Programming Microorganisms to Assemble Macroscopic Living Materials

Challenged by a changing climate, dwindling natural resources, and a growing global population, we need advanced, renewable materials that meld the sustainability of biological materials with the functionality of conventional materials. To help address this need, my research group creates sustainable and environmentally-responsive living materials by seamlessly integrating conventional materials with living systems. One major effort in our group is to engineer microorganisms to grow into multifunctional, hierarchically ordered macroscopic materials by introducing non-natural extracellular matrices.<br/>Living materials synthesized by organisms, such as bones and shells, exhibit remarkable mechanical properties due to their hierarchical assembly of hard and soft components across the nanometer to the micron scales. While engineering macroscopic analogs to these materials would open new frontiers, there is currently no bottom-up route to do so that enables control of the composition, hierarchical structure, and properties of living materials. In this talk, I will describe our approach to constructing such hierarchically ordered materials by programming bacteria. We report growth of macroscopic materials from freshwater bacteria that display and secrete an engineered self-interacting protein. This protein formed an extracellular de novo matrix and assembled cells into hierarchically-ordered, centimeter-scale materials. We showed that the mechanical, catalytic, and morphological properties of these materials can be tuned through genetic modification of the self-interacting protein. Our work identifies novel genetic tools, design and assembly rules for growing macroscopic materials with both wide-ranging mechanical properties and customizable functions. We anticipate the modularity of this approach will permit the incorporation of different protein polymers in the de novo matrix, thus allowing to generate materials with a variety of desired compositions, structures, and properties. We envision specific matrix properties that can be combined synergistically with existing cellular functions to greatly expand the opportunities for biological materials in human health, energy, and the environment.