Streptavidin-based conditional lethal system for biological containment of Pseudomonas putida

The soil bacterium Pseudomonas putida can potentially be applied in bioremediation of areas polluted with aromatic hydrocarbon-based organic solvents and petroleum. However, its use in the open environment has been hindered so far by the lack of reliable survival-control functions. To increase the predictability of P. putida, a novel cell suicide system was constructed, based on triple control of the expression of the lethal Streptomyces avidinii streptavidin gene (stv) coupled with P. putida TOL plasmid-derived Pm/xylS regulatory circuit. In the absence of hydrocarbon pollutants (3-methylbenzoate in described in vitro studies), all but one in 107 to 108 of genetically modified bacteria commits suicide. The stv-based conditional lethal design can thus effectively limit the spread of released microorganisms strictly to polluted localities and keep them alive only as long as the amount of contaminants keeps above a level determined by the sensitivity of their interaction with the XylS protein.