Biophysics of the morphology and motility of Borrelia burgdorferi in diverse envi

描述(申请人提供)：由伯氏疏螺旋体引起，是美国最常见的壁虱传播疾病。如果不治疗，莱姆病可能会导致一系列并发症，通常涉及心脏、关节或神经系统。人们普遍认为，伯氏杆菌的运动性在莱姆病的发病机制中是必不可少的。伯氏杆菌通过旋转位于周质空间(外膜和细胞壁材料之间的空间)的螺旋细丝(鞭毛)游泳。这些周质鞭毛相对于细胞壁的旋转导致细胞圆柱体的变形，这些变形对外部环境施加压力。这种细菌在节肢动物媒介(硬蜱)和哺乳动物宿主之间过渡。这种地方病循环要求细菌与非常不同的环境相互作用。例如，螺旋体必须能够定植在壁虱的中肠，然后从中肠迁移到血腔。一旦进入血腔，细菌必须导航到唾液腺，附着在腺泡表面，穿透基板，进入唾液管。然后，伯氏杆菌被接种到其哺乳动物宿主的皮肤中，在那里它必须通过细胞外基质移位，才能进入为通过血液传播提供门户的小血管。为了侵入关节和其他宿主组织，细胞必须附着在靶器官的血管内皮细胞上，并穿透它们。伯氏杆菌独特的运动性和形态被认为是驱动这些过程的许多因素，因此被认为是莱姆病发病的主要因素。该建议的主要假设是，当螺旋体在扁虱和哺乳动物宿主之间移动时，驱动伯氏杆菌运动的内部机制(即鞭毛旋转)在很大程度上没有变化，但由于与不同宿主组织相互作用的不同，其运动策略有很大不同。这一推理表明，形状、物理参数，如鞭毛和细胞圆柱体的硬度，以及驱动运动的内部机制已经进化，允许在这些不同的环境中进行定向迁移。因此，这项研究将首先对PI开发的数学模型的预测进行实验测试，该模型描述了伯氏杆菌的形状和运动性，该模型使用抗生素处理的细胞和改变细胞壁和鞭毛硬度的遗传操作。接下来，将在明胶基质中检测伯氏杆菌的运动性，以便通过模拟细胞外基质的可控模型系统来量化运动性。最后，将使用建模和延时荧光显微镜来确定上皮细胞层以及扁虱和小鼠的运动机制。这些目的是为了将目前对非生理液体和/或甲基纤维素溶液中运动性的理解转移到生物现实环境中，在生物现实环境中，螺旋体附着在细胞或ECM上，以完成它们的地方性循环和完成它们的寄生策略。 公共卫生相关性：本提案中描述的研究将确定莱姆病中宿主的传播和入侵所涉及的生物物理机制。具体地说，将建立莱姆病发展过程中病原体-宿主相互作用的定量模型并进行实验测试，这将提供对感染过程的详细了解，并可能导致新的治疗方法。

DESCRIPTION (provided by applicant): which is caused by the spirochete Borrelia burgdorferi, is the most common tick-transmitted illness in the United States. If untreated, Lyme disease can lead to a wide array of complications typically involving the heart, joints, or nervous system. It is widely believed that the motility of B. burgdorferi is essential for the pathogenesis of Lyme disease. B. burgdorferi swims by rotating helical filaments (flagella) that reside in the periplasmic space (the space between the outer membrane and the cell wall material). The rotation of these periplasmic flagella against the cell wall leads to deformations of the cell cylinder, and these deformations exert force against the external environment. The bacterium transitions between the arthropod vector (Ixodid ticks) and mammalian host. This enzootic cycle requires the bacterium to interact with extremely different environments. For example, spirochetes must be able to colonize the tick midgut, and then migrate out of the midgut into the hemocoel. Once in the hemocoel, the bacterium must navigate towards the salivary glands, attach to the acinar surface, penetrate the basal lamina, and enter the salivary ducts. B. burgdorferi is then inoculated into the skin of its mammalian host where it must translocate through the extracellular matrix in order to access small vessels which provide portals for dissemination through the blood. To invade joints and other host tissue, the cells must adhere to the endothelium of blood vessels in target organs and penetrate through them. The unique motility and morphology of B. burgdorferi are presumed to drive many of these processes and are, therefore, considered to be major factors in the pathogenesis of Lyme disease. The principal hypothesis of this proposal is that the internal mechanism driving the motility of B. burgdorferi (i.e., flagellar rotation) is largely unchanged when the spirochete moves between the tick and the mammalian host, but its strategy for motility is substantially different due to differences in the interactions with the different host tissues. This reasoning suggests that the shape; physical parameters, such as the stiffness of the flagella and cell cylinder; and the internal mechanism driving motility have evolved to allow for directed migration in these diverse environments. Therefore, this research will first experimentally test the predictions of a mathematical model developed by the PI that describes the shape and motility of B. burgdorferi using antibiotic-treated cells and genetic manipulations to alter the stiffnesses of the cell wall and flagella. Next, the motility of B. burgdorferi will be examined in gelatin matrices, in order to quantify motility through a controllable model system that mimics the ECM. Finally, modeling and time-lapse fluorescence microscopy will be used to determine the mechanisms of motility in epithelial cell layers, and in the tick and mouse. These aims are directed toward moving the current understanding of motility in non-physiological liquid and/or methycellulose solutions to biologically realistic environments in which spirochetes adhere to cells or ECM in order to complete their enzootic cycle and accomplish their parasitic strategy. PUBLIC HEALTH RELEVANCE: The research described in this proposal will determine the biophysical mechanisms that are involved in the transmission to and invasion of the host that occurs in Lyme disease. Specifically, a quantitative model of the pathogen-host interactions during the progression of Lyme disease will be developed and experimentally tested, which will provide a detailed understanding of the infection process and may lead to novel therapeutic methods.