Spirochete coordination of adhesion and motility in the presence of fluid shear forces

背景：螺旋体是一种侵袭性的、快速移动的革兰氏阴性细菌，呈螺旋状或平面波浪状，其胞质周围的鞭毛包裹着细胞体，并通过波动的波状或螺旋状的细胞体旋转来驱动运动，其流体外膜含有很少的跨膜蛋白。大多数螺旋体黏附蛋白（黏附素）通过脂质锚定在外膜上，可能具有高度的流动性。螺旋体在密集的生物材料中比在纯液体中移动得更快，这可能是由于细胞与其细胞外环境之间具有牵引力的粘附相互作用，这一特性对于其他细菌无法进入的环境的定植可能至关重要。如果运动性取决于粘附性，那么粘附素也可能是可移动的，特别是在流动条件下与表面粘附的情况下，细菌的运动性和流动性推动细胞体向前，因为将细菌锚定在表面的粘附复合物保持在固定位置。在存在和不存在流动的情况下，螺旋体粘附和运动的动态协调的性质和机制尚未定义，并且大多数细菌尚未定义。这主要是由于需要开发快速，高分辨率的活细胞成像工具来研究粘附和运动的协调。我的实验室擅长开发基于成像的方法来研究细菌在流动和非流动环境中的粘附、运动和运动，最近建立了第一个基于成像的粒子跟踪和生物物理分析工具来研究细菌在流动下的粘附和表面运动。我们主要研究莱姆病螺旋体伯氏疏螺旋体（Bb），已经确定了这些细菌在运动过程中靶向的多种粘附素和细胞外基质成分，并意外地发现，Bb的运动刺激并稳定了Bb与内皮细胞在流动中的相互作用。******研究计划的总体目标：研究Bb粘附和运动协调的基本性质和机制。短期目标：发展快速、高速的基于活细胞成像的方法来研究细菌的粘附和运动协调。长期目标：应用这些方法研究细菌的运动如何促进流动表面的粘附，以及粘附和运动如何协调。******意义：这些研究将为螺旋体的运动和粘附协调机制提供第一个动态的见解。这项研究对加拿大的微生物学家来说将具有根本的、与健康无关的意义，特别是因为它将为研究其他细菌（包括那些形成工业和医学上重要的抗流动生物膜的细菌）的粘附和运动性的协调建立有用的方法。

BACKGROUND: Spirochetes are invasive, fast-moving gram-negative-like bacteria with a helical or planar wave-form shape, internal periplasmic flagella that wrap around the cell body and drive movement by undulating wave- or corkscrew-like rotation of the cell body, and a fluid outer membrane containing few transmembrane proteins. Most spirochete adhesion proteins (adhesins) are anchored to the outer membrane by lipid anchors and are likely highly mobile. Spirochetes move faster in dense biological materials than in pure liquid, possible due to traction-conferring adhesive interactions between cells and their extracellular environment, a property that may be crucial for colonization of environments inaccessible to other bacteria. If motility depends on adhesion, then adhesins may also be mobile, especially under conditions such as adhesion to surfaces under flow in which bacterial motility and flow propel the cell body forward as the adhesion complex anchoring bacteria to surfaces remains in a fixed position. The properties and mechanisms underlying dynamic coordination of spirochete adhesion and motility in the presence and absence of flow are not yet defined, and have not been defined for most bacteria. This is largely due to the need to develop rapid, high resolution live cell imaging tools to study coordination of adhesion and motility. My laboratory is expert in developing imaging-based approaches for studying bacterial adhesion, motility and movement in flow and non-flow environments, and recently established the first imaging-based particle-tracking and biophysical analysis tools to studying bacterial adhesion and movement to surfaces under flow. We work primarily with the Lyme disease spirochete Borrelia burgdorferi (Bb), have identified multiple adhesins and extracellular matrix components targeted by these bacteria during movement, and found, unexpectedly, that Bb motility stimulates and stabilizes Bb interactions with endothelial cells under flow. ******OVERALL OBJECTIVE OF RESEARCH PROGRAM: To investigate the fundamental properties and mechanisms underlying coordination of adhesion and motility in Bb. Short-term objective: Develop rapid, high speed live cell imaging-based methods to study bacterial coordination of adhesion and motility. Long-term objective: Apply these methods to investigate how bacterial motility promotes adhesion to surfaces under flow, and how adhesion and motility are coordinated.******SIGNIFICANCE: These studies will provide the first dynamic insight into mechanisms coordinating motility and adhesion in spirochetes. This research will be of fundamental, non-health-related interest for Canadian microbiologists, especially because it will establish methods useful for studying coordination of adhesion and motility in other bacteria, including those that form industrially- and medically-important flow-resistant biofilms.