Abstract: The survival of cells is limited by introducing into the cells a regulatably expressible gene whose expression results in the formation of a cytoplasmatically active hydrolytic enzyme. Populations of cells containing, in addition to such a regulatably expressible gene, a DNA coding for an immunologically active, pesticidally active or environmental pollutant-degrading gene product, may be useful in immunologically active compositions, pesticidally active compositions and environmental pollutant-degrading compositions, respectively.

Abstract: The survival of cells is limited by introducing into the cells a regulatably expressible gene whose expression results in the formation of a cytoplasmatically active hydrolytic enzyme. Populations of cells containing, in addition to such a regulatably expressible gene, a DNA coding for a pesticidally active or environmental pollutant-degrading gene product, may be useful in pesticidally active compositions and environmental pollutant-degrading compositions, respectively.

Abstract: A replicon, in which a nucleotide sequence encoding a cell killing function is regulatably expressed when the replicon is harbored in one type of host cell (primary host cell), so that cells harboring the replicon are killed under conditions under which the cell killing function is expressed, and the nucleotide sequence encoding the cell killing function is regulatably or constitutively expressed when the replicon is harbored in another type of host cell (secondary host cell), so that cells harboring the replicon are invariably killed or killed under conditions under which the cell killing function is expressed, may be used in a method of active biological containment of cells under defined environmental conditions. The biological containment principle may be utilized in the industrial production of a biosynthetic product by recombinant DNA techniques, when deliberately releasing a genetically engineered microorganism to the natural environment or in the preparation of a live vaccine.

Abstract: A replicon, in which a nucleotide sequence encoding a cell killing function is regulatably expressed when the replicon is harboured in one type of host cell (primary host cell), so that cells harbouring the replicon are killed under conditions under which the cell killing function is expressed, and the nucleotide sequence encoding the cell killing function is regulatably or constitutively expressed when the replicon is harboured in another type of host cell (secondary host cell), so that cells harbouring the replicon are invariably killed or killed under conditions under which the cell killing function is expressed, may be used in a method of active biological containment of cells under defined environmental conditions.The biological containment principle may be utilized in the industrial production of a biosynthetic product by recombinant DNA techniques, when deliberately releasing a genetically engineered microorganism to the natural environment or in the preparation of a live vaccine.