I previously introduced a class of antibiotic-free small DNA vectors termed “Petit Plasmids”. These vectors can be maintained and replicated within engineered amino acid auxotrophic bacterial strains cultivated in a medium lacking one or more essential amino acids. In large-scale fermentation systems, these growing cells can scavenge lysed cells to obtain the essential amino acids, promoting the survival of cells lacking Petit Plasmid. To address this limitation, I present novel strains of engineered bacterial cells that require a specific inducing agent for growth in the absence of Petit Plasmid.