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Here are simulations from A Multiscale Model of Biofilm as a
Senescence-Structured Fluid. The model is one-dimensional in space
(depth) and uses a so-called structured variable to represent the
senescence of an individual cell (see E.J. Stewart
et al.), which is then used in functions that represent growth and
division rates and susceptibility to antimicrobial challenge.
(click on images for Quicktime animations)
Five different simulations are presented to show the qualitative
invariance of the results to reasonable changes in the senescence
function, which are, from top to bottom, a Monod form, an exponential
form, two linear forms, and a Hill form. Antimicrobial is introduced at time 35
days for 0.2 days. Further details are in
the manuscript.
The height of the colored region in each animation is the height of
the biofilm. The width of a given color is the volume fraction of
cells of the corresponding senescence, with black representing inert
cells.
The senescence structure of the population in
the stalk allows it to maintain itself even after the active layer at
the top is largely decimated.
Moreover, upon removal of the
antimicrobial agent, the population of older cells in the active
layer is quickly replaced by younger cells, which then return the
biofilm to its steady state over a longer maturation time. Note that
the height continues to drop after removal of the antimicrobial
agent prior to regrowth.
References:
Bruce P. Ayati and Isaac Klapper, A Multiscale Model of Biofilm as a Senescence-Structured Fluid, Multiscale Modeling & Simulation: A SIAM Interdisciplinary Journal, 6(2), 2007, pp. 347-365.
I. Klapper, P. Gilbert, B.P. Ayati, J. Dockery,
P.S. Stewart, Senescence Can Explain Microbial Persistence, Microbiology, 153(11), 2007, pp. 3623-3630.
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