Shaping Slime—How to Guide Bacterial Biofilm Architecture via Substrate Properties

As bio-sourced materials are raising interest for their sustainability, using bacteria to produce biofilms made of a protein and polysaccharide matrix has become a new strategy to make engineered living materials. Our group contributes to this emerging field by clarifying how bacteria adapt biofilm materials properties to their environment. For this, we culture <i>E. coli</i> producing curli amyloid and phosphoethanolamine-cellulose fibers on nutritive agar substrates. The resulting microbial tissue forms a film that expands at the surface of the agar and acquires a complex morphology through wrinkling and folding. We first demonstrated that varying physico-chemical properties of the agar substrates with polyelectrolyte coatings or by changing their water content, affects <i>E. coli</i> biofilm growth kinetics, wrinkling patterns and mechanical properties. We also explored how tuning the chemical environment of the bacteria can lead to biofilm biomineralization and expand the range of materials properties reachable with biofilm-based materials. We are now adapting fabrication methods to shape hydrogels and combining them with live and static microscopy techniques to explore if and how geometrical features of the agar substrates influence biofilm growth, morphology and matrix fiber orientation. Producing microbial tissues with various properties in an anisotropic and controlled manner could greatly enlarge the possibilities offered by synthetic biology to engineer living materials with broad functionalities.