The aim of our project is to engineer the first synthetic multicellular bacterium, the SMB. This new organism is a new tool for the engineering of complex biological systems. It consists in two interdependent cell lines. The first one, dedicated to reproduction will be called the germ line (red cells). It is able to differentiate into the second line: the soma (green cells), which is sterile and dedicated to support the germ line. The germ line is auxotroph for DAP (diaminopimelate) which is provided by the soma. There is thus an interdependency relationship. The soma, being sterile, doesn't exist without the germ line to generate it, and the germ line needs the soma to complement its auxotrophy. We provide here experimental and computational evidences that this system can work, as well as the almost complete construction of the SMB.