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Home | Seminars and Symposia | Past seminars/symposia: Wednesday, April 17, 2002

DTC Seminar Series

Mathematical and Computational Challenges Posed by Models of Biological Systems


Hans Othmer

Wednesday, April 17, 2002
1:00 pm

402 Walter Library

Slide presentation (pdf 3.9 MB) Chemotaxis in the bacterium E. coli is widely-studied because of its accessibility and because it incorporates processes that are important in the response of numerous sensory systems to stimuli: signal detection and transduction, excitation, adaptation, and a change in behavior. Quantitative data on the change in behavior is available for this system, and the major biochemical steps in the signal transduction/processing pathway have been identified. In this talk Professor Othmer will discuss a mathematical model of single cells that can reproduce many of the major features of signal transduction, adaptation and aggregation, and which incorporates the interaction of the chemotactic protein CheYp with the flagellar motor. He will show the results of Monte Carlo simulations of population behavior and discuss the problem of how to obtain macroscopic equations that incorporate essential features of the microscopic model.


Professor Hans Othmer received his Ph.D. in Chemical Engineering and has held faculty positions in Mathematics at Rutgers University, the University of Utah and the University of Minnesota. His major research interests include mathematical modeling of biological problems in physiology and developmental biology. These include signal transduction and behavioral response in cellular systems, gene control networks, and continuum and cell-based models of pattern formation and cell movement in early development. Major research interests (1) Mathematical modeling of signal transduction and behavioral response in cellular systems, including the bacterium E. coli and the cellular slime mold Dictyostelium discoideum. For instance, we have developed a model for signal transduction and adaptation in E. coli and we are currently incorporating this into a new model for interaction of the regulatory protein with the flagellar switch. Our goal is to determine whether the experimental observations on switching behavior can be reproduced and whether the combined model for signal transduction and motor control produces the observed gains under various stimulus protocols. If successful, this will be the first model that incorporates both signal transduction and motor control, and it will allow us to study the entire behavioral response following a change in the stimulus, and to simulate bacterial swarming using a cell-based model. This in turn will provide insight into pattern formation in bacterial colonies. (2) We study continuum and cell-based models of early development, with the aim of understanding how pattern formation and cell movement interact in formation of the skeletal elements and nervous system in vertebrates. One aspect deals with limb development, and here we are developing a 3D computational model of a growing limb that can be used to study the effects of known mutants, surgical interventions, and gene mis-expression. Another model system for which mathematical models are being developed is the cellular slime mold Dictyostelium discoideum. We have developed both cell-based and continuum models for collective movement, and simple gene control networks for cell differentiation, in order to determine whether a model can reproduce the patterns of cell differentiation observed in later development. The cell-based model has also been used to study cell sorting and the effect of adhesive interactions on the motion of an aggregate of cells under chemotactic stimuli.