Department of Chemical Engineering, Stanford University, Stanford, California.
Department of Chemistry, Stanford University, Stanford, California.
Biophys J. 2012 Aug 8;103(3):464-471. doi: 10.1016/j.bpj.2012.06.049.
Bacterial biofilms are complex multicellular assemblies, characterized by a heterogeneous extracellular polymeric matrix, that have emerged as hallmarks of persistent infectious diseases. New approaches and quantitative data are needed to elucidate the composition and architecture of biofilms, and such data need to be correlated with mechanical and physicochemical properties that relate to function. We performed a panel of interfacial rheological measurements during biofilm formation at the air-liquid interface by the Escherichia coli strain UTI89, which is noted for its importance in studies of urinary tract infection and for its assembly of functional amyloid fibers termed curli. Brewster-angle microscopy and measurements of the surface elasticity (G(s)') and stress-strain response provided sensitive and quantitative parameters that revealed distinct stages during bacterial colonization, aggregation, and eventual formation of a pellicle at the air-liquid interface. Pellicles that formed under conditions that upregulate curli production exhibited an increase in strength and viscoelastic properties as well as a greater ability to recover from stress-strain perturbation. The results suggest that curli, as hydrophobic extracellular amyloid fibers, enhance the strength, viscoelasticity, and resistance to strain of E. coli biofilms formed at the air-liquid interface.
细菌生物膜是复杂的多细胞组装体，其特征在于具有异质的细胞外聚合基质，已成为持续性传染病的标志。需要新的方法和定量数据来阐明生物膜的组成和结构，并且需要将这些数据与与功能相关的力学和物理化学性质相关联。我们通过大肠杆菌菌株 UTI89 在气液界面处进行生物膜形成期间进行了一系列界面流变测量，该菌株因其在尿路感染研究中的重要性以及其功能性淀粉样纤维（称为卷曲）的组装而受到关注。布鲁斯特角显微镜和表面弹性（G（s）'）和应力-应变响应的测量提供了敏感和定量的参数，这些参数揭示了细菌定植、聚集和最终在气液界面形成菌膜的不同阶段。在促进卷曲产生的条件下形成的菌膜表现出强度和粘弹性增加，以及从应力-应变扰动中恢复的能力增强。结果表明，作为疏水性细胞外淀粉样纤维的卷曲增强了在气液界面形成的大肠杆菌生物膜的强度、粘弹性和抗应变能力。
