A multiphase flow model of calcium induced morphology changes in true slime mold
- Date: 01/11/2007
Robert Guy (University of California at Davis)
University of British Columbia
The true slime mold Physarum polycephalum is a single cell organism
reaching up to meters in size. The cytoplasm shows periodic shuttle
streaming through a network of tubular structures attaining velocities
up to 1 mm/s. The motion is driven by the periodic contraction of an
actin-myosin gel that is regulated by a calcium oscillation.
When the organism is small (< 100 microns) no streaming is observed,
but as it gets larger regular rhythmic steaming suddenly emerges. We
present a mechanochemical multifluid model which is used to explore how
the sensitivity to changes in calcium concentration is related to the
stability of the sol/gel mixture. Stability of the homogeneous mixture
is explored analytically in one-dimension, and computational results
are presented for higher dimensions. The model demonstrates that as the
organism grows, a calcium-induced spatial instability occurs which may
be responsible for the initiation of streaming.
The overall goal of this work is to understand the interplay between
chemistry and fluid mechanics which is necessary to transmit chemical
signals and organize structures over very large distances. In addition
to streaming, some other problems related to spatial organization of
structure will be discussed.
MITACS Math Biology Seminar 2007