Spatial pattern formation with multi-scale ordering in living matter*

Emergence of regular spatial patterns is a hallmark in living matter ranging from subcellular organelles to developing embryos and to ecosystems. Mechanisms for the formation of ordered spatial patterns in biology often require chemical signaling that coordinates cellular behavior and differentiation. Here we discovered that dense bacterial living matter can spontaneously develop large-scale regular spatial patterns with multiscale order. Based on single-cell tracking data, numerical simulations invoking purely physical interactions reproduce the experimental phenomenon. Our findings highlight that simple physical mechanisms can lead to self-organized pattern formation in living systems and more generally, in other active matter systems near the boundary of fluidlike and solidlike behaviors.