Self-organized multicellular behaviors enable cells to adapt and tolerate stressors to a greater degree than isolated cells.However, whether and how cellular communities alter their collective behaviors adaptively upon exposure to stress is largely unclear.Here, we investigate this question using Bacillus subtilis, a model system for bacterial multicellularity.We discover that, upon exposure to a spatial gradient of kanamycin, swarming bacteria activate matrix genes and transit to biofilms.The initial stage Ball - Shoes Rubber - Junior of this transition is underpinned by a stress-induced multilayer formation, emerging from a biophysical mechanism reminiscent of motility-induced phase separation (MIPS).
The physical nature of the process suggests that stressors which suppress the expansion of swarms would induce biofilm formation.Indeed, a simple physical barrier also induces a swarm-to-biofilm transition.Based on the gained insight, we propose a strategy of antibiotic treatment to inhibit the transition from swarms to biofilms by FRENCH LENTILS targeting the localized phase transition.