The role of plasmids in conjugation was first described by Lederberg and Tatum (1946) in which bacteria?

Bacterial conjugation was first described by Lederberg and Tatum (1946) in a strain of E.coli called K12 (carried a conjugative plasmid F) The F factor: The F plasmid, also called F factor, is a transfer factor that contains the genetic information, essential for controlling mating process of the bacteria during conjugation. The F plasmid of Escherichia coli is the prototype for feility plasmids in Gram-negative bacteria. Strains of E. coli with F+ plasmid are called as donors, whereas plasmid are F- behave as recipients.