Exopolysaccharides of Rhizobium leguminosarum biovar trifolii harbouring cloned exo region.
Rhizobium leguminosarum bv. trifolii produces an acidic exopolysaccharide (EPS) which plays an important role in the development of nitrogen-fixing nodules. Tn5 mutant of R. trifolii 93 defective in EPS production (Exo-) forms ineffective (Fix-) nodules on red clover. This Exo- mutation is complemented by the pARF1368 and pARF25 cosmids isolated from gene bank of Rhizobium trifolii TA1, but the complementation is not correlated with restoration of Fix+ phenotype. Furthermore, these cosmids introduced to wild-type of R. trifolii 24 repress its ability to form nitrogen-fixing nodules. These results might suggest that bacteria with cosmids carrying the exo region form EPS of altered structure. It has been shown by 1H-n.m.r. that exopolysaccharides produced by R. trifolii 93pARF-1368 and 93pARF25 contain less non-carbohydrate residues (acetyl, pyruvyl and 3-hydroxybutanoyl) than the wild type EPS. These data suggest that the biological activity of the exopolysaccharide of R. trifolii depends on the contents of the non-carbohydrate substitutions.
Urbanik-Sypniewska
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Department of General Microbiology, University M. Curie-Skłodowska, Lublin, Poland.
Skorupska
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Deryło
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D003001:Cloning, Molecular; D003360:Cosmids / Q000235:genetics*; D005798:Genes, Bacterial; D005822:Genetic Vectors / Q000235:genetics; D009682:Magnetic Resonance Spectroscopy; D009586:Nitrogen Fixation / Q000235:genetics; D011135:Polysaccharides, Bacterial / Q000032:analysis / Q000235:genetics*; D016961:Rhizobium leguminosarum / Q000235:genetics*
D011135:Polysaccharides, Bacterial