Abstract:  Bacterial biofilms are communities of polymer-encased cells that thrive in nearly every earthly environment. Within these communities, cells differentiate into heterogeneous states of physiology and gene expression, much like in multicellular organisms. It is an open question how the conditions within biofilms, such as nutrient levels and cell density, control the phenotypic states of cells and, in turn, how these diverse cells determine biofilm-level properties like 3D morphology. We ask this question in biofilms composed of diverse strains of Bacillus subtilis. Specifically, we investigate the formation of dormant spores within biofilms. We find that spore formation depends strongly on cell-to-cell communication via chemical signals. In strains with high cell density sensitivities, spores form rapidly, with the vast majority of cells being dormant spores. These biofilms continue to expand by segregating growing cells to the colony exterior. Despite being almost entirely dormant spores, these biofilms create intricate, wrinkled, 3D structures. We hypothesize that this morphology emerges through soft matter physics: before sporulation, cells secrete extracellular matrix polymers that turn biofilms into gels that wrinkle due to the competing effects of osmotic swelling and cross-linking. Our results demonstrate the fundamental interplay of gene regulation and emergent physics in controlling the growth and form of cellular communities.