Self-organized patchiness facilitates survival in a cooperatively growing Bacillus subtilis population.

Abstract

Ecosystems are highly structured. Organisms are not randomly distributed but can be found in spatial aggregates at many scales, leading to spatial heterogeneity or even regular patterns(1). The widespread occurrence of these aggregates in many different ecosystems suggests that generic factors intrinsic to the populations-such as interactions between the organisms-play a major role in their emergence(1,2). Beyond the emergence of spatial patchiness, its functional consequences remain unclear. Here we show in Bacillus subtilis that cooperative interactions in a spatial environment are sufficient to form self-organized patches. These patches allow for survival even when the microbe density is too low to sustain growth in a well-mixed environment. Decreasing cell mobility leads to more compact patches that enhance this survival advantage but also reduce the overall growth. Our results highlight that even populations lacking specific group-forming mechanisms can nonetheless form spatial patterns that allow for group survival in challenging environments.