School of Engineering, Newcastle University, NE17RU, Newcastle upon Tyne, United Kingdom.
Department of Oncology, University of Oxford, Oxford, UK.
Sci Rep. 2019 Oct 10;9(1):14540. doi: 10.1038/s41598-019-51101-3.
Bacterial habitats are often associated with fluid flow environments. Bacterial twitching is important for initial bacterial colonization and biofilm formation. The existing research about bacteria twitching is largely experimental orientated. There is a lack of models of twitching motility of bacteria in shear flows, which could provide fundamental understanding about how bacterial twitching would be affected by bacteria associated properties such as number of pili and their distribution on the cell body and environmental factors such as flow and surface patterns. In this work, a three-dimensional modelling approach of Computational Fluid Dynamics (CFD) coupled with the Discrete Element Method (DEM) proposed to study bacterial twitching on flat and groove surfaces under shear flow conditions. Rod-shaped bacteria are modelled as groups of spherical particles and Type IV pili attached to bacteria are modelled as dynamic springs which can elongate, retract, attach and detach. The CFD-DEM model of rod-shape bacteria is validated against orbiting of immotile bacteria in shear flows. The effects of fluid flow rate and surface topography on twitching motility are studied. The model can successfully predict upstream twitching motility of rod-shaped bacteria in shear flows. Our model can predict that there would be an optimal range of wall shear stress in which bacterial upstream twitching is most efficient. The results also indicate that when bacteria twitch on groove surfaces, they are likely to accumulate around the downstream side of the groove walls.
细菌栖息地通常与流体流动环境有关。细菌的抽动对于初始细菌定殖和生物膜形成很重要。现有的关于细菌抽动的研究主要是实验性的。缺乏剪切流中细菌抽动的运动模型，这可能会提供关于细菌抽动如何受到与细菌相关的特性（例如菌毛数量及其在细胞体上的分布）和环境因素（例如流动和表面图案）影响的基本理解。在这项工作中，提出了一种基于计算流体动力学（CFD）和离散元法（DEM）的三维建模方法，用于研究剪切流条件下平板和槽面的细菌抽动。杆状细菌被建模为球形颗粒群，附着在细菌上的 IV 型菌毛被建模为可以伸长、收缩、附着和分离的动态弹簧。杆状细菌的 CFD-DEM 模型通过在剪切流中旋转不动细菌进行验证。研究了流体流速和表面形貌对抽动运动的影响。该模型可以成功预测剪切流中杆状细菌的向上抽动运动。我们的模型可以预测在壁面剪切应力的最佳范围内，细菌向上抽动的效率最高。结果还表明，当细菌在槽面抽动时，它们可能会聚集在槽壁的下游侧。
