Soft and Biological Matter Laboratory, Department of Physics, <a href="https://ror.org/05pjsgx75">Indian Institute of Technology, Kanpur</a>-208016, India.
Department of Biological Sciences and Bioengineering, <a href="https://ror.org/05pjsgx75">Indian Institute of Technology, Kanpur</a>-208016, India.
Phys Rev E. 2024 Jul;110(1):L012601. doi: 10.1103/PhysRevE.110.L012601.
Dense bacterial suspensions display collective motion exhibiting coherent flow structures reminiscent of turbulent flows. However, in contrast to inertial turbulence, the microscopic dynamics underlying bacterial turbulence is only beginning to be understood. Here, we report experiments revealing correlations between microscopic dynamics and the emergence of collective motion in bacterial suspensions. Our results demonstrate the existence of three microscopic dynamical regimes: initial ballistic dynamics followed by an intermittent Lévy walk before the intriguing decay to random Gaussian fluctuations. Our experiments capture that the fluid correlation time earmarks the transition from Lévy to Gaussian fluctuations demonstrating the microscopic reason underlying the observation. By harnessing the flow activity via bacterial concentration, we reveal systematic control over the flow correlation timescales, which, in turn, allows controlling the duration of the Lévy walk.
密集的细菌悬浮液表现出集体运动，表现出类似湍流的连贯流结构。然而，与惯性湍流不同，细菌湍流的微观动力学才刚刚开始被理解。在这里，我们报告了实验结果，揭示了微观动力学与细菌悬浮液中集体运动出现之间的相关性。我们的结果表明存在三种微观动力学状态：初始弹道动力学，然后是间歇性 Lévy 漫步，最后是有趣的随机高斯波动衰减。我们的实验表明，流体相关时间标志着从 Lévy 漫步到高斯波动的转变，证明了观察结果背后的微观原因。通过利用细菌浓度产生的流活动，我们揭示了对流动相关时间尺度的系统控制，这反过来又允许控制 Lévy 漫步的持续时间。
