Collaborative Research: Understanding Bacterial Flagellar Propulsion

大肠杆菌和鼠伤寒沙门氏菌等细菌通过旋转螺旋鞭毛在液体中游动。理解带鞭毛的细菌的游动机制是一项具有挑战性的课题，涉及生物、工程、数学和物理科学的相互作用。尽管许多科学家对细菌游泳进行了研究，但实验和理论研究都表明，由于鞭毛在运动过程中具有复杂的几何形状，因此很难理解其动态行为，并且仍然存在许多悬而未决的问题。该项目将开发和验证这种细菌运动的改进数学模型。本项目的目标是：(1)建立详细的数学模型和数值方案，通过鞭毛了解细菌的运动；(2)分析了细胞体在流体中产生的多个鞭毛之间复杂的流体动力学相互作用；(3)通过与实验数据的对比，验证模型的正确性；(4)利用这些模型进行预测，这些预测将通过进一步的实验得到验证。该项目还大量涉及广义浸入边界法的自适应版本的开发，该方法将在生物流体动力学中找到许多应用，例如超缠绕DNA动力学。新的数值算法将在IBAMR软件中免费在线发布。这项对自由游动细菌的研究结果可能为感染的传播和生物膜的形成提供新的信息，并可能有助于设计由鞭毛自我推进的纳米机器。

Bacteria such as Escherichia coli and Salmonella typhimurium swim through a fluid by rotating their helical flagella. Understanding the swimming mechanism of bacteria with flagella is a challenging subject that involves interactions between the biological, engineering, mathematical, and physical sciences. Although many scientists have studied bacterial swimming, experimental and theoretical studies have both shown that it is difficult to understand the dynamic behavior of the flagellum because of its complex geometry during locomotion, and many open questions remain. This project will develop and validate improved mathematical models for such bacterial motility. The goals of this project are to: (1) develop detailed mathematical models accompanied by the numerical schemes to understand bacterial motility by means of flagella; (2) analyze the complicated hydrodynamic interactions among multiple flagella arising from the cell body in fluids; (3) validate the models by comparing the results to experimental data; and (4) use these models to make predictions that will be verified by further experimentation. This project also heavily involves the development of an adaptive version of the generalized immersed boundary method which will find numerous applications in biological fluid dynamics such as supercoiling DNA dynamics. The new numerical algorithm will be freely distributed on-line within IBAMR software. The results obtained from this research on free swimming bacteria may provide new information about the spread of infections and biofilm formation, and may help to design nanomachines that are self-propelled by flagella.