Streptavidin-based containment systems for genetically engineered microorganisms

The use of genetically modified microorganisms for environmental remediatio n continues to be debated. Conditional lethal systems with tightly regulate d gene expression can be used to contain released microorganisms and amelio rate some of the concerns about horizontal gene transfer. We have described streptavidin-based suicide systems to address these concerns and evaluated their function in Pseudomona putida containing the TOL plasmid for aromati c hydrocarbon metabolism. Tight regulation of expression of a truncated str eptavidin gene was required to avoid premature production of the toxic prot ein. Streptavidin expression was induced by the absence of 3-methyl benzoat e (hydrocarbon substrate) which resulted in the elimination of 99.9% of the bacterial culture within eight hours. Low mutant escape rates at 10(-7) pe r cell per generation were also realized. (C) 1999 Elsevier Science B.V. Al l rights reserved.