Programmed hierarchical patterning of bacterial populations

Christian R Boehm,Paul K Grant,Jim Haseloff

doi:10.1038/s41467-018-03069-3

Abstract

Modern genetic tools allow the dissection and emulation of fundamental mechanisms shaping morphogenesis in multicellular organisms. Several synthetic genetic circuits for control of multicellular patterning have been reported to date. However, hierarchical induction of gene expression domains has received little attention from synthetic biologists, despite its importance in biological self-organization. Here we report a synthetic genetic system implementing population-based AND-logic for programmed autonomous induction of bacterial gene expression domains. We develop a ratiometric assay for bacteriophage T7 RNA polymerase activity and use it to systematically characterize different intact and split enzyme variants. We then utilize the best-performing variant to build a three-color patterning system responsive to two different homoserine lactones. We validate the AND gate-like behavior of this system both in cell suspension and in surface culture. Finally, we use the synthetic circuit in a membrane-based spatial assay to demonstrate programmed hierarchical patterning of gene expression across bacterial populations.

Highlights

Modern genetic tools allow the dissection and emulation of fundamental mechanisms shaping morphogenesis in multicellular organisms
In efforts to explain multicellular patterning, two types of models have been pre-eminent to date: the reaction-diffusion (RD) model proposed by Alan Turing[2], and the positional information (PI) model originating from Lewis Wolpert[3]
To emulate biological selforganization on this level of complexity, we require control over hierarchical induction of new domains within existing patterns. Approaching this challenge, we report the implementation of a synthetic genetic circuit that controls emergence of a new domain of gene expression at the interface of existing bacterial populations

Summary

Introduction

Modern genetic tools allow the dissection and emulation of fundamental mechanisms shaping morphogenesis in multicellular organisms. Several synthetic genetic circuits for control of multicellular patterning have been reported to date. Hierarchical induction of gene expression domains has received little attention from synthetic biologists, despite its importance in biological self-organization. We report a synthetic genetic system implementing population-based AND-logic for programmed autonomous induction of bacterial gene expression domains. We use the synthetic circuit in a membrane-based spatial assay to demonstrate programmed hierarchical patterning of gene expression across bacterial populations. A fundamental requirement for harnessing this potential is control over the differentiation of cell types to create domains of gene expression in spatially organized patterns. To emulate biological selforganization on this level of complexity, we require control over hierarchical induction of new domains within existing patterns

Methods

Results

Conclusion