Bacteria can exist in a motile planktonic state, or alternatively enter into a sessile multicellular lifestyle where they form organized communities called biofilms. I am interested in understanding the biophysical basis of how and why this transition occurs, resulting in bacteria being encased in a self-produced polymeric matrix.

The first step of this process often consists in the adhesion of individual bacteria to an immersed surface. We study this phenomenon experimentally in a controlled environment, by flowing a suspension of the biofilm-former Pseudomonas aeruginosa in a microfluidic device. The complexity of the adhesion process is highlighted by two surprising discoveries: the shear-induced adhesion and the upstream migration of the bacteria.

In a second part, I will discuss how the geometry of the channel strongly influences the subsequent development of a biofilm, sometimes leading to the formation of suspended 3D streamers that can in turn dramatically alter the flow.

I will conclude with recent results and future directions focused on the way mechanical constraints in general may influence the development of a biofilm.