Growing Diverse Macroscopic Living Materials from Engineered Bacteria

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 engineering microorganisms to synthesize such materials.<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 centimeter 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 mechanical properties of living materials. In this talk, I will describe our approach to constructing such hierarchically ordered materials by programming bacteria. First, I will describe how macroscopic materials can be grown from bacteria engineered to display and secrete a self-interacting protein. This protein formed an extracellular protein matrix and assembled cells into hierarchically ordered, centimeter-scale materials. Next, I will report on how genetic modification of this self-interacting protein, specifically changing the length of its biopolymer segment, can tune the microstructural properties of these materials. While these modest changes in the biopolymer region have unexpectedly complex effects on the microstructure, the changes in microstructure impact the mechanical properties of the material much like other non-living composites. Lastly, I will present on how changing the growth media affects the macroscopic structure of these materials, forming rope-like structures that are both stretchy and strong. Altogether, these studies show a complex relationship between protein matrix sequence, the resulting structure, and properties while introducing new materials with high elasticity and strength. 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.