Figure 1.

Insert modification of pORFES to pORFES IV to permit cloningof blunt-ended fragments. The original pORFES [12, 14] vector was designed to accept inserts as NheI-HindIII fragments. To create pORFES IV, the NheI – HindIII stuffer was replaced with aninsert to include a NaeI site, an additional bp and a (Gly)₄ spacer. The ligation of inserts restoring the correct frame of the β-lactamase confers carbenicillin resistance.