Institut Curie, Centre de Recherche, Paris, France.
Biophys J. 2012 Sep 19;103(6):1400-8. doi: 10.1016/j.bpj.2012.07.001.
Most bacteria live in the form of adherent communities forming three-dimensional material anchored to artificial or biological surfaces, with profound impact on many human activities. Biofilms are recognized as complex systems but their physical properties have been mainly studied from a macroscopic perspective. To determine biofilm local mechanical properties, reveal their potential heterogeneity, and investigate their relation to molecular traits, we have developed a seemingly new microrheology approach based on magnetic particle infiltration in growing biofilms. Using magnetic tweezers, we achieved what was, to our knowledge, the first three-dimensional mapping of the viscoelastic parameters on biofilms formed by the bacterium Escherichia coli. We demonstrate that its mechanical profile may exhibit elastic compliance values spread over three orders of magnitude in a given biofilm. We also prove that heterogeneity strongly depends on external conditions such as growth shear stress. Using strains genetically engineered to produce well-characterized cell surface adhesins, we show that the mechanical profile of biofilm is exquisitely sensitive to the expression of different surface appendages such as F pilus or curli. These results provide a quantitative view of local mechanical properties within intact biofilms and open up an additional avenue for elucidating the emergence and fate of the different microenvironments within these living materials.
大多数细菌以附着群落的形式存在，形成三维物质，附着在人工或生物表面，对许多人类活动都有深远的影响。生物膜被认为是复杂的系统，但它们的物理性质主要从宏观角度进行研究。为了确定生物膜的局部力学性能，揭示其潜在的异质性，并研究其与分子特征的关系，我们开发了一种基于在生长生物膜中渗透磁性颗粒的看似新颖的微流变学方法。使用磁镊，我们实现了我们所知的第一个由细菌大肠杆菌形成的生物膜的粘弹性参数的三维映射。我们证明，其力学特性可能表现出在给定生物膜中跨越三个数量级的弹性顺应值。我们还证明，异质性强烈取决于生长剪切应力等外部条件。使用经过基因工程改造以产生具有良好特征的细胞表面附着蛋白的菌株，我们表明生物膜的力学特性对不同表面附属物（如 F 菌毛或卷曲菌）的表达非常敏感。这些结果提供了对完整生物膜内局部力学性能的定量观察，并为阐明这些活材料内不同微环境的出现和命运开辟了一条新途径。
