Chronic lung infection with bacterial biofilms is a leading cause of death in cystic fibrosis (CF) patients. Pseudomonas aeruginosa, one of the many species colonizing the lung airways, can undergo pathoadaptation, leading to a mucoid phenotype with interesting material properties. We hypothesize that the surface properties and extracellular materials of mucoid P. aeruginosa cells greatly influence the mechanical behavior of their films at fluid interfaces. In this study, we investigate the interfacial properties of films formed by nonmucoid (PANT) and mucoid (PASL) strains of P. aeruginosa isolated from CF patients. We use pendant drop elastometry to analyze the interfacial response of the films formed by PANT and PASL at the hexadecane-water interface. The dynamic rheological analyses of the films highlight the distinctive signature of the mucoid strains at fluid interfaces. The mucoid films exhibit greater relaxation following a compressive strain than a tensile one, while a full hysteresis response is achieved by the nonmucoid films; this indicates that the material properties of the PANT films are conserved under both compression and tension. The wrinkling and shape analyses of the interfacial bacterial films elucidate that the mucoid strain exhibits remarkable viscoelastic properties, enabling the remodeling of the living films and dissipation of the compressive stress. The comparative analysis of the material properties of mucoid and nonmucoid P. aeruginosa cells indicates that mucoid switch can play an important role in protecting the bacteria from interfacial stresses. Further characterization of interfacial bacterial films will provide new insights into the development of methods for controlling interfacial films of bacteria.

细菌性生物膜对慢性肺部感染是导致囊性纤维化（CF）患者死亡的主要原因。铜绿假单胞菌（Pseudomonas aeruginosa）是在肺气道中定居的众多物种之一，可以进行病理适应，从而形成具有有趣物质特性的粘液表型。我们假设黏液状铜绿假单胞菌细胞的表面性质和细胞外物质极大地影响了它们在流体界面处的膜的机械行为。在这项研究中，我们调查了由CF患者分离出的铜绿假单胞菌的非粘液菌（PANT）和粘液菌（PASL）菌株形成的膜的界面特性。我们使用悬垂液滴弹性分析法来分析由PANT和PASL形成的薄膜在十六烷-水界面的界面响应。膜的动态流变分析突出了流体界面处粘液样菌株的独特特征。粘膜在压缩应变后比拉伸膜表现出更大的松弛，而非粘膜具有完全的磁滞响应。这表明PANT膜的材料性能在压缩和拉伸下均得以保留。界面细菌膜的起皱和形状分析表明，粘液样应变表现出显着的粘弹性，从而使活膜能够重塑并消除压应力。黏液样物质和非黏液样物质特性的比较分析铜绿假单胞菌细胞表明，粘液样转换可以在保护细菌免受界面胁迫中起重要作用。界面细菌膜的进一步表征将为控制细菌界面膜的方法的发展提供新的见解。