Confinement-induced self-organization in growing bacterial colonies

When confined in a long channel, colonies of rod-shaped sessile bacteria are observed to form highly ordered structures, where the cells are aligned along the channel's longitudinal direction. By contrast, freely expanding colonies on an open surface, give rise to a "mosaic" of microdomains consisting of mutually aligned cells, but whose average orientation does not propagate over the length scale of the entire colony. In this talk, I will describe our recent theoretical and experimental efforts toward understanding the origin of these fascinating examples of self-organisation in growing active matter.