Microswimmers in complex environments – PushPull

Most microorganisms developed the ability to navigate in their environment in order to find their ecological niche and/or participate to symbiotic relations with other living species. In many instances, in biological fluids or in natural environments, the rheology of the surrounding fluids displays non-Newtonian rheology which affects drastically the emerging transport processes. The project’s objective is to study the exploration and the transport properties, in environments of complex rheology and of designed confining geometries, for two model biological micro-swimmers i.e. a flagellated bacterium and a ciliated alga. These microorganisms feature two different swimming hydrodynamics strategies, called “pusher” and “puller”. The understanding of the swimming properties and of the spatial exploration characteristics will be assessed, based on reliable quantitative hydrodynamic and statistical modeling. In a second step, we will try to define a common environment were bacteria and algae can coexist. We will then study the self-organization properties of the mixture, hence opening new sets of questions in statistical physics of active matter. Thereafter, these studies will be linked specifically to two important medical and environmental applications: (i) the intestinal mucus penetration and (ii) the ecological consequences of marine foams blooming. First, in collaboration with a medical team, we will study the penetration of intestinal mucus using in-vitro models of mucosal environments obtained either from purified mucin or from native porcine mucus extracts, altered by dilution of by chemical attack. Second, in conjunction with marine biologists, we will investigate the mechanisms leading to phytoplankton trapping in marine foams using laboratory experiments to control the foam characteristics and the phytoplankton species, thus opening new perspectives for quantitative modelling in order to understand the emergence of marine blooms.