Undergraduate Identifies DNA Regions Involved in Bacterial Movement
By Jennifer Brouner
Alicia Purcell has spent the majority of her life asking questions about the world around her. She can remember herself as a ten-year-old sitting on the floor of her bedroom with only two feet separating her from the TV screen, wide brown eyes focused on her favorite channel: Discovery Health. At this point in her life, Purcell watched the TV with child-like curiosity, absolutely fascinated by the new scientific discoveries. She was unaware that in the future she would join the researchers she idolized as a child.
Photo by Tara Sripunvoraskul
Though Purcell has always enjoyed learning and asking questions, she had never taken on the mindset of a science researcher and extensively investigated any questions in a lab herself, at least not until recently. It wasn’t until her junior year of college that Purcell started seeking the answer to a much more complex question—a question that she has been researching for a little over a year now in Associate Professor Gladys Alexandre’s biochemistry lab at the University of Tennessee.
“We are trying to understand how cells make decisions,” explains Alexandre.
For the past year, Purcell has worked alongside Alexandre studying what urges the bacterium Azospirillum brasilense, nicknamed “azo,” to cluster together when food sources are scarce. In the Alexandre lab, Purcell studies how two groups of mutant azo behave in food-scarce environments in comparison to the normally functioning azo. While normal azo would cluster with one another, one of Purcell’s mutants clusters together more frequently than normal, and one mutant does not cluster together at all. Through comparison of their genetic compositions, she is able to “map” where these mutations are occurring, thus determining which genes are being interrupted as a result. This damaged region can then be identified as the source of the bacteria’s varying ability to cluster together during times of strife.
“Alicia is doing something that nobody has done before. We know nothing about this behavior and she is at the forefront of this research field,” says Alexandre proudly.
Purcell spends about 15 hours in the lab every week studying these microorganisms that can only be viewed under the most powerful of microscopes. She observes their behavior and runs molecular biology experiments to determine the DNA sequences that are on either side of the mutations. She then examines these sequences using specialized techniques and predicts their function in bacterial cells.
So far, Purcell has identified two distinct regions in the azo’s DNA sequence that, when damaged, prevent the bacteria from clustering as they normally would.
However, research is never predictable, and these bacteria are no exception. Despite how careful Purcell is when handling these bacteria, she often finds her prized subjects sharing space with other unwelcome bacterial species, a problem that is known in the lab as contamination. “Contamination is a problem that everyone in my group goes through,” says Purcell. “Sometimes you go months trying to clear them up.”
Having just spent three long and tedious months applying antibiotics to her contaminated azo plates to kill any intruders, she finally has pure cultures and is ready to get back to her work identifying damaged regions of DNA in the mutant bacteria.
Of her experience working with Purcell, Alexandre says, “I would not differentiate her research from mine. Alicia’s research directly contributes to what my lab is trying to understand.”
Although Purcell has only been working in the lab for a little over a year, Alexandre plans to publish a paper that will include Purcell’s discoveries, and she predicts that this research will have its largest impact in the agricultural industry. The ability of the azo to cluster together allows the bacteria to stay dormant, or in other words, hibernate when living conditions are harsh. If humans could control this clustering process, the biofertilizers containing azo would have a much longer shelf-life.
However, the impacts of this study could extend to the treatment of diseases if Alexandre and her research team can determine how cells respond in any given environment. While Purcell focuses on these mutant DNA sequences, another scope of the Alexandre lab is to research how bacteria move toward or away from specific environments depending on the conditions. Purcell’s findings could help to explain how bacteria detect favorable environments within the body and move toward them. If they can determine what causes these bacteria to move, then it is possible that they could control the bacteria’s movement. “Every step we make opens up new possibilities,” says Alexandre.
Regardless of where this research heads, Purcell is grateful to have been given an invaluable opportunity to apply the knowledge she has learned in her science courses at the University of Tennessee to answer questions that no one has ever researched before.
“I think that we are meant to figure everything out. That’s what science does, right?” says Purcell. “That’s why I like science. That’s why I like biology. That’s why I like research—because I am contributing to figuring out the world.”
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