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Transport Phenomena of Chemotactic Bacteria

Speaker: Roseanne M. Ford, University of Virginia
Series: CBE Departmental Seminars
Location: Elgin Room (E-Quad A224)
Date/Time: Wednesday, September 13, 2017, 4:00 p.m. - 5:00 p.m.

Chemotactic bacteria sense and respond to temporal and spatial gradients of chemical cues in their surroundings by swimming toward (away from) higher concentrations of chemicals that are beneficial (detrimental) to their survival. This phenomenon plays a critical role in many microbial processes such as groundwater bioremediation, microbial-enhanced oil recovery, nitrogen fixation in legumes, and pathogenesis of disease. Chemical heterogeneity in these natural systems often produces numerous competing signals from various directions. Predicting the migration behavior of bacterial populations under such conditions is necessary for designing effective treatment strategies.

Over the years we have employed experimental and modeling approaches that encompass a wide range of length and time scales 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. In this presentation I will focus on a molecular-level modeling approach that incorporates several key steps in the signal transduction pathway in order to represent the mechanism by which bacteria process multiple signal inputs to generate an integrated response (i.e. make a decision). The model was applied to predict the response of Escherichia coli bacteria to a mixture of a chemoattractant (?-methylaspartate) and a chemorepellent (nickel ion).