Presenter(s): Maria Dresser − Physics, Mathematics
Faculty Mentor(s): Tristan Ursell, Daniel Shoup
Poster 13
Research Area: Biophysics
Funding: Presidential Undergraduate Research Scholars (PURS) recipient
Communities of bacteria respond to environmental changes as a group with the combined behaviors of individual bacteria giving rise to unique collective behaviors that facilitate the growth and dispersal of bacteria. In particular, bacteria undergo a process called chemotaxis which utilizes a run and tumble method to move towards higher concentrations within a given chemical gradient. In liquid environments, collective consumption and chemotaxis towards nutrients results in a collective behavior known as an expansion wave which facilitates rapid range expansion. How environmental properties dictate the attributes of expansion waves is poorly understood yet critically important as expansion waves drive invasiveness, colonization, and may help bacteria define their interspecies boundaries in complex communities. Here we study the expansion of E. Coli in capillary tubes to replicate a one dimensional expansion environment. The use of various concentrations of galactose and three amino acids give rise to different expression profiles and observable behaviors. After inoculating cells into capillary tubes containing different nutrient media, we image the tubes using bright field microscopy and measure the wave speed and number of waves in each tube. Wave speed allows us to understand how quickly bacteria enter a new region and how this is affected by nutrient concentration. Because different waves may exhibit different phenotypic states such as consuming different nutrients and undergoing cell division at different rates, we are interested in understanding what nutrient concentrations give rise to multiple waves. We hypothesize that slower waves are undergoing cell division more rapidly, thus devoting more energy to division than to consumption. Results thus far show that expansion rate is constant until a threshold is met, and lower initial cell concentrations give rise to more waves.