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SUMMARY:Patterns of bacterial colonies - Martine Ben Amar (CNRS - Ecole No
rmale Superieure Paris)
DTSTART:20170922T080000Z
DTEND:20170922T084000Z
UID:TALK80631@talks.cam.ac.uk
CONTACT:INI IT
DESCRIPTION:In this talk I will present \; the genesis of patterns occ
urring in bacterial colonies: \; in biofilms and \; in fluid suspe
nsions. The first case concerns the growth of a simple drop containing bac
teria with moderate adhesion to a rigid substrate. The initial circular ge
ometry is lost during the growth expansion\, contour undulations and buckl
ing appear\, ultimately a rather regular periodic focusing of folds repart
ition emerges. Predictions of these morphological instabilities\, accordin
g simple rules\, \; will be presented as bifurcations of solutions in
nonlinear elasticity\, characterized by typical driving parameters. The su
bstrate plays a critical role limiting the geometry of the possible modes
of instabilities and anisotropic growth\, adhesion and toughness compete t
o eventually give rise to wrinkling\, buckling or both. \; In the seco
nd part\, I will present a continuous model for the self-organization of e
xpanding bacterial colonies under chemotaxis\, proliferation and eventuall
y active-reaction which either give cohesion or on the contrary dispersion
to the colony. Taking into account the diffusion and capture of morphogen
s complicates the model since it induces a bacterial density gradient coup
led to bacterial density fluctuations and dynamics. Nevertheless under som
e specific conditions\, it is possible to investigate the pattern formatio
n as a usual viscous fingering instability. This explains the similarity a
nd differences of patterns according to the physical bacterial suspension
properties and explain the factors which favor compactness or branching.&n
bsp\;
Joined work with Min Wu
LOCATION:Seminar Room 1\, Newton Institute
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