Biofilm Initiation via Extracellular Matrix Production Driven by Cell Orientation Patterning in Growing Escherichia coli Populations

Unicellular microorganisms can make a transition to multicellular states that enhance survival under environmental fluctuations. In bacteria, one of these states is the biofilm, defined by the production of an extracellular matrix. Although biofilm maturation and dispersion have been extensively studied, where and how initial matrix production is induced within a growing population remains largely unknown. Here we show that production of colanic acid, an important matrix component, is initiated around topological defects, where cell orientation mismatches and growth-induced pressure builds up, in bacterial monolayers. Using Escherichia coli reporting mechanically induced production of colanic acid in response to cell contact and deformation, we found matrix production accompanied by out-of-plane growth under agar-pad confinement. Controlling confinement geometry using microfluidic devices dictated the positions of topological defects and thereby localized regions of high matrix production. These findings reveal that the cell orientation patterning spatially organizes mechanical cues to induce matrix production for biofilm initiation of bacteria. ### Competing Interest Statement The authors have declared no competing interest.