Physical determinants of bacterial biofilm architecture development*

Bacterial biofilms are considered to be one of the most abundant forms of microbial life on earth. Their shape and architecture strongly depends on the environmental conditions in which they are grown as well as the specific properties of the species and strain used. In this study we set out to determine which distinct properties of a bacterial species or strains account for the differences between the structure of biofilm microcolonies. In order to achieve this, we introduce a metric to distinguish biofilms based on architectural measurements at single cell resolution. We use this metric to perform quantitative analysis of biofilms grown from the four different bacterial species E. coli, S. enterica, V. cholerae, and P. aeruginosa, revealing that multicellular structural parameters as well as the cell shape are highly correlated with the differences in architecture between these biofilms. Further experiments based on mutants of V. cholerae that exhibit key differences in biofilm architecture confirm our initial findings and can be matched by simulations based on physical interactions between cells.