Multispecies phase diagram reveals biophysical principles of bacterial biofilm architectures

Abstract

Bacterial biofilms are among the most abundant multicellular communities on Earth and play essential roles in a wide range of ecological, medical, and industrial processes. Recently developed imaging techniques offer unprecedented insights into the three-dimensional internal structure and external morphology of growing biofilms, but general ordering principles that govern the emergence of biofilm architecture across species remain unknown. Here, we combine experiments, simulations, and topological analysis to identify universal mechanical interaction properties that determine early-stage biofilm architectures of different bacterial species. Performing single-cell resolution imaging of Vibrio cholerae, Escherichia coli, Salmonella enterica, and Pseudomonas aeruginosa biofilms, we dis-covered that biofilm architectures up to a few thousand cells can be described by a two-dimensional phase diagram similar to nematic liquid crystals. Mechanistic simulations and experiments using single-species mutants for which the cell aspect ratio and the cell-cell adhesion are systematically varied, show that tuning these parameters reproduces biofilm architectures of different species. A topological analysis of biofilm architectures across species further reveals that cell neighborhood motifs can be described by a universal Tracy-Widom distribution. More generally, due to its generic mathematical formulation, the topological analysis framework enables a structural comparisons and classification of a wide range of multicellular life forms. Early-stage biofilm architectures of different species therefore display a universal topological structure, and their development is determined by conserved mechanical cell-cell interactions.