The Experts below are selected from a list of 234 Experts worldwide ranked by ideXlab platform

Rex Montgomery - One of the best experts on this subject based on the ideXlab platform.

  • Hydrodynamic properties of oxidized extracellular polysaccharides from Erwinia chrysanthemi spp.
    Carbohydrate research, 2003
    Co-Authors: Byung Yun Yang, Qiong Ding, Rex Montgomery
    Abstract:

    The molecular weights of the native polysaccharides of Erwinia chrysanthemi strains range from 1.8 to 7.1 x 10(6) and their hydrodynamic properties are those of polydisperse, polyanionic biopolymers with pseudoplastic, non-thixotropic flow characteristics in aqueous solutions. The effect on the hydrodynamic properties of the polysaccharides by adding carboxyl groups to increase the charge density is studied, with particular reference to their molecular weight (MW), viscosity and conformation. In general, it is found that periodate oxidation of the extracellular polysaccharides of E. chrysanthemi strains, Ech9Sm6 and Ech6S+, introduces little change in the hydrodynamic properties of the resulting polyaldehydes. However, bromine oxidation at neutral pH of the polyaldehydes results in polycarboxylate biopolymers that show significant reduction in MW and viscosity, but they are still characteristic polyanions.

  • β-Elimination of glucosyluronic residues during methylation of an acidic polysaccharide from Erwinia chrysanthemi CU 643
    Carbohydrate research, 2001
    Co-Authors: Byung Yun Yang, Rex Montgomery
    Abstract:

    The Erwinia chrysanthemi CU643 EPS has a linear hexasaccharide repeating unit in which a 4-linked uronic acid residue is present. The EPS was methylated by either the NaOH-Me2SO-MeI or Li-dimsyl procedure. MALDI-TOF MS analysis of the methylated products indicates that the beta-eliminative degradation occurs during the methylation, as characterized by serial fragments of the hexasaccharide repeating units. The degradation was clearly defined from the methylation of a glucosyluronic-containing pyruvated pentasaccharide.

  • Extracellular polysaccharide of Erwinia chrysanthemi A350 and ribotyping of Erwinia chrysanthemi spp.
    Carbohydrate research, 2000
    Co-Authors: James S.s. Gray, Byung Yun Yang, Rex Montgomery
    Abstract:

    Abstract Erwinia chrysanthemi spp. are Gram-negative bacterial phytopathogens causing soft rots in a number of plants. The structure of the extracellular polysaccharide (EPS) produced by the E. chrysanthemi strain A350, which is a lac Z − mutant of the wild type strain 3937, pathogenic to Saintpaulia, has been determined using a combination of chemical and physical techniques including methylation analysis, low-pressure gel-filtration and anion-exchange chromatography, high-pH anion-exchange chromatography, partial acid hydrolysis, mass spectrometry and 1- and 2D NMR spectroscopy. In contrast to the structures of the EPS reported for other strains of E. chrysanthemi , the EPS from strain A350 contains d -GalA, together with l -Rha p and d -Gal p in a 1:4:1 ratio. Evidence is presented for the following hexasaccharide repeat unit: Download full-size image All the Erwinia chrysanthemi spp. studied to date have been analyzed by ribotyping and collated into families, which are consistent with the related structures of their EPS.

  • Extracellular polysaccharide of Erwinia chrysanthemi CU643.
    Carbohydrate research, 1999
    Co-Authors: Byung Yun Yang, James S.s. Gray, Rex Montgomery
    Abstract:

    Erwinia chrysanthemi are gram-negative bacterial phytopathogens causing soft rots in a number of plants. The structure of the extracellular polysaccharide (EPS) produced by E. chrysanthemi strain CU643, pathogenic to Philodendron, has been determined using a combination of chemical and physical techniques including methylation analysis, high- and low-pressure gel-filtration and anion-exchange chromatography, high-pH anion-exchange chromatography, partial acid hydrolysis, mass spectrometry, and 1- and 2-D NMR spectroscopy. In contrast to the structures of the EPS reported for other strains of E. chrysanthemi, the EPS from strain CU643 is a linear polysaccharide containing L-Rhap, D-Galp, and D-GlcAp in the ratio 4:1:1. Evidence is presented for the following hexasaccharide repeat unit: -->3)-beta-D-Galp-(1-->2)-alpha-L-Rhap-(1-->4)-beta-D-GlcAp- (1-->2)-alpha-L- Rhap-(1-->2)-alpha-L-Rhap-(1-->2)-alpha-L-Rhap-(1-->(1 ).

  • Comparison of extracellular polysaccharides of Erwinia chrysanthemi spp.
    International journal of biological macromolecules, 1996
    Co-Authors: Byung Yun Yang, James S.s. Gray, Rex Montgomery
    Abstract:

    Abstract Two extracellular polysaccharides from strains of Erwinia chrysanthemi Ech 1 and 9, phytopathogens of potatoes, have been isolated and purified. Both have similar compositions and other properties to that produced by strain SR 260, a phytopathogen of corn. These polysaccharides are composed of l -rhamnose, d -mannose, d -glucose, d -glucuronic acid in the ratio 3:1:1:1. Initial structural aspects of these polysaccharides are reflected in the 600 MHz 1 H NMR spectra and the products of partial acid hydrolysis, which are presented for comparison.

Carlos Blanco - One of the best experts on this subject based on the ideXlab platform.

  • glutamine glutamate and α glucosylglycerate are the major osmotic solutes accumulated by Erwinia chrysanthemi strain 3937
    Applied and Environmental Microbiology, 2004
    Co-Authors: Renan Goude, Sta â â Phanie Renaud, Sylvie Bonnassie, Tha â â Ophile Bernard, Carlos Blanco
    Abstract:

    Erwinia chrysanthemi is a phytopathogenic soil enterobacterium closely related to Escherichia coli. Both species respond to hyperosmotic pressure and to external added osmoprotectants in a similar way. Unexpectedly, the pools of endogenous osmolytes show different compositions. Instead of the commonly accumulated glutamate and trehalose, E. chrysanthemi strain 3937 promotes the accumulation of glutamine and alpha-glucosylglycerate, which is a new osmolyte for enterobacteria, together with glutamine. The amounts of the three osmolytes increased with medium osmolarity and were reduced when betaine was provided in the growth medium. Both glutamine and glutamate showed a high rate of turnover, whereas glucosylglycerate stayed stable. In addition, the balance between the osmolytes depended on the osmolality of the medium. Glucosylglycerate and glutamate were the major intracellular compounds in low salt concentrations, whereas glutamine predominated at higher concentrations. Interestingly, the ammonium content of the medium also influenced the pool of osmolytes. During bacterial growth with 1 mM ammonium in stressing conditions, more glucosylglycerate accumulated by far than the other organic solutes. Glucosylglycerate synthesis has been described in some halophilic archaea and bacteria but not as a dominant osmolyte, and its role as an osmolyte in Erwinia chrysanthemi 3937 shows that nonhalophilic bacteria can also use ionic osmolytes.

  • Glutamine, glutamate, and alpha-glucosylglycerate are the major osmotic solutes accumulated by Erwinia chrysanthemi strain 3937.
    Applied and Environmental Microbiology, 2004
    Co-Authors: Renan Goude, Sylvie Bonnassie, Stéphanie Renaud, Théophile Bernard, Carlos Blanco
    Abstract:

    Erwinia chrysanthemi is a phytopathogenic soil enterobacterium closely related to Escherichia coli. Both species respond to hyperosmotic pressure and to external added osmoprotectants in a similar way. Unexpectedly, the pools of endogenous osmolytes show different compositions. Instead of the commonly accumulated glutamate and trehalose, E. chrysanthemi strain 3937 promotes the accumulation of glutamine and alpha-glucosylglycerate, which is a new osmolyte for enterobacteria, together with glutamine. The amounts of the three osmolytes increased with medium osmolarity and were reduced when betaine was provided in the growth medium. Both glutamine and glutamate showed a high rate of turnover, whereas glucosylglycerate stayed stable. In addition, the balance between the osmolytes depended on the osmolality of the medium. Glucosylglycerate and glutamate were the major intracellular compounds in low salt concentrations, whereas glutamine predominated at higher concentrations. Interestingly, the ammonium content of the medium also influenced the pool of osmolytes. During bacterial growth with 1 mM ammonium in stressing conditions, more glucosylglycerate accumulated by far than the other organic solutes. Glucosylglycerate synthesis has been described in some halophilic archaea and bacteria but not as a dominant osmolyte, and its role as an osmolyte in Erwinia chrysanthemi 3937 shows that nonhalophilic bacteria can also use ionic osmolytes.

  • Erwinia chrysanthemi O antigen is required for betaine osmoprotection in high-salt media.
    Journal of bacteriology, 2004
    Co-Authors: Thierry Touzé, Renan Goude, Carlos Blanco, Sylvie Georgeault, Sylvie Bonnassie
    Abstract:

    Cellular components necessary for osmoprotection are poorly known. In this study we show that O antigen is specifically required for the effectiveness of betaines as osmoprotectants for Erwinia chrysanthemi in saline media. The phenotype is correlated with the inability of rfb mutant strains to maintain a high accumulation level of betaines in hypersaline media.

  • Characterization of the Erwinia chrysanthemi osmoprotectant transporter gene ousA.
    Journal of bacteriology, 1996
    Co-Authors: Gwenola Gouesbet, A. Trautwetter, S. Bonnassie, Carlos Blanco
    Abstract:

    Growth of Erwinia chrysanthemi in media of elevated osmolarity can be achieved by the uptake and accumulation of various osmoprotectants. This study deals with the cloning and sequencing of the ousA gene-encoded osmoprotectant uptake system A from E. chrysanthemi 3937. OusA belongs to the superfamily of solute ion cotransporters. This osmotically inducible system allows the uptake of glycine betaine, proline, ectoine, and pipecolic acid and presents strong similarities in nucleotide sequence and protein function with the proline/betaine porter of Escherichia coli encoded by proP. The control of ousA expression is clearly different from that of proP. It is induced by osmotic strength and repressed by osmoprotectants. Its expression in E. coli is controlled by H-NS and is rpoS dependent in the exponential phase but unaffected by the stationary phase.

C. A. Rodrigues - One of the best experts on this subject based on the ideXlab platform.

  • Purification and properties of an endoxylanase from a corn stalk rot strain of Erwinia chrysanthemi
    Phytopathology, 1993
    Co-Authors: E. J. Braun, C. A. Rodrigues
    Abstract:

    An extracellular xylanase (EC 3.2.1.8) was purified approximately 20-fold from liquid cultures of Erwinia chrysanthemi strain SR120A grown with glycerol as a carbon source. Ammonium sulphate fractionation, cation-exchange chromatography (CM-Sephadex), chromatofocusing, and gel filtration (Sephadex G-75) isolated the enzyme from culture filtrates. The xylanase had a molecular mass of approximately 42 kDa and had a pI of 8.8. The pH optimum was 5.5, and the temperature optimum in a 10-min assay was 55 C. About 40% of the enzyme activity was lost after incubating for 1 h at 40 C []

M. Boccara - One of the best experts on this subject based on the ideXlab platform.

  • hrp genes of Erwinia chrysanthemi 3937 are important virulence factors
    Molecular Plant-microbe Interactions, 2002
    Co-Authors: Ching Hong Yang, M. Boccara, Marina Gavilanesruiz, Yasushi Okinaka, Regine Vedel, Isabelle Berthuy, Jason Weita Chen, Nicole T Perna, N T Keen
    Abstract:

    We developed improved virulence assays for Erwinia chrysanthemi 3937 on African violet varieties and devised a new method for the construction of precise bacterial gene knockouts. These methods were tested by constructing mutations in genes suspected to be involved with plant interactions. The virulence of the hrpG and hrcC mutant strains (both gene products presumed to be involved in protein secretion) was greatly reduced on leaves of semitolerant African violet varieties. An hrpN mutant strain produced delayed symptoms on African violet leaves and an hrpN Δpel (Δpel = five major pectate lyase genes deleted) double mutant was nonpathogenic. The hrcC and hrpG mutants did not produce a rapid hypersensitive response (HR) in tobacco, unlike the wild-type bacterium, and the hrpN mutant gave a reduced HR. The results, therefore, establish the importance of hrp genes in the virulence of E. chrysanthemi and their ability to elicit HR on nonhosts. The data also suggest that other effector proteins secreted by the...

  • Flavohaemoglobin HmpX: a new pathogenicity determinant in Erwinia chrysanthemi strain 3937.
    Microbiology (Reading England), 1995
    Co-Authors: S Favey, G Labesse, V Vouille, M. Boccara
    Abstract:

    Unlike wild-type Erwinia chrysanthemi strain 3937, which fully macerates inoculated Saintpaulia plants, HmpX- mutants produce necrotic lesions or no symptoms. The hmpX gene was sequenced and the corresponding protein sequence analysed. We show that HmpX belongs to a family of flavohaemoproteins (HMP), previously identified in two yeasts and in Escherichia coli. Comparisons of protein sequences at the secondary structure level by hydrophobic cluster analysis have shown that HmpX possesses two functional regions, a haemoglobin domain in its N-terminal part and a flavin reductase domain in its C-terminal part. In an HmpX- strain, the synthesis of pectate lyases, which are pathogenicity determinants in E. chrysanthemi, was reduced in conditions of low oxygen tension. Using gus fusion in hmpX, it was shown that hmpX transcription was induced in coculture with tobacco cells. A putative function for HmpX is discussed.

  • Role of endoglucanases in Erwinia chrysanthemi 3937 virulence on Saintpaulia ionantha.
    Journal of bacteriology, 1994
    Co-Authors: M. Boccara, J L Aymeric, C Camus
    Abstract:

    The role of endoglucanases (endoglucanases Z and Y) in Erwinia chrysanthemi pathogenicity on Saintpaulia ionantha was assessed by mutagenizing cloned cel genes (celZ and celY) and recombining them with the chromosomal alleles. Strains with an omega interposon in celZ, a deletion in celY, or a double cel mutant were as virulent as the wild-type strain. However, in the strain with a deletion in celY, a delay in the appearance of symptoms was observed, and then maceration progressed as in plants infected with the wild-type strain, suggesting that E. chrysanthemi endoglucanases play a minor role in soft rot disease development. Images

  • Role of endoglucanases in Erwinia chrysanthemi 3937 virulence on Saintpaulia ionantha.
    Journal of bacteriology, 1994
    Co-Authors: M. Boccara, J L Aymeric, C Camus
    Abstract:

    The role of endoglucanases (endoglucanases Z and Y) in Erwinia chrysanthemi pathogenicity on Saintpaulia ionantha was assessed by mutagenizing cloned cel genes (celZ and celY) and recombining them with the chromosomal alleles. Strains with an omega interposon in celZ, a deletion in celY, or a double cel mutant were as virulent as the wild-type strain. However, in the strain with a deletion in celY, a delay in the appearance of symptoms was observed, and then maceration progressed as in plants infected with the wild-type strain, suggesting that E. chrysanthemi endoglucanases play a minor role in soft rot disease development.

  • Plant Defense Elicitor Protein Produced by Erwinia chrysanthemi
    Developments in Plant Pathology, 1993
    Co-Authors: M. Boccara, R. Vedel, M. Dufresne
    Abstract:

    Erwinia chrysanthemi 3937 when inoculated to a number of plant hosts (tomato, potato, saintpaulia or lettuce) provokes tissue maceration, however, it elicits hypersensitive response (HR) when tobacco leaves were infiltrated by bacterial suspension.This necrosis is accompagnied with production of capsidiol which is one of the major phytoalexin produced by tobacco.

C Camus - One of the best experts on this subject based on the ideXlab platform.

  • Role of endoglucanases in Erwinia chrysanthemi 3937 virulence on Saintpaulia ionantha.
    Journal of bacteriology, 1994
    Co-Authors: M. Boccara, J L Aymeric, C Camus
    Abstract:

    The role of endoglucanases (endoglucanases Z and Y) in Erwinia chrysanthemi pathogenicity on Saintpaulia ionantha was assessed by mutagenizing cloned cel genes (celZ and celY) and recombining them with the chromosomal alleles. Strains with an omega interposon in celZ, a deletion in celY, or a double cel mutant were as virulent as the wild-type strain. However, in the strain with a deletion in celY, a delay in the appearance of symptoms was observed, and then maceration progressed as in plants infected with the wild-type strain, suggesting that E. chrysanthemi endoglucanases play a minor role in soft rot disease development. Images

  • Role of endoglucanases in Erwinia chrysanthemi 3937 virulence on Saintpaulia ionantha.
    Journal of bacteriology, 1994
    Co-Authors: M. Boccara, J L Aymeric, C Camus
    Abstract:

    The role of endoglucanases (endoglucanases Z and Y) in Erwinia chrysanthemi pathogenicity on Saintpaulia ionantha was assessed by mutagenizing cloned cel genes (celZ and celY) and recombining them with the chromosomal alleles. Strains with an omega interposon in celZ, a deletion in celY, or a double cel mutant were as virulent as the wild-type strain. However, in the strain with a deletion in celY, a delay in the appearance of symptoms was observed, and then maceration progressed as in plants infected with the wild-type strain, suggesting that E. chrysanthemi endoglucanases play a minor role in soft rot disease development.