Final answer:
Conjugation in E. coli is controlled by the F plasmid, which enables the transfer of DNA between cells through a structure called the F pilus.
Step-by-step explanation:
In E. coli, conjugation is controlled by an episome known as the F plasmid, or fertility factor. The process involves direct DNA transfer from one prokaryotic cell to another using a pilus called the F pilus. The F plasmid contains genes that encode the proteins forming the F pilus and those involved in the rolling circle replication of the plasmid. Donor cells, which have the F plasmid and can form the F pilus, are labeled as F+ cells. Recipient cells without the F plasmid are referred to as F- cells. The conjugation process leads to the recipient cell receiving the F plasmid and subsequently becoming an F+ cell capable of forming its own conjugation pilus.