Exploring the processes of bacteria self-organization using mathematical modelling and experimental studies

Tuesday, June 15 at 04:15am (PDT)
Tuesday, June 15 at 12:15pm (BST)
Tuesday, June 15 08:15pm (KST)

SMB2021 SMB2021 Follow Monday (Tuesday) during the "MS06" time block.
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Diane Peurichard (Inria Paris, France), Marie Doumic (Inria Paris, France)


Bacteria are ubiquitous unicellular organisms, whose biomass exceeds that of all other living organisms, and on which our survival is dependent. From a single organism, they quickly develop into complex and organized micro-colonies and biofilm structures, as a result of an interplay between various chemical and biological signaling as well as mechanical interactions. Understanding the mechanisms at play in this self-organization is not only essential for biological applications with medical and environmental perspectives (bioremediation of contaminants in soil, antibiotic resistance, food fermentation, filtration, antimicrobial action, wastewater treatment etc), but it also brings complex and more general theoretical questions about self-organization of interacting particle systems. The goal of this minisymposium is to bring together experts from different backgrounds to offer a state of the art view on the mechanisms at play in interacting particle systems, with a special focus on bacteria self-organization into micro-colonies. Through lab experiments, data driven modelling, theoretical and numerical analysis of mathematical models, this mini-symposium will emphasize the importance of interdisciplinarity in the study of biological systems, and illustrate how the synergy between biology and mathematics can lead to a new understanding of real systems, while bringing new challenges in both fields and enriching them greatly. The micro-colonies formation will be studied at different levels (individual or collective scales, deterministic or stochastic phenomena, etc) using different techniques (continuum/agent-based models, microscopy images, image processing tools, etc) with a particular focus on spatial organization and mechanical aspects.

Nicolas Desprat

(Laboratoire de Physique de l’École normale supérieure, ENS, Université PSL, CNRS, Sorbonne Université, Université de Paris, 75005 Paris, France)
"Mutliscale morphogenesis of bacterial microcolonies"
Unicellular microorganisms are unicellular in the sense, that each individual is able to establish a new population. However, populations of microorganisms are not limited to a collection of individuals, but are highly organized so that the group can perform better than the sum of its individuals. In this presentation, we'll explore how the asymmetric distribution of adhesins on single rod-shaped bacteria shapes the organization of the group and how this affects higher level functions.

Sophie Hecht

(Inria Paris, France)
"On the modelling of the morphogenesis of rod-shaped bacteria micro-colony."
Bacteria are abundant organisms whose roles are included in many processes such as medicine, agriculture, ecology, industry... From a single organism, they quickly develop into organised micro-colonies and biofilm structures. The formation of these microcolonies, while broadly studied in the past decade, is still poorly understood. We consider an individual-based model where each bacterium is modelled by a spherocylinder and bacteria interact only through non-overlapping constraints. Introducing asymmetric friction and mass for the bacterium, which are taking into account the asymmetry of the pole of the bacteria, we retrieve mechanical behaviours of micro-colony growth, this without implementing attraction or adhesion. We compare our model to various sets of experiments, discuss our results, and propose several quantifiers to compare model to data in a systematic way.

Laura Kanzler

(Laboratoire Jacques-Louis Lions, Sorbonne Université, France)
"Kinetic Modelling of Myxobacteria"
Myxobacteria are rod-shaped, social bacteria that are able to move on flat surfaces by ’gliding’ and form a fascinating example of how simple cell-cell interaction rules can lead to emergent, collective behavior. Observed movement patterns of individual bacteria in such a colony include straight runs with approximately constant velocity, alignment interactions and velocity reversals. Experimental evidence shows that above mentioned behavior is a consequence of direct cell-contact interaction rather than diffusion of chemical signals, which indicates the suitability of kinetic modeling. In this talk a new kinetic model of Boltzmann-type for such colonies of myxobacteria will be introduced and investigated. For the spatially homogeneous case an existence and uniqueness result will be shown, as well as exponential decay to an equilibrium for the Maxwellian collision operator. The methods used for the analysis combine several tools from kinetic theory, entropy methods as well as optimal transport. The talk will be concluded with numerical simulations confirming the analytical results.

Marc Hoffmann

(INRIA, Mamba team & University Paris-Dauphine, France)
"Statistical estimation of the interaction kernel in McKean-Vlasov model in a mean-field limit"
We consider the problem of detecting or estimating the interaction in a large system of particles over a fixed time horizon. The particles are subject to a common external force and diffusion, and they interact via a smooth interaction kernel in a mean-field sense, and possibly via a common noise term. We identify some properties of the model that enables one to identify the presence of interactions, in a large population limit, from a statistical perspective.

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Virtual conference of the Society for Mathematical Biology, 2021.