A strain of bacteria that possesses the F factor integrated into the bacterial genome, which is transferred to other adjacent bacteria at a high rate or frequency.
During conjugation, the Hfr bacterium would likely transfer its entire DNA to the F–bacterium. However, since the mating bridge is structurally fragile the genetic transfer is usually incomplete. Hence, the recipient bacterium may only receive a portion of, and rarely the entire, bacterial genome of the donor Hfr bacterium.
Abbreviation: Hfr strain
Compare (with other groups of bacteria in terms of F factor):