Spiral waves in a bacterial population*

Spiral waves are discovered in various chemical, biological and physical systems, such as chemical excitable medium, cardiac tissue, and neural networks. The onset of spiral waves in living systems is often associated with essential living functions. For example, spiral waves of electrochemical activities in neural tissues may serve as a rhythmic organizer in cortex neurons, while those in cardiac tissues may cause ventricular arrhythmia. Here, we discovered a unique type of spiral waves in a bacterial population resulting from cell density variation. The waves are highly stable in space and time and are resilient to perturbations. Our findings provide new insight to the synchronization phenomena and pattern formation in living matter.