As bio-sourced materials are raising interest for their sustainability, using the ability of bacteria to produce biofilms made of a protein and polysaccharide matrix has become a new strategy to make "engineered living materials" with various functionalities. Our group aims at contributing to this emerging field of research by clarifying how bacteria adapt biofilms to their environment, and at using this knowledge to engineer the materials properties of these microbial tissues.
For this, we culture E. coli producing curli amyloid and phosphoethanolamine-cellulose fibers, plate them on nutritive agar substrates with varying physico-chemical properties, and study the growth, morphology and mechanical properties of the resulting biofilms. For example, we demonstrated that changing the surface properties of the agar with cationic polyelectrolyte coatings limits biofilm spreading but increases their surface density via extended wrinkling in the third dimension [Ryzhkov et al, 2021]. Following similar strategies, we also showed that E. coli adapt their biofilm growth, morphology and mechanical properties to the water content of their substrate [Ziege et al, 2021]. Finally, we demonstrated that adding calcium and organic phosphate into the nutritive agar enables bacteria to mineralize the biofilm with hydroxyapatite crystals, thereby turning the soft tissue into an hybrid organic-inorganic material.
In collaboration with (bio)chemists, we also explore how post-processing biofilms can help tuning further their properties (e.g. by treatment with ionic solutions) and investigate the interactions between matrix components (e.g. curli, cellulose and water) at the molecular level to clarify their contribution to the ultimate materials properties.