UC San Diego

Engineered living materials (ELMs) live at the intersection between biotic and abiotic materials exploring how living microorganisms can modulate the performance of its composite material. A variety of microorganisms have been utilized in ELMs, however, photosynthetic microorganisms such as cyanobacteria have garnered attention for their ability produce relevant chemicals using sunlight and carbon dioxide. This dissertation examines utilizing cyanobacteria of differing morphologies (i.e., unicellular and filamentous) in ELMs and explores their interactions and impact on non-living hydrogels over extended periods of time. We leverage the photosynthetic nature of cyanobacteria in ELMs to be applied in soft biohybrid robots, mechanically reinforced biomaterials, and light-driven biosynthesis. First, we demonstrate a novel temperature-dependent diffusion mechanism to introduce cyanobacterium Synechococcus elongatus sp. PCC 7942 into a stimuli-responsive hydrogel, nanoclay-poly-N-isopropylacrylamide (NC-PNIPAm), circumventing toxic precursors. In investigating this ELM over 28-days, we discovered and characterized a previously undescribed enzyme that is responsible for an irreversible change in the ELM’s bending curvature and Young’s modulus. Secondly, inspired by non-living fiber-reinforced hydrogels, we explore using filamentous cyanobacterium Nostoc commune as living fibers to mechanically reinforce ELMs. We additionally observe the growth and morphology of filamentous cyanobacteria encapsulated within hydrogels manufactured with two distinct fabrication techniques, molding and direct-ink-writing 3D printing. Lastly, we visualize the motility of phototactic cyanobacterium Leptolyngbya BL0902m when embedded within bulk alginate hydrogels and identify the material properties favorable for phototaxis through hydrogel matrices. We then utilize this information and the innate phototactic behavior of Leptolyngbya BL0902m to guide cells to specific regions of the ELM to biosynthesize conductive polymer poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS). Together, these studies highlight the possible applications of cyanobacteria-based engineered living materials.