Tang, T.-C. | bioRxiv Science

bioRxiv2020

Tough Hydrogel-Based Biocontainment of Engineered Organisms for Continuous, Self-Powered Sensing and Computation

Genetically modified microorganisms (GMMs) can enable a wide range of important applications, including environmental sensing, precision therapeutics, and responsive materials. However, containment of GMMs to prevent environmental escape and satisfy regulatory requirements is a bottleneck for real-world use1-7. While biochemical strategies have been developed to restrict unwanted growth and replication of GMMs in the environment8-12, there is a need for deployable physical containment technologies to achieve redundant, multi-layered, and robust containment2. In addition, form factors that enable easy retrieval would be useful for environmental sensing. To address this challenge, we developed a hydrogel-based encapsulation system for GMMs that incorporates a biocompatible multilayer tough shell and an alginate-based core. This DEployable Physical COntainment Strategy (DEPCOS) allows no detectable GMM escape, bacteria to be protected against environmental insults including antibiotics and low pH, controllable lifespan, and easy retrieval of genetically recoded bacteria. To highlight the versatility of a DEPCOS, we demonstrate that robustly encapsulated cells can execute useful functions, including performing cell-cell communication with other encapsulated bacteria and sensing heavy metals in water samples from the Charles River. We envision that our multilayered physical and chemical containment strategy will facilitate the realization of a wide range of real-world applications for living biosensors.

synthetic biology↗

bioRxiv2019

Living materials with programmable functionalities grown from engineered microbial co-cultures

Biological systems assemble tissues and structures with advanced properties in ways that cannot be achieved by man-made materials. Living materials self-assemble under mild conditions, are autonomously patterned, can self-repair and sense and respond to their environment. Inspired by this, the field of engineered living materials (ELMs) aims to use genetically-engineered organisms to generate novel materials. Bacterial cellulose (BC) is a biological material with impressive physical properties and low cost of production that is an attractive substrate for ELMs. Inspired by how plants build materials from tissues with specialist cells we here developed a system for making novel BC-based ELMs by addition of engineered yeast programmed to add functional traits to a cellulose matrix. This is achieved via a synthetic symbiotic culture of bacteria and yeast (Syn-SCOBY) approach that uses a stable co-culture of Saccharomyces cerevisiae with BC-producing Komagataeibacter rhaeticus bacetria. Our Syn-SCOBY approach allows inoculation of engineered cells into simple growth media, and under mild conditions materials self-assemble with genetically-programmable functional properties in days. We show that co-cultured yeast can be engineered to secrete enzymes into BC, generating autonomously grown catalytic materials and enabling DNA-encoded modification of BC bulk material properties. We further developed a method for incorporating S. cerevisiae within the growing cellulose matrix, creating living materials that can sense chemical and optical inputs. This enabled growth of living sensor materials that can detect and respond to environmental pollutants, as well as living films that grow images based on projected patterns. This novel and robust Syn-SCOBY system empowers the sustainable production of BC-based ELMs.

synthetic biology↗