Fungal highways unlock new applications for genetic circuits in the soil microbiome

Study of natural soil microbiomes has revealed that bacterial migration and long-distance chemical signaling is facilitated by filamentous fungal highways. These emergent properties in soil are of particular interest for nutrient cycling, pollution remediation, and underground chemical detection, yet they are only just beginning to be understood. In this talk, I will describe a synthetic biology approach to construct a cross-kingdom consortium that enables bacterial migration and signaling with genetic circuits over several centimeters. We first defined a two-member consortium with a genetically tractable, motile bacterium and a filamentous fungal partner. Then, we designed and tested genetic circuits in soil with different chemical inducers, finding that circuits based on quorum sensing functioned best in dry soil. In testing the function of the system in soil columns, we also observe that the presence of the fungal partner accelerates propagation of the engineered bacteria and the quorum sensing signals over several centimeters. These results show that constructed microbiomes are key to achieving desired sensing and signaling functions in soil. Thus, this study builds the foundation for diverse applications of engineered biology in agriculture, nature, and the built environment.