Collaborative research: The effects of fluid flow on flagellar mechanics and microbial motility

游泳细胞包括浮游生物、精子和细菌，在环境、人类健康和工业系统中起着至关重要的作用。这些细胞分解污染物和废物，在繁殖过程中运输DNA，并提供了一种有前途的可再生生物燃料来源。游泳是许多单细胞的基本策略，它们使用毛发状的鞭毛游向营养物质和配偶，远离毒素。但是，有时候细胞必须？逆流而上？并克服无处不在的水流和它们所游泳的流体的环境流动。流体流动对鞭毛力学和细胞自发运动的作用还没有很好的理解。本研究计划是研究流体流动如何透过直接成像与数学模型的结合来改变鞭毛的运动。这项工作对医疗设备和医疗方法的发展，生物反应器和生物燃料生产效率的提高，以及对海洋，湖泊和地下水生态系统动态的理解具有广泛的意义。已知环境速度梯度导致细胞在以高剪切速率为特征的流动区域中的强烈积聚，并且细胞积聚的性质强烈依赖于细胞运动性、形状和鞭毛。该研究项目使用了一种协同方法，将微流体和高速成像与最先进的数值模拟相结合，以：（1）确定流动对单个拴系细胞鞭毛跳动的流体动力学效应;（2）确定外部施加的流动如何通过鞭毛变形影响自由游泳细胞的流体动力学和运输;（3）确定鞭毛力学如何耦合到集体，在活性细胞的稠密悬浮液中自发流动。该项目正在单细胞流体动力学领域开辟一个新的、丰富的研究方向，尽管流体流动对生物学、生态学和医学有许多影响，但其作用在很大程度上被忽视了。该项目的研究人员正在建立独特的经验数据集和数值模型，以绘制外部流体力对鞭毛内主动力产生的影响，这些信息将成为对细胞运动建模感兴趣的微生物学家，生态学家和生物学家的资产。该项目还扩展了现有的方法，通过表征具有内力生成的柔性附件（即鞭毛）的变形来量化流-结构相互作用。 该项目支持的研究生和本科生正在接受流体动力学和微生物生物物理学方面的独特跨学科培训。 印第安纳州博物馆的一个动手高速成像互动展览将这些研究主题纳入其中，这将影响到参加博物馆的中学生。

Swimming cells including plankton, sperm, and bacteria play a crucial role in the environment, in human health, and in industrial systems. These cells breakdown pollutants and waste products, transport DNA during reproduction, and provide a promising source of renewable biofuel. Swimming is a fundamental strategy of many single cells, which use hair-like flagella to swim toward nutrients and mates, and away from toxins. However, sometimes cells must ?swim upstream?, and overcome ubiquitous currents and ambient flow of the fluid in which they swim. The role of fluid flow on flagellar mechanics and the spontaneous movement of cells is not well understood. This research project is studying how fluid flow modifies flagellar motion through a combination of direct imaging and mathematical modeling. This work has broad implications for the development of medical devices and medical treatments, the improvement of bioreactors and biofuel production efficiency, and understanding ecosystem dynamics in oceans, lakes, and groundwater. Ambient velocity gradients are known to lead to strong accumulations of cells in flow regions characterized by high shear rates, and the nature of the cell accumulation is strongly dependent on cell motility, shape, and flagellation. This research project uses a synergistic approach incorporating microfluidics and high-speed imaging with state-of-the-art numerical simulations to: (1) Determine the hydrodynamic effects of flow on the flagellar beating of single, tethered cells; (2) Determine how externally-imposed flow affects the hydrodynamics and transport of free swimming cells through flagellar deformation; (3) Establish how flagellar mechanics couple to collective, self-generated flows in dense suspensions of active cells. This project is opening a new, rich research direction in single cell hydrodynamics, where the role of fluid flow has been largely neglected, despite its many implications for biology, ecology and medicine. The researchers on this project are establishing unique empirical data sets and numerical models that map the effects of external fluid forces on active force generation inside flagella, and such information will be an asset to microbiologists, ecologists, and biophysicists interested in modeling cell locomotion. The project is also extending existing methods to quantify flow-structure interactions by characterizing the deformation of flexible appendages having internal force generation, i.e. flagella. Graduate and undergraduate students supported by this project are receiving unique interdisciplinary training in fluid dynamics and microbial biophysics. A hands-on high-speed imaging interactive exhibit at the Indiana State Museum is incorporating these research themes, which will reach middle school students who attend the museum.