Abstract: Method of conditionally controlling the survivability of a recombinant cell population and of containing such cells to an environment or containing replicons to a host cell is based on the use of proteic killer systems including E. coli relBE locus and similar systems found in Gram-negative and Gram-positive bacteria and Archae. Such systems are generally based on a cytotoxin polypeptide and an antitoxin or antidote polypeptide that in contrast to the cytotoxin is degradable by proteases. The recombinant cells are useful as vaccines, pollutant degrading organisms or as biological pest control organism e.g. expressing B. thuringiensis crystalline proteins.

Abstract: Method of conditionally controlling the survivability of a recombinant cell population and of containing such cells to an environment or containing replicons to a host cell is based on the use of proteic killer systems including the E. coli relBE locus and similar systems found in Gram-negative and Gram-positive bacteria and Archae. Such system are generally based on a cytotoxin polypeptide and an antitoxin or antidote polypeptide that in contrast to the cytotoxin is degradable by proteases. The recombinant cells are useful as vaccines, pollutant degrading organisms or as biological pest control organisms e.g. expressing B. thuringiensis crystalline proteins.

Abstract: Method of conditionally controlling the survivability of a recombinant cell population and of containing such cells to an environment or containing replicons to a host cell is based on the use of proteic killer systems including E. coli relBE locus and similar systems found in Gram-negative and Gram-positive bacteria and Archae. Such systems are generally based on a cytotoxin polypeptide and an antitoxin or antidote polypeptide that in contrast to the cytotoxin is degradable by proteases. The recombinant cells are useful as vaccines, pollutant degrading organisms or as biological pest control organism e.g. expressing B. thuringiensis crystalline proteins.

Abstract: Method of conditionally controlling the survivability of a recombinant cell population and of containing such cells to an environment or containing replicons to a host cell is based on the use of proteic killer systems including the E. coli relBE locus and similar systems found in Gram-negative and Gram-positive bacteria and Archae. Such system are generally based on a cytotoxin polypeptide and an antitoxin or antidote polypeptide that in contrast to the cytotoxin is degradable by proteases. The recombinant cells are useful as vaccines, pollutant degrading organisms or as biological pest control organisms e.g. expressing B. thuringiensis crystalline proteins.

Abstract: Method of conditionally controlling the survivability of a recombinant cell population and of containing such cells to an environment or containing replicons to a host cell is based on the use of proteic killer systems including the E. coli relBE locus and similar systems found in Gram-negative and Gram-positive bacteria and Archae. Such system are generally based on a cytotoxin polypeptide and an antitoxin or antidote polypeptide that in contrast to the cytotoxin is degradable by proteases. The recombinant cells are useful as vaccines, pollulant degrading organisms or as biogical pest control organisms e.g. expressing B. thuringiensis crystalline proteins.

Abstract: The stable maintenance of a replicon in a population of growing cells is ensured by providing the replicon with a sequence which encodes a product capable of killing the cell harboring the replicon or the progeny of the cell (or encodes a precursor for the product) and a sequence encoding an antagonist for the killing product (or a precursor for the antagonist). The antagonist is one which suppresses the killing product (or a precursor for the killing product) in cells harboring the replicon, whereas the antagonist activity decays when the replicon is lost from the cell so that the antagonist (or its precursor) is no longer continuously expressed. This means that the killing product (or its precursor) present in the now replicon-free cell is no longer suppressed by the antagonist, resulting in cell death.Cells containing the thus stabilized replicon may be grown on a large scale without any significant loss of the replicon from the cell population even when no selection pressure is applied.

Abstract: Plasmids which are in themselves unstably inherited or which have become unstable due to the insertion of a DNA fragment comprising one or more genes not naturally related to the plasmid are stablized by means of a partitioning function exerted by a par region, especially a plasmid R1 par region, inserted into the plasmid on a DNA fragment which may be the length of the wild-type R1 EcoR1-. A fragment, but which is preferably shorter than this fragment, and which may comprise the R1 par region A, the R1 par region B or both these R1 par regions. The stabilization obtained for several different types of plasmid, especially by employing both R1 par regions, approaches the stability level of wild-type plasmids, i.e. they typically have a frequency of loss of less than 5.times.10.sup.31 6 per cell per generation.