Plasmid incompatibility: cloning analysis of an incFII determinant of R6-5

SalI and PstI restriction endonuclease-generated DNA fragments that specify an FII-type incompatibility function (incFII) of the low copy number antibiotic resistance plasmid R6-5 have been cloned in the high copy number pBR322 plasmid vector. A 1-kilobase DNA sequence that contains this incFII determinant has been identified and is shown to have coordinates of 95.5 and 96.5 kilobases on the R6-5 plasmid physical map. Expression of incompatibility by the cloned PstI fragment depends on its orientation within the vector molecule. The behaviour of pBR322-incFII hybrid plasmids suggests that plasmid replication control is not the only mechanism that can cause incompatibility between two plasmids.