Bacillus velezensis Pulse Versus Press Stress and How It Affects Future Growth
Faculty Mentor Information
Dr. Leonora Bittleston, Boise State University; and Jaycee Fahrner, Boise State University
Presentation Date
7-16-2026
Abstract
Every creature undergoes evolution. Over time, organisms with more successful traits will go on to reproduce, and eventually one trait will dominate the population. For larger organisms like humans, these changes happen rather slowly, over thousands of years. For smaller creatures like bacteria, these changes happen very rapidly due to their high rate of reproduction. The environment that organisms live in shapes their short-term expression and long-term evolution. Environmental conditions that impact microorganisms include temperature, resource availability, and solute concentration, among others. In Bacillus velezensis, a common plant-associated microbe, changes in these conditions create a stressful environment that can change multiple phenotypes such as growth rate and lag time. To test how different types, frequencies and intensities of stress affect these bacteria, we are using either press or pulse regimes across a range of environmentally relevant stress conditions. During our press trials, B. velezensis is grown in the stress condition for the entire incubation period. For our pulse trials, B. velezensis is subjected to acute stress conditions for 60 minutes then transferred to ambient conditions. After stress application, bacterial growth characteristics including lag time, total growth, and maximum growth rate are measured using optical density. During our press trials, we saw that there were changes in the shape of the curve as well as lag time and growth rate. During our pulse trials, we saw that there were only changes in lag time, as there wasn’t enough time to induce phenotypic variation. Observing the stress-induced changes of these bacteria will allow us to determine how past stress history affects response to future stress, and which conditions best prepare these bacteria for a myriad of future stressors.
Bacillus velezensis Pulse Versus Press Stress and How It Affects Future Growth
Every creature undergoes evolution. Over time, organisms with more successful traits will go on to reproduce, and eventually one trait will dominate the population. For larger organisms like humans, these changes happen rather slowly, over thousands of years. For smaller creatures like bacteria, these changes happen very rapidly due to their high rate of reproduction. The environment that organisms live in shapes their short-term expression and long-term evolution. Environmental conditions that impact microorganisms include temperature, resource availability, and solute concentration, among others. In Bacillus velezensis, a common plant-associated microbe, changes in these conditions create a stressful environment that can change multiple phenotypes such as growth rate and lag time. To test how different types, frequencies and intensities of stress affect these bacteria, we are using either press or pulse regimes across a range of environmentally relevant stress conditions. During our press trials, B. velezensis is grown in the stress condition for the entire incubation period. For our pulse trials, B. velezensis is subjected to acute stress conditions for 60 minutes then transferred to ambient conditions. After stress application, bacterial growth characteristics including lag time, total growth, and maximum growth rate are measured using optical density. During our press trials, we saw that there were changes in the shape of the curve as well as lag time and growth rate. During our pulse trials, we saw that there were only changes in lag time, as there wasn’t enough time to induce phenotypic variation. Observing the stress-induced changes of these bacteria will allow us to determine how past stress history affects response to future stress, and which conditions best prepare these bacteria for a myriad of future stressors.