Taking It Slow: Exploring the Effects of Stepwise Stressor Introduction to Bacterial Populations
Faculty Mentor Information
Dr. Chris Marx, University of Idaho
Presentation Date
7-15-2026
Abstract
In nature, microbes experience an array of stressors. They must grow in these stressful environments, or else face extinction. To respond to environmental shifts, microbes can modulate their gene expression profiles. However, microbes must mount a quick response before suffering irreparable damage from the stressor. In this context, we ask how microbial populations fare with different rates of environmental change. We use Methylobacterium extorquens, a bacterium commonly found on leaves, as our model organism, and study how different rates of formaldehyde exposure affect the ability of the population to mount a successful response. A methylotroph by nature, M. extorquens metabolizes methanol released by plants, with formaldehyde—a potent stressor—as an intermediate. To study how rates of environmental change affect population growth, we exposed growing Methylobacterium populations to the same concentration of formaldehyde at different rates. We discovered that slower rates of formaldehyde introduction correlated with increased survival and hypothesize that slower stressor exposure enables individuals to optimally regulate their gene expression before formaldehyde levels become lethal, allowing an increased fraction of the population to survive. We found that differentially expressed genes are primarily involved in the serine cycle. Moreover, we develop a mathematical model to explain the observed dynamics.
Taking It Slow: Exploring the Effects of Stepwise Stressor Introduction to Bacterial Populations
In nature, microbes experience an array of stressors. They must grow in these stressful environments, or else face extinction. To respond to environmental shifts, microbes can modulate their gene expression profiles. However, microbes must mount a quick response before suffering irreparable damage from the stressor. In this context, we ask how microbial populations fare with different rates of environmental change. We use Methylobacterium extorquens, a bacterium commonly found on leaves, as our model organism, and study how different rates of formaldehyde exposure affect the ability of the population to mount a successful response. A methylotroph by nature, M. extorquens metabolizes methanol released by plants, with formaldehyde—a potent stressor—as an intermediate. To study how rates of environmental change affect population growth, we exposed growing Methylobacterium populations to the same concentration of formaldehyde at different rates. We discovered that slower rates of formaldehyde introduction correlated with increased survival and hypothesize that slower stressor exposure enables individuals to optimally regulate their gene expression before formaldehyde levels become lethal, allowing an increased fraction of the population to survive. We found that differentially expressed genes are primarily involved in the serine cycle. Moreover, we develop a mathematical model to explain the observed dynamics.