DK240384A - STABILIZED PLASMIDS - Google Patents

Abstract

Plasmids which are in themselves inherited unstably, or which have become unstable as a consequence of the insertion of a DNA fragment which comprises one or more genes which are not naturally associated with plasmid, are stabilised with the aid of distribution function which is exerted by a par region, in particular a plasmid R1 par region, which is inserted into the plasmid on a DNA fragment which can be as long as the wild-type EcoR1 A fragment but which is preferably shorter than this fragment, and which can comprise R1 par region A, R1 par region B, or both these R1 par regions. The stabilisation which is achieved for several different types of plasmid, in particular by using both R1 par regions, approaches the stability level of the wild-type plasmids, i.e. they typically have a loss frequency of less than 5 x 10-6 per cell per generation. Such stabilised plasmids can be used for producing gene products on a large scale since no particular bacterial strains or mutants are required for ensuring that the plasmid is preserved and since it is not necessary to use a particular composition of the nutrient medium, in which the host cells are cultured, in order to prevent the plasmid being lost from the bacterial population.