Control of Flagellated Bacteria Motion in Anisotropic Fluids

细菌是地球上最丰富的生物体，它们显著影响碳循环和封存、生物质的分解以及环境中污染物的转化。它们形成人类微生物群，也引起许多传染病。细菌通常在性质与各向同性流体的性质非常不同的环境中游动。例如，许多生物流体（例如，粘液、DNA溶液）表现为液晶（LC）。本项目的目的是通过结合定量体外实验和多尺度计算建模，全面研究细菌和各向异性流体之间的相互作用。这些研究工具的结合将导致更好地了解各向异性生物流体中细菌-流体和细菌-表面相互作用的一般特征。将有两个主要的研究方向：实验和理论。实验推力将基于最近发现的LC纳米显微镜方法，该方法能够同时观察细菌轨迹及其鞭毛。PI有着悠久的合作历史：联合论文，研究生和博士后的联合监督，以及联合赠款。在这项工作中获得的知识可能会导致基于新的生物启发材料的实用概念。拟议的工作将通过为研究生和本科生以及博士后提供跨学科培训来培养下一代科学家。这些初出茅庐的科学家将与PI在理论和实验方面进行互动，并参加PI组织的课程和研讨会。这项工作结合了新颖的实验，分析和数值方法。实验推力将导致更好地了解细菌在各向异性生物流体中的运动，例如液晶。除了对自推进生物系统的基础研究具有明显的意义外，这项工作还将对生物医学研究具有价值，例如细菌如何在生物液体中移动并粘附在内部器官的表面。所提出的多尺度计算分析和数值技术的发展将有助于发现结合活（细菌）和合成（液晶）成分的活性生物启发材料。了解自推进元件的柔性和悬浮流体的各向异性之间的相互作用对于预测这些材料的新材料性质是重要的。理论推力将基于多尺度模型耦合完善Leslie-Ericksen方程LC和各向同性流体中的鞭毛细菌的计算模型的扩展。该项目由物理学部的生命系统物理学计划和分子与细胞生物科学部的细胞簇联合支持。

Bacteria are the most abundant organisms on Earth and they significantly influence carbon cycling and sequestration, decomposition of biomass, and transformation of contaminants in the environment. They form human microbiota and also cause many infectious diseases. Bacteria often swim in environments with properties which are very different from those of an isotropic fluid. For example, many biological fluids (e.g., mucus, DNA solutions) behave as liquid crystals (LC). The purpose of this project is a comprehensive study of interactions between bacteria and anisotropic fluids by combining quantitative in vitro experiments and multi-scale computational modeling. The combination of these research tools will lead to a much better understanding of the generic features of bacteria-fluid and bacteria-surface interactions in anisotropic biological fluids. There will be two main research thrusts: experimental and theoretical. The experimental thrust will be based on the recently discovered method of the LC nanoscopy which enables simultaneous observation of bacterial trajectories and their flagella. The PIs have a long history of collaboration: joint papers, joint supervision of graduate students and postdocs, as well as joint grants. The knowledge gained in this work may lead to practical concepts based on novel bio-inspired materials. The proposed work will prepare the next generation of scientists by providing interdisciplinary training for graduate and undergraduate students as well as for postdocs. These beginning scientists will work interactively with the PIs on theoretical and experimental thrusts and attend courses and workshops organized by the PIs. This work combines novel experimental, analytical and numerical methods. The experimental thrust will result in a much better understanding of motion of bacteria in anisotropic biological fluids exemplified by a nematic liquid crystal. In addition to obvious significance to fundamental studies of self-propelled biological systems, this work will have merits for bio-medical research, for example how the bacteria move in biological fluids and adhere to surfaces of internal organs. The proposed multi-scale computational analysis and development of numerical techniques will be useful for the discovery of active bio-inspired materials combining living (bacteria) and synthetic (liquid crystal) components. Understanding the interplay between the flexibility of self-propelled elements and anisotropy of the suspending fluid is important for the prediction of novel materials properties of these materials. The theoretical thrust will be based on the multi-scale model coupling the well-established Leslie-Ericksen equations for the LC and an extension of the computational model of a flagellated bacterium in an isotropic fluid.This project is being jointly supported by the Physics of Living Systems program in the Division of Physics and the Cellular Cluster in the Division of Molecular and Cellular Biosciences.