Bacterial conjugation was discovered over 50 years ago and was attributed to the F or fertility factor a few years later. Early research showed that the F factor was a plasmid that assembled long structures called pili that were essential for transferring DNA from bacterial cell to bacterial cell. These pili were also the site of attachment of many bacteriophages, the most notable being f1 and its relatives. Many systems turn out to be related to F conjugation including the process that gives rise to tumours in plants and the secretion of toxins and other virulence factors by many enteropathogenic bacteria. These are now called type IV secretion systems with the F DNA transfer system representing a complex version that is capable of attaching to, and reeling in, suitable recipient cells
