A clock and wavefront mechanism organizes cell types in a bacterial biofilm

Multicellular organisms organize cell types in a segmented manner during development. In contrast, communities of unicellular organisms are not thought to be able to organize in such a sophisticated way. We find that a Bacillus subtilis bacterial biofilm organizes nitrogen stress response in a segmented pattern. Mathematical modeling and genetic probing of the underlying circuit show that this patterning is generated by a clock and wavefront mechanism, similar to that driving vertebrate somitogenesis. Single cell tracking show that individual bacteria oscillate in nitrogen stress response, creating segments as the biofilm expands. We show that the clock and wavefront process spatially organizes distinct cell types in different segments of the biofilm. Together, these findings reveal that a clock and wavefront mechanism organizes differentiated bacterial cell types in space and time, thereby challenging the paradigm that such patterning mechanisms are exclusive to plant and animal development.