8 research outputs found
Spreading of liquid drops on Agar gels
We study the spreading of pure water drops or water drops
with surfactine (surfactant produced by bacteria Bacillus Subtilis) on gels
(Agar/Water gel). We find that, surprisingly, the drops do not
spread indefinitely, but remain in a state of partial wetting.
Eventually the liquid diffuses into the gel on a time scale short
with respect to evaporation times. The drops containing surfactant
show a complex dynamics: at first the spreading velocity decreases,
until the front stops and starts receding at about constant
velocity. Concurrently, a second front detaches from the rim of the
drop if the agar concentration is sufficiently low, and continues to
move outwards
Models of self-organizing bacterial communities and comparisons with experimental observations
Abstract. Bacillus subtilis swarms rapidly over the surface of a synthetic medium creating remarkable hyperbranched dendritic communities. Models to reproduce such effects have been proposed under the form of parabolic Partial Differential Equations representing the dynamics of the active cells (both motile and multiplying), the passive cells (non-motile and non-growing) and nutrient concentration. We test the numerical behavior of such models and compare them to relevant experimental data together with a critical analysis of the validity of the model based on recent observations of the swarming bacteria which show that nutrients are not limitating but distinct subpopulations growing at different rates are likely present