FIG. 4.

Stabilization of mini-F plasmids containing putative parS sequences by coresident plasmids carrying the VC2773-VC2772 parAB locus. Experiments were performed multiply, and the graphs are from a representative experiment. Bacteria were grown in M9-CSA with chloramphenicol to maintain the mini-F derivative; at an OD of ∼0.3, they were back diluted into medium lacking chloramphenicol (time zero) and plated at the specified generation times. Colonies were patched onto chloramphenicol to assay for the presence of the mini-F plasmid. The y axes in all panels show the percentages of colonies still retaining the mini-F derivative. (A) Stability of the sop⁺ mini-F plasmid pDAG114, as well as its unstable derivative pDAG203, in the presence of a coresident pBluescript vector or pSD25 (carrying both parA and parB). (B to D) Stabilities of pDS38, pSD39, and pSD44 (pDAG203 carrying IR1, IR2, and IR3, respectively). Each plasmid was assayed in the presence of empty pBluescript vector, pSD9 (with an in-frame deletion of VC2773, thus carrying parB), pSD21 (with an in-frame deletion of VC2772, thus carrying parA), or pSD25 (carrying both parA and parB). The legend for each graph indicates the par genes supplied in trans.