Fabbri Stefania, Li Jian, Howlin Robert P, Rmaile Amir, Gottenbos Bart, De Jager Marko, Starke E Michelle, Aspiras Marcelo, Ward Marilyn T, Cogan Nicholas G, Stoodley Paul
National Centre for Advanced Tribology at Southampton (nCATS), Mechanical Engineering Department, University of Southampton, Southampton SO17 1BJ, UK.
Department of Mathematics, Florida State University, Tallahassee, FL 32306, USA.
Environ Microbiol. 2017 Nov;19(11):4417-4431. doi: 10.1111/1462-2920.13883. Epub 2017 Sep 14.
Biofilms are thin layers of bacteria embedded within a slime matrix that live on surfaces. They are ubiquitous in nature and responsible for many medical and dental infections, industrial fouling and are also evident in ancient fossils. A biofilm structure is shaped by growth, detachment and response to mechanical forces acting on them. The main contribution to biofilm versatility in response to physical forces is the matrix that provides a platform for the bacteria to grow. The interaction between biofilm structure and hydrodynamics remains a fundamental question concerning biofilm dynamics. Here, we document the appearance of ripples and wrinkles in biofilms grown from three species of bacteria when subjected to high-velocity fluid flows. Linear stability analysis suggested that the ripples were Kelvin-Helmholtz Instabilities. The analysis also predicted a strong dependence of the instability formation on biofilm viscosity explaining the different surface corrugations observed. Turbulence through Kelvin-Helmholtz instabilities occurring at the interface demonstrated that the biofilm flows like a viscous liquid under high flow velocities applied within milliseconds. Biofilm fluid-like behavior may have important implications for our understanding of how fluid flow influences biofilm biology since turbulence will likely disrupt metabolite and signal gradients as well as community stratification.
生物膜是嵌入黏液基质中的细菌薄层，存在于各种表面。它们在自然界中无处不在，是许多医学和牙科感染、工业污垢的罪魁祸首，在古代化石中也很明显。生物膜结构由生长、脱离以及对作用于其上的机械力的响应所塑造。生物膜对物理力的多功能性的主要贡献在于其基质，它为细菌生长提供了一个平台。生物膜结构与流体动力学之间的相互作用仍然是一个关于生物膜动力学的基本问题。在此，我们记录了三种细菌形成的生物膜在高速流体流动作用下出现的波纹和褶皱。线性稳定性分析表明，这些波纹是开尔文 - 亥姆霍兹不稳定性。该分析还预测，不稳定性的形成强烈依赖于生物膜的粘度，这解释了所观察到的不同表面波纹。在界面处通过开尔文 - 亥姆霍兹不稳定性产生的湍流表明，在毫秒级施加的高流速下，生物膜像粘性液体一样流动。生物膜的类流体行为可能对我们理解流体流动如何影响生物膜生物学具有重要意义，因为湍流可能会扰乱代谢物和信号梯度以及群落分层。
