Mathematicians solve a biology problem: How do yeast cells communicate?
By Andrea Gibson
Although yeast may call to mind rising bread and brewing beer, these microorganisms have played a much different role in the world of science and technology. Researchers first mapped the DNA of yeast before moving on to bigger life forms, and also have used it to understand issues in cell biology—such as the spread of cancer. Engineers rely on yeast to produce biofuels for energy.
The researchers who cultivate large populations of yeast in bioreactors have noticed an interesting phenomenon: The microorganisms start, stop, and change levels of their consumption of oxygen en masse.
“You have a huge tank of these cells doing this. How do they coordinate this activity? How do they know it’s time to process oxygen?” asks researcher Todd Young.
Young, a professor of mathematics at Ohio University, thought he could help seek an answer. He’s an expert in dynamical systems—in other words, he knows how to use math to describe how systems change over time.
Working with a team of Ohio University undergraduate and graduate math students, Young developed a mathematical model that suggested how these changes, or oscillations, in yeast activity occur. They theorized that negative feedback caused by chemicals produced in the process of growth and division prompts groups of cells to grow in sync, while inhibiting other groups.
Collaborator Erik Boczko, a biologist and mathematician at Vanderbilt University Medical Center, tested and confirmed the model in his lab. He looked for where the oscillations occurred in the yeast cell life cycle. He observed that during one phase, about half of the cells grew and divided, while the other cells were inhibited. Then, in the next phase, the first half were inhibited while the second half divided.
There could be an evolutionary benefit to the process, Young notes, as it could help the yeast cells regulate resources while they go through the important DNA transcription process that ensures proper growth and survival. (Young clarifies that the study did not conclude this, but it’s one possibility.)
The researchers were supported by a joint award from the National Institutes of Health and National Science Foundation, which funded the project for four years. They published their findings in the Journal of Theoretical Biology.
Understanding how the yeast move through these oscillations could help scientists who rely on the microorganisms for genetic research, Young explains. In addition, it could help engineers use yeast more efficiently.
This article appears in the Spring/Summer 2013 issue of Perspectives magazine, which covers Ohio University research, scholarship and creative activity of faculty, staff and students.