A Quorum Sensing-Based Lateral Inhibition System to Generate Contrasting Patterns

Authors: 
Tei, M., UC Berkeley
Perkins, M. L., University of California, Berkeley
Hsia, J., University of Washington, Seattle
Arkin, A., University of California, Berkeley
Arcak, M., University of California, Berkeley

Inhibitory interactions play an important role in the design and function of both natural and engineered biological systems. Lateral inhibition, which occurs when spatially adjacent units inhibit each other, facilitates pattern formation in multicellular organisms during development; for example, somitogenesis via the Notch/Delta pathway in metazoans. Here, we combine quorum sensing and compartmentalization to implement lateral inhibition between neighboring bacterial colonies connected by a channel. Unlike the Notch/Delta pathway, our system does not employ contact-mediated inhibition, as there are no known contact-dependent signaling pathways in bacteria that do not involve growth inhibition. Instead, we harness intercellular communication via diffusible molecules to drive divergence in reporter gene expression between neighboring colonies. Contrasting patterns emerge when, at steady state, colonies producing high levels of reporter are immediately adjacent to colonies producing low levels of reporter. We develop a mathematical model for a series of interconnected, mutually inhibitory compartments to predict quantitatively the parameters and spatial configurations that allow contrasting patterns to emerge. We then engineer two bacterial strains that repress each other’s transcription of a reporter gene and demonstrate that contrasting patterns do indeed arise. Establishing patterning in a simple bacterial system will permit us to explore the mathematical principles underlying biological development in a controlled manner.