F conjugation: Back to the beginning

• Cell–cell interactions in bacterial conjugation generate a signal to begin transfer.
• The pilus is essential in mediating this signal through both cell envelopes.
• Pilus -specific phages hijack these signals during infection.
• Mating pair stabilization involves inner as well as outer membrane events.
• Entry and surface exclusion block cell–cell interactions and signal transmission.

Bacterial conjugation as mediated by the F plasmid has been a topic of study for the past 65 years. Early research focused on events that occur on the cell surface including the pilus and its phages, recipient cell receptors, mating pair formation and its prevention via surface or entry exclusion. This short review is a reminder of the progress made in those days that will hopefully kindle renewed interest in these subjects as we approach a complete understanding of the mechanism of conjugation.