A method for the stabilisation of recombinant plasmids in yeast.

The stability of a yeast plasmid can be improved using deliberately induced cyclic changes in the dissolved oxygen tension (DOT), during continuous culture in a non-selective, undefined medium. The resultant stability of the plasmid under DOT cycled conditions is strongly dependent on the growth rate of the culture, with complete stabilisation at lower growth rates. We propose a mechanism for the stabilisation and suggest that the method can be applied to other recombinant yeast strains.