2 Instituto de Biofísica Carlos Chagas Filho, Centro de Ciências da Saúde, Bloco G, Universidade Federal do Rio de Janeiro, 21944-970, Cidade Universitária, Ilha do Fundão, Rio de Janeiro, RJ, Brazil; and 3 Laboratory for Molecular Structure, NIBSC, Herts EN6 3QG, U.K.
Received on September 29, 2004; revised on October 20, 2004; accepted on October 20, 2004
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Abstract |
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Key words: Burkholderia / lipopolysaccharide / nitrogen-fixing bacterium / yersiniose
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Introduction |
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The best studied nitrogen-fixing bacteriaplant interaction is the Rhizobium/legume symbiosis. The extensive literature on the complex molecular mechanism of this interaction suggests an important role for glycopolymers, such as bacterial lipopolysaccharide (LPS) (Cullimore and Dénarie, 2003; Lerouge and Vanderleyden, 2001
). The LPS is required for effective symbiosis (Gao et al., 2001
), playing an important role in recognition (Noel and Duelli, 2000
); for root hair infection (Dazzo et al., 1991
), nodule invasion, and bacterial adaptation to the nodule microenvironment (Fraysse et al., 2003
; Lerouge and Vanderleyden, 2001
); and for avoiding host defense responses (Lerouge and Vanderleyden, 2001
). Mutations of genes coding for rhizobial LPS has revealed the biological importance of the O-antigen structure on the symbiontplant interaction (Brink et al., 1990
; Gao et al., 2001
; Jabbouri et al., 1996
; Noel and Duelli, 2000
; Noel et al., 1986
, 2000
). Mutants that lack the O-chain polysaccharide of their LPS are symbiotically defective (Fraysse et al., 2003
; Lerouge and Vanderleyden, 2001
). In addition, it has been shown that structural changes in LPS occur during symbiotic process and that most of these changes appear to take place in the O-chain polysaccharide (Noel et al., 1996
, 2004
). The LPS recognition may be mediated by host-encoded receptor, as demonstrated for the interaction of R. leguminosarum bv. trifolli LPS by trifoliin A (Noel et al., 2004
). Interestingly, quinovosamine (2-amino-2,6-dideoxyglucose) has been identified as a potent saccharide hapten inhibitor of trifoliin ARhizobium polysaccharide association, suggesting that the interaction between the bacterial LPS and plant receptor is structure-specific (Dazzo and Wopereis, 2000
; Hrabak et al., 1981
). Moreover, LPS/trifoliin A recognition was shown to be a host speciesspecific event (Dazzo et al., 1991
).
Despite the growing understanding of the role of bacterial polysaccharides in the establishment of symbiosis, the involvement of glycomolecules in the endophytic interaction of nitrogen-fixing bacteria has not been determined. To understand the basis of this alternative association, characterization of the structure of the bacterial cell wall components is required. Here we report the isolation and characterization of a novel O-antigen containing yersiniose A (YerA) synthesized by B. brasiliensis.
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Results |
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For isolation of the C4-branched 3,6-dideoxyhexose, the B. brasiliensis LPS was submitted to hydrolysis with 1% acetic acid, sufficient to release significant amounts of this compound, which was purified by gel filtration chromatography on a Bio-Gel P-6 column (Figure 1, peak II), and identified as YerA by electron impact (EI)- and chemical ionization (CI)-MS and nuclear magnetic resonance (NMR) spectroscopic analyses. The EI-MS of the alditol acetate derivative of this C-4 branched monosaccharide showed prominent fragment ions at m/z 95, 109, 113, 143, 155, and 215, identical with those found for alditol acetates derivatives of Yer present in the LPS isolated from species of Legionella and Yersinia (Gorshkova et al., 1984; Sonesson and Jantzen, 1992
). CI-MS of the TMS-methyl-glycosides showed the presence of two pseudo-molecular ions at m/z 351 (M+H+) and m/z 368 (
), the expected masses for TMS-methylglycosides of Yer.
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GC and GC-MS analyses of the material eluted of the void volume of P-6 column chromatography (Figure 1, peak I) was mainly composed of Rha and Yer in molar ratio 6:1. These observations suggest that the O-polysaccharide isolated by the conventional methodology using mild acid conditions is partially degraded. Together, sugar analysis, MS, and NMR data indicated the presence of Rha and YerA in the O-polysaccharide from LPS isolated from B. brasiliensis. The fatty acid composition of the LPS showed the presence of myristic, 2-hydroxymyristic, and 3-hydroxypalmitic acids.
Alternatively, the B. brasiliensis LPS was hydrolyzed with ammonium hydroxide, yielding only one carbohydrate-containing fraction on the P-6 column (void volume). The compositional analysis of this fraction by GC and GC-MS of the trimethylsilylated methylglycosides, in conjunction with analysis of alditol acetate derivatives, showed that the presence of Rha and YerA in a molar ratio of 3:1.
Determination of the sugar linkages of intact LPS
To determine the linkages between sugars, a methylation analysis of intact LPS was carried out by analysis the O-acetylated partially O-methylated methylglycosides, which were characterized by GC and CG-MS. The derivatives were observed (Figure 3A), arising from terminal YerA, 2-O-, 3-O-, and 2,3-di-O-substituted Rhap. These data suggest that the repeating unit of B. brasiliensis LPS is a branched tetrasaccharide structure. To determine the arrangements of substituents at the 2,3-di-O-Rhap, intact LPS was subjected to different trifluoracetic acid (TFA) hydrolysis conditions prior to the methylation analysis, resulting in a time-dependent in Yer release. Two carbohydrate-containing fractions were observed on Bio Gel P-4 chromatography when the LPS was treated with 40 mM TFA at 100°C for 1 h. Sugar analysis of the fraction eluted in the void volume showed the presence of Rha, whereas in the included fraction it contained Rha and Yer residues.
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Characterization of glycosyl sequence of the O-polysaccharide repeating unit
As mild acid hydrolysis with 1% acetic acid used to selectively cleave KDO ketosidic linkage also releases Yer residues, the structure of the repeating unit was determined by NMR analysis of the polysaccharide portion obtained by ammonolysis of the intact LPS. As expected, ammonolysis yielded a single carbohydrate-containing fraction on Bio-Gel P-6 column chromatography. GC-MS of TMS-methyl-glycoside derivatives showed Rha and Yer as the major components, together with trace of glucose and heptose. The 1D 1H NMR spectrum of this fraction (Figure 4) contained four low field signals, between 4.80 and 5.30 ppm, due to four anomeric protons; resonances between 4.23 and 3.40 ppm arising from ring protons; a triplet and a double doublet at 1.96 and 1.82 ppm, respectively; and high-field resonances between 1.34 and 1.11 ppm from methyl groups. The 2D COSY, TOCSY, and heteronuclear single quantum coherence (HSQC) spectra (Table I) showed the presence of three a-Rhap, labeled A, B, and C (Table I; Figure 4) and one -YerAp residues. The downfield anomeric resonance Rha(A) at 5.248 and 101.32 ppm was assigned 2,3-disubstitued
-Rhap, consistent with downfield shifts of the C2 and C3 resonances at 77.89 and 78.25 ppm. Anomeric resonances of Rha(B) at 4.965 and 102.42 ppm were assigned 3-substituted
-Rhap, supported by its lowfield C3 resonance at 78.31 ppm. The 2-substituted
-Rhap(C) with anomeric resonances at 5.215 and 101.32 ppm was characterized by a C2 resonance at 78.42 ppm. Finally, the
-YerAp anomeric H1 resonated at 5.038, with C1 at 99.89 ppm.
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On the basis of these results, Scheme I presents the structure proposed for the repeating unit of specific polysaccharide from the LPS of B. brasiliensis.
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Discussion |
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The approach used in the structural analysis allowed the characterization of Yer as a component of the B. brasiliensis LPS, a novel feature for Burkholderia polysaccharides and more frequently encountered in the O-polysaccharides of LPS produced by species of Yersinia (Gorshkova et al., 1976, 1983
, 1989
) and Legionella (Sonesson and Jantzen, 1992
). Furthermore, the presence of 3,6-dideoxy-4-C-branched sugars in the cell wall components has already been described for B. caryophylli, as caryophyllose (3,6,10-trideoxy-4-C-[D-glycero-1-hydroyethyl]-D-erythro-D-gulo-decose) (Adinolfi et al., 1996
) and for Mycobacterium gastri, as tridecose (3,6-dideoxy-4-C-[1,3-di-O-methylpropyl]-
-hexopyranose) (Gilleron et al., 1994
).
Mild acid hydrolysis has long been the method of choice for isolation of O-polysaccharides from LPS. An interesting finding of our work is that the hydrolysis of the B. brasiliensis LPS with 1% acetic acid releases Yer residues, yielding an O-polysaccharide with nonstoichiometric substitution. The hydrolysis of Yer under dilute acid treatment may explain the results found by Gorshkova et al. (1989) that YerA was present in nonstoichiometric amounts in the O-antigen isolated from Yersinia frederiksenii LPS. Cleavage of other susceptible glycosidic linkages under identical acid conditions should be investigated. Using ammonolysis we were able to isolate the B. brasiliensis polysaccharide while maintaining the fidelity of the repeating structure, a general feature that applies to most bacterial polysaccharides (Whitfield, 1995
).
The exact role of LPS molecules in endophytic interaction is still obscure, but our data may allow parallels to be drawn with the involvement of LPS in symbiontplant association. The presence of YerA residues in the B. brasiliensis LPS might confer a higher hydrophobicity for the polysaccharide, which may be important for interaction between the bacterial and plant cell surface. In agreement with this hypothesis, we have shown that the polysaccharide interacts with the reverse-phase LC-18 SPE column. Furthermore the results obtained by Jabbouri et al. (1996) showed that mutants lacking smooth LPS, provoking a loss of hydrophobicity of the bacterial membrane, infect Vigna nodules in the usual way but do not produce efficient bacteroids. In this context, Kannenberg and Carlson (2001)
observed structural modifications in the LPS of R. leguminosarum during bacteroid development. The importance of hydrophobic character given to the O-antigen by the presence of deoxy-sugars can also be exemplified by the findings that R. etli mutant CE166, expressing a LPS lacking the O-antigenic 2-amino-2,6-dideoxyglucose (quinovosamine) forms nonfixing pseudonodules on Phaseolus vulgaris (Noel and Duelli, 2000
). In addition, the presence of these unusual deoxy-sugars in the LPS polymers, especially on terminal position, confers immunological specificity of the O-antigen, contributing to the wide variety of antigenic types between species and even strains in Gram-negative bacteria (Liu and Thorson, 1994
).
Another characteristic of the O-polysaccharide described in this article is the presence of Rha residues, frequently encountered in O-polysaccharide of LPS of several Burkholderia species, including B. cepacia, B. gladioli, B. vietnamiensis, and B. plantarii (Cérantola and Montrozier, 1997; Galbraith and Wilkinson, 1997
; Gaur et al., 1998
; Zähringer et al., 1997
). The Rha is the main or the only constituent of the O-specific polysaccharide in Azospirillum brasiliensis (Fedonenko et al., 2002
), Pseudomonas syringae (Ovod et al., 1999
; Zdorovenko et al., 2003
), and Xanthomonas campestris pathovars (Senchenkova et al., 1999
) and is thus common for phytopathogenic bacteria. This observation may be an indication that this sugar plays an important role in the recognition and interaction between bacteria and plants. Impairment of Rha biosynthesis by knocking out the dTDP-L-Rha synthase of Azorhizobium caulinodans disabled symbiosis with Sesbania rostrata (Gao et al., 2001
).
Current data from Rhizobiumlegume symbiosis support some of the general proposed functions for LPS and underscore the importance of LPS structural versatility and adaptability. In this work, appropriate methodology applied to the isolation of the O-antigen from B. brasiliensis LPS allowed a novel YerA-containing polysaccharide to be characterized. This structural knowledge can contribute to further investigation of the participation of glycomolecules in the plantendophyte association and highlights the uniqueness of polysaccharides expressed by this bacterium.
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Materials and methods |
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Preparation of LPS
After removal of capsular polysaccharide (Stephan et al., 1995) the cells were mechanically disrupted by ultrasonic treatment and the cell wall fraction recovered by centrifugation (8000 x g, 4°C, 15 min). The LPS was extracted from the cell wall preparation by hot aqueous phenol, recovered from the aqueous phase after exhaustive dialysis and lyophilization. The dry material containing LPS was suspended in water to 3% (w/v) and purified by ultracentrifugation (105,000 x g, 4°C, 16 h) (Westphal and Jann, 1965
). The intact LPS was characterized by carbohydrate and fatty acid compositon, methylation analysis, and NMR spectroscopy.
Treatment of LPS by acid conditions
For mild acid hydrolysis, LPS (50 mg) was treated with 1% acetic acid at 100°C for 1 h. After cooling, the sample was centrifuged (3000 x g, 4°C, 30 min), and the precipitated lipid A was removed. The water-soluble product was lyophilized, dissolved in water, and chromatographed on a Bio Gel P-6 (fine) column (90 cm x 1.7 cm) equilibrated with 0.05 M pyridine acetate buffer (pH 4.6). Two carbohydrate-containing fractions were detected by phenol/sulfuric acid assay (Dubois et al., 1956). The O-polysaccharide partially hydrolyzed was recovered from the void volume and a monosaccharide fraction in the included volume. An aliquote of the monosaccharide fraction was reduced with sodium borohydride at room temperature for 2 h. The excess borohydride was destroyed by addition of BioRad (Hercules, CA) AG50X8 H+ (200400 mesh) and the boric acid removed by repeated evaporation with methanol. The native and reduced monosaccharides were lyophilized for further NMR spectroscopic analysis.
For selective release of monosaccharide from intact LPS, various conditions of hydrolysis were assayed. The LPS (3 mg) was submitted to 40 mM TFA, at 100°C for 18 h. The products were evaporated, dissolved in water, and subjected to chromatography on BioGel P-4 column. The carbohydrate-containing fractions, detected by phenol/sulfuric acid assay (Dubois et al., 1956), eluted in the void and included volumes, were analyzed by GC and GC-MS. For methylation analysis, the product of LPS was treated with 40 mM TFA at 100°C for 1 h and recovered in void volume.
Preparation of polysaccharide moiety from LPS by ammonolysis
The LPS (50 mg) was hydrolyzed in 10 M ammonium hydroxide (4 ml) at 150°C for 18 h (Barr and Lester, 1984). After cooling, the product was concentrated by evaporation under N2, lyophilized, and dissolved in water; the insoluble components were removed by centrifugation (3000 x g, 4°C, 30 min). The supernatant was evaporated and dissolved in water, and the polysaccharide recovered by lyophilization after gel filtration chromatography on Bio Gel P-6 eluted with water or on a reverse-phase LC-18 SPE column (Supelco, Bellefonte, PA) eluted with a solution containing 40% isopropanol and 5% acetic acid.
Carbohydrate analysis
Monosaccharides from intact LPS, polysaccharide moiety, or O-polysaccharide chain were analyzed as their TMS-methyl glycosides after methanolysis with 50 mM HCl in methanol at 80°C for 18 h (Sweeley et al., 1963). The monosaccharides were also analyzed as alditol acetate derivatives, after acid hydrolysis with 40 mM TFA at 100°C for 6 h, reduction with sodium borohydride, and acetylation with acetic anhydride/pyridine (9:1, v/v) at room temperature for 18 h. The monosaccharide derivatives were characterized by GC and GC-MS.
The absolute configuration of sugar residues were established by GC of their TMS-(-)-2-butylglycosides (Gerwig et al., 1978).
Lipid analysis
For fatty acid analysis, the LPS (500 mg) was methanolyzed (0.5 M HCl in methanol at 80°C for 18 h), and fatty acid methyl esters (FAMEs) were extracted into heptane and analyzed by GC after O-trimethylsilylation with bis-(trimethylsilyl)trifluoracetamide/pyridine (1:1, v/v) at room temperature for 1 h (Sweeley et al., 1963). Peaks were identified by their retention time compared to authentic standards and by GC-MS.
Methylation analysis
The methylation analysis of intact and TFA-treated LPS was carried out according to Parente et al. (1985), using dimethyl sulfoxide/lithium methylsulfinyl carbanion and methyl iodide. The permethylated materials were methanolyzed (50 mM HCl in methanol at 80°C for 18 h) and acetylated at room temperature for 18 h. The resulting O-acetylated partially O-methylated methylglycosides were identified by GC and GC-MS.
GC and GC-MS
GC was performed on a Varian Star 3400 gas chromatograph equipped with a capillary column (25 m x 0.2 mm) DB-1 fused silica (30 m x 0.25 mm) with hydrogen (10 psi) as the carrier gas. GC-MS analysis were performed on a Shimadzu GC 17 A gas chromatograph, equipped with a DB-1 capillary column, interfaced with a GC-MS-QP5050 quadruple mass spectrometer (Shimadzu, Kyoto, Japan). EI was performed using an ionization potential of 70 eV and an ionization current of 0.2 mA. Ammonia was the reagent gas used in the CI. The temperature program for the analysis of TMS-methyl glycoside and alditol acetate derivatives was 120 to 240°C at 2°C min1 and for FAME was 110 to 280°C at 3°C min1. For the analysis of TMS-(-)-2-butylglycosides the temperature program was 135 to 200°C at 1°C min1.
NMR spectroscopy
NMR spectra were obtained on a Bruker DRX 600 with a 5-mm triple resonance probe at 25°C, or on a Varian Inova 500 spectrometer equipped with a 5 mm inverse-detection heteronuclear probe, at 30°C. The samples were deuterium exchange by repeated lyophilization from deuterated water (M&G Chemicals, Stockport, U.K.; 99.9% deuterium, 500 ml) and dissolved in 0.5 ml D2O. Proton NMR spectra were assigned from COSY and TOCSY (Griesinger et al., 1988) experiments. Information on the sequence and linkage of the sugar residues were obtained from ROESY (Bax and Davis, 1985
). TOCSY and ROESY experiments were collected with 32 transients of 2k data points and 512 x 2 increments in F1, with mixing times of 80 and 150 ms, respectively. Carbon chemical shifts were assigned from the HSQC (Wider and Wüthrich, 1993
) spectra recorded with carbon decoupling. Proton chemical shifts were referenced to internal acetate anion at 1.908 ppm and 13C chemical shifts to external methanol at 50 ppm.
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Acknowledgements |
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Abbreviations |
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References |
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---|
Baldani, J.I., Caruso, L., Baldani, V.L.D., Goi, S.R., and Döbereiner, J. (1997a) Recent advances in BNF with non-legume plants. Soil Biol. Biochem., 29, 911922.[CrossRef][ISI]
Baldani, V.L.D., Oliveira, E., Balota, E., Baldani, J.I., Kirchhof, G., and Döbereiner, J. (1997b) Burkholderia brasiliensis sp. nov., uma nova espécie de bactéria diazotrófica endofitica. An. Acad. Bras. Ciências, 69, 116.
Barr, K. and Lester, R.L. (1984) Occurence of novel antigenic phosphoinositol-containing sphingolipids in the pathogenic yeast Histoplasma capsulatum. Biochemistry, 23, 55815588.[ISI][Medline]
Bax, A. and Davis, D.G. (1985) Practical aspects of two-dimensional transverse NOE spectroscopy. J. Magn. Reson., 63, 207213.[ISI]
Brink, B., Miller, A.J., Carlson, R.W., and Noel, K.D. (1990) Expression of Rhizobium leguminosarum CFN42 genes for lipopolysaccharide in strains derived from different R. leguminosarum soil isolates. J. Bacteriol., 172, 548555.[ISI][Medline]
Cérantola, S. and Montrozier, H. (1997) Structural elucidation of two polysaccharides present in the lipopolysaccharide of a clinical isolate of Burkholderia cepacia. Eur. J. Biochem., 246, 360366.[Abstract]
Cullimore, J. and Dénarie, J. (2003) Plant sciences. How legumes select their sweet talking symbionts. Science, 302, 575578.
Dazzo, F.B. and Wopereis, J. (2000) Unraveling the infection process in the Rhizobium-legume symbiosis by microscopy. In Triplett, E.W. (Ed.), Prokaryotic nitrogen fixation: a model system for analysis of a biological process. Horizon Scientific Press, Wymondham, U.K., pp. 295347.
Dazzo, F.B., Truchet, G.L., Hollingsworth, R.I., Hrabak, E.M., Pankratz, H.S., Philip-Hollingsworth, S., Salzwedel, J.L., Chapman, K., Appenzeller, L., Squartini, A., and others. (1991) Rhizobium LPS modulates infection thread development in white clover root hairs. J. Bacteriol., 173, 53715384.[ISI][Medline]
Dubois, M., Gilles, K.A., Hamilton, J.K., Rebers, P.A., and Smith, F. (1956) Colorimetric method for determination of sugars and related substances. Anal. Chem., 28, 350356.[ISI]
Fedonenko, Y.P., Zatonsky, G.V., Konnova, S.A., Zdorovenko, E.L., and Ignatov, V.V. (2002) Structure of the O-specific polysaccharide of the lipopolysaccharide of Azospirillum brasiliensis Sp245. Carbohydr. Res., 337, 869872.[CrossRef][ISI][Medline]
Fraysse, N., Couderc, F., and Poinsot, V. (2003) Surface polysaccharide involvement in establishing the rhizobium-legume symbiosis. Eur. J. Biochem., 270, 13651380.
Galbraith, L. and Wilkinson, S.G. (1997) Structural studies of the O-specific side-chain of lipopolysaccharide from Burkholderia gladioli pv. gladioli strain NCPPB 1891. Carbohydr. Res., 303, 245249.[CrossRef][ISI][Medline]
Gao, M., D'Haeze, W., De Rycke, R., Wolucka, B., and Holsters, M. (2001) Knockout of an azorhizobial dTDP-L-Rhamnose synthase affects lipopolysaccharide and extracelullar polysaccharide production and disables symbiosis with Sesbania rostrata. Mol. Plant. Microbe Interact., 14, 857866.[ISI][Medline]
Gaur, D., Galbraith, L., and Wilkinson, S.G. (1998) Structural characterisation of a rhamnan and a fucorhamnan, both present in the lipopolysaccharide of Burkholderia vietnamiensis strain LMG 10926. Eur. J. Biochem., 258, 696701.[Abstract]
Gerwig, G.J., Kamerling, J.P., and Vliegenthart, J.F.G. (1978) Determination of the D and L configuration of neutral monosaccharides by high-resolution capillary G.L.C. Carbohydr. Res., 62, 349357.[CrossRef][ISI]
Gilleron, M., Vercauteren, J., and Puzo, G. (1994) Lipo-oligosaccharidic antigen from Mycobacterium gastri. Complete structure of a novel C4 branched 3,6-dideoxy-alpha-xylo-hexopyranose. Biochemistry, 33, 19301937.[ISI][Medline]
Gillis, M., Tran Van, V., Bardin, R., Goor, M., Hebbar, P., Willems, A., Segers, P., Kersters, K., Heulin, T., and Fernandez, M.P. (1995) Polyphasic taxonomy in the genus Burkholderia leading to an emended description of the genus and proposition of Burkholderia vietnamiensis sp. nov. for N2-fixing isolates from rice in Vietnam. Int. J. Syst. Bacteriol., 45, 274289.
Gorshkova, R.P., Zubkov, V.A., and Ovodov, Y.S. (1976) Chemical and immunochemical studies on lipopolysaccharide from Yersinia pseudotuberculosis type IV. Immunochemistry, 13, 581583.[CrossRef][ISI][Medline]
Gorshkova, R.P., Zubkov, V.A., Isako, V.V., and Ovodov, Y.S. (1983) Structural features of O-specific polysaccharide from lipopolysaccharide of Yersinia pseudotuberculosis VI serovar. Bioorg. Khim., 9, 106881073.[ISI][Medline]
Gorshkova, R.P., Zubkov, V.A., Isakov, V.V., and Ovodov, Y.S. (1984) Yersiniose, a new branched-chain sugar. Carbohydr. Res., 126, 308312.[CrossRef][ISI][Medline]
Gorshkova, R.P., Isakov, V.V., Zubkov, V.A., and Ovodov, Y.S. (1989) Structure of the O-specific polysaccharide of the lipopolysaccharide of the Yersinia frederiksenii serovar O:16,29. Bioor. Khim., 15, 16271633.
Griesinger, C., Otting, G., Wüthrich, K., and Ernst, R.R. (1988) Clean TOCSY for 1H spin system identification in macromolecules. J. Am. Chem. Soc., 110, 78707872.[ISI]
He, X.M. and Liu, H-W. (2002) Formation of unusual sugars: mechanistic studies and biosynthetic applications. Annu. Rev. Biochem., 71, 701754.[CrossRef][ISI][Medline]
Hrabak, E.M., Urbano, M.R., and Dazzo, F.B. (1981) Growth-phase-dependent immunodeterminants of Rhizobium trifolli lipopolysaccharide which bind trifoliin A, a white clover lectin. J. Bacteriol., 148, 697711.[ISI][Medline]
Jabbouri, S., Hannin, M., Fellay, R., Quesada-Vincens, D., Ruehs, B.L., Carlson, R.W., and Broughton, W.J. (1996) Rhizobium species NGR234 host-specificity of nodulation locus III contains nod and fix genes. In Stacey, G., Mullin, B., and Gresshoff, P.M. (Eds.), Biology of plant-microbe interactions. International Society for Plant-Microbe Interactions, St. Paul, MN, pp. 319324.
Jansson, P.E., Kenne, L., and Widmalm, G. (1989) Computer-assisted structural analysis of polysaccharides with an extended version of CASPER using 1H and 13C-NMR data. Carbohydr. Res., 188, 169191.[CrossRef][ISI][Medline]
Kannenberg, E.L. and Carlson, R.W. (2001) Lipid A and O-chain modifications cause Rhizobium lipopolysaccharides to become hydrophobic during bacteroid development. Mol. Microbiol., 39, 379391.[CrossRef][ISI][Medline]
Krusell, L., Madsen, L.H., Sato, S., Aubert, G., Genua, A., Szczyglowski, K., Duc, G., Kaneko, T., Tabata, S., Bruijn, F., and others. (2002) Shoot control of root development and nodulation is mediated by a receptor-like kinase. Nature, 420, 422426.[CrossRef][ISI][Medline]
Lerouge, I., and Vanderleyden, J. (2001) O-antigen structural variation: mechanisms and possible roles in animal/plant-microbe interactions. FEMS Microbiol. Rev., 26, 1747.[ISI]
Limpens, E., Franken, C., Smit, P., Willemse, J., Bisseling, T., and Geurts, R. (2003) LysM domain receptor kinases regulating rhizobial Nod factor-induced infection. Science, 302, 630633.
Liu, H.W. and Thorson, J.S. (1994) Pathways and mechanisms in the biogenesis of novel deoxysugars by bacteria. Annu. Rev. Microbiol., 48, 223256.[CrossRef][ISI][Medline]
Madsen, E.B., Madsen, L.H., Radutoiu, S., Olbryt, M., Rakwalska, M., Szczyglowski, K., Sato, S., Kaneko, T., Tabata, S., Sandal, N., and Stougaard, J. (2003) A receptor kinase gene of the LysM type is involved in legume perception of rhizobial signals. Nature, 425, 637640.[CrossRef][ISI][Medline]
Mattos, K.A., Jones, C., Heise, N., Previato, J.O., and Mendonça-Previato, L. (2001) Structure of an acidic exopolysaccharide produced by the diazotrophic endophytic bacterium Burkholderia brasiliensis. Eur. J. Biochem., 268, 31743179.
Moulin, L., Munive, A., Dreyfus, B., and Bolvin-Masson, C. (2001) Nodulation of legumes by members of the beta-subclass of Proteobacteria. Nature, 411, 948950.[CrossRef][ISI][Medline]
Noel, K.D. and Duelli, D.M. (2000) Rhizobium lipopolysaccharide and its role in symbiosis. In Triplett, E.W. (Ed.), Prokaryotic nitrogen fixation: a model system for analysis of biological process. Horizon Scientific Press, Wymondham, U.K., pp. 415431.
Noel, K.D., Dueli, D.M., Tão, H., and Brewin, N.J. (1996) Antigenic change in the lipopolysaccharide of Rhizobium etli CFN42 induced by exudates of Phaseolus vulgaris. Mol. Plant-Microbe Interact., 9, 180186.[ISI]
Noel, K.D., Van den Bosch, K.A., and Kulpaca, B. (1986) Mutations in Rhizobium phaseoli that lead to arrested development of infection threads. J. Bacteriol., 168, 13921401.[ISI][Medline]
Noel, K.D., Forsberg, L.S., and Carlson, R.W. (2000) Varying the abundance of O antigen in Rhizobium etli and its effect on symbiosis with Phaseolus vulgaris. J. Bacteriol., 182, 53175324.
Noel, K.D., Box, J.M., and Bonne, V.J. (2004) 2-O-methylation of fucosyl residues of a rhizobial lipopolysaccharide is increased in response to host exudate and is eliminated in a symbiotically defective mutant. Appl. Environm. Microbiol., 70, 15371544.
Ovod, V.V., Knirel, Y.A., Samson, R., and Krohn, K.J. (1999) Immunochemical characterization and taxonomic evaluation of the O polysaccharides of the lipopolysaccharides of Pseudomonas syringae serogroup O1 strains. J. Bacteriol., 181, 69376947.
Parente, J.P., Cardon, P., Leroy, Y., Montreuil, J., Fournet, B., and Ricart, G. (1985) A convenient method for the methylation of glycoprotein glycans in small amounts by using lithium methylsulfinyl carbanion. Carbohydr. Res., 141, 4147.[CrossRef][ISI][Medline]
Radutoiu, S., Madsen, L.H., Madsen, E.B., Felle, H.H., Umehara, Y., Gronlund, M., Sato, S., Nakamura, Y., Tabata, S., Sandal, N., and Stougaard, J. (2003) Plant recognition of symbiotic bacteria requires two LysM receptor-like kinases. Nature, 425, 585592.[CrossRef][ISI][Medline]
Senchenkova, S.N., Shashkov, A.S., Laux, P., Knirel, Y.A., and Rudolph, K. (1999) The O-chain polysaccharide of the lipopolysaccharide of Xanthomonas campestris pv. begoniae GSPB 525 is a partially L-xylosylated L-rhamnan. Carbohydr. Res., 319, 148153.[CrossRef][ISI][Medline]
Sonesson, A. and Jantzen, E. (1992) The branched-chain octose yersiniose A is a lipopolysaccharide constituent of Legionella micdadei and Legionella maceachernii. J. Microbiol. Methods, 15, 241248.[CrossRef][ISI]
Stephan, M.P., Fontaine, T., Previato, J.O., and Mendonça-Previato, L. (1995) Differentiation of capsular polysaccharides from Acetobacter diazotrophicus strains isolated from sugarcane. Microbiol. Immunol., 39, 237242.[ISI][Medline]
Sweeley, C.C., Bentley, R., Makita, M., and Well, W.W. (1963) Gas-liquid chromatography of trimethylsilyl derivatives of sugars and related substances. J. Am. Chem. Soc., 85, 2497.[ISI]
Urakami, T., Ito-Yoshida, C., Araki, H., Kijima, T., Suzuki, K.I., and Komagata, K. (1994) Transfer of Pseudomonas plantarii and Pseudomonas glumae to Burkholderia as Burkholderia spp. and description of Burkholderia vandii sp. nov. Int. J. Syst. Bacteriol., 44, 235245.
Vandamme, P., Goris, J., Chen, W.M., de Vos, P., and Willems, A. (2002) Burkholderia tuberum sp. nov. and Burkholderia phymatum sp. nov., nodulate the roots of tropical legumes. Syst. Appl. Microbiol., 25, 507512.[CrossRef][ISI][Medline]
Vandamme, P., Holmes, B., Vancanneyt, M., Coenye, T., Hoste, B., Coopman, R., Revets, H., Lauwers, S., Gillis, M., Kersters, K., and Govan, J.R. (1997) Occurence of multiple genomovars of Burkholderia cepacia in cystic fibrosis patients and proposal of Burkholderia multivorans sp. nov. Int. J. Syst. Bacteriol., 47, 11881200.
Viallard, V., Poirier, I., Cournoyer, B., Haurat, J., Wiebkin, S., Ophel-Keller, K., and Balandreau, J. (1998) Burkholderia graminis sp. nov., a rhizospheric Burkholderia species, and reassessment of [Pseudomonas] phenazinium, [Pseudomonas] pyrrocinia and [Pseudomonas] glathei as Burkholderia. Int. J. Syst. Bacteriol., 48, 549563.
Westphal, O. and Jann, K. (1965) Bacterial lipopolysaccharides. Extraction with phenol-water and further applications of the procedure. Methods Carbohydr. Chem., 5, 8391.
Whitfield, C. (1995) Biosynthesis of lipopolysaccharide O antigens. Trends Microbiol., 3, 178185.[CrossRef][ISI][Medline]
Wider, G. and Wüthrich, K. (1993) A simple experimental scheme using pulsed field gradients for coherence pathway rejection and solvent suppression in phase-sensitive heteronuclear correlation spectra. J. Magn. Reson., 102, 239241.[CrossRef]
Zähringer, U., Rettenmaier, H., Moll, H., Senchenkova, S.N., and Knirel, Y.A. (1997) Structure of a new 6-deoxy-a-D-talan from Burkholderia (Pseudomonas) plantarii strain DSM 6535, which is different from the O-chain of the lipopolysaccharide. Carbohydr. Res., 300, 143151.[CrossRef][ISI][Medline]
Zdorovenko, E.L., Zatonskii, G.V., Kocharova, N.A., Shashkov, A.S., Knirel, Y.A., and Ovod, V.V. (2003) Structure of the O polysaccharides and serological classification of Pseudomonas syringae pv. porri from genomospecies 4. Eur. J. Biochem., 270, 2027.
Zubkov, V.A., Gorshkova, R.P., and Odov, Y.S. (1992) Synthesis of 3,6-dideoxy-4-C-(4(1)-hydroxyethyl)hexopiranoses (yersinioses) from 1,6-anhydro-ß-D-glucopyranose. Carbohydr. Res., 225, 189207.[CrossRef][ISI][Medline]
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