STRUCTURAL DETERMINATION OF THE LPS FROM RHIZOBIUM

来自革兰氏阴性菌的脂多糖（LPS）是 重要的分子来决定一个菌株是否 细菌将成为成功的病原体或将被识别， 被宿主细胞的防御机制破坏。 固氮根瘤菌的脂多糖 也被认为在共生感染中起着关键作用 它们的寄主豆科植物。 如果这项提议获得批准， 用于确定来自一个菌株的LPS的结构 R. trifolii（三叶草共生体）、三叶草R.豆科植物 豌豆共生体）和R.菜豆（菜豆的共生体）。 为了 以确定是否需要基因感染和繁殖（节点 基因）影响LPS的结构，这些分子来自一个 或者将表征两个明确定义的共生突变体。 在 R.三叶草感兴趣的nod基因位于 pSym质粒，它是进行细菌培养所必需的。 这些基因 需要豆类黄酮的诱导， 还将表征细菌。 从一个人的LPS分析 R.豆类根瘤菌菌株缺乏其自身的pSym，但含有 R.三叶草和结瘤三叶草也将决定 pSym nod基因影响LPS结构。 从一个突变体的LPS R.菜豆将被表征，因为它已经被证明是 这种突变产生了一种有缺陷的LPS， 与一种共生缺陷有关， 中止. LPS将通过苯酚/水萃取分离， 凝胶过滤色谱法。 所述多糖的多糖部分 将分离LPS，并通过以下方法确定其结构： 组成，甲基化和GC/MS分析，并通过1H-和 13C-n.m. r分析。

The lipopolysaccharides (LPSs) from Gram-negative bacteria are important molecules in determining whether or not a strain of bacteria will be a successful pathogen or will be recognized and destroyed by the defense mechanisms of the host cell. Lipopolysaccharides from the nitrogen-fixing Rhizobium bacteria are also thought to play a crucial role in the symbiotic infection of their host legumes. If this proposal is approved the funds will be used to determine the structures of the LPSs from one strain each of R. trifolii (symbiont of clover), R. leguminosarum (the symbiont of pea) and R. phaseoli (the symbiont of bean). In order to determine if genes required for infection and nodulation (nod genes) affect the structure of the LPSs, these molecules from one or two well defined symbiotic mutants will be characterized. In the case of R. trifolii the nod genes of interest reside on a plasmid which is required for nodulation (the pSym). These genes require induction by a legume flavone so the LPSs from induced bacteria will also be characterized. Analysis of the LPS from an R. leguminosarum strain which lacks its own pSym but contains an R. trifolii pSym and nodulates clover will also determine if the pSym nod genes affect LPS structure. The LPS from a mutant of R. phaseoli will be characterized since it has already been shown that this mutation produces a defective LPS and that this defect is linked to a symbiotic defect in which infection threads are aborted. The LPS will be isolated by phenol/water extraction and gel-filtration chromatography. The polysaccharide portions of the LPSs will be isolated and their structures determined by composition, methylation and GC/MS analyses and by 1H- and 13C-n.m.r analyses.