Department of Mathematics, Florida State University, 208 Love Building, Tallahassee, FL 32317, USA.
Bull Math Biol. 2011 Jan;73(1):212-29. doi: 10.1007/s11538-010-9536-1. Epub 2010 Apr 8.
The behavior of collections of oceanic bacteria is controlled by metabolic (chemotaxis) and physical (fluid motion) processes. Some sulfur-oxidizing bacteria, such as Thiovulum majus, unite these two processes via a material interface produced by the bacteria and upon which the bacteria are transiently attached. This interface, termed a bacterial veil, is formed by exo-polymeric substances (EPS) produced by the bacteria. By adhering to the veil while continuing to rotate their flagella, the bacteria are able to exert force on the fluid surroundings. This behavior induces a fluid flow that, in turn, causes the bacteria to aggregate leading to the formation of a physical pattern in the veil. These striking patterns are very similar in flavor to the classic convection instability observed when a shallow fluid is heated from below. However, the physics are very different since the flow around the veil is mediated by the bacteria and affects the bacterial densities. In this study, we extend a model of a one-dimensional veil in a two-dimensional fluid to the more realistic two-dimensional veil in a three-dimensional fluid. The linear stability analysis indicates that the Peclet number serves as a bifurcation parameter, which is consistent with experimental observations. We also solve the nonlinear problem numerically and are able to obtain patterns that are similar to those observed in the experiments.
海洋细菌群体的行为受到代谢（趋化性）和物理（流体运动）过程的控制。一些硫氧化细菌，如 Thiovulum majus，通过细菌产生的物质界面和细菌暂时附着在其上的方式将这两个过程结合起来。这个界面被称为细菌面纱，由细菌产生的外聚合物物质（EPS）形成。通过在继续旋转鞭毛的同时附着在面纱上，细菌能够对周围的流体施加力。这种行为会引起流体流动，从而导致细菌聚集，导致面纱中形成物理图案。这些引人注目的图案与经典的对流不稳定性非常相似，当浅层流体从下方被加热时会观察到这种不稳定性。然而，物理情况却大不相同，因为围绕面纱的流动是由细菌介导的，并影响细菌密度。在这项研究中，我们将二维流体中一维面纱的模型扩展到三维流体中的更现实的二维面纱。线性稳定性分析表明，佩克莱数是分岔参数，这与实验观察结果一致。我们还通过数值方法解决了非线性问题，能够获得与实验观察到的相似的图案。
