Genetic Basis of Abscess Formation by B. fragilis

脆弱拟杆菌形成脓肿的遗传基础

• 批准号: 6569528
• 负责人: LAURIE E COMSTOCK
• 金额: $ 9.08万
• 依托单位: BRIGHAM AND WOMEN'S HOSPITAL
• 依托单位国家: 美国
• 财政年份: 2003
• 资助国家: 美国
• 起止时间: 2003-09-30 至 2007-01-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6569528
• 关键词: Bacteroides; Enterobacteriaceae disease; aminosugar; bacterial cytopathogenic effect; carbohydrate biosynthesis; gene expression; genetic strain; genetic susceptibility; inflammation; laboratory mouse; polymerase chain reaction; polysaccharides; southern blotting; stomach disorder; western blottings

DESCRIPTION (provided by applicant): Bacteroides fragilis is the leading cause of anaerobic bacteremia and intraabdominal abscesses. The capsular polysaccharide complex of the prototype strain, 9343, confers the abscessogenic properties of the organism. The capsular polysaccharide complex of 9343 is comprised of at least eight distinct capsular polysaccharides (PSA1 - PSH1). For strain 9343, PSA1 is not only crucial for abscess formation, but is the only polysaccharide necessary for abscess formation by this organism. The region of the B. fragilis chromosome containing the PSA1 biosynthesis locus is heterogeneous, therefore, the PSA molecules synthesized by different B. fragilis strains are structurally distinct. It is not known whether the PSA molecules of other virulent strains also confer the abscessogenic potential of that organism. The zwitterionic nature of PSA1 of 9343, having both a positive and negative charge per repeating unit, is essential for its abscessogenic potential. Two genes of the PSA1 biosynthesis locus, wcfR and wcfS, are conserved in the PSA biosynthesis loci of all strains analyzed. Homology-based data suggest that the products of these genes are involved in the formation of the positively charged monosaccharide of PSA1, AATGaI. Therefore, it is likely that all B. fragilis strains synthesize a PSA molecule with this same positively charged monosaccharide (AATGal). Based on the importance of AATGal to the virulence of the PSA1 of 9343, our overall hypothesis is that the PSA molecule confers the abscessogenic potential of each virulent strain. This application is divided into three aims that will address this hypothesis, first at the species level by mutating the PSA loci of various strains that produce structurally distinct PSA molecules and testing these mutants for their ability to induce abscesses. Next, the genes and their products that are predicted to be involved in the synthesis of AATGal will be analyzed biochemically and genetically. We now have the tools and an adequate scientific foundation to determine why the species B. fragilis as a whole has abscessogenic capabilities rather than only understanding this phenomenon for the prototype strain. The data gained from these aims may allow us to realize our goal of elucidating the genetic basis of abscess formation by this species.

描述（由申请方提供）：脆弱拟杆菌是厌氧菌血症和腹腔内脓肿的主要原因。原型菌株9343的荚膜多糖复合物赋予了生物体的产酶特性。9343的荚膜多糖复合物由至少八种不同的荚膜多糖（PSA 1-PSH 1）组成。对于菌株9343，PSA 1不仅对脓肿形成至关重要，而且是该生物体形成脓肿所必需的唯一多糖。B区。含有PSA 1生物合成位点的fragilis染色体是异质的，因此，PSA分子由不同的B合成。fragilis菌株在结构上不同。目前尚不清楚其他强毒株的PSA分子是否也赋予该生物体的致病潜力。PSA 1的两性离子性质9343，每个重复单元具有正电荷和负电荷，是其潜在的生物活性所必需的。PSA 1生物合成位点的两个基因wcfR和wcfS在所有分析菌株的PSA生物合成位点中是保守的。基于同源性的数据表明，这些基因的产物参与了PSA 1的带正电荷单糖AATGaI的形成。因此，很可能所有的B。脆壁菌菌株合成具有该相同的带正电荷的单糖（AATGal）的PSA分子。基于AATGal对9343的PSA 1的毒力的重要性，我们的总体假设是PSA分子赋予每种毒力菌株的致病潜力。本申请分为三个目标，将解决这一假设，首先在物种水平上通过突变产生结构不同的PSA分子的各种菌株的PSA基因座，并测试这些突变体的能力，以诱导p53。 接下来，将对预测参与AATGal合成的基因及其产物进行生化和遗传分析。 我们现在有了工具和充分的科学基础来确定物种B。fragilis作为一个整体具有生物合成能力，而不仅仅是了解原型菌株的这种现象。从这些目标中获得的数据可能使我们能够实现我们的目标，阐明脓肿形成的遗传基础，这一物种。