RUI: Reducing Permeability in Sands Using Biofilm-Forming Bacteria and Quorum Sensing Inhibitors to Create Uniform Growth

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The movement of water through soil (seepage) can cause dams and levees to fail, which may be expensive to repair, cause extensive damage to infrastructure, and possibly the loss of life. Traditional methods to reduce seepage can be cost-prohibitive and create environmental concerns. Preliminary work has shown the feasibility of using biofilm-forming bacteria to reduce seepage. Biofilm-forming bacteria secrete a sticky material that connects the bacteria together, attaches the bacteria to solid surfaces, and blocks the flow of water through the soil. However, the reduction in seepage only occurred close to the bacteria's nutrient source and seepage further from the source (more than five centimeters) was not significantly reduced. Uniform reduction of seepage across a distance of at least one meter will be needed if using bacteria to form biofilms is to be a feasible method to reduce seepage and the likelihood of the types of failures listed above. This project will determine whether a quorum sensing inhibitor (a chemical that prevents bacteria from forming a biofilm) can be used to control the location and timing of biofilm formation so that the biofilm develops uniformly across the length of a one-meter column of sand. If successful, further research would look at the application of this methodology to field applications. In addition, this grant will support a partnership between Lafayette College (LC) and one of the National Science Foundation's Engineering Research Centers (ERCs)--the new Center for Bio-mediated & Bio-inspired Geotechnics (CBBG). The research partnership between faculty at LC (the project PIs) and the CBBG will create an exchange of information that will allow the PIs to develop their research programs in cooperation with the CBBG, and will introduce a minimum of six undergraduate students to this new interdisciplinary field of research. Because of high percentages of women students at LC, this grant is anticipated to broaden research participation with respect to this underrepresented group.This research will develop methods to create a uniform growth of bacterial biofilm in sand by using quorum sensing inhibitors and the manipulation of flow rates and nutrients. Initially, Pseudomonas fluorescens, a known biofilm former, will be introduced to columns containing sterile sand. The manipulation of the concentration and timing of water containing nutrients and a quorum sensing inhibitor, Furanone 56--a halogenated compound known to inhibit biofilm formation, will be used to create a uniform distribution of bacterial biofilm in these soils. Once a protocol is established for the development of a uniform biofilm distribution under these conditions, columns will be constructed using non-sterile sand. Similar manipulation of the nutrient and quorum sensing inhibitor will be used to investigate whether the approach developed can stimulate native biofilm-forming bacteria to create a uniform distribution of biofilm. A final testing setup will confirm that native bacterial biofilm can be uniformly distributed along a one-meter soil column. Through a partnership between LC and the CBBG, this grant will also support innovative research by an interdisciplinary team of faculty at a strictly undergraduate institution and provide robust mentoring and research experiences for undergraduate students. The research partnership between faculty at LC and the CBBG will create an exchange of information that will allow the faculty at LC to develop their research in cooperation with the CBBG and will introduce a minimum of six undergraduate students to this newly developing interdisciplinary field of research.