Unique Colony Housing the Coexisting Escherichia coli and Dictyostelium discoideum.

Two well-characterized and phylogenetically diverse species, Escherichiacoli and Dictyostelium discoideum, were used as the modelorganisms. When the two species were mixed and allowed to grow onminimal agar plates at 22 (°)C, instead of the predator Dictyostelium exterminating E.coli, the two species remarkablyachieved a state of stable coexistence in about two weeks. In addition, theemerged colonies housing the coexisting species have a mucoidal naturethat is distinctive from its origin. The simplicity of the system and the shorttime span for the two species to develop the coexistence state, that isproven stable and reproducible on laboratory conditions, hence, providesa new model system for the study of symbiosis, particularly with referenceto the initial stages.