STRUCTURAL DETERMINATION OF THE LPS FROM RHIZOBIUM

根瘤菌 LPS 的结构测定

• 批准号: 3296709
• 负责人: RUSSELL W CARLSON
• 金额: $ 11.82万
• 依托单位: UNIVERSITY OF GEORGIA
• 依托单位国家: 美国
• 财政年份: 1988
• 资助国家: 美国
• 起止时间: 1988-06-01 至 1994-06-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/3296709
• 关键词: Bacteroides; Leguminoseae; Rhizobiaceae; bacterial genetics; bacterial polysaccharides; carbohydrate structure; enzyme linked immunosorbent assay; gas chromatography; gel filtration chromatography; gene expression; genetic strain; gram negative bacteria; host organism interaction; lipopolysaccharides; monoclonal antibody; mutant; nitrogen fixation; nuclear magnetic resonance spectroscopy; plant growth /development; symbiosis

Nitrogen fixing symbioss between a Rhizobium and its legume host is a complex process involving the recognition of signal molecules from both the symbiont and the host legume which results in a highly coordinated expression of genes in both the plant and symbiont. The result of this process is a root nodule which contains nitrogen-fixing bacteria, called bacteroids. Many recent reports have shown that the major outer membrane component of rhizobia, the lipopolysaccharide (LPS), is essential in this symbiotic infection process. Mutants which lack a portion of the LPS known as the O-antigen polysaccharide (O-chain) are defective either infection thread formation or in the release of the bacteria into the cortical root cells. Additionally it has been shown, using monoclonal antibodies, that subtle structural changes occur in the LPS during symbiotic infection and that these changes are likely to be crucial in forming a nitrogen-fixing nodule. These structural alterations are also observed when the bacteria are grown under conditions which, in part, mimic those inside the root nodule, e.g. low pH (4.8). The main objective of this proposal is to characterize these important LPS structural alterations that are required for symbiotic infection. Specifically, with regard to the LPSs R. leguminosarum bv. phaseoli CE3 (symbiont of bean) and bv. victae (symbiont of pea), the objectives are to: determine the structure of the O-antigen polysaccharides; determine how the LPS core oligosaccharide, lipid A and O- antigen structural regions are joined to form a complete LPS molecule; and determine the LPS structural changes that occur during symbiosis. The O- antigen structures will be determined using methylation, GC-MS, FAB-MS and NMR analytical techniques. The LPSs with and without the O-chain will be characterized to determine how the lipid A, core oligosaccharide and O- chain are joined together. The LPSs from bacteria grown at pH 4.8 will be characterized to determine the structural alterations that are occuring during nodulation. Based on the results of this proposed work, it should (in the future) be able to identify the genes required for these LPS alterations and to determined how their expression is regulated by the host plant.

根瘤菌与其豆科植物宿主之间的固氮共生关系是一种 复杂的过程涉及识别来自两种细胞的信号分子 共生体和宿主豆科植物，这导致了一个高度协调的 植物和共生体中基因的表达。 这样做的结果 过程是一个根瘤，其中含有固氮细菌，称为 拟杆菌 最近的许多报道表明， 根瘤菌的组成部分，脂多糖（LPS），是必不可少的， 共生感染过程 缺乏已知LPS的一部分的突变体 由于O-抗原多糖（O-链）是有缺陷的， 线的形成或细菌释放到皮层根中 细胞 此外，使用单克隆抗体已经表明， 在共生体感染期间LPS中发生细微的结构变化， 这些变化可能是形成固氮系统的关键， 结节。 这些结构上的改变也可以在细菌 在某种程度上， 根瘤，例如低pH值（4.8）。 这项建议的主要目的是 表征这些重要的LPS结构改变， 共生体感染 具体而言，关于LPS R. 豆科植物phaseoli CE 3（菜豆共生体）和bv.共生体 豌豆），目标是：确定O-抗原的结构 多糖;确定如何LPS核心寡糖，脂质A和O- 抗原结构区连接以形成完整的LPS分子;和 确定在共生过程中发生的LPS结构变化。 O- 抗原结构将使用甲基化、GC-MS、FAB-MS和 NMR分析技术。 有和没有O链的LPS将是 表征以确定脂质A、核心寡糖和O- 链条连接在一起。 来自在pH 4.8下生长的细菌的LPS将是 其特征在于确定正在发生的结构变化 在分娩过程中。 根据这项拟议工作的结果， (in未来）能够识别这些LPS所需的基因， 改变，并确定它们的表达是如何调节的主机 厂