INTELLECTUAL MERIT: The objective of this project is to quantify how surface properties influence the motility of bacteria, with high spatial and temporal resolution. Motility is a critical factor in the formation of surface-associated bacterial biofilms. Once biofilms form, they are notoriously difficult to remove, resulting in billions of dollars of damage to oil and water pipelines, biomedical implants, and food. Reducing these costs requires new strategies to prevent bacteria from forming biofilms. In the initial stage of biofilm formation, bacteria modify their motility mechanisms to enable irreversible attachment to nearby surfaces. To test the hypothesis that motility characteristics and rates of bacterial attachment and detachment are affected by the interactions between bacteria and surfaces, the specific aims are: (1) To elucidate the effects of surface chemistry and elasticity on dispersal by measuring velocity and persistence of motion on surfaces. Single-bacterium tracking algorithms will be used to track thousands of bacteria moving on surfaces with controlled surface charge and elastic modulus engineered using layer-by-layer deposition, yielding optimized surface properties to minimize dispersal. (2) To quantify directional persistence in response to surface patterns. The mean-square displacement, mean speed, persistence time, and angle of motion of bacteria on gradient surfaces with feature sizes of 1-100 microns will be analyzed using models for chemotaxis, yielding fundamental data on how surface patterns direct motion in bacteria. (3) To develop assays to evaluate antifouling surfaces by measuring attachment and detachment rates of individual bacteria. These rates will be correlated to the structure of the resultant biofilms on two types of surfaces with demonstrated antifouling efficacy, amphiphilic polymer films and hierarchically wrinkled surfaces. By generating new fundamental understanding of the effects of surface properties on motility, adhesion, and biofilm formation, this project aims to enable the rational design of coatings that inhibit colonization by bacteria and thereby impede biofilm formation.
BROADER IMPACTS: Optimized antifouling coatings will help to reduce the billions of dollars in biocorrosion damage in water and resource pipelines each year and in costs related to hospital-acquired infections. More broadly, detailed microscopic investigations of near-surface motility will yield new insights on the interactions between bacteria and the surfaces on which they move, enabling qualitatively new studies of infection and pathology as well as antifouling surface properties. The information-rich data generated by this work will improve existing models for directed motility and for bacterial adhesion. Finally, these techniques can be applied to correlate bacterial attachment and fouling to surface properties across a wide range of species and surfaces. The proposed research will be integrated with educational and outreach efforts aimed at increasing the participation of underserved populations in engineering in Houston. First, training and learning activities on biofouling that inspire students to study engineering will be developed in collaboration with two minority-serving local high schools (KIPP-Houston and DeBakey), leveraging the PI's ongoing work with NSF-RET and the UH GRADE Camp program for introducing precollege women to engineering. Second, the PI will continue to mentor undergraduate students in research through UH and NSF-REU. Finally, two graduate students will be mentored in research on antifouling surfaces, and interdisciplinary workshops on engineering for biology will be initiated by the PI. The proposed teaching and outreach efforts will broaden participation in engineering throughout the diverse population of Houston, reflected by the high proportions of African American and Latino (95% and 56%) and low income (80% and 49%) students at KIPP-Houston and DeBakey, respectively. Likewise, the PI will pursue these activities at the University of Houston (13% African American and 21% Latino), the second most diverse research university in the US. The results from this study will be widely disseminated by the PI and her students in both the scientific literature and to the petroleum and biomedical industries, leveraging the PI's experience as an industrially sponsored postdoctoral researcher and her ongoing collaborations at the Texas Medical Center.
