Romeu Maria J, Miranda João M, de Jong Ed D, Morais João, Vasconcelos Vítor, Sjollema Jelmer, Mergulhão Filipe J
LEPABE - Laboratory for Process Engineering, Environment, Biotechnology and Energy, Faculty of Engineering, University of Porto, Rua Dr. Roberto Frias, 4200-465, Porto, Portugal.
ALiCE - Associate Laboratory in Chemical Engineering, Faculty of Engineering, University of Porto, Rua Dr. Roberto Frias, 4200-465, Porto, Portugal.
Biofilm. 2024 May 29;7:100204. doi: 10.1016/j.bioflm.2024.100204. eCollection 2024 Jun.
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.
能够模拟自然水生环境中普遍存在的流体动力学条件的平台此前已经得到验证，并用于预测不同表面上的生物污垢行为。计算流体动力学（CFD）已被用于预测这些平台中产生的剪切力。一般来说，这些预测是针对生物膜形成的初始阶段进行的，在这个阶段生物膜的数量不会影响流动行为，从而能够估计初始附着生物必须承受的剪切力。在这项工作中，我们进一步了解当此类平台中存在成熟生物膜时的流动行为，以便更好地理解影响海洋生物膜的剪切速率分布。利用光学相干断层扫描获得的三维图像生成网格，并将其用于CFD模拟。在两个不同振荡频率下孵育7周的搅拌微孔板中培养了两种不同海洋蓝细菌的生物膜。根据速度场和剪切速率分布对生物膜与流动的相互作用进行了表征。结果表明，不同振荡频率施加的整体流体动力学影响生物膜结构，而且这种结构也影响局部流体动力学，导致剪切速率场出现很大的不均匀性。位于生物膜拖尾部分的生物膜细胞所承受的剪切值比位于拖尾底部的细胞要高得多，并且在较低的主体流体速度下，这种剪切速率值的分散性会增加。剪切力场中的这种不均匀性可能是导致生物膜内代谢活性、生长状态、基因表达模式和抗生素抗性等通常与营养物质可用性相关的异质性行为的一个因素。
