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Abstract

Surface-attached bacterial biofilms are self-replicating active liquid
crystals and the dominant form of bacterial life on Earth(1-4). In
conventional liquid crystals and solid-state materials, the interaction
potentials between the molecules that comprise the system determine the
material properties. However, for growth-active biofilms it is unclear
whether potential-based descriptions can account for the experimentally
observed morphologies, and which potentials would be relevant. Here, we
have overcome previous limitations of single-cell imaging
techniques(5,6) to reconstruct and track all individual cells inside
growing three-dimensional biofilms with up to 10,000 individuals. Based
on these data, we identify, constrain and provide a microscopic basis
for an effective cell-cell interaction potential, which captures and
predicts the growth dynamics, emergent architecture and local
liquid-crystalline order of Vibrio cholerae biofilms. Furthermore, we
show how external fluid flows control the microscopic structure and
three-dimensional morphology of biofilms. Our analysis implies that
local cellular order and global biofilm architecture in these active
bacterial communities can arise from mechanical cell-cell interactions,
which cells can modulate by regulating the production of particular
matrix components. These results establish an experimentally validated
foundation for improved continuum theories of active matter and thereby
contribute to solving the important problem of controlling biofilm
growth.