PDF(Pubmed)
Abstract：
In vitro platforms capable of mimicking the hydrodynamic conditions prevailing in natural aquatic environments have been previously validated and used to predict the fouling behavior on different surfaces. Computational Fluid Dynamics (CFD) has been used to predict the shear forces occurring in these platforms. In general, these predictions are made for the initial stages of biofilm formation, where the amount of biofilm does not affect the flow behavior, enabling the estimation of the shear forces that initial adhering organisms have to withstand. In this work, we go a step further in understanding the flow behavior when a mature biofilm is present in such platforms to better understand the shear rate distribution affecting marine biofilms. Using 3D images obtained by Optical Coherence Tomography, a mesh was produced and used in CFD simulations. Biofilms of two different marine cyanobacteria were developed in agitated microtiter plates incubated at two different shaking frequencies for 7 weeks. The biofilm-flow interactions were characterized in terms of the velocity field and shear rate distribution. Results show that global hydrodynamics imposed by the different shaking frequencies affect biofilm architecture and also that this architecture affects local hydrodynamics, causing a large heterogeneity in the shear rate field. Biofilm cells located in the streamers of the biofilm are subjected to much higher shear values than those located on the bottom of the streamers and this dispersion in shear rate values increases at lower bulk fluid velocities. This heterogeneity in the shear force field may be a contributing factor for the heterogeneous behavior in metabolic activity, growth status, gene expression pattern, and antibiotic resistance often associated with nutrient availability within the biofilm.
摘要：
先前已经验证了能够模拟天然水生环境中普遍存在的水动力条件的体外平台，并用于预测不同表面上的结垢行为。计算流体动力学（CFD）已用于预测这些平台中发生的剪切力。总的来说,这些预测是针对生物膜形成的初始阶段，其中生物膜的量不影响流动行为，能够估计最初粘附的生物必须承受的剪切力。在这项工作中,当成熟的生物膜存在于这样的平台中时，我们进一步了解流动行为，以更好地了解影响海洋生物膜的剪切速率分布。使用光学相干断层扫描获得的3D图像，网格产生并用于CFD模拟。在搅拌的微量滴定板中，以两种不同的摇动频率孵育7周，形成了两种不同的海洋蓝细菌的生物膜。根据速度场和剪切速率分布来表征生物膜-流相互作用。结果表明，由不同的振动频率施加的整体流体动力学影响生物膜结构，并且这种结构也影响局部流体动力学。在剪切速率场中造成较大的非均质性。位于生物膜的拖缆中的生物膜细胞比位于拖缆底部的生物膜细胞经受高得多的剪切值,并且剪切速率值的这种分散在较低的整体流体速度下增加。剪切力场中的这种异质性可能是代谢活动中异质性行为的促成因素，生长状态，基因表达模式，和抗生素抗性通常与生物膜内的营养可用性有关。
