Diffusion of Bacterial Cells in Porous Media
Diffusion of Bacterial Cells in Porous Media
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DOI：
10.1016/j.bpj.2015.09.035
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发表时间：
2016-01-05
影响因子：
3.4
通讯作者：
Setayeshgar, Sima
中科院分区：
文献类型：
--
作者：
Licata, Nicholas A.;Mohari, Bitan;Setayeshgar, Sima
趋化性信号转导网络通过调节定向重定向的频率，调节多种细菌向有利方向和远离有害方向的偏倚随机游走。在缺乏趋化反应的多种细菌突变体中，在构成充满液体的多孔介质的经典运动琼脂中的迁移受到损害；直线游动的细胞不能翻滚，被困在琼脂基质中。以前在肠道细菌大肠杆菌中观察到恢复传播的自发突变，最近在其他细菌物种中的工作已经分离并量化了表现出相同传播表型的不同类别的非趋化突变。我们提出了细菌在多孔介质中扩散的理论描述——多孔介质是许多细胞类型的自然栖息地——它阐明了运动装置的不同修改如何导致非零的翻转频率，从而允许在内部边界解除其他笔直游动的细胞的干扰，并导致净迁移。我们分析的一个独特结果是，在小孔隙极限下，随着翻滚频率的增加，扩散扩散也在增加，这与早期的实验观察结果一致，但没有被以前的模型捕获。我们的理论结果，结合细菌在琼脂中的扩散和生长的简单模型，与我们的实验测量的游泳环膨胀作为时间的函数进行了比较，证明了良好的定量一致。我们的研究结果表明，细胞翻滚过程的细节可能被适应，使细菌能够在复杂的环境中有效地繁殖。对于通过交替直行和改变方向进行导航的工程、自推进微型游泳者来说，这些结果表明了在给定微结构的多孔环境中有效迁移的最佳重新定向策略。
The chemotaxis signal transduction network regulates the biased random walk of many bacteria in favorable directions and away from harmful ones through modulating the frequency of directional reorientations. In mutants of diverse bacteria lacking the chemotaxis response, migration in classic motility agar, which constitutes a fluid-filled porous medium, is compromised; straight-swimming cells unable to tumble become trapped within the agar matrix. Spontaneous mutations that restore spreading have been previously observed in the enteric bacterium Escherichia coli, and recent work in other bacterial species has isolated and quantified different classes of nonchemotacting mutants exhibiting the same spreading phenotype. We present a theoretical description of bacterial diffusion in a porous medium-the natural habitat for many cell types-which elucidates how diverse modifications of the motility apparatus resulting in a nonzero tumbling frequency allows for unjamming of otherwise straight-swimming cells at internal boundaries and leads to net migration. A unique result of our analysis is increasing diffusive spread with increasing tumbling frequency in the small pore limit, consistent with earlier experimental observations but not captured by previous models. Our theoretical results, combined with a simple model of bacterial diffusion and growth in agar, are compared with our experimental measurements of swim ring expansion as a function of time, demonstrating good quantitative agreement. Our results suggest that the details of the cellular tumbling process may be adapted to enable bacteria to propagate efficiently through complex environments. For engineered, self-propelled microswimmers that navigate via alternating straight runs and changes in direction, these results suggest an optimal reorientation strategy for efficient migration in a porous environment with a given microarchitecture.