A Conditional Suicide System for Genetically Engineered Bacteria Based on the Endonuclease I Gene of Escherichia coli

Abstract

The use of genetically engineered microorganisms (GEMs) in science and industrial production bears the risk of their unintended release into the environment. Moreover, several applications (e.g., in agriculture or waste treatment) rely directly on the intended release of large quantities of GEMs. Such releases may interfere with the balanced microbial ecosystems by the survival and reproduction of GEMs and/or by horizontal transfer of their recombinant DNA to indigenous bacteria via conjugation, transduction or transformation (see Lorenz and Wackernagel 1993). Such considerations have led to the development of biological containment systems which cause a controlled cell death by the regulated expression of genes with cell-killing functions. Mostly, these functions cause cell death by membrane destabilization or cell lysis (for a review, see Molin et al. 1993). As a consequence, genetic material may be released from cells into microbial habitats after induction of the killing genes. In other studies it was shown that free DNA can persist in soils for weeks and months (Romanowski et al. 1992, 1993) and may be taken up by cells in the course of natural genetic transformation (for a review, see Lorenz and Wackernagel 1994).