Maintenance of broad host range plasmid RK2 replicons in Pseudomonas aeruginosa

Abstract

Certain members of the Escherichia coli plasmid incompatibility group P are capable of efficient transfer between and maintenance in most Gram-negative bacterial species^1–4. Of fundamental interest is whether this broad host range results from differences between the mechanisms of replication and partitioning during cell division used by IncP plasmids and by narrow host range plasmids. The genetic regions of IncP plasmid RK2 (similar or identical to RP4 and RP1) required for plasmid maintenance in E. coli have previously been defined as a vegetative replication origin (ori_RK2) and a gene specifying a positively required trans-acting product (trfA)^5–8. Here we have tested various mini RK2 replicons for their ability to become established after transformation into Pseudomonas aeruginosa PAO as a model non-E. coli host. We chose P. aeruginosa for this purpose as it is a Gram-negative species relatively phylogenetically distant from E. coli. Our studies have defined a plasmid segment that contains a region which must be linked in cis to the ori_RK2 replicon to allow mini RK2 plasmid maintenance in P. aeruginosa PAO and suggest that RK2 may carry genes which adapt the basic replicon to allow autonomous maintenance in specific groups of hosts.