A Synthetic Developmental Circuit to Investigate the Effects of Adhesion

The design and engineering of multicellular systems is an important step for the future of synthetic biology. A crucial hurdle to the engineering of such systems is the understanding of the self-organisation that shapes the organism, often involving a multitude of intercellular interactions. In order to begin to simplify and disentangle such interactions, we express a primitive synthetic developmental circuit in E. coli colonies to investigate cell-cell adhesion. Adhesion is an important developmental mechanism, and here we isolate and observe its effects in a well-defined context. We first characterize a method to segregate bacterial colonies into spatially distinct domains of gene expression. This is achieved by transforming the cells with two similar inducible copy number plasmids in the high copy number regime. The inducer is then removed so plasmid copy number falls whereby plasmid incompatibility ensures that each cell is eventually left with only one of the original two plasmids. The segregating plasmids also contain an inducible ag43 protein that causes adhesion between cells. By observing and measuring boundaries between domains with differing adhesive properties, we demonstrate the effects of adhesion on the boundary formation process. CellModeller software is used to model the cells and their physical interactions, providing insight into the mechanistic details.