(193g) Transport Phenomena of Chemotactic Bacteria: Diffusion and Dispersion in Porous Media

Chemotaxis describes the ability of motile bacteria to sense chemical gradients in their surroundings and swim toward higher concentrations of chemicals that are beneficial to their survival. The chemotactic response in Escherichia coli bacteria is a well-characterized signal transduction mechanism that controls the run-and-tumble swimming behavior of individual cells. The motivation behind our experimental work has been to build on this fundamental knowledge of the underlying mechanisms to develop predictive models for bacterial migration in complex natural systems. Our focus has been on migration of chemotactic bacteria in porous media with application to bioremediation of polluted groundwater systems where chemical and structural heterogeneity influence their transport phenomena. I will present a series of experimental approaches that range from imaging chemotactic bands in microfluidic devices to monitoring dispersion within bench-scale microcosms to tracking the migration of bacteria introduced into a natural groundwater aquifer. Apparent diffusion and dispersion coefficients determined from the experimental observations are used in mathematical models to predict macroscopic-scale transport of bacterial populations. A dimensionless chemotaxis number is proposed to ascertain a priori the conditions under which a chemotactic response will impact bacterial transport relative to other processes such as advection and dispersion.