Xia Z, Woo L, van de Ven T G
Pulp and Paper Research Institute, Canada.
Biorheology. 1989;26(2):359-75. doi: 10.3233/bir-1989-26219.
The adhesion of both live and fixed bacteria (Escherichia coli) on glass has been studied under well-defined hydrodynamic conditions, created in an impinging jet apparatus. With this technique one can accurately measure the initial deposition rate jo on the surface, the average lifetime of a bacterium on the surface, tau esc, and the surface area blocked per deposited bacterium, normalized by its projected area, gamma. The experimental results are compared to theoretical results for equivalent spheres. It is found that near the stagnation point the deposition rate jo is mainly controlled by convective diffusive transport which, for rod-shaped Eschericia coli, with an axis ratio of about 2, is found to be equal to that for spheres. No differences in jo and tau esc were found between live and fixed bacteria at low flow rates. At high flow rates fixed bacteria adhered to the surface at a slower rate. In both systems jo was found to decrease suddenly at a distance of about 150 microns from the stagnation point, in contrast to systems of spherical particles for which jo is uniform over the surface. Most likely this is due to the rotation of the rod-shaped particles, which vary their distance to the surface periodically with time. The main difference between live and fixed bacteria, besides different deposition rates in strong flows, is that gamma is about 30% larger for fixed bacteria than for live ones, resulting in a much lower final coverage for fixed bacteria. These results imply a larger repulsion between fixed bacteria than between living ones. From detachment experiments we can conclude that not all bacteria stick to the surface with the same bond strength. The variation in the bond strength is due to the aging of the bonds between the bacteria and the surface. The average bond strength corresponds to an energy of about 13-15 kT.
在撞击射流装置中创建的明确流体动力学条件下，研究了活细菌和固定细菌（大肠杆菌）在玻璃上的附着力。使用该技术，可以准确测量表面上的初始沉积速率jo、细菌在表面上的平均寿命tau esc，以及每个沉积细菌所占据的表面积（通过其投影面积归一化）gamma。将实验结果与等效球体的理论结果进行了比较。发现在驻点附近，沉积速率jo主要由对流扩散传输控制，对于轴比约为2的杆状大肠杆菌，发现其与球体的对流扩散传输相同。在低流速下，活细菌和固定细菌在jo和tau esc方面没有差异。在高流速下，固定细菌以较慢的速率附着在表面上。在这两个系统中，都发现jo在距驻点约150微米处突然下降，这与球形颗粒系统不同，在球形颗粒系统中jo在整个表面上是均匀的。最有可能的原因是杆状颗粒的旋转，其与表面的距离随时间周期性变化。活细菌和固定细菌之间的主要区别，除了在强流中不同的沉积速率外，还在于固定细菌的gamma比活细菌大约30%，导致固定细菌的最终覆盖率低得多。这些结果意味着固定细菌之间的排斥力比活细菌之间的排斥力更大。从脱离实验中我们可以得出结论，并非所有细菌都以相同的结合强度附着在表面上。结合强度的变化是由于细菌与表面之间的键老化。平均结合强度对应于约13 - 15 kT的能量。
