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. Here, we took a synthetic biology approach to construct a cross-kingdom consortium that enables bacterial migration and quorum sensing over several centimeters. First, we identified Pseudomonas putida as the ideal bacterial host since it survives in soil and is genetically tractable. Yet, it was unknown which genetic parts would function in soil. Therefore, we tested several genetic circuits, eventually identifying quorum sensing systems Lux and Las as the most robust, achieving 15-fold induction in soil. Next, we investigated several potential fungal partners, quantifying growth rate, soil penetration, and compatibility with P. putida. We found that Lyophyllum atratum extends P. putida soil survival and accelerates migration. Finally, we tested bacterial migration and quorum sensing signal propagation through soil. Without fungal highways, signal propagated 35 mm and fluorescent protein expression lasted for 48 hours in response to inducer. With L. atratum, signal propagated 80 mm and P. putida fluorescent protein expression lasted for 120 hours. These results show that interkingdom networks are key to engineering robust genetic circuit function in soil. Thus, this study builds the foundation for diverse applications of engineered biology in agriculture, nature, and the built environment.

Fungal highways enable migration and communication of engineered bacteria in soil

ACS Spring 2022

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.