Diffusiophoretic Bioaugmentation: Boosting the Bacterial Motility in Soil Matrix by Chemical Gradients for Enhanced Bioremediation

当有毒化学物质泄漏发生时，这些化学物质通常会泄漏到土壤中，使其难以清除，因为这些化学物质很容易渗入地下深处。为了清理泄漏，可以将化学降解细菌注入被污染的土壤中。这种方法的主要挑战之一是将细菌直接运送到污染地点。如果化学物质在土壤深处，注入的细菌必须感知并向污染物游去，这可能是一个缓慢的过程。该项目的目标是通过向细菌注入额外的无毒化学物质来加速细菌向污染地点的运动，这些化学物质可以通过产生化学梯度来增强细菌的运动。这一项目的成功完成将通过制定环境补救战略来减轻有毒污染物对生态和人类健康的影响，从而造福社会。对社会的额外好处将通过学生教育和培训来实现，包括在布法罗大学指导一名研究生。有毒化学品泄漏需要对化学品进行降解，以避免对环境和人类健康造成影响。成功的化学泄漏生物修复需要将分解细菌引导到目标土壤微孔，这些微孔位于污染物可能持续存在的地下深处。小细菌可以通过孔隙流被动地平流穿过地下的可渗透区域。然而，在土壤基质中普遍存在的不透水微孔只能通过主动运动或布朗运动进入。这些区域往往含有大量的污染物，因为它们不容易被孔隙流冲走，从而限制了修复效果。因此，迫切需要开发一种有效的方法将细菌分散到难以到达的空间。本提案的主要目的是通过在土壤中引入化学异质性来实现增强的生物修复。核心假设是，在生物修复过程中，土壤基质内产生的化学梯度不仅可以通过趋化性（生物体响应化学刺激的细胞内转导运动）加速细菌的运输，还可以通过扩散电泳（由于周围化学物质与颗粒表面之间的物理化学相互作用，胶体颗粒沿着化学梯度定向迁移）加速细菌的运输。当化学和细胞表面条件满足时，无论细菌类型如何，扩散泳动都能比布朗运动提高几个数量级的细菌运输。这项研究将包括微流体系统中趋化性和扩散电泳之间相互作用的实验表征，以及实验室规模的土壤基质生物修复示范。本研究旨在阐明细菌扩散泳术的基本方面，并展示一种有效的、低成本的策略来增强生物修复。进一步的社会效益包括通过实践课程向本科工程专业学生介绍微生物工程，该课程将发展到包括从细胞培养和微流体制造到实验室规模的生物修复的各个方面，以及指导研究生。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。

When a toxic chemical spill occurs, the chemicals often leak into the soil, making it difficult to remove because the chemicals can easily seep deep underground. To clean up the spill, chemical-degrading bacteria can be injected into the contaminated soil. One of the major challenges of this approach is delivering the bacteria directly to the contaminated site. If the chemicals are deep in the soil, the injected bacteria must sense and swim towards the contaminants which can be a slow process. The goal of this project is to speed up the movement of the bacteria toward the contaminated site by injecting the bacteria into the ground with additional non-toxic chemicals that can enhance their motion by creating chemical gradients. Successful completion of this project will benefit society by developing environmental remediation strategies to mitigate ecological and human health impacts of toxic pollutants. Additional benefits to society will be accomplished through student education and training including the mentoring of a graduate student at the University at Buffalo.Toxic chemical spills require processes to degrade the chemicals to avoid environmental and human health impacts. Successful bioremediation of chemical spills requires directing decomposer bacteria to the target soil micropores that are deep in the subsurface where contaminants are likely to persist. The small bacteria can passively advect across permeable regions of the subsurface via pore flow. However, impervious micropores, which are prevalent in the soil matrix, can only be accessed by active motility or Brownian motion. These areas often tend to hold a significant amount of contaminants since they cannot be easily swept away by the pore flow, thus limiting the remediation efficacy. Therefore, there is a critical need to develop an effective way to disperse bacteria to hard-to reach spaces. The main objective of this proposal is to achieve enhanced bioremediation by introducing chemical heterogeneity in the soil. The central hypothesis is that the chemical gradients created within the soil matrix during bioremediation can accelerate the bacterial transport not only by chemotaxis, the movement by intracellular transduction of an organism in response to chemical stimulus, but also by diffusiophoresis, the directed migration of colloidal particles along chemical gradients due to the physicochemical interactions between the surrounding chemicals and the particle surface. When the chemical and cell surface conditions are met, diffusiophoresis can enhance the transport of bacteria by orders of magnitude compared to Brownian motion regardless of the bacteria type. This investigation will include experimental characterization of the interplay between chemotaxis and diffusiophoresis in microfluidic systems and laboratory-scale bioremediation demonstration in the soil matrix. This research aims to elucidate the fundamental aspects of bacterial diffusiophoresis and demonstrate an effective, low-cost strategy to enhance bioremediation . Further societal benefits include introducing undergraduate engineering students to microbial engineering through a hands-on course that will be developed to include various aspects from cell culture and microfluidic fabrication to laboratory-scale bioremediation as well as mentoring of a graduate student.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.