Rhizobial Lipopolysaccharides Essential for Infection

感染必需的根瘤菌脂多糖

• 批准号: 8008946
• 负责人: RUSSELL W CARLSON
• 金额: $ 12万
• 依托单位: UNIVERSITY OF GEORGIA
• 依托单位国家: 美国
• 财政年份: 2010
• 资助国家: 美国
• 起止时间: 2010-01-28 至 2010-12-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8008946
• 关键词: Acetylation; Acids; Animals; Bacteria; Bartonella; Biological Models; Brucella; Cell surface; Cells; Chronic; Environment; Fabaceae; Francisella; Glucosamine; Gram-Negative Bacteria; Host Defense Mechanism; Hydrophobicity; Infection; Invaded; Legionella; Lipid A; Lipopolysaccharides; Methylation; Modification; Molecular; Nitrogen; Nodule; Osmolar Concentration; Oxygen measurement, partial pressure, arterial; Phenotype; Pisum sativum; Plant Roots; Polysaccharides; Process; Rhizobium; Symbiosis; System; Very Long Chain Fatty Acid; base; bean; galacturonic acid; inorganic phosphate; mutant; oxidation; pathogen; Acetylation; Acids; Animals; Bacteria; Bartonella; Biological Models; Brucella; Cell surface; Cells; Chronic; Environment; Fabaceae; Francisella; Glucosamine; Gram-Negative Bacteria; Host Defense Mechanism; Hydrophobicity; Infection; Invaded; Legionella; Lipid A; Lipopolysaccharides; Methylation; Modification; Molecular; Nitrogen; Nodule; Osmolar Concentration; Oxygen measurement, partial pressure, arterial; Phenotype; Pisum sativum; Plant Roots; Polysaccharides; Process; Rhizobium; Symbiosis; System; Very Long Chain Fatty Acid; base; bean; galacturonic acid; inorganic phosphate; mutant; oxidation; pathogen

DESCRIPTION (provided by applicant): Rhizobium-legume symbioses involve processes that are fundamental to all bacterial-host interactions. These include (a.) prokaryotic-eukaryotic recognition, (b.) interaction with the host defense mechanism, and (c.) bacterial and host differentiation processes (i.e. formation of nitrogen-fixing bacteroids and root nodules, respectively). As with animal pathogens, the invading rhizobia must adapt to the environment of the host to avoid destruction and persist in the host cell. These adaptations involve changes to cell surface polysaccharides, such as lipopolysaccharides (LPSs) and capsular polysaccharides. Rhizobium-legume symbiosis is an excellent model system to examine the molecular bases by which Gram-negative bacteria infect and survive within their host since both the bacteria and the host cells are viable throughout the infection process, and the LPSs from the invading bacteria can be isolated and characterized as a function of the infection process. The symbiosis system is particularly relevant to a number of intracellular pathogens that form chronic infections such as species of Brucella, Bartonella, Legionella, as well as Francisella. We have observed that unique structural features of Rhizobium LPSs are also present on LPSs from these pathogens. Our project focuses on the adaptation that rhizobia (R. etli and R. leguminosarum; symbionts of bean and pea, respectively) make to their LPSs as they encounter the stressful environment (e.g. changes in pH, osmolarity, oxygen tension, etc.) of the host cell. We hypothesize that unique structural features of rhizobial LPSs are essential for infection and persistence in the legume hosts. Unique structural features include a replacement of phosphate with galacturonic acid residues, oxidation of the lipid-A proximal glucosamine residue to 2-aminogluconate, and the presence of the very long chain fatty acid, 27- hydroxyoctacosaonic acid (27OHC28:0), on the lipid-A. Methylation and acetylation changes to the O-chain polysaccharide and an overall change in the hydrophobicity of the LPS and the whole rhizobial cell occur during symbiosis. Our Specific Aims are: (1.) characterize the modifications to the O-chain polysaccharide of the LPS during symbiosis, (2.) create specific LPS mutants and characterize their structural and symbiotic phenotypes, and (3.) determine how a 27OHC28:0-lacking mutant, acpXL::kan, is able to activate an alternative mechanism within the host cell.

描述（由申请人提供）：根茎 - 肠道共生性涉及对所有细菌 - 宿主相互作用至关重要的过程。这些包括（a。）原核生物 - 核识别，（b。）与宿主防御机制的相互作用，以及（c。）细菌和宿主分化过程（即分别形成氮的细菌和根结节）。与动物病原体一样，入侵的根瘤菌必须适应宿主的环境，以避免破坏并持续存在于宿主细胞中。这些适应性涉及细胞表面多糖，例如脂多糖（LPS）和囊囊多糖。根瘤菌共生是一个出色的模型系统，可以检查革兰氏阴性细菌感染并在其宿主中生存的分子基础，因为细菌和宿主细胞在整个感染过程中均可生存，并且可以隔离入侵细菌的LPS，并且可以通过感染过程来隔离并表征性。共生系统与形成慢性感染的许多细胞内病原体特别相关，例如布鲁氏菌，Bartonella，军团菌以及Francisella。我们已经观察到，这些病原体的LPS也存在根茎LPS的独特结构特征。我们的项目着重于根瘤菌（R. Etli和R. feleminosarum;豆类和豌豆的共生体）在遇到压力的环境时对其LPS进行的，例如宿主细胞的pH，渗透压，氧气张力等）。我们假设Rhizobial LPS的独特结构特征对于豆科植物宿主的感染和持久性至关重要。独特的结构特征包括用半乳酸酸残基替代磷酸盐，将脂质-A近端葡萄糖胺残基氧化为2-氨基糖苷酸盐，以及在Lipid-a上的长链脂肪酸（27-羟基辛酸27-羟基二辛酸）的存在（27-Hohc28：0）。甲基化和乙酰化对O链多糖的变化以及LPS疏水性和整个根茎细胞的总体变化发生在共生期间。我们的具体目的是：（1.）表征在共生期间对LPS的O链多糖的修改，（2。）创建特定的LPS突变体并表征其结构和共生表型，（3。）确定27OHC28：0-lacking突变体，ACPXL :: kan :: kan，可以激活一个替代机构的机构。