Department of Applied Mathematics, University of Colorado, Boulder, CO 80309, United States.
Math Biosci. 2013 Oct;245(2):314-21. doi: 10.1016/j.mbs.2013.07.018. Epub 2013 Aug 2.
To understand the adhesion-fragmentation dynamics of bacterial aggregates (i.e., flocs), we model the aggregates as two ligand-covered rigid spheres. We develop and investigate a model for the attachment/detachment dynamics in a fluid subject to a homogeneous planar shear-flow. The binding ligands on the surface of the flocs experience attractive and repulsive surface forces in an ionic medium and exhibit finite resistance to rotation (via bond tilting). For certain range of material and fluid parameters, our results predict a nonlinear or hysteretic relationship between the binding/unbinding of the floc surface and the net floc velocity (translational plus rotational velocity). We show that the surface adhesion is promoted by increased fluid flow until a critical value, beyond which the bonds starts to yield. Moreover, adhesion is not promoted in a medium with low ionic strength, or flocs with bigger size or higher binder stiffness. The numerical simulations of floc-aggregate number density studies support these findings.
为了理解细菌聚集体（即絮体）的黏附-断裂动力学，我们将聚集体建模为两个覆盖有配体的刚性球体。我们开发并研究了在均匀平面剪切流中附着/脱附动力学的模型。絮体表面上的结合配体在离子介质中受到吸引力和排斥力，并表现出对旋转的有限阻力（通过键倾斜）。对于某些材料和流体参数范围，我们的结果预测了絮体表面的结合/解吸与絮体净速度（平移速度加旋转速度）之间的非线性或滞后关系。我们表明，随着流体流动的增加，表面黏附力会增强，直到达到一个临界值，超过这个值后，键就开始失效。此外，在离子强度低的介质中，或者絮体尺寸更大或结合剂硬度更高的情况下，黏附力不会增强。絮体-聚集体数密度研究的数值模拟支持这些发现。
