Functional features of oriV of the broad host range plasmid RSF1010 in Pseudomonas aeruginosa

The broad host range plasmid RSF1010 requires for its replication in Escherichia coli three plasmid-encoded proteins and specific nucleotide sequences ssiA, ssiB, and iterons in the oriVRSF1010. In Pseudomonas aeruginosa, a recombinant mini-RSF1010 plasmid lacking ssiB lost its replication ability, but a miniplasmid lacking ssiA or carrying a primosome assembly site in place of ssiA could replicate. Moreover, ssiA, as a sole ssi signal, in the orientation that ssiB had originally taken was sufficient for replication of the miniplasmid. These results indicated that only one RSF1010-specific ssi signal in the orientation that ssiB takes in wild-type oriVRSF1010 was essential for replication of RSF1010. Replication of the miniplasmids was dependent on the three plasmid-encoded proteins, RepA, B', and C, as in E. coli.