气液边界细菌集体运动的研究

Collective motion of bacteria is an emerging topic in the interdisciplinary research field of biology and physics. The study of bacterial collective behavior can not only promote our comprehending of non-equilibrium statistical physics, but also deepen biologists’ understanding of the formation of self-organized structure in complex life systems. As an important factor affecting the collective behavior of bacteria, the dynamic characteristics of the long rod-shaped bacterial active nematic system under low friction are an area to be explored urgently. Previous studies on bacterial collective motion and colony growth on solid surfaces have pointed out that friction between bacteria and contact surfaces plays an Collective motion of bacteria is an emerging topic in the interdisciplinary research field of biology and physics. The study of bacterial collective behavior can not only promote our comprehending of non-equilibrium statistical physics, but also deepen biologists’ understanding of the formation of self-organized structure in complex life systems. As an important factor affecting the collective behavior of bacteria, the dynamic characteristics of the long rod-shaped bacterial active nematic system under low friction are an area to be explored urgently. Previous studies on bacterial collective motion and colony growth on solid surfaces have pointed out that friction between bacteria and contact surfaces plays an important role in the properties of active nematic systems, so gas-liquid interface systems with strong fluid disturbances may exhibit novel properties unknown before. The experimental observation and theoretical prediction of system dynamics depending on bacterial aspect ratio need to be verified and supplemented by systematic experiments under different boundary conditions. This project will develop and improve a bacterial observation system with multiple controllable parameters based on gas-liquid interface. It will explore how important experimental parameters such as boundary conditions, cell aspect ratio and density affect the dynamic characteristics of bacterial collective behavior, so as to build a quantitative numerical model of the system, reveal the new physical images behind the collective motion of bacteria, and provide new ideas for developing intelligent materials for industry.

细菌的集体运动是当前生物学和物理学交叉研究领域的新兴课题。对细菌集群行为的研究既有助于促进人们对非平衡态统计物理问题的认知，也能够加深生物学家对复杂生命系统自组织结构形成的理解。边界条件作为影响细菌集体行为的重要因素，低摩擦力下长杆形细菌活性向列相体系的动力学特性是一块亟待深入探索的区域。此前固体表面细菌集体运动和菌落生长的研究工作均指出，细菌与接触面的摩擦作用对活性向列相体系的性质有着重要影响，因此流体扰动强烈的气液界面系统有可能表现出前所未知的全新特性。体系动力学依赖细菌长宽比的实验观测和理论预测亟需不同边界条件下的系统性实验做出验证和补充。本项目将开发完善一个基于气液界面的、具有多个可控参数的细菌观测系统，探究边界条件、胞体长宽比、密度等重要实验参数如何影响细菌的集群动力学特性，以此构建该体系的定量化数值模型，揭示细菌集体运动背后的新物理图像，并为工业界开发智能材料提供新思路。

微生物在增殖扩张的过程中往往会形成各种复杂而有序的自组织结构，并依赖于参数条件的影响，不同自组织现象的特性和成因成为困扰学界以及工业界的难题。本项目以细菌为主要研究对象，探究了胞体长宽比、系统密度、细菌运动性、边界条件等多个可控参数如何影响细菌集体行为，取得的主要结果包括：（1）对不同边界条件下细菌动能能谱的特征、特征结构的统计性质等进行系统性测量，探明了边界条件、细菌密度、系统干湿性质等具体的参数条件对杆状细菌能谱幂律标度和能谱峰值位置的影响；（2）研究了密集状态下气液边界附近杆菌系统的玻璃态动力学特征，而半固体界面上高密度的细长杆菌系统呈现活性向列相并形成拓扑缺陷，揭示系统很可能正处于向生物被膜发育早期转变的阶段，具有重要的生物学意义；（3）研究了非运动细菌内生芽孢杆菌菌落刺突状斑图的形成机理并提出一种力学模型，揭示了微生物群落与物理环境之间的力学相互作用可以成为非运动细菌菌落的一种扩张机制。研究结果为微生物定殖生长过程中的自组织行为提供了更系统化的物理图像，也为工业界设计智能材料、医学界预测控制病原菌传播提供了新的思路和有效策略。