Gatekeeper Residue Replacement in a Phosphite Transporter Enhances Mutational Robustness of the Biocontainment Strategy.

Biocontainment is a key methodology to reduce environmental risk through the deliberate release of genetically modified microorganisms. Previously, we developed a phosphite (HPO)-dependent biocontainment strategy, by expressing a phosphite-specific transporter HtxBCDE and phosphite dehydrogenase in bacteria devoid of their indigenous phosphate (HPO) transporters. This strategy did not allow to generate escape mutants (EMs) in growth media containing phosphate as a phosphorus source using an assay with a detection limit of 1.