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，并在我们的环境中定居，从浅层土壤到地下深处、人体和工程系统。生物膜是微生物的聚集体，它们相互粘附，并且通常也粘附在表面上。它们嵌入称为聚合物质的粘稠细胞外基质中。生物膜是有生命的，并且具有复杂的结构，科学家和工程师仍在试图了解这一点。这种复杂的结构可以保护生物膜并使其茁壮成长——人多力量大，因此存活率大大提高。生物膜阻止入侵者（例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（例如土壤和岩石、填充床、滴滤器、反渗透膜）中生物膜的发育和功能的了解，对于地下水修复、水处理、土壤和农业科学，以及机械和医疗系统和植入物的污垢问题等领域具有重要影响。在不饱和条件下，即当孔隙空间仅部分充满水时，毛细管力（如吸管或海绵中的水）将主导流体相对于重力的流动。这会对生物膜的生存和繁荣产生重大影响，因为它们需要水来提供营养和氧气。 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管力在地球多孔介质中生物膜形成中各自发挥的作用。通过在太空/微重力和地球上进行生物膜生长实验，研究小组可以分离出重力和毛细管作用的影响，从而更好地了解在没有其他影响的情况下，两者在生物膜发育中所扮演的角色。这将使研究人员能够更好地了解生物膜 3D 形状和功能如何受到这些力的影响，并将允许更好地设计利用生物膜为我们服务的系统，或者防止生物膜污染系统（在不希望的情况下）。参与国际空间站上进行的研究将提供独特的外展机会，既可以通过国际空间站的直播，也可以在样本返回地球后用 X 射线扫描时探索 3D 物体。 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实践学习。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”物体的印象。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，这些数据首先支持对多孔介质中生物膜功能的机械和定量理解的发展。 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管作用（界面力）在地球多孔介质中生物膜形成中各自发挥的作用。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，可以评估在没有毛细作用的情况下重力在生物膜结构发展中所起的作用。通过在不饱和条件下（微重力和1重力）进行一组补充实验，将研究重力和毛细管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。研究团队旨在利用 3D 成像，建立生物膜生长的“相图”，沿着用于概念化不同多相（不饱和）流态的相图。假设可以建立一个类似的图表，将无量纲数（毛细管数和邦德数，代表重力和毛细管作用之间力平衡的变化）与不同类型的生物膜生长和结构联系起来，范围从稀疏到密集，从平坦表面生长到“蘑菇”或“柱和冠”型结构。该研究将有助于使用高分辨率 X 射线断层扫描成像对不同重力环境中生长的生物膜的详细图像进行比较。生成的数据将为多孔介质中生物膜的形成提供前所未有的见解，并揭示重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。成像工作将包括在饱和或不饱和条件下在多孔介质中生长的生物膜的高分辨率成像（1G 和 microG）。该研究将生成生物膜分布和结构的 3D 图像，并允许测量由于孔隙堵塞而导致的孔隙率、渗透率和弯曲度的变化。其他测量包括生物膜体积；表面积；生物膜和营养物（生物膜-流体）区域之间的界面接触面积；以及生物膜和多孔介质（生物膜-固体）区域。为了表征生物膜/孔隙空间的结构演化，还将建立许多结构和拓扑测量的轴向分布。最后，研究团队将模拟生物膜生长前后的单相流，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拟议的生物膜生长“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贡献新的知识，这些知识可以揭示地球多孔介质中生物膜生长和结构演化的机制。参与国际空间站上进行的研究将提供独特的外展机会，既可以通过国际空间站的直播，也可以在样本返回地球后用 X 射线扫描时探索 3D 物体。 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实践学习。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”物体的印象。该奖项反映了 NSF 的法定使命，并通过使用基金会的智力价值和更广泛的影响审查标准进行评估，被认为值得支持。