Senior Michaela Miller spent her summer researching biofilm growth of Rhodobacter sphaeroides — an environmental microorganism with history as complex as its spelling.
She presented a poster summarizing her project Nov. 4 at the Western Michigan Regional Undergraduate Science Research Conference at Van Andel Research Institute in Grand Rapids, Michigan.
Over the summer, Miller spent roughly 7 – 10 hours a day in the lab at Hillsdale College growing and examining sphaeroides because it is the ancestor to all gram-negative bacteria.
These are organisms that often happen to be pathogenic, while sphaeroides itself is not.
“It’s good to study because the more we learn about the way biofilm grows, the more we can learn about pathogens in the end,” Miller said. “It’s a model organism, meaning it is studied often and has good systems that can be applied to other bacteria.”
Growing organisms in biofilms on coverslips allows for group interactions between the bacterial cells. Certain chemicals called auto-inducers are sent out and help parts of the organism perform group-based behavior.
“In some cases, this makes them more resistant to things like antibiotics and harder to kill,” Miller said.
She wanted to study the quorum sensing, or signaling systems, of sphaeroides. Miller focused on measuring the effect of additional acyl homoserine lactone, a chemical that prevents bacteria from aggregating, and its effect on the live-to-dead cell ratio in her biofilms.
When she grew the biofilms, she grew some normally as a control, but she added extra AHL to others. She stained them to distinguish live and dead cells on the coverslip where the biofilms grew.
The stain colored the living cells green and the dead cells red. She then used software to quantify the live to dead cells. Miller found that additional AHL does not seem to have an effect on the biofilm growth, or the live-to-dead ratio of sphaeroides. She originally predicted that the addition of AHL would affect the aggregation of the bacteria more.
“I think the reason that that’s not what happened is because the bacteria does produce this chemical naturally, and we just added extra, so I’m assuming there’s a threshold concentration,” Miller said. “When it reaches that, it doesn’t affect it anymore.”
She said the research was still successful since it was the first time the experiment had been done in this particular way.
“A lot of the techniques we used in this experiment have really not been used, as far as we know, or frequently used, outside of Hillsdale,” Miller said.
During her junior year, Miller assisted Stevan Lukich ’17 and her now-research adviser Francis Steiner, biology department chairman, by writing up the live-dead staining protocol in which biofilms could be stained without disturbing their growth on the coverslips.
“Her working out that staining procedure was very advantageous,” Steiner said. “Her quantitation in her research was excellent, and she realized she needed to normalize her data.”
Seniors Genevieve Chiara and Lydia Siepel were both able to use the staining protocol in their research last summer as well while working in the same lab as Miller and seniors Monicah Wanjiru and Steve Sartore.
“I love all the processes associated with lab work — how you become friends with the people you are working with,” Miller said.
Chiara added that the environment in the lab was relaxed and the researchers were always willing to help each other out, from taking turns grabbing coffees for the whole group to giving advice about their individual projects.
“I found a helpful article with a procedure explaining that an efficient way to grow biofilms is to replace the media with fresh broth after four hours of adhesion and then let them continue to grow overnight,” Chiara said. “Michaela and Lydia also followed that procedure.”
Chiara and junior Christine Ausherman also accompanied Miller and Steiner to Grand Rapids to present their own posters at the conference.
Miller said fellow undergraduates, recruiters, and graduate students were all interested in learning about other people’s research and that it was not a critical environment. She added that she learned many important things from her summer research.
“Sometimes you’re not always going to see what you expected to see or what you hoped to see,” she said. “That doesn’t mean your research is a failure.”
She said she now sees many directions that the project could be taken, which is a success in and of itself.
“In the future, I think we could completely knock out the gene that produces AHL and see sphaeroides truly with AHL and truly without,” Miller said.