Rhizobia, polysaccharides

By 1945, Stacey speculated about the possibility of a structural relationship between Pneumococcus capsular polysaccharides and those produced by other organisms. With Miss Schliichterer, he had examined the capsular polysaccharide of Rhizobium radicicolum. This polysaccharide gave a precipitin reaction in high dilution, not only with Type III Pneumococcus antiserum, but also mixed with antisera from other Pneumococcus types. The chemical evidence indicated that the polysaccharide resembled the specific polysaccharides of Types I and II Pneumococcus. A decade later, the acidic capsular polysaccharide from Azoto-bacter chroococcum, a soil organism, was studied. It, too, produced serological cross-reactions with certain pneumococcal specific antisera. Although the molecular structure of the polysaccharide was not established, adequate evidence was accumulated to show a structural relationship to Type III Pneumococcus-specific polysaccharide. This was sufficiently close to account for the Type III serological cross-relationship. 

Mutant YE-2 of Rhizobium meliloti excretes a mixture of soluble polysaccharides that include a complex succinoglycan having a branched octasaccharide repeat as well as a simple galactoglucan (22) having a linear disaccharide repeat.102 In contrast to the case of the succinoglycan, oriented fibers of the potassium salt of 22 have yielded good X-ray data and its three-dimensional structure has been established.39 The polymer forms a two-fold helix of pitch... 

Table A31 Structure 47 Rhizobium trifolii Capsular Polysaccharide ...

Treatment of an extracellular polysaccharide of Rhizobium japonicum (an important factor for nitrogen-fixing symbiosis between bacteria and soybeans) with liquid HF (—40°, 30 min) gave mono- and oligo-saccharides involving 0- -D-glucopyranosyl-( 1 - 3)-C>-(4-0-acetyl-a-D-galactopyrano-syluronic acid)-(l— 3)-D-mannose and its 1-fluoride. 

The capsular polysaccharide from Rhizobium meliloti IFO 13336 contains terminal ct-D-ribofuranosyluronic groups (19). With this obvious exception, all known glycuronic acids in bacterial polysaccharides are py-ranosidic. 

In a recent paper650 the relationships between Rhizobium radicicolum polysaccharides and those of pneumococcus are indicated by crossprecipitin reactions of the former with Types III and VI anti-pneumococcus horse sera. In addition, hydrolysis of the methylated polysaccharide of Rhizobium radicicolum yields equal amounts of 2,3,6-trimethyl-D-glucose, 2,3-dimethyl-D-glucose and 2,3-dimethyl-D-glucuronic acid.65 1 The minimum trisaccharide repeating unit consists, in part, of cello-biuronic acid, and may be represented ... 

The isolation of 2,3-dimethyl-D-glucose from the hydrolysis products of certain methylated polysaccharides has been an important factor in assigning structures to these polysaccharides. From trimethyl-starch it has been recovered in about 3% yield, together with 2,3,4,6-tetra-methyl- and 2,3,6-trimethyl-D-glucopyranose, and arises from the points of linkage of the repeating chains of the amylopectin component.67,69,70 From a dimethyl-starch the yield is considerably higher (75%).71 Other sources are the methylated capsular polysaccharide of Rhizobium radici-... 

Using computer modeling, jointly with x-ray fiber diffraction data, the molecular architectures of two different gel-forming polysaccharides have been examined. Preliminary results indicate that the neutral and doubly branched capsular polysaccharide from Rhizobium trifolii can form a 2-fold single helix of pitch 1.96 nm or a half-staggered, 4-fold doublehelix of pitch 3.92 nm. The molecules are likely to be stabilized by main chain — side chain interactions. 

RHIZOBIUM TRIFOLII CAFSULAR FOLYSACCHARIDE. This polysaccharide is very unusual in that it has a doubly branched, neutral hexasaccharide repeating unit (25) shown below. 

Figure 1. An x-ray diffraction pattern from an oriented, noncrystalline fiber of the Rhizobium trifolii capsular polysaccharide using CuKa radiation. (Reproduced with permission from Ref. 16. Copyright 1987 Gordon and Breach.)...

When the extracellular, acidic polysaccharide from Rhizobium meliloti IFO 13336 was hydrolyzed with extracellular /3-D-glycanase and then intracellular endo-(l - 6)-/J-D-glucanase, two tetrasaccharides were... 

The extracellular polysaccharides of Rhizobium meliloti 201 have been examined by using enzymic degradation and chemical procedures.314 A mixture of polysaccharides produced by the bacterium, when incubated with a bacterial enzyme that hydrolyzed one of these, gave oligosaccharides that could be separated by DEAE-cellulose chromatography. The major fraction was a pentasaccharide, for which methylation analysis and Smith... 

Other monosaccharide components (of bacterial polysaccharides) that are structurally related to D-ribose include D-riburonic acid,232 identified in the exocellular polysaccharide produced by a strain of Rhizobium meliloti, and D-arabinose, frequently present as the furanose, in polysaccharides of mycobacterial cell-wall.233,234 L-Xylose235,236 should probably be included in the group, as it may be derived from D-arabinose through epimerization at C-4. Biosynthesis of these monosaccharides was not investigated. 

In the biosynthesis of the capsular polysaccharide from Xanthomonas campestris, the modification was shown265 to occur at the level of a polyprenyl pentasaccharide diphosphate intermediate prior to polymerization of the repeating units, and enolpyruvate phosphate was a precursor of the pyruvic acid residues. A similar observation was made during a study of the biosynthesis of Rhizobium meliloti exopolysaccharide.266... 

The extracellular polysaccharide of Rhizobium meliloti, having the structure339 shown in formula 29 (some of the 6-hydroxyl groups of the D-glucosyl... 

Studies on the white clover -Rhizobium trifolii interaction are the most advanced. Trifoliin A, a lectin present in clover-seedling roots, binds hapten reversibly to carbohydrate antigens cross-reactive on the capsular polysaccharide of R. trifolii and clover epidermal-cells.244 A specific hapten that inhibits binding of trifoliin A to both surfaces is 2-deoxy-D-arabino-hexose.245 It has also been shown that levels of trifoliin A on root hairs decline with increasing concentrations of nitrate, in parallel to root-nodule development,246 and that lectin receptors are transient on R. trifolii, in a way coinciding with its capacity to be adsorbed to clover roots.247... 

B. L. Reuhs, R. W. Carlson, and J. S. Kim, Rhizobium fredii and Rhizobium meliloti produce 3-deoxy-D-marmo-2-octulosonic acid-containing polysaccharides that are structurally analogous to group II K antigens (capsular polysaccharides) found in Escherichia coli, J. Bacteriol., 175 (1993) 3570-3580. 

Most of the research on bacteria from the genus Rhizobium is conducted in the field of genetics and bacteria-host plant simbiotic interactions. Little is known about the production of extracellular polysaccharides produced by Rhizobium as well as their properties in solution in particular, no studies have been conducted on the effect of substrate concentration, agitation, and aeration as relevant parameters to monitor in the process of exopolysaccharide (EPS) production. The present work aimed to determine the extent to which some variables affect the production of polysaccharides by Rhizobium sp. 

Forsberg, L.S., Bhat, U.R., Carlson, R.W. Structural characterization of the O-antigenic polysaccharide of the lipopolysaccharide from Rhizobium etli strain CE3. A unique O-acetylated gly-can of discrete size, containing 3-0-methyl-6-deoxy-L-talose and 2,3,4-tri-O-methyl-L-fucose. J Biol Chem 275 (2000) 18851-18863. 

Forsberg, L.S., Noel, K.D., Box, J., Carlson, R.W. Genetic locus and structural characterization of the biochemical defect in the O-antigenic polysaccharide of the symbiotically deficient Rhizobium etli mutant, CE166 Replacement of N-acetylquinovosamine with its hexosyl-4-ulose precursor. J Biol Chem 278 (2003) 51347-51359. 

Lopez-Lara, I.M., Orgambide, G., Dazzo, F.B., Olivares, J., Toro, N. Surface polysaccharide mutants of Rhizobium sp. (Acacia) strain GRH2 Major requirement of lipopolysaccharide for successful invasion of Acacia nodules and host range determination. Microbiology 141 (1995) 573-581. 

Laus, M.C., Logman, T.J., van Brussel, A.A.N., Carlson, R.W., Azadi, R, Gao, M.Y., Kijne, J.W. Involvement of exo5 in production of surface polysaccharides in Rhizobium leguminosarum and its role in nodulation of Vicia sativa subsp. nigra. J Bacteriol 186 (2004) 6617-6625. 

Reuhs, B.L., Kim, J.S., Badgett, A., Carlson, R.W. Production of cell-associated polysaccharides of Rhizobium fredii USDA205 is modulated by apigenin and host root extract. Mol Plant Microbe Interact 7 (1994) 240-247. 

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