Bacillus subtilis biofilm expansion mediated by the interaction between matrix-producing cells formed “Van Gogh bundles” and other phenotypic cells

Abstract

During the expansion of Bacillus subtilis biofilm on a solid MSgg substrate, cells within the biofilm form highly organized structures through interactions, growth and differentiation. This organized structure evolves from an initial single chain to bundles known as “Van Gogh bundles,” which guild the biofilm' expansion. In this paper, we present a model for biofilm growth based on cell interaction forces. In this model, cell interactions within Van Gogh bundles are represented by spring connections, and the interactions between Van Gogh bundles and other phenotypic cells are confined to a specific region (repulsive inside the region, attractive outside it). In a single-biofilm system, as nutrients are depleted, increasing numbers of motile cells transform into matrix-producing cells, forming Van Gogh bundles that guide the biofilm expansion towards areas with higher nutrient concentrations, thereby enhancing its expansion ability. In a muti-biofilm system, extreme nutrient depletion leads to the transformation of matrix-producing cells into spores, which affects the number and folding characteristics of Van Gogh bundles, thereby influencing the biofilm expansion. Our study illustrates how the simple organization of cells within a community can provide a significant ecological advantage.