**5. Perspectives**

Recombinant bacteria have shown great potential in the preclinical trials. Their clinical potential relies on their safety and biological containment. Most of the studies were just looking for proof-of-concept rather than a final product that could be put directly to use. Given the global needs, future research challenges should focus on the balance between the optimization of gene therapy through effectiveness of gene delivery to target cells and the biological control of recombinant bacteria to ensure not only an appropriate shutoff mechanism but also to minimize the risks of insertional mutagenesis and aberrant genomic location of delivered genes.
