Transfer of pRD1 to Pseudomonas syringae and evidence for its integration into the chromosome

Plasmid pRD1 was conjugatively transferred from Escherichia coli to Pseudomonas syringae. Subculturing the transconjugate on a medium that selected for pRD1-determined His+ Kmr resulted in the loss of pRD1 as an extrachromosomal element as detected by agarose gel electrophoresis. DNA hybridization provided evidence for the integration of pRD1 into the P. syringae chromosome.