Characterizing chemical signaling between engineered "microbial sentinels" in porous microplates.

Living materials combine a material scaffold, that is often porous, with engineered cells that perform sensing, computing, and biosynthetic tasks. Designing such systems is difficult because little is known regarding signaling transport parameters in the material. Here, the development of a porous microplate is presented. Hydrogel barriers between wells have a porosity of 60% and a tortuosity factor of 1.6, allowing molecular diffusion between wells. The permeability of dyes, antibiotics, inducers, and quorum signals between wells were characterized. A "sentinel" strain was constructed by introducing orthogonal sensors into the genome of Escherichia coli MG1655 for IPTG, anhydrotetracycline, L‐arabinose, and four quorum signals. The strain's response to inducer diffusion through the wells was quantified up to 14 mm, and quorum and antibacterial signaling were measured over 16 h. Signaling distance is dictated by hydrogel adsorption, quantified using a linear finite element model that yields adsorption coefficients from 0 to 0.1 mol m−3. Parameters derived herein will aid the design of living materials for pathogen remediation, computation, and self‐organizing biofilms. Synopsis: Microbes interact by chemical diffusion through materials, a concept that inspires "engineered living materials". To parameterize signaling through materials, a porous culture microplate is fabricated to measure chemical signaling between isolated wells of engineered E. coli. A porous microplate is fabricated by soft lithography of the co‐polymer hydroxyethyl methacrylate‐co‐ethylene glycol dimethacrylate.Four homoserine lactone quorum sensors are evolved to minimize cross‐talk via directed evolution.Seven total orthogonal sensors are encoded into the genome of E. coli MG1655, which serves as a "sentinel strain."The biological response of the sentinel strain to inducer, quorum, and antibiotic signaling between isolated wells of the microplate are experimentally measured.A quantitative model is developed that explains the difference in transport kinetics of the various biological signals by differential absorption of the molecules to the hydrogel matrix. [ABSTRACT FROM AUTHOR]