UC Merced

Diversity among individual microbial responses to environments is essential for understanding their adaptive nature but challenging for experimental studies. These environments include porous media or structured surfaces that are widespread in ecological systems, public health, and industrial applications. However, a traditional laboratory setting that relies on static microscope observations can only provide a given spatial and temporal resolution, which cannot resolve simultaneously the detailed individual features as well as their responses to environments at much different spatial and temporal scales. My research focuses on enriching experimental studies of the mechanical effects of environments on bacterial transport by a multiscale platform and understanding the roles played by diversified characteristics of individual cells. By employing a digital 3D tracking microscope to follow individual microorganisms over exceedingly long durations, my studies enable a multiscale platform for such studies and achieve the long-term cellular behaviors at a single-cell resolution. Combining the above experimental platform with artificial microscale structures achieved through microfabrication, we explore the mutual geometric effects of both the environments and individual cells on bacterial transport in a controlled fashion. My finding illustrates that microstructures may induce non-trivial size-dependent transport for swimming bacteria. For instance, an array of micropillars tends to reduce the long-term transport of shorter cells while it promotes that of longer ones for a smooth-swimming Escherichia coli strain, which contradicts the common belief that longer individuals are more easily blocked by obstacles. I also found that such anomalous size-dependence in transport can be attributed to the geometric constraints associated with the pillar arrays, which prevent longer cells from being trapped by a single pillar. By introducing a wild type E. coli strain that is capable of self-reorientation, I extended this result to understand the transport of bacteria in a more natural scenario.