Department of Civil and Environmental Engineering, The George Washington University, Washington, DC 20052, USA.
Nanoscale. 2019 May 9;11(18):8918-8929. doi: 10.1039/c8nr10287b.
Biofilms are a cluster of bacteria embedded in extracellular polymeric substances (EPS) that contain a complex composition of polysaccharides, proteins, and extracellular DNA (eDNA). Desirable mechanical properties of the biofilms are critical for their survival, propagation, and dispersal, and the response of mechanical properties to different treatment conditions also sheds light on biofilm control and eradication in vivo and on engineering surfaces. However, it is challenging yet important to investigate mechanical behaviors of biofilms with a high spatial resolution because biofilms are very heterogeneous. Moreover, biofilms are viscoelastic, and their time-dependent mechanical behavior is difficult to capture. Herein, we develop a powerful technique that combines the high spatial resolution of an atomic force microscope (AFM) with a rigorous history-dependent viscoelastic analysis to deliver highly spatial-localized biofilm properties within a wide time-frequency window. By exploiting the use of static force spectroscopy in combination with an appropriate viscoelastic framework, we highlight the intensive amount of time-dependent information experimentally available that has been largely overlooked. It is shown that this technique provides a detailed nanorheological signature of the biofilms even at the single-cell level. We share the computational routines that would allow any user to perform the analysis from experimental raw data. The detailed localization of mechanical properties in space and in time-frequency domain provides insights into the understanding of biofilm stability, cohesiveness, dispersal, and control.
生物膜是一簇嵌入细胞外聚合物 (EPS) 中的细菌，其中包含多糖、蛋白质和细胞外 DNA (eDNA) 的复杂成分。生物膜的理想机械性能对于其生存、繁殖和扩散至关重要，而机械性能对不同处理条件的响应也揭示了生物膜在体内和工程表面的控制和消除。然而，由于生物膜非常不均匀，因此具有高空间分辨率研究生物膜的机械行为具有挑战性但很重要。此外，生物膜具有粘弹性，其随时间变化的机械行为难以捕捉。在这里，我们开发了一种强大的技术，该技术结合了原子力显微镜 (AFM) 的高空间分辨率和严格的依赖历史的粘弹性分析，在宽时间-频率窗口内提供高度空间局部化的生物膜特性。通过利用静电力谱学与适当的粘弹性框架相结合，我们突出了实验上可获得的大量随时间变化的信息，这些信息在很大程度上被忽视了。结果表明，即使在单细胞水平上，该技术也能提供生物膜的详细纳米流变学特征。我们共享计算例程，允许任何用户从实验原始数据中执行分析。机械性能在空间和时频域中的详细定位提供了对生物膜稳定性、内聚性、分散性和控制的深入了解。
