Collaborative Research: Elucidating the Diversity of Bacterial Flagellation and Motility Through Mechanics

细菌的游泳能力对其生存至关重要。游泳是通过旋转被称为鞭毛的细丝来实现的。细菌上的鞭毛有很多种不同的排列方式，也有很多种不同的运动模式，所有这些都使它们能够游泳。尽管细菌在游泳方面取得了成功，但人们对这些机制知之甚少。这个项目的目的是确定鞭毛的排列和灵活的力学是如何结合在一起产生细菌运动的差异。该项目的结果将产生许多潜在的社会影响，因为运动性使细菌能够通过供水传播，并在人体中建立微生物群或感染。这项工作将在多个层面产生重要影响。在细胞水平上，更好地了解细菌运动将有助于我们理解细胞资源摄取。在生态系统尺度上，流动性影响着食物网。这项工作的结果可能会导致介导细菌感染的新方法，进一步加深我们对细菌进化的理解，并激发具有增强功能的仿生微型机器人。此外，该奖项将支持外展项目，向公众宣传细菌的运动及其通过健康和生态对社会的重要性。细菌鞭毛运动在很大程度上分别被降级为单鞭毛细胞和多鞭毛细胞的两种理想范式。然而，越来越多的证据表明，细菌表现出过多的鞭毛排列和相关的运动模式，不符合现有的范式。目前还不清楚鞭毛的运动模式是如何从排列的变化和鞭毛的灵活力学中产生的。这项工作将通过将鞭毛的几何和力学联系起来，对尚未充分研究的鞭毛排列和运动模式的多样性进行机械理解。由于缺乏鞭毛的定量成像，实验干扰鞭毛性质的能力有限，以及模型过于简化，这种生物力学的理解受到了阻碍。我们将利用独特的成像能力来克服这些挑战，从而实现数据驱动和实验验证的数值建模和假设检验。实验上，这项工作结合了先进的高速视频显微镜技术来捕捉10纳米直径鞭毛的时间分辨运动学，推动了现有的流体-结构相互作用量化方法的极限。在数值上，这项工作推进了最先进的模拟受动细丝的弹性流体动力学。这项工作将建立一个独特的数据集，包括鞭毛的机械特性和不同物种细菌运动的运动学。它将使用建模来确定导致观察到的运动模式的物理机制，并结合物理和数值实验来阐明和分类起源。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的智力价值和更广泛的影响审查标准进行评估，被认为值得支持。

The ability of bacteria to swim crucial to survival. Swimming is made possible by rotating thin filaments called flagella. There are many different ways that flagella are arranged on bacteria, and many different movement patterns, all of which enable swimming. Despite the success of bacteria swimming, few of these mechanisms are well understood. The objective of this project is to determine how the arrangements and flexible mechanics of flagella combine to produce differences in bacterial motility. The results of this project will have numerous potential societal impacts, since motility enables bacteria to spread through water supplies, and to establish microbiomes or infections in humans. This work will have important effects at multiple levels. At the cellular level, better understanding bacterial motility will help us understand cell resource uptake. At the ecosystem scale, motility affects the food web. The results of this work could lead to new approaches to mediate bacterial infection, further our understanding of bacterial evolution, and inspire biomimetic microrobots with enhanced functionality. In addition, the award will support outreach programs that teach the public about bacterial locomotion and its importance to society through health and ecology.Bacterial flagellar motility has largely been relegated to two idealized paradigms for uni- and multiflagellated cells, respectively. However, mounting evidence suggests that bacteria exhibit a plethora of flagellar arrangements and associated motility patterns that do not fit into the existing paradigms. It is not understood how flagellar motility patterns emerge from variations in arrangements and the flexible mechanics of flagella. This work will develop a mechanistic understanding of the vast understudied diversity of flagellar arrangements and motility patterns by linking them to the geometry and mechanics of flagella. This biomechanical understanding has been hindered by a lack of quantitative imaging of flagella, limited ability to experimentally perturb flagellar properties, and overly simplified models. We will overcome these challenges by using unique imaging capabilities, which enable data-driven and experimentally validated numerical modeling and hypothesis testing. Experimentally, this work incorporates advanced high-speed video microscopy techniques to capture the time-resolved kinematics of 10-nanometer diameter flagella, pushing the envelope of existing quantification methods for fluid-structure interactions. Numerically, this work advances the state-of-the-art in modeling elastohydrodynamics of actuated filaments. This work will establish a unique data set comprising the mechanical properties of flagella and the kinematics of bacterial motility from diverse species. It will use modeling to determine the physical mechanisms leading to observed motility patterns, and combine physical and numerical experiments to elucidate and classify the originsThis award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.