Bacillus subtilis spatial organization

Many microbial populations differentiate from free-living planktonic cells into surface-associated multicellular communities known as biofilms. Within a biofilm, motile Bacillus subtilis cells differentiate into non-motile chains of cells that form parallel bundles held together by an extracellular matrix.  These bundles eventually produce aerial structures that serve as preferential sites for sporulation. By analyzing strains harboring multiple cell-type specific promoter fusions we can visualize the spatial anatomy of at least three physiologically distinct cell populations within mature biofilms. Motile, matrix-producing, and sporulating cells localize to distinct regions within the biofilm and the localization and percentage of each cell type is dynamic.  Mutants unable to produce extracellular matrix form unstructured biofilms that are deficient in sporulation.  This suggests that in architecturally complex biofilms, spore formation is coupled to the production of extracellular matrix.  I am currently working to understand the molecular mechanisms underlying this regulation.