MOLECULAR MECHANISMS OF VARIATION AND ADAPTATION IN BORRELIA BURGDORFERI

我们的总体目标是了解疏螺旋体 伯氏杆菌(BB)建立了一种感染：在 扁虱载体和哺乳动物宿主，这两者都是需要的 保持自然界中的螺旋体。 1.外表面蛋白变异。BB的外膜含有 几种丰富的蛋白质(OSP)，其大小和表达方式各不相同，并且 未知功能的。很可能不同的OSP授予不同的 螺旋体上与不同的 它必须生存的环境。与Dr进行合作研究 Schwan已经证明在中肠的螺旋体上可以检测到Ospc。 只有在吃了一顿血餐后才会感染扁虱，而且 温度在一定程度上导致了SPC合成的增加。Dr。 史蒂文森已经证明，至少还有5种其他蛋白质 由于培养温度的不同而不同地合成。Dr。 史蒂文森分析了OspC基因的5‘侧翼序列 多个菌株鉴定保守的启动子元件。费舍尔 史蒂文森和蒂莉已经开始了使用基因和 鉴定改变OSP启动子的成分的生化方法 活动。史蒂文森、蒂莉和罗莎正试图改变BB和 整合失活OSP基因和其他感兴趣基因 可选标记。这类基因敲除突变体是 未来的研究将确定各种蛋白质的作用，包括 OSPs，在BB的感染循环中。 2.质粒结构与复制。了解其结构和 不同寻常的线形和环状螺旋体基因组的复制是 与生俱来的兴趣和实际价值。蒂莉医生继续她的 BBHU/IHF同系物的研究她和塞缪尔博士(RMLMB) 开发了一种纯化方案，并使用凝胶漂移试验来鉴定 与端粒DNA片段结合的蛋白质片段，端粒DNA片段包含 推测为IHF结合部位。蒂莉和罗莎已经制定了一种策略 分析端粒序列重组的位置。罗莎和蒂莉 已经扩展了他们对独特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)的比较 与B.hermsii中关系密切但更典型的同源物。上一首 研究确定了一种多肽结合蛋白的基因同源 与26-kB环状质粒上的guaB相邻。罗莎医生已经延长了 这项研究通过确定一个与An同源的染色体基因座 寡肽渗透酶系统。

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.