noun, plural: F- bacteria
F- bacterium serves as the recipient cell of F factor from a bacterium that has it. A copy of F factor is transferred to the F- bacterium through conjugation. The result following conjugation becomes F+ and thereby acquires the ability to form sex pilus essential in initiating conjugation with other bacteria. The now F+ cell becomes a potential donor of F factor to other bacteria.
Compare (with other groups of bacteria in terms of F factor):