Relation between F, R1, R100 and R144 Escherichia coli K-12 donor strains in mating.

E. coli K-12 recipient mutants defective in conjugation with a F donor (ConF- mutants) were tested for recipient ability with donor strains carrying a R1drd19, R100-1 or R144drd3 plasmid. It appeared from these tests that F and R1 donor strains are closely related in mating in that they both, unlike the R100 and R144 donor, use the recipient outer membrane protein pOmpA for the initial steps of the mating process. The isolation of recipient mutants defective in conjugation with a R100 donor (ConR100- mutants) yielded some mutants that were defective in crosses with F, R1 and R100 donors. This result was taken as evidence that F, R1 and R100 donors share some property in their mating interaction with E. coli K-12 recipient strains. A R144 donor is completely different from F, R1 and R100 donors in initial mating interactions with a recipient.