ISS: Biofilm growth and architecture in porous media: exploring the effect of gravitational and interfacial forces on biofilm growth patterns

ISS：多孔介质中的生物膜生长和结构：探索重力和界面力对生物膜生长模式的影响

• 批准号: 2323014
• 负责人: Dorthe Wildenschild
• 金额: $ 52.54万
• 依托单位: Oregon State University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2023
• 资助国家: 美国
• 起止时间: 2023-10-01 至 2026-09-30
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2323014&HistoricalAwards=false
• 关键词: ISS; Biofilm; growth; architecture; porous

Microbes are ubiquitous in nature and colonize our environments from shallow soils to the deep subsurface, the human body, and engineered systems. Biofilms are aggregates of microorganisms that stick to each other and often also to a surface. They are embedded within a slimy extracellular matrix known as polymeric substances. Biofilms are alive and have a complex structure that scientists and engineers are still trying to understand. This complex structure protects the biofilms and allows them to thrive – there is strength in numbers, so survival rates improve greatly. Biofilms block the penetration of intruders (e.g. immune cells and antimicrobials), promoting bacterial survival. Improved understanding of the development and function of biofilms in porous media (e.g. soils and rocks, packed beds, trickling filters, reverse osmosis membranes) is impactful in fields ranging from groundwater remediation, water treatment, and soil and agricultural science, to the vast problem of fouling of mechanical and medical systems and implants. Under unsaturated conditions, meaning when pore spaces are only partially filled with water, capillary forces (as what holds water in a straw or sponge) will dominate fluid flow relative to gravity. This can have a significant impact on how biofilms survive and thrive since they need water to deliver nutrients and oxygen. The overarching goal of the research is to use the microgravity environment on the International Space Station to study the respective roles that gravity and capillary forces play in the development of biofilms in porous media on Earth. By conducting biofilm growth experiments in space/microgravity and on Earth, the research team can isolate the effects of gravity and capillarity, forming a better understanding of the role that each plays in the development of biofilms in the absence of the other. This will enable researchers to better understand how biofilm 3D shape and function are affected by either of these forces and will allow better designs of systems that make use of biofilms to work for us, or to prevent biofilms from fouling systems where that is undesirable. The involvement of research conducted on the International Space Station will provide unique outreach opportunities, both via live-streaming from the International Space Station, and also in terms of opportunities to explore 3D objects as samples are scanned with x-rays upon return to Earth. The visualization capabilities of the x-ray imaging facility are ideally suited to support hands-on learning for young students interested in science, technology, engineering, and math. The resulting volumetric images can be rendered in 3D, giving observers the impression of “flying through” the object.This project aims to improve existing theories describing biofilm growth and functional processes by generating data that will first and foremost support the development of a mechanistic and quantitative understanding of biofilm function in porous media. The overarching goal of the research is to use the microgravity environment on the International Space Station to study the respective roles that gravity and capillarity (interfacial forces) play in the development of biofilms in porous media on Earth. By conducting biofilm growth experiments under saturated conditions in microgravity (microG) and on Earth (1G), the role that gravity plays in the development of biofilm architecture in the absence of capillarity can be assessed. By conducting a complementary set of experiments under unsaturated conditions (in both microG and 1G), the role of the force balance between gravity and capillarity will be studied, along with the effects on both hydrodynamics and associated differences in biofilm growth. Using 3D imaging, the research team aims to establish a “phase diagram” for biofilm growth along the lines of those used to conceptualize different multi-phase (unsaturated) flow regimes. The hypothesis is that a similar diagram could be established that relates dimensionless numbers (Capillary and Bond numbers, representing variations in the force balance between gravity and capillarity) to different types of biofilm growth and architecture, ranging from sparse to dense, and from flat surface growth to “mushroom” or “column-and-canopy” type architectures. The research will facilitate comparison among detailed images of biofilms grown in different gravitational environments using high-resolution x-ray tomographic imaging. The data generated will provide unprecedented insight regarding biofilm formation in porous media and reveal the relative significance of gravitational and interfacial forces as dominant mechanisms governing biofilm growth and architecture. The imaging effort will include high-resolution imaging of biofilms, grown in porous media under saturated or unsaturated conditions, in both 1G and microG. The research will generate 3D images of biofilm distribution and architecture, and allow for measurements such as changes in porosity, permeability, and tortuosity due to clogging of pores. Additional measurements include biofilm volume; surface area; interfacial contact area between biofilm and nutrients (biofilm-fluid) area; and biofilm and porous medium (biofilm-solid) area. To characterize the structural evolution of the biofilm/pore space, axial distributions of a number of structural and topological measures will also be established. Finally, the research team will simulate single-phase flow before and after biofilm growth to visualize and quantify changes in the flow field and velocity distribution caused by biofilm growth. All of these measurements will help populate the proposed biofilm growth “phase diagram," and can be used to evaluate existing theories and models, as well as support the development of new models. Thus, the significance of this research consists of contributing new knowledge that can shed light on the mechanisms governing biofilm growth and structural evolution in porous media on Earth. The involvement of research conducted on the International Space Station will provide unique outreach opportunities, both via live-streaming from the International Space Station, and also in terms of opportunities to explore 3D objects as samples are scanned with x-rays upon return to Earth. The visualization capabilities of the x-ray imaging facility are ideally suited to support hands-on learning for young students interested in science, technology, engineering, and math. The resulting volumetric images can be rendered in 3D, giving observers the impression of “flying through” the object.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

微生物在自然界中无处不在，从浅层土壤到深层地下、人体和工程系统，它们都是我们环境的殖民地。生物膜是微生物的聚集体，它们相互粘在一起，通常也粘在表面上。它们被嵌入一种粘稠的细胞外基质中，这种基质被称为聚合物质。生物膜是有生命的，具有复杂的结构，科学家和工程师仍在努力理解。这种复杂的结构保护了生物膜，并使它们茁壮成长——数量越多，存活率就会大大提高。生物膜阻止入侵者（如免疫细胞和抗菌剂）的渗透，促进细菌存活。提高对多孔介质（如土壤和岩石、填充床、滴流过滤器、反渗透膜）中生物膜的发育和功能的理解，对地下水修复、水处理、土壤和农业科学，以及机械和医疗系统和植入物污染的巨大问题等领域都有影响。在非饱和条件下，也就是说当孔隙空间只有部分充满水时，相对于重力，毛细力（就像吸管或海绵中保持水的力量）将主导流体的流动。这可能会对生物膜的生存和繁荣产生重大影响，因为它们需要水来输送营养和氧气。该研究的总体目标是利用国际空间站的微重力环境来研究重力和毛细力在地球多孔介质中生物膜发展中的各自作用。通过在太空/微重力和地球上进行生物膜生长实验，研究小组可以分离重力和毛细作用的影响，从而更好地了解在没有另一方的情况下，每一方在生物膜的发展中所起的作用。这将使研究人员能够更好地了解生物膜的3D形状和功能是如何受到这两种力量的影响的，并将允许更好地设计利用生物膜为我们工作的系统，或者防止生物膜在不希望的情况下污染系统。在国际空间站进行的研究的参与将提供独特的外展机会，既可以通过国际空间站的直播，也可以通过探索3D物体的机会，因为样品在返回地球时用x射线扫描。x射线成像设备的可视化功能非常适合支持对科学、技术、工程和数学感兴趣的年轻学生的动手学习。由此产生的体积图像可以以3D形式呈现，给观察者一种“飞过”物体的感觉。该项目旨在通过生成数据来改进描述生物膜生长和功能过程的现有理论，这些数据将首先支持对多孔介质中生物膜功能的机制和定量理解的发展。该研究的总体目标是利用国际空间站的微重力环境来研究重力和毛细作用（界面力）在地球上多孔介质中生物膜发展中的各自作用。通过在微重力（microG）和地球（1G）饱和条件下进行生物膜生长实验，可以评估重力在没有毛细作用的情况下对生物膜结构发展的作用。通过在不饱和条件下（微g和1G）进行一组补充实验，将研究重力和毛细作用之间的力平衡的作用，以及对流体动力学和生物膜生长相关差异的影响。利用3D成像技术，研究小组的目标是建立一个生物膜生长的“相图”，沿着那些用于概念化不同多相（不饱和）流动机制的线。假设可以建立一个类似的图表，将无因次数（毛细数和键数，代表重力和毛细力之间平衡的变化）与不同类型的生物膜生长和结构联系起来，从稀疏到密集，从平面生长到“蘑菇”或“柱冠”型结构。这项研究将利用高分辨率x射线断层成像技术，促进在不同重力环境下生长的生物膜的详细图像的比较。生成的数据将提供关于多孔介质中生物膜形成的前所未有的见解，并揭示引力和界面力作为控制生物膜生长和结构的主要机制的相对重要性。成像工作将包括生物膜的高分辨率成像，在饱和或不饱和条件下，在1G和微g条件下在多孔介质中生长。该研究将生成生物膜分布和结构的3D图像，并允许测量孔隙度、渗透率和孔隙堵塞引起的扭曲度的变化。其他测量包括生物膜体积；表面积;生物膜与营养物的界面接触面积（生物膜-流体）面积；以及生物膜和多孔介质（生物膜-固体）区域。为了表征生物膜/孔空间的结构演化，还将建立一些结构和拓扑措施的轴向分布。最后，研究小组将模拟生物膜生长前后的单相流动，以可视化和量化生物膜生长引起的流场和速度分布的变化。所有这些测量将有助于填充所提出的生物膜生长“相图”，并可用于评估现有的理论和模型，以及支持新模型的开发。因此，这项研究的意义在于提供新的知识，可以阐明地球上多孔介质中生物膜生长和结构演化的机制。在国际空间站进行的研究的参与将提供独特的外展机会，既可以通过国际空间站的直播，也可以通过探索3D物体的机会，因为样品在返回地球时用x射线扫描。x射线成像设备的可视化功能非常适合支持对科学、技术、工程和数学感兴趣的年轻学生的动手学习。由此产生的体积图像可以以3D形式呈现，给观察者一种“飞过”物体的感觉。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。