Molecular Genetic Basis of the Infectious Cycle of Borrelia burgdorferi

莱姆病是美国和欧洲最常见的蜱传播疾病。它是由伯氏疏螺旋体引起的，伯氏疏螺旋体是一种细菌病原体，在自然界中在各种小型哺乳动物和硬蜱媒介之间的人畜共患病循环中维持。莱姆病螺旋体的一个标志是其不寻常的分段基因组，包括一个线性染色体和大约20个线性和环状质粒。越来越多的数据表明，质粒编码的功能是成功适应B的关键。螺旋体在其自然感染周期中遇到的不同环境。我们已经开发了遗传工具来研究B的不寻常的基因组组织、细胞结构和代谢的基本方面。burgdorferi。我们已经将这项调查扩展到了一个体内环境，该实验系统密切模仿了天然节肢动物载体/啮齿动物宿主的感染循环。通过对生物体的基本分子生物学的理解，我们希望深入了解这种重要的媒介传播病原体所利用的感染策略，从而促进预防，诊断和治疗莱姆病的努力。 替代性σ因子RpoS在莱姆病螺旋体的关键适应性反应中起核心作用，所述关键适应性反应在蜱喂食期间诱导并准备螺旋体用于脊椎动物宿主的感染。我们实验室以前的工作确定了质粒编码的BBD 18蛋白作为RpoS的负调节因子，但从未实现野生型螺旋体中bbd 18基因的失活。我们利用条件bbd 18突变体，全基因组转录组，代谢组学和蛋白质分析，以及所有cp 32原噬菌体质粒的第一个工程置换，研究伴随BBD 18耗尽和感染性B中RpoS未调节产生的致死表型。burgdorferi。此外，我们进行了体内研究，以确定在小鼠-蜱感染周期中螺旋体需要BBD 18才能生存的精确阶段和位置。作为这些实验的结果，我们提供了第一份报告之间的联系转导噬菌体和RPOS依赖的适应性反应，莱姆病螺旋体在蜱喂养过程中进行。我们推断，疏螺旋体基因组的多分结构有利于噬菌体介导的遗传交换和重配，从而促进螺旋体在自然地方病循环中维持所需的多样性水平。 注：主要研究者于2023年4月退休，本项目将被终止/停用。

Lyme disease is the most common tick-borne illness in the United States and Europe. It is caused by Borrelia burgdorferi, a bacterial pathogen that is maintained in nature in a zoonotic cycle between various species of small mammals and an ixodid tick vector. A hallmark of the Lyme disease spirochete is its unusual, segmented genome, comprising a linear chromosome and approximately 20 linear and circular plasmids. An increasing body of data demonstrates that plasmid-encoded functions are critical for successful adaptation of B. burgdorferi to the different environments that the spirochete encounters during its natural infectious cycle. We have developed genetic tools to investigate basic aspects of the unusual genomic organization, cellular structure and metabolism of B. burgdorferi. We have extended this investigation to an in vivo setting with an experimental system that closely mimics the natural arthropod vector/rodent host infectious cycle. Through an understanding of the basic molecular biology of the organism, we hope to gain insight into the infectious strategy utilized by this significant vector-borne pathogen and thereby facilitate efforts to prevent, diagnose and treat Lyme disease. The alternative sigma factor RpoS plays a central role in a critical adaptive response of the Lyme disease spirochete that is induced during tick feeding and prepares the spirochete for infection of the vertebrate host. Previous work from our lab identified the plasmid-encoded BBD18 protein as a negative regulator of RpoS, but inactivation of the bbd18 gene in wild-type spirochetes was never achieved. We utilized a conditional bbd18 mutant, genome-wide transcriptomic, metabolomic, and protein profiling, and the first engineered displacement of all cp32 prophage plasmids, to investigate the lethal phenotype that accompanies BBD18 depletion and unmodulated production of RpoS in infectious B. burgdorferi. Additionally, we conducted in vivo studies to identify the precise stage and location during the mouse-tick infectious cycle at which spirochetes require BBD18 for survival. As a result of these experiments, we provide the first report of a link between transducing phage and the RpoS-dependent adaptive response that Lyme disease spirochete undergo during tick feeding. We infer that the multipartite structure of the Borrelia genome facilitates phage-mediated genetic exchange and reassortment, and thereby fosters the level of diversity that is required for spirochete maintenance in the natural enzootic cycle. NOTE: The Principal Investigator retired in April 2023 and this project will be terminated/inactivated.