One ring to rule them all: tuning bacteria collective motion via geometric confinement

Suspensions of swimming bacteria are known to self-organize into turbulent-like flows for sufficiently high density and nutrients concentration. This spectacular example of collective behavior, on which the survival of the colony itself is believed to rely, appears however impossible to control. In a recent experimental and computational study, Wioland et al (2016 New J. Phys. 18 075002) have demonstrated that the collective motion of B. subtilis can be in fact selectively tuned by confining the system into a ring-shaped channel.