Affiliations: Department of Computer Science and Engineering,
Chalmers University of Technology, SE-412 96 Göteborg, Sweden | Department of Cell and Molecular Biology/Microbiology,
Göteborg University, SE-405 30 Göteborg, Sweden
Abstract: We present a simple ordinary differential equation (ODE) model of
the adaptive response to an osmotic shock in the yeast Saccharomyces
cerevisiae. The model consists of two main components. First, a biophysical
model describing how the cell volume and the turgor pressure are affected by
varying extra-cellular osmolarity. The second component describes how the cell
controls the biophysical system in order to keep turgor pressure, or
equivalently volume, constant. This is done by adjusting the glycerol
production and the glycerol outflow from the cell. The complete model consists
of 4 ODEs, 3 algebraic equations and 10 parameters. The parameters are
constrained from various literature sources and estimated from new and
previously published absolute time series data on intra-cellular and total
glycerol. The qualitative behaviour of the model has been successfully tested
on data from other genetically modified strains as well as data for different
input signals. Compared to a previous detailed model of osmoregulation, the
main strength of our model is its lower complexity, contributing to a better
understanding of osmoregulation by focusing on relationships which are obscured
in the more detailed model. Besides, the low complexity makes it possible to
obtain more reliable parameter estimates.
