In conjugation, DNA is transferred from one bacterium to another. After the donor cell pulls itself close to the recipient using a structure called a pilus, DNA is transferred between cells. In most cases, this DNA is in the form of a plasmid.
- An F+ donor cell contains its chromosomal DNA and an F plasmid. It has a rodlike pilus. A recipient F- cell has only a chromosome and no F plasmid.
- The donor cell uses its pilus to attach to the recipient cell, and the two cells are pulled together.
- A channel forms between the cytoplasms of the two cells, and a single strand of the F plasmid is fed through.
- Both of the cells now have an F plasmid and are F+. The former recipient cell is now a new donor and can form a pilus.
Image modified from “Conjugation,” by Adenosine (CC BY-SA 3.0). The modified image is licensed under a CC BY-SA 3.0 license.Donor cells typically act as donors because they have a chunk of DNA called the fertility factor (or F factor). This chunk of DNA codes for the proteins that make up the sex pilus. It also contains a special site where DNA transfer during conjugation begins^22squared.If the F factor is transferred during conjugation, the receiving cell turns into an F^++start superscript, plus, end superscript donor that can make its own pilus and transfer DNA to other cells. Here’s one analogy: this process is sort of like how a vampire can turn other people into vampires by biting them.