Mechanics of Bacterial Swarming

细菌群聚的机制

• 批准号: 7061704
• 负责人: HOWARD C BERG
• 金额: $ 27.4万
• 依托单位: HARVARD UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 2005
• 资助国家: 美国
• 起止时间: 2005-07-01 至 2008-06-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7061704
• 关键词: Escherichia coli; bacteria characteristic; bacteria infection mechanism; cell migration; chemotaxis; cilium /flagellum motility; digital imaging; fluidity; surfactant; video recording system

DESCRIPTION (provided by applicant): Swarming is a specialized form of bacterial motility that develops when cells that swim in broth are grown in a rich medium on the surface of moist agar. They become multinucleate, elongate, synthesize large numbers of flagella, excrete surfactants, and advance across the surface in coordinated packs. Most studies of swarming have sought to define the developmental processes leading from the vegetative to the swarming state and to discover the role played by swarming in invasiveness and pathogenicity. Here, we will look to see what the flagella actually do in swarming, how they determine the coordinate motion of groups of cells and promote fluid flow at the swarm boundary. These questions are pertinent not only to basic flagellar mechanics on a surface, but also to larger ramifications of this process, such as the group behavior of cells during surface colonization, including pattern generation and biofilm formation. 1) Using single and multi-color fluorescent labeling of flagellar filaments, pulsed laser illumination, digital video recording, and frame-by-frame computer analysis, we will characterize the motion of flagella on cells at the leading edge of the swarm and on cells moving in packs near that edge. We will repeat these measurements with swarm-defective chemotaxis (che) mutants and revertants of these mutants. What is the flagellar mechanics of swarming motility? 2) By tracking fluorescent cells, we will measure correlation distances and times of cells in different regions of the swarm, in particular, near its leading edge. How coordinated are these motions? 3) By tracking small fluorescent beads, we will study fluid motion at the leading edge of the swarm. Is fluid driven outward by flagellar motion? 4) To learn more about the role played by surfactants, we will measure the interfacial tension of fluid sampled near the leading edge of a swarm. Is production of surfactant coupled to flagellar motion? In brief, we hope to understand the underlying mechanical mechanisms that enable flagellated bacteria to colonize surfaces, a process important for multicellularity, invasiveness, and pathogenicity.

描述（由申请方提供）：群集是细菌运动的一种特殊形式，当在肉汤中游动的细胞在潮湿琼脂表面的丰富培养基中生长时，会出现群集。它们变成多核的，伸长的，合成大量的鞭毛，分泌表面活性剂，并在协调的包装中穿过表面。大多数关于群集的研究都试图确定从营养状态到群集状态的发育过程，并发现群集在入侵和致病性中所起的作用。在这里，我们将看看鞭毛在群集中实际上做了什么，它们如何决定细胞群的协调运动并促进群体边界的流体流动。这些问题不仅与表面上的基本鞭毛力学有关，而且与该过程的更大分支有关，例如表面定殖期间细胞的群体行为，包括图案生成和生物膜形成。1)使用单一和多色荧光标记的鞭毛丝，脉冲激光照明，数字视频记录，和逐帧的计算机分析，我们将表征鞭毛的运动细胞在群的前沿和细胞移动包附近的边缘。我们将对群体缺陷趋化性（che）突变体和这些突变体的回复突变体重复这些测量。什么是群集运动的鞭毛机制？2)通过跟踪荧光细胞，我们将测量在群体的不同区域，特别是在其前沿附近的细胞的相关距离和时间。这些动作有多协调？3)通过跟踪小荧光珠，我们将研究流体运动的领先优势的群体。液体是通过鞭毛运动向外驱动的吗？4)为了进一步了解表面活性剂所起的作用，我们将测量在群前缘附近取样的流体的界面张力。表面活性剂的产生与鞭毛运动有关吗？简而言之，我们希望了解使鞭毛细菌能够在表面定居的潜在机械机制，这是多细胞性，侵袭性和致病性的重要过程。