A genetically encoded toolbox of orthogonal adhesins for bacterial self-assembly

In over a decade, synthetic biology has developed increasingly robust gene networks within single cells, but constructed very few systems that demonstrate multicellular spatio-temporal dynamics. In particular, to our knowledge there exists no convenient method for engineering cell-cell adhesion. Towards filling this gap in synthetic biology's toolbox, here we report the first 100% genetically encoded self-assembly platform, based on modular cell-cell adhesion in Escherichia coli. Adhesive selectivity is provided by a library of outer membrane-displayed peptides with orthogonal intra-library specificities, while affinity is provided by intrinsic adhesin affinity, media conditions, and inducible expression across the entire library. We demonstrate this tool by building well-defined multicellular patterns, including multiple cell types in cluster-, mesh-, and lattice-like arrangements, even during cell growth and division. We further quantify these structures using nearest-neighbor graphs, fractal dimension, and density distribution. This adhesion system will enable future development of synthetic multicellular systems for use in consortia-based metabolic engineering, in living materials, in tissue engineering, and in controlled study of minimal multicellular systems.