Self-organization of bacteria in confined interstitial biofilms

Biofilms are communities of bacteria embedded in an extracellular matrix and are one of the dominant forms of bacterial life on earth. Recent studies have shown how bacteria grow from single cells to communities of many thousands of cells; however, this work has been limited to free-growing biofilms that are not confined by any external mechanical forces. Using Vibrio Cholerae as a model biofilm former, we examine the growth of biofilms confined at the interface of a glass and gel surface. At the macroscopic level, we find that the degree of mechanical confinement plays an important role in controlling the overall shape of the biofilm, and at the single-cell level, we find that increasing mechanical confinement drives long-range ordering consisting of bacteria radially aligned along the glass and gel surfaces. Finally, we use theoretical and computational tools to elucidate the fundamental physics driving the cellular ordering inside these biofilms.