Fig. 1. Formation of a living silica biocomposite material.

B. subtilis is designed to secrete a protein matrix from self-assembling EutM scaffold building blocks. Cells are engineered to display a SpyTag on clustered, polar flagella for covalent cross-linking via isopeptide bond formation with SpyCatcher domains fused to secreted scaffold building blocks. Scaffold building blocks are genetically fused with peptides to enhance silica polymerization on scaffolds. Finally, cells are engineered to retain spores as endospores. This allows cells to persist as structural components of the material and creates a durable biocomposite material that can be regenerated from a piece of silica material containing cells. (BM biomineralization peptide, SP, secretion signal peptide).