Tools for quantifying bacterial motility and chemotaxis after simulated microgravity using digital holographic microscopy

Motility enables organisms to navigate their environment, obtain nutrients and avoid predators. Characterizing motility in different environments can provide insight into an organism’s fitness and in the case of bacteria, changes in motility may result in increased pathogenicity to humans. The focus of this work was on how bacterial motility and chemotaxis may change in response to an environment like the international space station and the tools we could use to understand this. Digital holographic microscopy (DHM) is a useful tool for studying bacterial motility as it is label-free and hologram reconstruction provides 3D information. We studied the information provided by the DHM, comparing 2D vs. 3D tracking, and found that 3D tracking was especially useful to study motility by surfaces. Since the environment of interest, the international space station, presented unique challenges to study, we simulated this environment using high aspect ratio vessels (HARVs). We compiled literature information on how well the simulated environment seemed to mimic the environment of interest using growth and gene expression studies with a particular focus on motility and chemotaxis. With these tools in hand, we studied the motility and chemotaxis of Vibrio alginolyticus using digital holographic microscopy after simulated microgravity. While we found little to no difference in motility between normal and simulated microgravity, there was some indication of change in chemotactic behavior. Future work would compare these responses with the actual microgravity environment. 

Dr. Jackie Acres currently works as a Visiting Assistant Professor of Physics and Biophysics at Whitman College in Walla Walla, Washington. She earned her B.S. in Chemical Engineering from Colorado State University (2008), her M.S. in Biomedical Engineering from the University of Nevada, Las Vegas (2010) and a PhD in Applied Physics from Portland State University (2023). Her research interests include biomimicry and robotics, and artificial intelligence as applied to biophysics and biophysics education.  She has also been actively involved in the American Physical Society with both advocacy efforts and public engagement initiatives.