Collaborative Research: Creating Synthetic Lichen to Elucidate how Morphology Impacts Mutualistic Exchanges in Microbial Communities.

Michigan State University, East Lansing MI

Investigators

Abstract

Complex communities of microbes colonize most surfaces on the planet including rocks, leaves, and our organs. Their activities and interactions on these surfaces have major impacts on human, plant, animal, and ecosystem health. However, the impact of the 3D structure of these microbial communities on their capacity to exchange resources remains poorly understood. This has limited the capacity both to predict the growth rate and resilience of natural microbes in changing environments, as well as to engineer synthetic microbiomes for industrial applications. This work uses synthetic biology to engineer industrial microbes to recapitulate aspects of lichen symbiosis, where structure plays a central role in microbial exchange. This approach facilitates generating novel insights into the contribution of morphology to symbiosis and powerful new tools for engineering the growth and communication between microbes. The synthetic lichen created through this work is a powerful new platform to study symbiosis, as well as a novel photosynthetic biomanufacturing platform. Additionally, this project uses synthetic lichen as both a tool and a metaphor to create art that can communicate the ideas underpinning this work to undergraduate students and the broader public. In this project a synthetic lichen is created from free living cyanobacteria as photobiont and filamentous fungi as mycobiont, to explore how the physical coupling created by morphology impacts the physiological outcomes of metabolic exchanges. The morphological patterning of the fungi is implemented using a previously validated synthetic cell-cell signaling system consisting of an Indole 3-Acetic Acid (auxin) biosynthesis pathway and a library of auxin-inducible Cas9-based transcription factors (HACRs) with a range of sensitivities. The cyanobacteria is engineered to generate auxin-based patterning cues and HACRs are used to connect these signals to the expression of genes regulating morphology in the fungus, to generate a lichen-like morphology. In parallel, morphological features of the cyanobacterium are modulated by utilizing either a filamentous or single-celled strain, or established pathways for converting rod-shaped unicellular cyanobacteria into elongated filaments of varying lengths. These microbes are also engineered to perform altruistic metabolic behaviors, namely the secretion of sucrose and extracellular polysaccharide by the photobiont and mycobiont respectively, resulting in symbioses that mimic the relationship observed in lichens. This project elucidates how the different degrees of physical coupling that morphology generates between microbes impact the metabolic exchanges which drive consortia-level physiology. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.