Using Active Materials at Liquid Interfaces to Regulate Bacterial Biofilm Mechanical Properties

细菌可以在液体/空气界面上生长，通过附着在界面上，排泄蛋白质，并繁殖。这就产生了一种粘稠的、有弹性的薄膜，称为薄膜(生长在空气/水界面的生物膜)。细胞膜出现在囊性纤维化患者的肺部，使感染得以传播，或者在石油泄漏清理中，使石油降解菌能够接触到原油。为了减少感染，膜应该变得不那么稳定；为了加强油污清除，膜应该变得更稳定。膜的稳定性在一定程度上取决于细菌类型，而在现实应用中，细菌类型是不能改变的。因此，要改变膜的特性，需要改变局部环境以影响细菌的行为。PI将通过直接向液体界面添加材料来改变膜层特性。例如，向界面添加肥皂会削弱生物膜，而添加小颗粒会增强它们。这项研究将研究一系列可以改变界面的材料，并确定界面的性质如何以及为什么可以用来控制薄膜的机械强度。为小学生举办的有趣的“超级星期六”科学俱乐部将得到支持。面向5年级和11年级学生的《科学是女生的事情》也将被创建。PI教授流体，也是向本科生推广研究生院的服务。他是机械工程正式方案的一部分，该方案旨在提高多样性和妇女参与度，这在工程学，特别是机械工程学中是很低的。他将教授一门新课程，并将研究和教育计划牢固地结合在一起。当表面活性物质吸附到液体界面上时，就会影响薄膜的粘弹性。然而，对这一现象的研究很少，至于是什么机制导致了观察到的变化，仍然令人困惑。这项研究将确定界面的机械和化学性质，如粘弹性、电荷和润湿性如何影响铜绿假单胞菌膜的界面粘弹性。这将通过使用特定的吸附颗粒、蛋白质和表面活性剂来系统地控制界面属性来实现。将使用定制的流变仪来表征界面粘弹性存储和损失模数，并同时监测细菌在生物膜中的运动。这将允许以一种以前没有完成的方式来辨别界面属性对膜形成的影响以及生物行为与界面力学的关联。关于界面性质对薄膜形成的作用所得出的结论将广泛适用于所有薄膜形成细菌，因为重点是机械过程。由此得到的数据将提供对薄膜形成的独特理解，并为改变薄膜的最终机械性能提供新的手段。

Bacteria can grow on liquid/air interfaces by attaching to the interface, excreting proteins, and reproducing. This creates a slimy, elastic sheet called a pellicle (a biofilm grown at an air/water interface). Pellicles occur in the lungs of cystic fibrosis patients, where they allow infection to spread, or in oil spill cleanup where they enable oil-degrading bacteria access to crude. To reduce infection, pellicles should be made less stable; to enhance oil cleanup, pellicles should be made more stable. The stability of pellicles depends in part on the bacteria type, which in real-world applications cannot be changed. Therefore, to alter pellicle properties, the local environment needs to be changed to affect bacteria behavior. The PI will alter pellicle properties by adding materials directly to liquid interfaces. For instance, adding soap to an interface weakens biofilms, whereas adding small particles strengthens them. This research will study a range of materials that can modify interfaces and determine how and why the properties of interfaces can be used to control pellicle mechanical strength. An interesting 'super Saturday' science club for elementary students will be supported. 'Science it's a girl thing' for 5th and 11th grade students will also be created. The PI teaches fluids and also serves to promote graduate school to undergraduates. He is part of a formal program in mechanical engineering to enhance diversity and women participation which is low in engineering in particular for mechanical engineering. He will teach a new course and solidly integrates research and educational plans.When surface active materials adsorb to an change the properties of a liquid interface, it is known to affect the viscoelasticity of a pellicle. However, there is little study of this phenomenon and still confusion as to what mechanisms cause observed changes. This research will determine how mechanical and chemical properties of an interface such as viscoelasticity, charge, and wettability affect interfacial viscoelasticity of P. aeruginosa pellicles. This will be done by using specific adsorbed particles, proteins, and surfactants to systematically control interfacial properties. A custom-built rheometer will be employed to characterize interfacial viscoelastic storage and loss moduli and simultaneously monitor bacteria movement within the biofilm. This will allow discernment of the impacts of interface properties on pellicle formation and correlation of biological behavior to interfacial mechanics in a way that has not been previously accomplished. The conclusions drawn about the role of interface properties on pellicle formation will be broadly applicable to all pellicle-forming bacteria due to the focus on mechanistic processes. The resulting data will provide a unique understanding of pellicle formation and a new means to change ultimate mechanical properties of pellicles.