Despite their microscopic size, bacteria play a major role in our environment. They can clean up oil spills and radioactive chemicals or eat through plastic waste and toxic soil. But making use of these microorganisms requires a better understanding of how they navigate through different materials.
That’s what Ph.D. candidate Rhea Braun and undergraduate student Eliza Mills hope to learn through their research. In 2023, the chemical engineering duo received a Double Hoo award for their project that investigates how bacteria move through porous materials and what might impact those movements.
Navigating Microscopic Mazes
Bacteria move in response to chemicals in their environment. This movement — chemotaxis — depends in part on the size, shape and spacing of obstacles. In porous media such as sand or soil, the size of the grains and how tightly they’re packed can affect bacteria’s ability to efficiently move and eventually break down these materials. While previous research has investigated how bacteria move in substances without obstacles, there’s less known about how bacteria maneuver in porous environments.
To study chemotaxis, Braun and Mills used a confocal microscope to view thin layers of E. coli bacteria in a porous medium at a high resolution. They observed how the bacteria naturally moved then ran additional tests with a chemical that attracts the bacteria. By testing multiple concentrations of porous media with the attractor chemical, they learned how the bacteria respond in various scenarios.
Braun described how observing the bacteria was like watching them in a see-through labyrinth. “We can tell exactly where they’re going, how they’re getting lost and how they figure out where they are,” she said.
By the end of the academic year, Braun and Mills settled on a system that allowed them to simulate varying pore sizes in a solution, demonstrating how chemotaxis changed in response to different environments.
The team hopes to figure out how to maneuver the bacteria using chemicals so that one day bacteria can be recruited as a targeted cleanup crew for those oil spills and help quell infectious diseases. In the future, scientists may be able to choose the bacteria best suited to a particular task by considering their movement patterns.
Mills said her project is evolving. Now she will add another bacterium to her investigation: Pseudomonas putida, an organism that can reverse itself when it meets an obstacle. Mills intends to compare this bacterium’s responses to that of E. coli, which can change directions but cannot go backwards, helping her better understand how unique features can affect the bacteria’s movements in porous media.
Building Future Scientists
Braun and Mills’ project was initially funded through the Double Hoo Research Grant, a unique opportunity at UVA that pairs undergraduate and graduate students together for research. The program builds collaborative interactions between the two student communities. Undergraduates gain advanced research experience and graduate students become mentors.
“The procedures we used to study the bacteria’s movement has allowed me to refine my lab skills and become proficient with microscopes,” Mills said. “Using the confocal microscope through the UVA Keck Center has been a great learning experience, and I know the skills I learned from this project will help me in my next years as a graduate student.”
Braun also felt the collaboration aided her growth, especially as a mentor. “I’ve watched Eliza grow into someone who is not only incredibly competent and independent in the lab but can take concepts from her coursework and use them to understand all of the fundamentals that underlie the work we do,” she said.
I’ve watched Eliza grow into someone who … can take concepts from her coursework and use them to understand all of the fundamentals that underlie the work we do.
The opportunity to collaborate can be especially impactful for undergraduate students. “Working with Rhea has been such a special experience to me,” Mills said. “From the beginning, she went out of her way to help me and set me up for success. Not only has she been an incredible mentor, she’s also been an incredible role model and friend. Seeing her ask questions and explain concepts has made me much more passionate about science, just by seeing how much she cares.”
In addition to the Double Hoo award, Mills received the Gregory J. Canty Research Award, which helps outstanding undergraduate students continue their research into future semesters. Most recently, she received a Dean’s Undergraduate Engineering Research Fellowship. The initiative, created by Dean Jennifer L. West, provides support for undergraduate students who want to get lab experience in the summer.
“Double Hoo has been one of the most worthwhile experiences in my undergraduate career,” Mills said. “It gave me a taste of what pursuing research is all about, and I would recommend it to anyone who is thinking of graduate school or who wants to get more comfortable in the lab.”