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是 涉及识别信号分子的复杂过程 共生体和宿主豆科植物形成高度协调的 植物和共生体中基因的表达。 这样的结果 过程是含有固氮细菌的根瘤，称为 类菌。 最近的许多报告表明，主要的外膜 根瘤菌的成分脂多糖（LPS）在此过程中至关重要 共生感染过程。 缺乏已知 LPS 一部分的突变体 因为 O 抗原多糖（O 链）有缺陷，无论是感染还是感染 线的形成或细菌释放到皮质根中 细胞。 此外，使用单克隆抗体已表明， 在共生感染过程中，LPS 会发生微妙的结构变化， 这些变化可能对于形成固氮作用至关重要 结核。 当细菌 生长条件部分模仿根部内部的条件 结节，例如低pH值（4.8）。 该提案的主要目标是 表征所需的这些重要的 LPS 结构改变 用于共生感染。 具体来说，关于 LPS R. 豆科植物有限公司Phaseoli CE3（豆的共生体）和bv。 victae（共生体 豌豆），目标是：确定 O 抗原的结构 多糖；确定 LPS 核心寡糖、脂质 A 和 O- 抗原结构区连接形成完整的LPS分子；和 确定共生过程中发生的 LPS 结构变化。 奥- 抗原结构将使用甲基化、GC-MS、FAB-MS 和 核磁共振分析技术。 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。 在 pH 4.8 下生长的细菌产生的 LPS 将是 表征以确定正在发生的结构变化 结瘤期间。 根据这项拟议工作的结果，应该 （将来）能够识别这些 LPS 所需的基因 改变并确定宿主如何调节它们的表达 植物。