Stabilization of a miniderivative of the broad-host-range IncW plasmid pSa by insertion of plasmid R1 parB region.

The plasmid vector pEM100 (13.5 kb) constructed from pGV1106, a miniderivative of the broad-host-range IncW pSa plasmid, and the pAM330 plasmid of Brevibacterium lactofermentum is not stably maintained in Escherichia coli host cells under nonselective growth conditions. By insertion of a 0.9 kb DNA fragment containing the parB locus (responsible for the maintenance of plasmid R1 in E. coli cells) to plasmid pEM100, plasmid pEM110 was prepared which is maintained in a population of E. coli cells growing without a selection pressure very stably.