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Universität Münster, Germany
Wed 22 May 2019, 3:15pm
Mathematical Biology Seminar
ESB 4127
Long-wave modelling of spreading biofilms
ESB 4127
Wed 22 May 2019, 3:15pm-4:15pm

Abstract

First, we review recent experiments on and biophysical modelling approaches for the early stages of osmotically spreading biofilms at an agar-air interface (e.g. [1,2]). Doing so, we highlight important experimental features and successes/limitations of the various models. In particular, it is pointed out that modelling has paid little attention to the physico-chemical interactions of the film and the agar (adhesion, wettability, etc) [3]. We propose to incorporate these surface forces in the form of a wetting potential that accounts for finite contact angles  at the three-phase contact line where biofilm, agar and gas phase meet.

Second, we establish the basic modelling principles of thin-film hydrodynamics for the dynamics of free surface films of mixtures and suspensions where all aspects of capillarity and wettability may, in principle, depend on the local film composition. We argue that in a passive (non-bioactive) limit one has to be able to write all such models in the form of a gradient dynamics.  The passive model is then extended by bioactive terms like bacterial proliferation and matrix or biosurfactant production to reach a set of simplified models for the growth dynamics of biofilms [4].

Finally, we employ such models to investigate two phenomena: (i) It is shown that surface forces determine whether a biofilm can expand laterally over a substrate. In particular, we discuss modelling results and experimental evidence related to a transition between continuous and arrested spreading for Bacillus subtilis biofilms [5]. In the case of arrested spreading, the lateral expansion of the biofilm is confined, albeit the colony is biologically active. However, a small reduction in the surface tension of the biofilm is sufficient to induce spreading. (ii) As second phenomenon we discuss the relation of fingering instabilities of an advancing biofilm edge and the production of biosurfactant within the biofilm. As a result we distinguish four dynamical (morphological) modes of biofilm growth [6]. We conclude with an outlook.

[1] Fauvart, M. et al., Surface tension gradient control of bacterial swarming in colonies of Pseudomonas aeruginosa, Soft Matter, 2012, 8, 70-76.
[2] Seminara, A. et al., Osmotic spreading of Bacillus subtilis biofilms driven by an extracellular matrix, Proc. Natl. Acad. Sci. U. S. A., 2012, 109, 1116-1121.
[3] Tuson, H., Weibel, D. Bacteria-surface interactions, Soft Matter, 2013, 9, 4368-4380.
[4] Trinschek, S.; John, K.; Thiele, U., From a thin film model for passive suspensions towards the description of osmotic biofilm spreading, AIMS Materials Science, 2016, 3, 1138-1159.
[5] Trinschek, S.; John, K.; Lecuyer, S.; Thiele, U., Continuous vs. arrested spreading of biofilms at solid-gas interfaces - the role of surface forces, Phys. Rev. Lett., 2017, 119, 078003.
[6] Trinschek, S.; John, K.; Thiele, U.; Modelling of surfactant-driven front instabilities in spreading bacterial colonies Soft Matter, 2018, 14, 4464-4476.
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Mon 27 May 2019, 11:15am SPECIAL
MATH 125
Mathematics Grad Reception
MATH 125
Mon 27 May 2019, 11:15am-12:45pm

Details

The light refreshments will be followed by the awards presentation.
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EHESS, France
Mon 27 May 2019, 1:00pm SPECIAL
MATX 1100
Niven Lecture: Of Predators and Prey
MATX 1100
Mon 27 May 2019, 1:00pm-2:00pm

Details

Abstract: The speaker will give an introduction to predator prey math modeling and then bridge it with recent research on animal territory.

About the Niven Lectures: Ivan Niven was a famous number theorist and expositor; his textbooks won numerous awards, have been translated into many languages and are widely used to this day.  Niven was born in Vancouver in 1915, earned his Bachelor's and Master's degrees at UBC in 1934 and 1936 and his Ph.D. at the University of Chicago in 1938.  He was a faculty member at the University of Oregon from 1947 until his retirement in 1982.  The annual Niven Lecture Series, held at UBC since 2005, is funded in part through a generous bequest from Ivan and Betty Niven to the UBC Mathematics Department.

Note for Attendees

The Mathematics Grad Reception will be held in the MATH 125/126 Lounge prior to the Niven Lecture.
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McGill University
Wed 29 May 2019, 2:45pm
Mathematical Biology Seminar
ESB 4127
Understanding cellular polarity and adhesion dynamics involved in cell motility using spatiotemporal models
ESB 4127
Wed 29 May 2019, 2:45pm-3:45pm

Abstract

Cellular movement plays important roles in many (patho)physiological processes, such as immune cell response, growth of neuronal axons and cancer. The regulation of this movement depends on the interaction of several key proteins implicated in the development of cellular polarity (consisting of a front and a back) and the formation of protein complexes called adhesions. Adhesions anchor the cell to its substrate, allowing it to migrate. In CHO cells, three classes of adhesion can be identified based on size and dynamic properties: nascent adhesions, focal complexes and focal adhesions. When cells extends forward at the front, nascent adhesions assemble and anchor the leading edge to the substrate, while focal adhesions at the back disassemble, allowing detachment, retraction and forward movement. The dynamics of these processes are controlled by a number of regulatory factors, occurring on both cell-wide and adhesion-level scales. The coordination of these regulatory factors is complex, but insights into their dynamics can be gained from the use of mathematical/biophysical modeling techniques which integrate many of these components together. In this talk, I will present our recently developed molecularly-explicit and mechanosensitive models of cell polarity and adhesion dynamics to explore how local regulation of key adhesion proteins (including paxillin, rho family of GTPases and integrin) produce cell-wide polarization and nascent adhesion assembly/disassembly. The dynamics associated with various parameter regimes will be presented and insights into the mechanisms regulating adhesion dynamics will be provided.
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Marc Stephan
Wed 5 Jun 2019, 3:00pm
Topology and related seminars
ESB 4133
TBA
ESB 4133
Wed 5 Jun 2019, 3:00pm-4:00pm

Abstract

 
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Zhejiang University
Thu 5 Sep 2019, 3:30pm
Diff. Geom, Math. Phys., PDE Seminar
TBA
TBA
TBA
Thu 5 Sep 2019, 3:30pm-4:30pm

Abstract

 
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University of Washington
Tue 17 Sep 2019, 4:00pm
Discrete Math Seminar
ESB 4127
TBA
ESB 4127
Tue 17 Sep 2019, 4:00pm-5:00pm

Abstract


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U. Bath
Wed 18 Sep 2019, 3:00pm
Probability Seminar
TBA
Wed 18 Sep 2019, 3:00pm-4:00pm

Abstract

 
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U. Bath
Fri 20 Sep 2019, 3:00pm
Department Colloquium
ESB 2012
Rising Stars Colloquium - TBA
ESB 2012
Fri 20 Sep 2019, 3:00pm-4:00pm

Abstract

 

Note for Attendees

Refreshments will be served at 2:30 p.m. in ESB 4133 (Lounge).
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Cornell University
Wed 16 Oct 2019, 4:00pm
Probability Seminar
TBA
Wed 16 Oct 2019, 4:00pm-5:00pm

Abstract

 
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Cornell University
Fri 18 Oct 2019, 3:00pm
Department Colloquium
ESB 2012
(PIMS/UBC distinguished colloquium) TBA
ESB 2012
Fri 18 Oct 2019, 3:00pm-4:00pm

Abstract

 

Note for Attendees

Refreshments will be served at 2:30 p.m. in ESB 4133 (Lounge).
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Fri 15 Nov 2019, 3:00pm
Department Colloquium
ESB 2012
(reserved for PIMS UBC Mathematical Sciences Young Faculty Award)
ESB 2012
Fri 15 Nov 2019, 3:00pm-4:00pm

Abstract

A link to be provided later.
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