(385j) Chemotactic Migration of Bacteria in Porous Media
AIChE Annual Meeting
Tuesday, November 17, 2020 - 10:00am to 10:15am
The chemotactic migration of bacteriaâtheir ability to direct collective motion along chemical gradientsâis central to processes ranging from sustaining plant growth, remediating contaminants, sensing and reporting stimuli, and mitigating or causing infection. However, while migration is well-studied in bulk liquid, most bacterial habitatsâsoils, sediments, and biological gelsâare tight and tortuous porous media. Unfortunately, how confinement in a porous medium alters the ability of bacteria to move remains poorly understood: typical media are opaque and have ill-defined pore structures, making systematic studies challenging. Thus, current understanding of migration is based on studies performed in bulk liquid. Here, using confocal microscopy inside three-dimensional (3D) porous media, we elucidate how pore-scale confinement fundamentally alters the chemotactic migration of bacteria. We find that confinement forces the cells to use a completely different mechanism to direct their motion than in bulk liquid: they bias the total extent by which they reorient their bodies, instead of biasing the reorientation frequencyâsuggesting a revision to the current paradigm of E. coli chemotaxis. Further, we demonstrate that the spatiotemporal dynamics of chemotactic migration can be quantitatively described using a continuum modelâbut only when conventionally-used motility parameters are altered substantially from their bulk liquid values in a pore-size dependent manner. Our work thus provides a framework to predict and control the migration of bacteria, and active matter in general, in heterogeneous environments.