MOLECULAR MECHANISMS OF VARIATION AND ADAPTATION IN BORRELIA BURGDORFERI

我们的主要目标是了解疏螺旋体 Burgdorferi（Bb）建立感染： 蜱虫载体和哺乳动物储库宿主，两者都需要 保持螺旋体的自然状态 1. 外表面蛋白变异。 Bb的外膜含有 几种丰富的蛋白质（Osps），大小和表达不同， 未知的功能。不同的OSP可能赋予不同的 螺旋体上的特性， 它必须生存的环境。与博士合作研究。 Schwan已经表明，OspC在中肠的螺旋体上是可检测的 感染蜱虫的数量增加， 温度升高部分地导致OspC合成增加。博士 史蒂文森已经证明，至少有5种其他蛋白质是 作为培养温度的结果差异合成。博士 史蒂文森已经分析了来自 多个菌株以鉴定保守的启动子元件。费希尔， 史蒂文森和蒂利已经开始了利用基因和 鉴定改变OSP启动子的组分的生物化学方法 活动 史蒂文森、蒂利和罗莎正试图改造BB， 目的基因和其它感兴趣的基因 选择标记这样的敲除突变体是一个关键的组成部分， 未来的研究，以确定各种蛋白质，包括 Osps在Bb. 2. 质粒结构和复制。了解结构和 不寻常的线性和环状疏螺旋体基因组的复制是 内在利益和实际价值。蒂利医生继续她的 Bb HU/IHF同系物的研究。她和塞缪尔博士（RMLMB） 开发了一种纯化方案，并使用凝胶迁移试验来鉴定 结合到端粒DNA片段的蛋白质部分，所述端粒DNA片段含有 推定的IHF结合位点。 蒂利和罗莎制定了一个策略， 分析端粒序列重组的位点。罗莎和蒂利 已经扩展了他们的结构和功能的分析， 质粒编码的Bb IMP脱氢酶基因同源物（guaB），通过比较 与B中密切相关但更典型的同源物。赫姆斯。先前 研究已经鉴定了一种肽结合蛋白的基因同源物 在26-kB环状质粒上与guaB相邻。罗莎医生已经延长了 这项研究通过鉴定一个染色体位点同源的一个 寡肽通透酶系统。

Our broad objective is to understand the means by which Borrelia burgdorferi (Bb) establishes an infection:transmission cycle between the tick vector and mammalian reservoir host, both of which are needed to maintain the spirochete in nature. 1. Outer surface protein variation. The outer membrane of Bb contains several abundant proteins (Osps) that vary in size and expression and are of unknown function. It is likely that the different Osps confer distinct properties on the spirochete that are pertinent to the different environments in which it must survive. Collaborative studies with Dr. Schwan have shown that OspC is detectable on spirochetes in the midgut of infected ticks only after a bloodmeal, and that an increase in temperature is in part responsible for increased OspC synthesis. Dr. Stevenson has documented that at least 5 other proteins are differentially synthesized as a consequence of culture temperature. Dr. Stevenson has analyzed the 5' flanking sequence of the ospC gene from multiple strains to identify conserved promoter elements. Fisher, Stevenson and Tilly have initiated studies using both genetic and biochemical approaches to identify components that alter osp promoter activity. Stevenson, Tilly and Rosa are attempting to transform Bb and inactivate osp genes and other genes of interest by integrating selectable markers. Such knockout mutants are a critical component of future studies to determine the roles of various proteins, including Osps, in the infectious cycle of Bb. 2. Plasmid structure and replication. Understanding the structure and replication of the unusual linear and circular Borrelia genome is of intrinsic interest and practical merit. Dr. Tilly has continued her studies of a Bb HU/IHF homolog. She and Dr. Samuels (RMLMB) have developed a purification scheme and used a gel shift assay to identify protein fractions that bind to a telomeric DNA fragment that contains a putative IHF binding site. Tilly and Rosa have developed a strategy to analyze the site at which telomeric sequences recombine. Rosa and Tilly have extended their analysis of the structure and function of the unique plasmid-encoded Bb IMP dehydrogenase gene homolog (guaB) by comparing it to the closely related, but more typical, homolog in B. hermsii. Previous studies have identified a gene homolog of a peptide binding protein adjacent to guaB on the 26-kB circular plasmid. Dr. Rosa has extended this study by identifying a chromosomal locus homologous to an oligopeptide permease system.