Engineered living material based on protein-mediated bacterial assembly

Abstract

Living materials offer the prospect of autonomous, adaptive and self-healing properties. Inspired by the way natural biofilms assemble through intercellular adhesion and matrix secretion, we engineered the model bacterium Escherichia coli to display associative proteins on the cell surface. These engineered bacteria, when growing on polycarbonate membrane filters on agar media, form soft, cohesive living films with kPa stiffness. We show that the dynamic mech. properties of such films can be tuned by expressing proteins with different modes of assocn. and varying interaction strength. Two types of covalent protein interaction were explored: the irreversible SpyTag-SpyCatcher isopeptide bond and the reversible cysteine-cysteine disulfide bridge. After achieving the goal of forming cohesive living bacterial films, we further engineered the constituent bacteria to express enzymes and peptide domains that catalyze the formation and deposition of calcium phosphate, silica, and polyaniline. This approach provides a novel route to a wide range of functional living composite materials from protein-mediated bacterial assembly.