RK 2 was first isolated in connection with an outbreak of antibotic-resistant Pseudomonas aeruginosa and Klebsiella aerogenes in Birmingham in 1969, as one of a family of plasmids implicated in transfer of Ampicillin resistance between bacterial strains.
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PFF1 consists of an origin of replication, oriV, an origin of transfer, oriT, a gene coding for plasmid replication proteins, trfA, and two antibiotic resistance genes, bla and cat, which confer resistance to Ampicillin and Chloramphenicol, respectively.