INSERTIONS OF THE TRANSPOSON Tn1 INTO THE PSEUDOMONAS AERUGINOSA CHROMOSOME

The transposon Tnl has been translocated to the chromosome of Pseudomonas aeruginosa from plasmid R18, iollowing hydro,xylamine mutagenesis of the plasmid. Twelve insertions were mapped to six distinct sites distal to 55 min of the origin of chromosome transfer by the plasmid FP2. These map locations were confirmed by host chromosome mobilization tests mediated by plasmids RI8 or R91-5, due to Tni homology between plasmid and host chromosome. All the Tnl chromosomal inserts were retransposable to other plasmids (Sa, R931 and R38). The behavior of Tnl in P. aemginosa was very similar to its behavior in Escherichia coli with respect to regional specificity, orientation of insertion and in serving as regions of homology for host chromosome mobilization by plasmids. This last property has permitted the demonstration that Tnl on RI8 and R91-5 is in opposite orientation with respect to the origin of transfer (oriT) of the two plasmids.