Quantitative Studies of Bacterial Chemotaxis: Relationship to Cell Growth Optimization and Metabolic Preferences

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Bacteria in natural habitats are continually changing environmental conditions. In order to maximize their growth and survival, they need to optimize the metabolic response to these varying conditions. Their primary behavioral responses are to modify their own metabolism and to change their location by migration. Migration is the quickest mode of response available to them. Chemotaxis, or the biased movement of cells in the direction of a chemical gradient favorable to their survival, is a phenomena found to be ubiquitous among a variety of motile bacteria. Basic scientific understanding of the biochemical mechanisms underlying chemotaxis has increased tremendously over the past two decades. However, the implications of chemotaxis for applications of biotechnological importance have largely been neglected. The PIs propose a set of combined experimental and theoretical studies intended to address two major questions relevant to microbial population behavior in biological and biotechnological applications. l.) How does the chemotactic response to nutrient attractants change as cell growth conditions are varied, and how is this related to optimization of cell growth in a non-mixed environment? 2.) What is the net cell movement response to multiple, perhaps conflicting, chemotactic stimuli, and how does this depend on cell metabolic preferences? The experimental work will include measurements of bacterial motility using two quantitative assays of the PIs' own design. The theoretical work will involve analysis of the effects of the experimentally observed chemotactic responses on population growth. Fundamental insights gained from these investigation may have implications on a number of important areas, such as microbial population dynamics in non-mixed systems, cell separations, biosensor and the monitoring of cell metabolic states. The PIs are considered to be extremely well qualified to carry out the proposed research and I recommend that this proposal be funded for three years in accordance with the adjusted revised budget submitted with this proposal.