Fluid dynamics and noise in bacterial cell-cell and cell-surface scattering
Fluid dynamics and noise in bacterial cell-cell and cell-surface scattering
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DOI：
10.1073/pnas.1019079108
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发表时间：
2011-07-05
影响因子：
11.1
通讯作者：
Goldstein, Raymond E.
中科院分区：
文献类型：
--
作者：
Drescher, Knut;Dunkel, Joern;Goldstein, Raymond E.
细菌的过程从基因表达到运动和生物膜的形成，不断受到内部和外部噪音的挑战。虽然随机波动对趋化作用的重要性已被认识到，但目前认为，确定性的长期流体动力学效应控制着细胞-细胞和细胞表面的散射--这些基本事件导致活性悬浮液中的群体和集体游泳，以及生物膜的形成。在这里，我们报告了由单个游泳的大肠杆菌产生的细菌流场的直接测量，无论是远离固体表面还是靠近固体表面。这些实验使我们能够检验流体动力学和旋转扩散对细菌的相对重要性。对于细胞-细胞相互作用，研究表明，热性和本征随机性掩盖了长程流体动力学的影响，这意味着细菌之间的物理相互作用是由空间碰撞和近场润滑力决定的。这种短程作用力的支配地位将细菌悬浮液中的集体运动与驱动颗粒系统、生物丝集合和动物群体中的自组织紧密联系在一起。对于细菌与表面的分散，在碰撞之前，远程流体动力学相互作用也被证明是可以忽略的；然而，一旦细菌在排列碰撞后在几微米内沿着表面游泳，流体动力学效应可能有助于实验观察到的长停留时间。因为这些结果是基于纯粹的机械性能，所以它们适用于广泛的微生物。
Bacterial processes ranging from gene expression to motility and biofilm formation are constantly challenged by internal and external noise. While the importance of stochastic fluctuations has been appreciated for chemotaxis, it is currently believed that deterministic long-range fluid dynamical effects govern cell-cell and cell-surface scattering-the elementary events that lead to swarming and collective swimming in active suspensions and to the formation of biofilms. Here, we report direct measurements of the bacterial flow field generated by individual swimming Escherichia coli both far from and near to a solid surface. These experiments allowed us to examine the relative importance of fluid dynamics and rotational diffusion for bacteria. For cell-cell interactions it is shown that thermal and intrinsic stochasticity drown the effects of long-range fluid dynamics, implying that physical interactions between bacteria are determined by steric collisions and near-field lubrication forces. This dominance of short-range forces closely links collective motion in bacterial suspensions to self-organization in driven granular systems, assemblages of biofilaments, and animal flocks. For the scattering of bacteria with surfaces, long-range fluid dynamical interactions are also shown to be negligible before collisions; however, once the bacterium swims along the surface within a few microns after an aligning collision, hydrodynamic effects can contribute to the experimentally observed, long residence times. Because these results are based on purely mechanical properties, they apply to a wide range of microorganisms.