  We study a generic model for quorum-sensing bacteria in circular confinement.
Every bacterium produces signaling molecules, the local concentration of which
triggers a response when a certain threshold is reached. If this response
lowers the motility then an aggregation of bacteria occurs, which differs
fundamentally from standard motility-induced phase separation due to the
long-ranged nature of the concentration of signal molecules. We analyze this
phenomenon analytically and by numerical simulations employing two different
protocols leading to stationary cluster and ring morphologies, respectively.
