texte intégral

Styles APA, Harvard, Vancouver, ISO, etc.

11

Brom, Susana, Lourdes Girard, Alejandro García-de los Santos, Julio M. Sanjuan-Pinilla, José Olivares et Juan Sanjuan. « Conservation of Plasmid-Encoded Traits among Bean-Nodulating Rhizobium Species ». Applied and Environmental Microbiology 68, n^o 5 (mai 2002) : 2555–61. http://dx.doi.org/10.1128/aem.68.5.2555-2561.2002.

Texte intégral

Résumé :

ABSTRACT 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 organization. In contrast, strains belonging to other bean-nodulating species seem to have acquired only the pSym plasmid from R. etli.

Styles APA, Harvard, Vancouver, ISO, etc.

12

FUDI, LI, CHEN WENLI et ZHOU JUNCHU. « Variation of Sym Plasmid and Symbiotic Effectiveness in Isolates of Rhizobium fredii ». Biodiversity Science 03, Suppl1 (1995) : 36–42. http://dx.doi.org/10.17520/biods.1995042.

Texte intégral

Styles APA, Harvard, Vancouver, ISO, etc.

13

Barbour, W. M., J. N. Mathis et G. H. Elkan. « Evidence for plasmid- and chromosome-borne multiple nif genes in Rhizobium fredii. » Applied and Environmental Microbiology 50, n^o 1 (1985) : 41–44. http://dx.doi.org/10.1128/aem.50.1.41-44.1985.

Texte intégral

Styles APA, Harvard, Vancouver, ISO, etc.

14

Noreen, Sadaf, Helmi R. M. Schlaman, Ramón A. Bellogín, Ana M. Buendía-Clavería, MaríaRosario Espuny, Marga Harteveld, Carlos Medina et al. « Alfalfa nodulation by Sinorhizobium fredii does not require sulfated Nod-factors ». Functional Plant Biology 30, n^o 12 (2003) : 1219. http://dx.doi.org/10.1071/fp03093.

Texte intégral

Résumé :

Rhizobium strain 042B(s) is able to nodulate both soybean and alfalfa cultivars. We have demonstrated, by mass spectrometry, that the nodulation (Nod) factors produced by this strain are characteristic of those produced by Sinorhizobium fredii, which typically nodulates soybean; they have 3–5 N-acetylglucosamine (GlcNAc) residues, a mono-unsaturated or saturated C16, C18 or C20 fatty-acyl chain, and a (methyl)fucosyl residue on C6 of the reducing-terminal GlcNAc. In order to study Rhizobium strain 042B(s) and its nodulation behaviour further, we introduced an insertion mutation in the noeL gene, which is responsible for the presence of the (methyl)fucose residue on the reducing terminal GlcNAc of the Nod-factors, yielding mutant strain SVQ523. A plasmid (pHM500) carrying nodH, nodP and nodQ, the genes involved in sulfation of Nod-factors on C6 of the reducing-terminal GlcNAc, was introduced into SVQ523, generating SVQ523.pHM500. As expected, strain SVQ523 produces unfucosylated Nod-factors, while SVQ523.pHM500 produces both unfucosylated and unfucosylated sulfated Nod-factors. Plant tests showed that soybean nodulation was reduced if the inoculant (SVQ523.pHM500) produced sulfated Nod-factors. In the Asiatic alfalfa cultivar Baoding, SVQ523 (absence of a substitution at C6) failed to nodulate, but both 042B(s) (fucosyl at C6) and SVQ523.pHM500 (sulfate at C6) formed nodules. In contrast, SVQ523 showed enhanced nodulation capacity with the western alfalfa cultivars ORCA and ARC. These results indicate that Nod-factor sulfation is not a requisite for S. fredii to nodulate alfalfa.

Styles APA, Harvard, Vancouver, ISO, etc.

15

Richaume, A., J. S. Angle et M. J. Sadowsky. « Influence of soil variables on in situ plasmid transfer from Escherichia coli to Rhizobium fredii. » Applied and Environmental Microbiology 55, n^o 7 (1989) : 1730–34. http://dx.doi.org/10.1128/aem.55.7.1730-1734.1989.

Texte intégral

Styles APA, Harvard, Vancouver, ISO, etc.

16

Miao, Lihong, Kui Zhou, Junchu Zhou, Dasong Chen et Fuli Xie. « Apparent incompatibility of plasmid pSfrYC4b of Sinorhizobium fredii with two different plasmids in another strain ». Archives of Microbiology 183, n^o 5 (12 juillet 2005) : 359–67. http://dx.doi.org/10.1007/s00203-005-0780-y.

Texte intégral

Styles APA, Harvard, Vancouver, ISO, etc.

17

Cervantes, Laura, Fabiola Miranda-Sánchez, Gonzalo Torres Tejerizo, David Romero et Susana Brom. « Plasmid pSfr64a and the symbiotic plasmid pSfr64b of Sinorhizobium fredii GR64 control each other's conjugative transfer through quorum-sensing elements ». Plasmid 106 (novembre 2019) : 102443. http://dx.doi.org/10.1016/j.plasmid.2019.102443.

Texte intégral

Styles APA, Harvard, Vancouver, ISO, etc.

18

Cubo, Teresa, Francisco Romero, Jose M. Vinardell et Jose E. Ruiz-Sainz. « Expression of the Rhizobium leguminosarum biovar phaseoli melA Gene in Other Rhizobia Does Not Require the Presence of the nifA Gene ». Functional Plant Biology 24, n^o 2 (1997) : 195. http://dx.doi.org/10.1071/pp96076.

Texte intégral

Résumé :

Many different Rhizobium strains produce melanin (Mel+) when grown on solid media supplemented with L-tyrosine. The composition of the media and the culture conditions are of great importance for pigment production. Previous reports showed that some Rhizobium leguminosarum biovar phaseoli strains that produce the pigment in complete solid media (TY) failed to produce the pigment in minimal media (SY) supplemented with L-tyrosine or in TY liquid media. In this paper we have investigated different R. fredii, R. meliloti, R. etli and R. leguminosarum bv. trifolii and phaseoli strains (all of them Mel+ in solid media) for their ability to produce the pigment in liquid media. All Rhizobium species tested, except Rhizobium etli, were Mel+ in liquid media and in all cases the pigment yielded maximum absorption peaks at 280 and 315 nm. Melanin production by other bacteria (such as Vibrio, Streptomyces or Azospirillum) is enhanced by the presence of amino acids other that tyrosine. In this paper we show that the addition of L-methionine, which is not a precursor of rhizobial melanins, stimulated pigment production by Rhizobium cultures supplemented with L-tyrosine. The role of melanin production by Rhizobium strains is unclear. One hypothesis is that the Rhizobium tyrosinase, a bifunctional copper-containing enzyme that is essential for melanin biosynthesis, could detoxify polyphenolic compounds which might accumulate in senescing nodules. We show here that R. etli and R. fredii bacteroids produced melanin, which supports the idea that bacteroids contain the enzyme tyrosinase. Previous reports showed that, in R. leguminosarum bv. phaseoli strain 8002, the expression of the tyrosinase gene (melA) is dependent on the presence of nifA, a regulatory gene that is located in the symbiotic plasmid. However, transfer of R. leguminosarum bv. phaseoli melA gene to pSym-cured derivatives of R. leguminosarum bv. trifolii and viciae, R. fredii and Rhizobium sp. (Hedysarum) produced Mel+ transconjugants. DNA-hybridisation experiments showed that the pSym-cured strains did not contain any copy of nifA. Therefore, in contrast to the results reported on R. leguminosarum bv. phaseoli strain 8002, the expression of the melA gene in other rhizobia is not nifA-dependent. Key words: Rhizobium, melanin.

Styles APA, Harvard, Vancouver, ISO, etc.

19

García-de los Santos, Alejandro, et Susana Brom. « Characterization of Two Plasmid-borne lpsβ Loci of Rhizobium etli Required for Lipopolysaccharide Synthesis and for Optimal Interaction with Plants ». Molecular Plant-Microbe Interactions® 10, n^o 7 (septembre 1997) : 891–902. http://dx.doi.org/10.1094/mpmi.1997.10.7.891.

Texte intégral

Résumé :

In Rhizobium etli CFN42, both the symbiotic plasmid (pd) and plasmid b (pb) are required for effective bean nodulation. This is due to the presence on pb of a region (lpsβ) involved in lipopolysaccharide (LPS) biosynthesis. We report here the genetic array and functional features of this plasmid-borne region. The sequence analysis of a 3,595-bp fragment revealed the presence of a transcriptional unit integrated by two open reading frames (lpsβ1 and lpsβ2) essential for LPS biosynthesis and symbiosis. The lpsβ1 encodes a putative 193 amino acid polypeptide that shows strong homology with glucosyl-1P and galactosyl-1P transferases. The deduced amino acid sequence of the protein encoded by lpsβ2 was very similar to that of proteins involved in surface polysaccharide biosynthesis, such as Pseudomonas aeruginosa WpbM, Bordetella pertussis BplL, and Yersinia enterocolitica TrsG. DNA sequences homologous to lpsβ1 and lpsβ2 of R. etli CFN42 were consistently found in functionally equivalent plasmids of R. etli, R. leguminosarum bv. viciae, and R. leguminosarum bv. trifolii strains, but not in R. meliloti, R. loti, R. tropici, R. fredii, Bradyrhizobium, Azorhizobium, and Agrobacterium tumefaciens. Even though Rhizobium and Agrobacterium do not share lpsβ sequences, their presence is required for crown-gall tumor induction by R. etli transconjugants carrying the Ti plasmid.

Styles APA, Harvard, Vancouver, ISO, etc.

20

Buendia-Claveria, Ana M., Francisco Romero, Teresa Cubo, Julio Perez-Silva et Jose E. Ruiz-Sainz. « Inter and Intraspecific Transfer of a Rhizobium fredii Symbiotic Plasmid : Expression and Incompatibility of Symbiotic Plasmids ». Systematic and Applied Microbiology 12, n^o 2 (octobre 1989) : 210–15. http://dx.doi.org/10.1016/s0723-2020(89)80016-5.

Texte intégral

Styles APA, Harvard, Vancouver, ISO, etc.

21

Machado, Daphne, Steven G. Pueppke, José Maria Vinardel, José E. Ruiz-Sainz et Hari B. Krishnan. « Expression of nodD1 and nodD2 in Sinorhizobium fredii, a Nitrogen-Fixing Symbiont of Soybean and Other Legumes ». Molecular Plant-Microbe Interactions® 11, n^o 5 (mai 1998) : 375–82. http://dx.doi.org/10.1094/mpmi.1998.11.5.375.

Texte intégral

Résumé :

The ability of Sinorhizobium fredii strains USDA191 and USDA257 to form nitrogen-fixing root nodules on legume plants is regulated by nodD1 and nodD2, which sense flavonoid signals from host roots and then activate the expression of inducible nodulation genes. We assessed the interactions between these two loci with nodD1-negative and nodD2-negative mutants and with strains containing extra copies of these genes. Although both nodD1 and nodD2 are expressed constitutively, levels of nodD1 are much higher, as measured by RNA dot blots. Extra plasmid-borne copies of nodD2 reduced transcription of nodD1 to below the level of detection. We employed gel mobility shift assays to demonstrate that cellular proteins from flavonoid-treated cultures of strain USDA191 bind to DNA sequences that lie upstream from nodD1, but not to the corresponding region upstream from nodD2. Extra plasmid-borne copies of nodD2 enhanced protein binding to the nodD1-associated region and rendered the process flavonoid independent. DNase I footprinting analysis and gel retardation experiments with an oligonucleotide DNA probe localized the protein-binding site to a nod box-like sequence that lies just upstream from the nodD1 coding region. Antibodies raised against a NodD2 fusion protein and capable of reacting both with NodD1 and NodD2 blocked formation of the retarded protein-DNA complex.

Styles APA, Harvard, Vancouver, ISO, etc.

22

Lamrabet, Youssef, Ramón A. Bellogín, Teresa Cubo, Rosario Espuny, Antonio Gil, Hari B. Krishnan, Manuel Megias et al. « Mutation in GDP-Fucose Synthesis Genes of Sinorhizobium fredii Alters Nod Factors and Significantly Decreases Competitiveness to Nodulate Soybeans ». Molecular Plant-Microbe Interactions® 12, n^o 3 (mars 1999) : 207–17. http://dx.doi.org/10.1094/mpmi.1999.12.3.207.

Texte intégral

Résumé :

We mutagenized Sinorhizobium fredii HH103-1 with Tn5- B20 and screened about 2,000 colonies for increased β-galactosidase activity in the presence of the flavonoid naringenin. One mutant, designated SVQ287, produces lipochitooligosaccharide Nod factors (LCOs) that differ from those of the parental strain. The nonreducing N-acetylglucosamine residues of all of the LCOs of mutant SVQ287 lack fucose and 2-O-methylfucose substituents. In addition, SVQ287 synthesizes an LCO with an unusually long, C20:1 fatty acyl side chain. The transposon insertion of mutant SVQ287 lies within a 1.1-kb HindIII fragment. This and an adjacent 2.4-kb HindIII fragment were sequenced. The sequence contains the 3′ end of noeK, nodZ, and noeL (the gene interrupted by Tn5-B20), and the 5′ end of nolK, all in the same orientation. Although each of these genes has a similarly oriented counterpart on the symbiosis plasmid of the broad-host-range Rhizobium sp. strain NGR234, there are significant differences in the noeK/nodZ intergenic region. Based on amino acid sequence homology, noeL encodes GDP-D-mannose dehydratase, an enzyme involved in the synthesis of GDP-Lfucose, and nolK encodes a NAD-dependent nucleotide sugar epimerase/dehydrogenase. We show that expression of the noeL gene is under the control of NodD1 in S. fredii and is most probably mediated by the nod box that precedes nodZ. Transposon insertion into noeL has two impacts on symbiosis with Williams soybean: nodulation rate is reduced slightly and competitiveness for nodulation is decreased significantly. Mutant SVQ287 retains its ability to form nitrogen-fixing nodules on other legumes, but final nodule number is attenuated on Cajanus cajan.

Styles APA, Harvard, Vancouver, ISO, etc.

23

Buendia-Claveria, Ana M., Manuel Chamber et Jose E. Ruiz-Sainz. « A Comparative Study of the Physiological Characteristics, Plasmid Content and Symbiotic Properties of Different Rhizobium fredii Strains ». Systematic and Applied Microbiology 12, n^o 2 (octobre 1989) : 203–9. http://dx.doi.org/10.1016/s0723-2020(89)80015-3.

Texte intégral

Styles APA, Harvard, Vancouver, ISO, etc.

24

Shantharam, S., Kim S. Engwall et Alan G. Atherly. « Symbiotic Phenotypes of Soybean Root Nodules Associated with Deletions and Rearrangements in the Symbiotic Plasmid of R. fredii USDA191 ». Journal of Plant Physiology 132, n^o 4 (mai 1988) : 431–38. http://dx.doi.org/10.1016/s0176-1617(88)80057-9.

Texte intégral

Styles APA, Harvard, Vancouver, ISO, etc.

25

Lorio, Julio C., Demosthenis Chronis et Hari B. Krishnan. « y4xP, an Open Reading Frame Located in a Type III Protein Secretion System Locus of Sinorhizobium fredii USDA257 and USDA191, Encodes Cysteine Synthase ». Molecular Plant-Microbe Interactions® 19, n^o 6 (juin 2006) : 635–43. http://dx.doi.org/10.1094/mpmi-19-0635.

Texte intégral

Résumé :

Sinorhizobium fredii USDA257, a soybean symbiont, exports several nodulation outer proteins (Nops) into the rhizo-sphere. These proteins, which are exported by a type III secretion system (TTSS), have a pivotal role in host-specific nodulation. The entire TTSS of S. fredii lies within a 31-kb region that includes conserved genes that code for secretion machinery proteins, Nops, and several open reading frames (ORF) of unknown function. Identifying the functions of these ORF is essential to understand fully the role of TTSS in nodulation. Here, we report the characterization of y4xP, an ORF of previously unknown function. Southern blot analysis revealed that USDA257 contains two copies of y4xP, while a sibling, USDA191, contains a single copy. The amino acid sequence of Y4XP is homologous to both eukaryotic and prokaryotic cysteine synthase, a key enzyme in sulfur assimilation. The coding region of USDA257 y4xP under control of T7 promoter was expressed in Escherichia coli, and the recombinant protein was purified by nickel-affinity chromatography. Antibodies generated against soybean cys-teine synthase cross-reacted with the recombinant protein. A nonpolar mutant of y4xP of USDA191 showed a marked reduction in cysteine synthase activity. Enzyme activity was completely restored when the mutant was complemented with a plasmid containing the y4xP sequence. Cysteine syn-thase activity was confined to the cell cytosol. Extracellular protein fraction from genistein-induced USDA191 showed no cysteine synthase activity. This observation indicates that cysteine synthase, which is located in the TTSS locus, is not a type III secreted protein. A nonpolar cysteine synthase mutant was able to export all the Nops to the rhizosphere, albeit in reduced amounts compared with the wild-type USDA191. Interestingly, USDA191 cysteine synthase mutant was able to initiate nodules on ‘McCall’ soybean more efficiently than the wild-type. Our results demonstrate that y4xP encodes a cysteine synthase and inactivation of this gene enhances the ability of USDA191 to form nodules on ‘McCall’ soybean by regulating Nops production.

Styles APA, Harvard, Vancouver, ISO, etc.

26

Lorio, Julio C., Won Seok Kim et Hari B. Krishnan. « NopB, a Soybean Cultivar-Specificity Protein from Sinorhizobium fredii USDA257, Is a Type III Secreted Protein ». Molecular Plant-Microbe Interactions® 17, n^o 11 (novembre 2004) : 1259–68. http://dx.doi.org/10.1094/mpmi.2004.17.11.1259.

Texte intégral

Résumé :

The type III secretion system (TTSS) of plant- and animal-pathogenic bacteria is involved in translocation of virulence factors into the host cell cytosol where they modulate cellular processes. Sinorhizobium fredii USDA257 is a gram-negative soil bacterium that forms nitrogen-fixing nodules on specific soybean cultivars (Glycine max (L.) Merr.). This microsymbiont is known to secrete at least five nodulation outer proteins (Nops) in response to flavonoid induction. Some of these Nops have been shown to be secreted by TTSS in this symbiotic bacterium. We have isolated and purified an 18-kDa extracellular protein from flavonoid-induced cultures of USDA257. The N-terminal amino acid sequence of this purified protein was identical to the published sequence of the soybean cultivar-specificity protein, NopB (formerly NolB). Inactivation of rhcN, which encodes an ATPase, abolished secretion of NopB. Similarly, a nonpolar nopB deletion mutant was compromised in its ability to secrete several Nops. A construct containing the coding region of nopB under control of a T7 promoter was expressed successfully in Escherichia coli and, subsequently, the recombinant NopB was purified by nickel-affinity column chromatography. Polyclonal antibodies raised against purified recombinant NopB were used in Western blot analysis to demonstrate the association of NopB with pilus-like surface appendages. Deletion analysis indicated that the first 33 N-terminal residues of NopB were necessary and sufficient to mediate the secretion of a green fluorescent protein reporter. Introduction of plasmid-borne extra copies of nopB into USDA257 resulted in lower accumulation of native NopB. We also show that USDA257 and its nonpolar nopB deletion mutant exhibited discernible differences in their ability to nodulate legume hosts.

Styles APA, Harvard, Vancouver, ISO, etc.

27

Meinhardt, L. W., H. B. Krishnan, P. A. Balatti et S. G. Pueppke. « Molecular cloning and characterization of a sym plasmid locus that regulates cultivar-specific nodulation of soybean by Rhizobium fredii USDA257 ». Molecular Microbiology 9, n^o 1 (juillet 1993) : 17–29. http://dx.doi.org/10.1111/j.1365-2958.1993.tb01665.x.

Texte intégral

Styles APA, Harvard, Vancouver, ISO, etc.

28

Unay, Jovelyn, et Xavier Perret. « A Minimal Genetic Passkey to Unlock Many Legume Doors to Root Nodulation by Rhizobia ». Genes 11, n^o 5 (7 mai 2020) : 521. http://dx.doi.org/10.3390/genes11050521.

Texte intégral

Résumé :

In legume crops, formation of developmentally mature nodules is a prerequisite for efficient nitrogen fixation by populations of rhizobial bacteroids established inside nodule cells. Development of root nodules, and concomitant microbial colonization of plant cells, are constrained by sets of recognition signals exchanged by infecting rhizobia and their legume hosts, with much of the specificity of symbiotic interactions being determined by the flavonoid cocktails released by legume roots and the strain-specific nodulation factors (NFs) secreted by rhizobia. Hence, much of Sinorhizobium fredii strain NGR234 symbiotic promiscuity was thought to stem from a family of >80 structurally diverse NFs and associated nodulation keys in the form of secreted effector proteins and rhamnose-rich surface polysaccharides. Here, we show instead that a mini-symbiotic plasmid (pMiniSym2) carrying only the nodABCIJ, nodS and nodD1 genes of NGR234 conferred promiscuous nodulation to ANU265, a derivative strain cured of the large symbiotic plasmid pNGR234a. The ANU265::pMiniSym2 transconjugant triggered nodulation responses on 12 of the 22 legumes we tested. On roots of Macroptilium atropurpureum, Leucaena leucocephala and Vigna unguiculata, ANU265::pMiniSym2 formed mature-like nodule and successfully infected nodule cells. While cowpea and siratro responded to nodule colonization with defense responses that eventually eliminated bacteria, L. leucocephala formed leghemoglobin-containing mature-like nodules inside which the pMiniSym2 transconjugant established persistent intracellular colonies. These data show seven nodulation genes of NGR234 suffice to trigger nodule formation on roots of many hosts and to establish chronic infections in Leucaena cells.

Styles APA, Harvard, Vancouver, ISO, etc.

29

Dorigo, Ermes. « Il rapporto di amicizia tra Pietro Metastasio e il conte udinese Daniele Florio attraverso l'Epistolario del «poeta cesareo» ». Forum Italicum : A Journal of Italian Studies 46, n^o 1 (mars 2012) : 110–40. http://dx.doi.org/10.1177/001458581204600105.

Texte intégral

Résumé :

Questo scritto utilizza essenzialmente l' Epistolario di Pietro Metastasio (1698–1782), per analizzare il suo rapporto di amicizia col «ciambellano imperial cesareo» di Maria Teresa, il conte udinese Daniele Florio (1710–1789), «poeta de' Sovrani, Sovrano de' poeti», lungo tre direttrici adeguatamente approfondite. Amicizia come reciproco sostegno e guida, fraterna paterna filiale, a seconda dei casi, che comprende e travalica sincerità e onestà, di cui pur si nutre, per rasentare, con la tenerezza e l'affetto che la plasma, un sentimento di puro amore e disinteressata dedizione. Il tema dell'Amicizia costituisce il fulcro della canzone poetica scritta da Daniele Florio in morte del Metastasio come si legge già nella premessa A GLI AMICI: «[…] io ho perduto un impareggiabile Amico. Voi, che portate scolpite nell'animo le Sacre Leggi dell'Amicizia […] rendere una pubblica testimonianza […] di tenerezza, e gratitudine all'Amico»; parole riprese nella poesia, soprattutto nella prima e terza strofa, che danno il ‘tono’ a tutto il componimento: «Mai più soavi lacrime / Non versa un infelice / Di quelle che Amicizia / Dal fido cor gli elice […] Io su le fredde ceneri / Piango d'un chiaro Amico, / A cui mi strinse il genio / Con forte nodo antico».

Styles APA, Harvard, Vancouver, ISO, etc.

30

Ausmees, Nora, Hajime Kobayashi, William J. Deakin, Corinne Marie, Hari B. Krishnan, William J. Broughton et Xavier Perret. « Characterization of NopP, a Type III Secreted Effector of Rhizobium sp. Strain NGR234 ». Journal of Bacteriology 186, n^o 14 (15 juillet 2004) : 4774–80. http://dx.doi.org/10.1128/jb.186.14.4774-4780.2004.

Texte intégral

Résumé :

ABSTRACT The type three secretion system (TTSS) encoded by pNGR234a, the symbiotic plasmid of Rhizobium sp. strain NGR234, is responsible for the flavonoid- and NodD1-dependent secretion of n odulation o uter p roteins (Nops). Abolition of secretion of all or specific Nops significantly alters the nodulation ability of NGR234 on many of its hosts. In the closely related strain Rhizobium fredii USDA257, inactivation of the TTSS modifies the host range of the mutant so that it includes the improved Glycine max variety McCall. To assess the impact of individual TTSS-secreted proteins on symbioses with legumes, various attempts were made to identify nop genes. Amino-terminal sequencing of peptides purified from gels was used to characterize NopA, NopL, and NopX, but it failed to identify SR3, a TTSS-dependent product of USDA257. By using phage display and antibodies that recognize SR3, the corresponding protein of NGR234 was identified as NopP. NopP, like NopL, is an effector secreted by the TTSS of NGR234, and depending on the legume host, it may have a deleterious or beneficial effect on nodulation or it may have little effect.

Styles APA, Harvard, Vancouver, ISO, etc.

31

Berck, S., X. Perret, D. Quesada-Vincens, J. C. Promé, W. J. Broughton et S. Jabbouri. « NolL of Rhizobium sp. Strain NGR234 Is Required for O-Acetyltransferase Activity ». Journal of Bacteriology 181, n^o 3 (1 février 1999) : 957–64. http://dx.doi.org/10.1128/jb.181.3.957-964.1999.

Texte intégral

Résumé :

ABSTRACT Following (iso)flavonoid induction, nodulation genes of the symbiotic nitrogen-fixing bacterium Rhizobium sp. strain NGR234 elaborate a large family of lipooligosaccharidic Nod factors (NodNGR factors). When secreted into the rhizosphere of compatible legumes, these signal molecules initiate root hair deformation and nodule development. The nonreducing glucosamine residue of NodNGR factors are N acylated, N methylated, and mono- or biscarbamoylated, while position C-6 of the reducing extremity is fucosylated. This fucose residue is normally 2-O methylated and either sulfated or acetylated. Here we present an analysis of all acetylated NodNGR factors, which clearly shows that the acetate group may occupy position C-3 or C-4 of the fucose moiety. Disruption of the flavonoid-inducible nolL gene, which is preceded by anod box, results in the synthesis of NodNGR factors that lack the 3-O- or 4-O-acetate groups. Interestingly, the nodulation capacity of the mutant NGRΩnolL is not impaired, whereas introduction of thenod box::nolL construct into the related strain Rhizobium fredii USDA257 extends the host range of this bacterium to Calopogonium caeruleum,Leucaena leucocephala, and Lotus halophilus. Nod factors produced by a USDA257(pnolL) transconjugant were also acetylated. The nodbox::nolL construct was also introduced into ANU265 (NGR234 cured of its symbiotic plasmid), along with extra copies of the nodD1 gene. When permeabilized, these cells possessed acetyltransferase activity, although crude extracts did not.

Styles APA, Harvard, Vancouver, ISO, etc.

32

Fumeaux, Coralie, Nadia Bakkou, Joanna Kopcińska, Wladyslav Golinowski, David J. Westenberg, Peter Müller et Xavier Perret. « Functional analysis of the nifQdctA1y4vGHIJ operon of Sinorhizobium fredii strain NGR234 using a transposon with a NifA-dependent read-out promoter ». Microbiology 157, n^o 10 (1 octobre 2011) : 2745–58. http://dx.doi.org/10.1099/mic.0.049999-0.

Texte intégral

Résumé :

Rhizobia are a disparate collection of soil bacteria capable of reducing atmospheric nitrogen in symbiosis with legumes (Fix phenotype). Synthesis of the nitrogenase and its accessory components is under the transcriptional control of the key regulator NifA and is generally restricted to the endosymbiotic forms of rhizobia known as bacteroids. Amongst studied rhizobia, Sinorhizobium fredii strain NGR234 has the remarkable ability to fix nitrogen in association with more than 130 species in 73 legume genera that form either determinate, indeterminate or aeschynomenoid nodules. Hence, NGR234 is a model organism to study nitrogen fixation in association with a variety of legumes. The symbiotic plasmid pSfrNGR234a carries more than 50 genes that are under the transcriptional control of NifA. To facilitate the functional analysis of NifA-regulated genes a new transposable element, TnEKm-PwA, was constructed. This transposon combines the advantages of in vitro mutagenesis of cloned DNA fragments with a conditional read-out promoter from NGR234 (PwA) that reinitiates NifA-dependent transcription downstream of transposition sites. To test the characteristics of the new transposon, the nifQdctA1y4vGHIJ operon was mutated using either the Omega interposon or TnEKm-PwA. The symbiotic phenotypes on various hosts as well as the transcriptional characteristics of these mutants were analysed in detail and compared with the ineffective (Fix−) phenotype of strain NGRΔnifA, which lacks a functional copy of nifA. De novo transcription from inserted copies of TnEKm-PwA inside bacteroids was confirmed by qRT-PCR. Unexpectedly, polar mutants in dctA1 and nifQ were Fix+ on all of the hosts tested, indicating that none of the six genes of the nifQ operon of NGR234 is essential for symbiotic nitrogen fixation on plants that form nodules of either determinate or indeterminate types.

Styles APA, Harvard, Vancouver, ISO, etc.

33

Cervantes, Laura, Patricia Bustos, Lourdes Girard, Rosa Santamaría, Guillermo Dávila, Pablo Vinuesa, David Romero et Susana Brom. « The conjugative plasmid of a bean-nodulating Sinorhizobium fredii strain is assembled from sequences of two Rhizobium plasmids and the chromosome of a Sinorhizobium strain ». BMC Microbiology 11, n^o 1 (2011) : 149. http://dx.doi.org/10.1186/1471-2180-11-149.

Texte intégral

Styles APA, Harvard, Vancouver, ISO, etc.

34

Krishnan, Hari B., Julio Lorio, Won Seok Kim, Guoqiao Jiang, Kil Yong Kim, Margreet DeBoer et Steven G. Pueppke. « Extracellular Proteins Involved in Soybean Cultivar-Specific Nodulation Are Associated with Pilus-Like Surface Appendages and Exported by a Type III Protein Secretion System in Sinorhizobium fredii USDA257 ». Molecular Plant-Microbe Interactions® 16, n^o 7 (juillet 2003) : 617–25. http://dx.doi.org/10.1094/mpmi.2003.16.7.617.

Texte intégral

Résumé :

Several gram-negative plant and animal pathogenic bacteria have evolved a type III secretion system (TTSS) to deliver effector proteins directly into the host cell cytosol. Sinorhizobium fredii USDA257, a symbiont of soybean and many other legumes, secretes proteins called Nops (nodulation outer proteins) into the extracellular environment upon flavonoid induction. Mutation analysis and the nucleotide sequence of a 31.2-kb symbiosis (sym) plasmid DNA region of USDA257 revealed the existence of a TTSS locus in this symbiotic bacterium. This locus includes rhc (rhizobia conserved) genes that encode components of a TTSS and proteins that are secreted into the environment (Nops). The genomic organization of the TTSS locus of USDA257 is remarkably similar to that of another broad-host range symbiont, Rhizobium sp. strain NGR234. Flavonoids that activate the transcription of the nod genes of USDA257 also stimulate the production of novel filamentous appendages known as pili. Electron microscope examination of isolated pili reveals needle-like filaments of 6 to 8 nm in diameter. The production of the pili is dependent on a functional nodD1 and the presence of a nod gene-inducing compound. Mutations in several of the TTSS genes negate the ability of USDA257 to elaborate pili. Western blot analysis using antibodies raised against purified NopX, Nop38, and Nop7 reveals that these proteins were associated with the pili. Mutations in rhcN, rhcJ, rhcC, and ttsI alter the ability of USDA257 to form nodules on Glycine max and Macroptilium atropurpureum.

Styles APA, Harvard, Vancouver, ISO, etc.

35

Krysciak, Dagmar, Jessica Grote, Mariita Rodriguez Orbegoso, Christian Utpatel, Konrad U. Förstner, Lei Li, Christel Schmeisser, Hari B. Krishnan et Wolfgang R. Streit. « RNA Sequencing Analysis of the Broad-Host-Range Strain Sinorhizobium fredii NGR234 Identifies a Large Set of Genes Linked to Quorum Sensing-Dependent Regulation in the Background of atraIandngrIDeletion Mutant ». Applied and Environmental Microbiology 80, n^o 18 (7 juillet 2014) : 5655–71. http://dx.doi.org/10.1128/aem.01835-14.

Texte intégral

Résumé :

ABSTRACTThe alphaproteobacteriumSinorhizobium frediiNGR234 has an exceptionally wide host range, as it forms nitrogen-fixing nodules with more legumes than any other known microsymbiont. Within its 6.9-Mbp genome, it encodes twoN-acyl-homoserine-lactone synthase genes (i.e.,traIandngrI) involved in the biosynthesis of two distinct autoinducer I-type molecules. Here, we report on the construction of an NGR234-ΔtraIand an NGR234-ΔngrImutant and their genome-wide transcriptome analysis. A high-resolution RNA sequencing (RNA-seq) analysis of early-stationary-phase cultures in the NGR234-ΔtraIbackground suggested that up to 316 genes were differentially expressed in the NGR234-ΔtraImutant versus the parent strain. Similarly, in the background of NGR234-ΔngrI466 differentially regulated genes were identified. Accordingly, a common set of 186 genes was regulated by the TraI/R and NgrI/R regulon. Coregulated genes included 42 flagellar biosynthesis genes and 22 genes linked to exopolysaccharide (EPS) biosynthesis. Among the genes and open reading frames (ORFs) that were differentially regulated in NGR234-ΔtraIwere those linked to replication of the pNGR234asymbiotic plasmid and cytochromecoxidases. Biotin and pyrroloquinoline quinone biosynthesis genes were differentially expressed in the NGR234-ΔngrImutant as well as the entire cluster of 21 genes linked to assembly of the NGR234 type III secretion system (T3SS-II). Further, we also discovered that genes responsible for rhizopine catabolism in NGR234 were strongly repressed in the presence of high levels ofN-acyl-homoserine-lactones. Together with nodulation assays, the RNA-seq-based findings suggested that quorum sensing (QS)-dependent gene regulation appears to be of higher relevance during nonsymbiotic growth rather than for life within root nodules.

Styles APA, Harvard, Vancouver, ISO, etc.

36

Wärnberg, Fredrik, Andreas Karakatsanis, Liliya Shcherbina, Folke Sjöberg, Paul Hargreaves, Ioan-Dan Curiac, Edvin Johansson, Oskar Axelsson et Mats Hansen. « Abstract P3-04-03 : Safety, tolerability, and efficacy of the novel intravenous manganese-based contrast agent SN132D in patients with breast cancer : initial results of a Phase I, First-In-Human clinical trial SPAGOPIX-01 ». Cancer Research 83, n^o 5_Supplement (1 mars 2023) : P3–04–03—P3–04–03. http://dx.doi.org/10.1158/1538-7445.sabcs22-p3-04-03.

Texte intégral

Résumé :

Abstract Introduction: SN132D is a manganese (Mn) -containing, polymeric nanomaterial developed as an intravenous contrast agent for tumor selective MRI. It was designed for optimal physiological targeting and preferential accumulation in malignant lesions by means of the Enhanced Permeability and Retention (EPR) effect. Combined non-clinical data have demonstrated proof of concept (PoC) in various in vivo cancer models and a safety profile in line with FIH administration of SN132D in the SPAGOPIX-01 clinical study. Methods: SPAGOPIX-01 is a Phase I, FIH, open-label, non-randomized and non-placebo-controlled study in participants with diagnosed breast cancer. MRI was performed prior to and at 2 h and 4 h after the end of the SN132D infusion. SN132D safety and tolerability were the primary objectives. MRI enhancing properties of SN132D in primary tumor, liver, and pancreas as well as pharmacokinetics of SN132D were secondary objectives. Results: So far, 12 female breast cancer patients of planned up to 20 have been enrolled between September 2019 and December 2021. Of these, six patients received SN132D at 10 μmol Mn/kg (cohort 1) and six patients at 20 μmol Mn/kg (cohort 2). In cohort 1 (10 μmol Mn/kg), SN132D was well-tolerated. No clinically significant findings were observed for clinical laboratory tests, vital signs, 12-lead electrocardiogram (ECG), or physical examination. No serious adverse events (SAEs) were registered; nine mild AEs were reported for four subjects. The most reported AEs in patients administered 10 μmol Mn/kg SN132D were injection site reactions (2 AEs) and flushing (2 AEs). In cohort 2, SN132D was also well-tolerated. No clinically significant findings were observed for vital signs, ECG, or physical examination. No SAEs were registered; 12 AEs were reported for six patients. The most common AE was transiently elevated transaminase levels, with single reports from four patients. The second and third most common AEs were moderate vomiting (reported twice from a single patient) and mild flushing. Remaining AEs were single events reported by single patients. None of the AEs required treatment and all resolved without any intervention. Pharmacokinetics of SN132D was assessed at up to 24 h post dose. In cohort 1, SN132D, based on Mn plasma concentrations, had a mean Cmax of 0.915±0.187 μg/mL, a mean initial half-life of 7.17± 1.02 min, a mean AUCinf of 0.890±0.20 h*μg/mL and a mean plasma clearance of 0.646±0.157 L/h/kg. In cohort 2, SN132D had a mean Cmax of 2.0±0.341μg/mL, a mean initial half-life of 7.0±1.60 min, a mean AUCinf of 2.04±0.28 h*μg/mL and a mean plasma clearance of 0.548±0.068 L/h/kg. MR image analysis in cohort 1 revealed that although contrast was insufficient for the generation of clinically relevant tumor images at the 10 μmol Mn/kg dose level, there was still a measurable enhancement. In cohort 2, MR images were analyzed for five subjects and clinically relevant contrast increase in the primary tumor without signal increase in the background was observed in all patients. In addition, all MRI images, including both dose cohorts, showed contrast increase in both liver and pancreas at post-dose imaging timepoints. Conclusions: Initial clinical data generated to date demonstrate an acceptable safety profile and PoC for SN132D in the breast cancer patients. Physiological targeting with functional nanoparticles appears suitable for tumor MRI imaging. Our data are in agreement with preclinical data in rodent tumor models. The data are supporting the continuation of the SPAGOPIX-01 clinical trial and we will further explore SN132D in a cohort of pancreatic cancer patients with liver involvement. Citation Format: Fredrik Wärnberg, Andreas Karakatsanis, Liliya Shcherbina, Folke Sjöberg, Paul Hargreaves, Ioan-Dan Curiac, Edvin Johansson, Oskar Axelsson, Mats Hansen. Safety, tolerability, and efficacy of the novel intravenous manganese-based contrast agent SN132D in patients with breast cancer: initial results of a Phase I, First-In-Human clinical trial SPAGOPIX-01 [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P3-04-03.

Styles APA, Harvard, Vancouver, ISO, etc.

37

Deshpande, Lalitagauri M., Andrew P. Davis, Fredrik Dyrkell, Dimitrios Arnellos et Mariana Castanheira. « 831. Analysis of a Worldwide Collection of Klebsiella pneumoniae CC258 with Reference to Carbapenemase Production Using the 1928 Core Genome (cg) Multilocus Sequence Type (MLST) Reveals Endemicity and Global Dissemination of Clones ». Open Forum Infectious Diseases 7, Supplement_1 (1 octobre 2020) : S456—S457. http://dx.doi.org/10.1093/ofid/ofaa439.1020.

Texte intégral

Résumé :

Abstract Background K. pneumoniae (KPN) has emerged as a major hospital associated pathogen in the recent years. Clonal complex (CC) 258 constitutes an international epidemic clone responsible for spread of extended spectrum beta-lactamases (ESBL) and carbapenemases. We evaluated the core genome (cg) MLST, resistance (R) gene and plasmid profiles of a worldwide collection of KPN using the 1928 bioinformatic cloud platform. Methods A total of 155 KPN clinical isolates (CC258, n=129; non-CC258, n=26) collected from 19 countries during 2018 of SENTRY Program were analyzed. Isolates included carbapenem resistant (CR; n=120) and non-CR (n=35). Whole genome sequencing FASTQ files were uploaded to the 1928 pipeline for analysis. Results Most CC258 isolates belonged to ST258, ST11 and ST512 (Table), and separated from unrelated ST by allelic distance (ad) > 2000. cgMLST grouped together isolates from the same STs, and those from similar geographies had greater homology, except isolates from US showed greater heterogenicity (ad 620). Applying an ad cutoff of < 100, ST258 isolates grouped in 4 clades with a predominance of either KPC-2 or -3. An ad cutoff of < 200 identified 7 clades within ST11 that were related by geography and R genes. Among CC258 isolates KPC was the major carbapenemase (58.1%) and associated with Tn4401 (a or b in 84% KPC); NDM-1 was detected (8.5%) only in ST11 and ST395. KPC-2 was more prevalent in Latin America and the isolates were closely related (ad 104) among ST258 compared to ST11 (ad 355). KPC-3 CC258 isolates showed ad of 164 and were from Italy, Russia, Greece, and US. CTX-M-14 was prevalent in ST258 while CTX-M-15 was common in other STs, except ST512 which carried no CTX-M despite clustering within ST258. Conclusion 1928 generated cgMLST showed good correlation with MLST in classifying all KPN isolates. ST258 isolates showed tight clustering, no NDM genes and distribution in the Americas while ST11 showed global dissemination and diversity of carbapenemases. Table 1 Disclosures Fredrik Dyrkell, n/a, 1928 Diagnostics (Employee) Dimitrios Arnellos, n/a, 1928 Diagnostics (Employee) Mariana Castanheira, PhD, 1928 Diagnostics (Research Grant or Support)A. Menarini Industrie Farmaceutiche Riunite S.R.L. (Research Grant or Support)Allergan (Research Grant or Support)Allergan (Research Grant or Support)Amplyx Pharmaceuticals (Research Grant or Support)Cidara Therapeutics (Research Grant or Support)Cidara Therapeutics (Research Grant or Support)Cipla Ltd. (Research Grant or Support)Cipla Ltd. (Research Grant or Support)Fox Chase Chemical Diversity Center (Research Grant or Support)GlaxoSmithKline (Research Grant or Support)Melinta Therapeutics, Inc. (Research Grant or Support)Melinta Therapeutics, Inc. (Research Grant or Support)Melinta Therapeutics, Inc. (Research Grant or Support)Merck (Research Grant or Support)Merck (Research Grant or Support)Merck & Co, Inc. (Research Grant or Support)Merck & Co, Inc. (Research Grant or Support)Paratek Pharma, LLC (Research Grant or Support)Pfizer (Research Grant or Support)Qpex Biopharma (Research Grant or Support)

Styles APA, Harvard, Vancouver, ISO, etc.

38

Sun, Yan-Wei, Yan Li, Yue Hu, Wen-Xin Chen et Chang-Fu Tian. « Coordinated Regulation of the Size and Number of Polyhydroxybutyrate Granules by Core and Accessory Phasins in the Facultative Microsymbiont Sinorhizobium fredii NGR234 ». Applied and Environmental Microbiology 85, n^o 19 (2 août 2019). http://dx.doi.org/10.1128/aem.00717-19.

Texte intégral

Résumé :

ABSTRACT The exact roles of various granule-associated proteins (GAPs) of polyhydroxybutyrate (PHB) are poorly investigated, particularly for bacteria associated with plants. In this study, four structural GAPs, named phasins PhaP1 to PhaP4, were identified and demonstrated as true phasins colocalized with PHB granules in Sinorhizobium fredii NGR234, a facultative microsymbiont of Vigna unguiculata and many other legumes. The conserved PhaP2 dominated in regulation of granule size under both free-living and symbiotic conditions. PhaP1, another conserved phasin, made a higher contribution than accessory phasins PhaP4 and PhaP3 to PHB biosynthesis at stationary phase. PhaP3, with limited phyletic distribution on the symbiosis plasmid of Sinorhizobium, was more important than PhaP1 in regulating PHB biosynthesis in V. unguiculata nodules. Under the test conditions, no significant symbiotic defects were observed for mutants lacking individual or multiple phaP genes. The mutant lacking two PHB synthases showed impaired symbiotic performance, while mutations in individual PHB synthases or a PHB depolymerase yielded no symbiotic defects. This phenomenon is not related to either the number or size of PHB granules in test mutants within nodules. Distinct metabolic profiles and cocktail pools of GAPs of different phaP mutants imply that core and accessory phasins can be differentially involved in regulating other cellular processes in the facultative microsymbiont S. fredii NGR234. IMPORTANCE Polyhydroxybutyrate (PHB) granules are a store of carbon and energy in bacteria and archaea and play an important role in stress adaptation. Recent studies have highlighted distinct roles of several granule-associated proteins (GAPs) in regulating the size, number, and localization of PHB granules in free-living bacteria, though our knowledge of the role of GAPs in bacteria associated with plants is still limited. Here we report distinct roles of core and accessory phasins associated with PHB granules of Sinorhizobium fredii NGR234, a broad-host-range microsymbiont of diverse legumes. Core phasins PhaP2 and PhaP1 are conserved major phasins in free-living cells. PhaP2 and accessory phasin PhaP3, encoded by an auxiliary gene on the symbiosis plasmid, are major phasins in nitrogen-fixing bacteroids in cowpea nodules. GAPs and metabolic profiles can vary in different phaP mutants. Contrasting symbiotic performances between mutants lacking PHB synthases, depolymerase, or phasins were revealed.

Styles APA, Harvard, Vancouver, ISO, etc.

39

Barbour, W. Mark, et G. H. Elkan. « Physiological characteristics and competitive ability of plasmid-cured derivatives of Rhizobium fredii USDA 206 ». Archives of Microbiology 154, n^o 1 (juin 1990). http://dx.doi.org/10.1007/bf00249169.

Texte intégral

Styles APA, Harvard, Vancouver, ISO, etc.

40

Shi, Wen-Tao, Biliang Zhang, Meng-Lin Li, Ke-Han Liu, Jian Jiao et Chang-Fu Tian. « The convergent xenogeneic silencer MucR predisposes α-proteobacteria to integrate AT-rich symbiosis genes ». Nucleic Acids Research, 4 août 2022. http://dx.doi.org/10.1093/nar/gkac664.

Texte intégral

Résumé :

Abstract Bacterial adaptation is largely shaped by horizontal gene transfer, xenogeneic silencing mediated by lineage-specific DNA bridgers (H-NS, Lsr2, MvaT and Rok), and various anti-silencing mechanisms. No xenogeneic silencing DNA bridger is known for α-proteobacteria, from which mitochondria evolved. By investigating α-proteobacterium Sinorhizobium fredii, a facultative legume microsymbiont, here we report the conserved zinc-finger bearing MucR as a novel xenogeneic silencing DNA bridger. Self-association mediated by its N-terminal domain (NTD) is required for DNA–MucR–DNA bridging complex formation, maximizing MucR stability, transcriptional silencing, and efficient symbiosis in legume nodules. Essential roles of NTD, CTD (C-terminal DNA-binding domain), or full-length MucR in symbiosis can be replaced by non-homologous NTD, CTD, or full-length protein of H-NS from γ-proteobacterium Escherichia coli, while NTD rather than CTD of Lsr2 from Gram-positive Mycobacterium tuberculosis can replace the corresponding domain of MucR in symbiosis. Chromatin immunoprecipitation sequencing reveals similar recruitment profiles of H-NS, MucR and various functional chimeric xenogeneic silencers across the multipartite genome of S. fredii, i.e. preferring AT-rich genomic islands and symbiosis plasmid with key symbiosis genes as shared targets. Collectively, the convergently evolved DNA bridger MucR predisposed α-proteobacteria to integrate AT-rich foreign DNA including symbiosis genes, horizontal transfer of which is strongly selected in nature.

Styles APA, Harvard, Vancouver, ISO, etc.

41

Grote, Jessica, Dagmar Krysciak, Katrin Petersen, Simon Güllert, Christel Schmeisser, Konrad U. Förstner, Hari B. Krishnan, Harald Schwalbe, Nina Kubatova et Wolfgang R. Streit. « The Absence of the N-acyl-homoserine-lactone Autoinducer Synthase Genes traI and ngrI Increases the Copy Number of the Symbiotic Plasmid in Sinorhizobium fredii NGR234 ». Frontiers in Microbiology 7 (18 novembre 2016). http://dx.doi.org/10.3389/fmicb.2016.01858.

Texte intégral

Styles APA, Harvard, Vancouver, ISO, etc.

Articles de revues sur le sujet « Plasmi freddi »

Créez une référence correcte selon les styles APA, MLA, Chicago, Harvard et plusieurs autres