Control of Flagellated Bacteria Motion in Anisotropic Fluids

细菌是地球上最丰富的生物，它们对环境中碳循环和固存、生物质分解和污染物转化具有重要影响。它们形成人体微生物群，并引起许多传染病。细菌经常在性质与各向同性流体非常不同的环境中游泳。例如，许多生物液体（如粘液、DNA溶液）表现为液晶（LC）。本项目旨在通过体外定量实验和多尺度计算建模相结合的方法，对细菌与各向异性流体的相互作用进行综合研究。这些研究工具的结合将有助于更好地理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重点：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，该方法可以同时观察细菌轨迹及其鞭毛。ppi的合作历史悠久：联合发表论文，联合指导研究生和博士后，以及联合资助。在这项工作中获得的知识可能会导致基于新型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。这些初级科学家将与项目负责人在理论和实验方面进行互动，并参加项目负责人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理解细菌在各向异性生物流体中的运动，以向列液晶为例。这项工作除了对自推进生物系统的基础研究有明显的意义外，对生物医学研究也有价值，例如细菌如何在生物液体中运动和粘附在内脏表面。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。了解自行式元件的柔韧性与悬浮流体各向异性之间的相互作用，对于预测这些材料的新性能具有重要意义。理论推力将基于多尺度模型，结合已建立的LC的Leslie-Ericksen方程和各向同性流体中鞭毛细菌计算模型的扩展。该项目由物理系的生命系统物理学项目和分子与细胞生物科学系的细胞集群共同支持。

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.