Institute of Environmental Engineering, ETH Zürich, 8093, Zürich, Switzerland.
Department of Biomedical Sciences, Humanitas University, 20072, Pieve Emanuele, MI, Italy.
Soft Matter. 2022 May 25;18(20):3878-3890. doi: 10.1039/d2sm00258b.
Biofilm formation is the most successful survival strategy for bacterial communities. In the biofilm lifestyle, bacteria embed themselves in a self-secreted matrix of extracellular polymeric substances (EPS), which acts as a shield against mechanical and chemical insults. When ambient flow is present, this viscoelastic scaffold can take a streamlined shape, forming biofilm filaments suspended in flow, called streamers. Streamers significantly disrupt the fluid flow by causing rapid clogging and affect transport in aquatic environments. Despite their relevance, the structural and rheological characterization of biofilm streamers is still at an early stage. In this work, we present a microfluidic platform that allows the reproducible growth of biofilm streamers in controlled physico-chemical conditions and the characterization of their biochemical composition, morphology, and rheology . We employed isolated micropillars as nucleation sites for the growth of single biofilm streamers under the continuous flow of a diluted bacterial suspension. By combining fluorescent staining of the EPS components and epifluorescence microscopy, we were able to characterize the biochemical composition and morphology of the streamers. Additionally, we optimized a protocol to perform hydrodynamic stress tests , by inducing controlled variations of the fluid shear stress exerted on the streamers by the flow. Thus, the reproducibility of the formation process and the testing protocol make it possible to perform several consistent experimental replicates that provide statistically significant information. By allowing the systematic investigation of the role of biochemical composition on the structure and rheology of streamers, this platform will advance our understanding of biofilm formation.
生物膜的形成是细菌群落最成功的生存策略。在生物膜生活方式中，细菌将自身嵌入由细胞外聚合物（EPS）自我分泌的基质中，这起到了抵御机械和化学损伤的屏障作用。当环境中存在流动时，这种粘弹性支架可以形成流线型形状，形成悬浮在流动中的生物膜丝状结构，称为流丝。流丝通过导致快速堵塞显著扰乱流体流动，并影响水生环境中的传输。尽管它们具有相关性，但生物膜流丝的结构和流变学特性的表征仍处于早期阶段。在这项工作中，我们提出了一种微流控平台，允许在受控的物理化学条件下可重复地生长生物膜流丝，并对其生化组成、形态和流变学进行表征。我们采用孤立的微柱作为核化位点，在稀释细菌悬浮液的连续流动下，生长单个生物膜流丝。通过对 EPS 成分进行荧光染色和落射荧光显微镜观察，我们能够对流丝的生化组成和形态进行表征。此外，我们优化了一种方案来进行流体动力应力测试，通过诱导流对流丝施加的流体剪切应力的受控变化来实现。因此，形成过程和测试方案的可重复性使得可以进行几个一致的实验重复，从而提供具有统计学意义的信息。通过允许系统地研究生化组成对流丝结构和流变学的作用，该平台将推进我们对生物膜形成的理解。
