Urbanik-Sypniewska T, Skorupska A, Deryło M
Department of General Microbiology, University M. Curie-Skłodowska, Lublin, Poland.
Acta Biochim Pol. 1992;39(2):177-91.
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.
三叶草根瘤菌三叶草生物变种产生一种酸性胞外多糖（EPS），它在固氮根瘤的形成中起重要作用。EPS产生缺陷（Exo-）的三叶草根瘤菌93的Tn5突变体在红三叶草上形成无效（Fix-）根瘤。这种Exo-突变可被从三叶草根瘤菌TA1基因文库中分离出的pARF1368和pARF25黏粒互补，但这种互补与Fix+表型的恢复不相关。此外，将这些黏粒导入三叶草根瘤菌24野生型会抑制其形成固氮根瘤的能力。这些结果可能表明，携带exo区域黏粒的细菌形成了结构改变的EPS。1H-核磁共振已表明，三叶草根瘤菌93pARF - 1368和93pARF25产生的胞外多糖比野生型EPS含有更少的非碳水化合物残基（乙酰基、丙酮酸基和3-羟基丁酰基）。这些数据表明，三叶草根瘤菌胞外多糖的生物活性取决于非碳水化合物取代基的含量。
