arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 2003.02207physics.bio-ph
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活性流体扩散系数的光控制

Light control of the diffusion coefficient of active fluids

Thomas Vourc'h, Julien Léopoldès, Hassan Peerhossaini

摘要:

主动流体是指含有自推进颗粒(如细菌或微藻)的流体,其性质与被动流体根本不同。这种颗粒通常表现出间歇性运动,高运动性(运行)周期被低运动性(翻滚)周期打破。平均运动可以通过外部应力(例如营养或光梯度)进行修改,从而导致分别称为趋化性和趋光性的定向运动。使用蓝细菌集胞藻属PCC 6803,一种模式微生物来研究光合作用,我们跟踪细菌对光刺激的反应,在各向同性和非各向同性(定向)条件下。特别是,我们调查如何间歇运动的影响照明。我们发现,光强度上升后,在运行状态的概率增加。当初始概率恢复时,该特征在约1小时的典型特征时间后消失。我们的结果很好地描述了基于线性响应理论的数学模型。当微扰是各向异性的,我们观察到一个集体运动的光源(趋光性)。我们表明,出现的偏见,由于更频繁的运行在光的方向,而运行的持续时间更长的方向。

英文摘要:

Active fluids refer to the fluids that contain self-propelled particles such as bacteria or micro-algae, whose properties differ fundamentally from the passive fluids. Such particles often exhibit an intermittent motion, with high-motility (run) periods broken by low-motility (tumble) periods. The average motion can be modified with external stresses, such as nutrient or light gradients, leading to a directed movement called chemotaxis and phototaxis, respectively. Using cyanobacterium Synechocystis sp.PCC 6803, a model micro-organism to study photosynthesis, we track the bacterial response to light stimuli, under isotropic and non-isotropic (directed) conditions. In particular, we investigate how the intermittent motility is influenced by illumination. We find that just after a rise in light intensity, the probability to be in the run state increases. This feature vanishes after a typical characteristic time of about 1 hour, when initial probability is recovered. Our results are well described by a mathematical model based on the linear response theory. When the perturbation is anisotropic, we observe a collective motion toward the light source (phototaxis). We show that the bias emerges due to more frequent runs in the direction of the light, whereas the run durations are longer whatever the direction.

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