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Mathematical modeling helps to characterize internally triggered biofilm cell disprsal

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Title: Mathematical modeling helps to characterize internally triggered biofilm cell disprsal
Author: Emerenini, Blessing O.
Department: Department of Mathematics and Statistics
Program: Mathematics and Statistics
Advisor: Eberl, Hermann J.
Abstract: Cell dispersal (detachment) from mature biofilm is part of the developmental cycle of microbial biofilms. It can be externally or internally induced, leading to sloughing, erosion or seeding. We considered two potential triggers, which are studied independently in a two-dimensional setting. These triggers are quorum sensing and nutrient limitation. Quorum sensing is a cell-cell communication mechanism used to coordinate gene expression and behaviour in groups based on population densities; while the nutrient here is the growth limiting substrate. First, we develop a dynamic, spatially extended mathematical model that includes biofilm growth, production of quorum sensing molecules, cell dispersal triggered by quorum sensing, and re-attachment of cells. This is a highly nonlinear system of diffusion-reaction equations with nonlinear diffusion effect in the diffusion coefficient of the sessile biomass, which highly degenerates as the biomass hits maximum. We study the model in computer simulations. The results show that dispersal can be discrete or continuous leading to hollow colonies. Furthermore, we study the well-posedness of the quorum sensing induced biofilm dispersal model in order to establish the existence and uniqueness of bounded non-negative solutions of the degenerate system. By considering smooth non-degenerate auxiliary system we showed that the solution of the non-degenerate approximations converge to the solution of the degenerate problem. Finally, by using the same modeling approach we develop a mathematical model of nutrient limitation induced biofilm dispersal, having the same nonlinear effect in the diffusion coefficient of the sessile biomass. We study the model in computer simulations; and comment on the well-posedness of the model. Depending on parameter values, we observe a continuous, erosion-like biomass loss and hollow colonies resulting from the local nutrient limitation in the biofilm.
Date: 2015-09
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