Parameter-free and robust collective pattern formation of 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 recently found that a Bacillus subtilis bacterial biofilm organizes nitrogen stress response in a segmented pattern (Chou et al., Cell 2022). Mathematical modeling and genetic probing of the underlying circuit showed that this patterning is generated by a clock and wavefront mechanism, similar to that driving vertebrate somitogeneisis. Single cell tracking showed that individual bacteria oscillate in nitrogen stress response, creating segments as the biofilm expands. We showed that the clock and wavefront process spatially organizes distinct cell types in different segments of the biofilm. We now show that this patterning is parameter-free and robust against growth conditions. Biofilms grown in diverse conditions are capable of forming the concentric ring pattern, and the oscillation can be predicted in a parameter-free manner. 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.