How does conjugation transfer plasmids between bacteria?

Conjugation is a mechanism of horizontal gene transfer that enables bacteria to exchange genetic material through direct cell-to-cell contact. This process is mediated by plasmids, which are extrachromosomal DNA molecules.123

The transfer process typically follows these steps:

• Initiation: A donor cell, which contains a conjugative plasmid, produces a specialized structure called a sex pilus. This structure attaches to a recipient cell, drawing the two bacteria into direct physical contact.1
• Bridge Formation: Once the cells are connected, a conjugal bridge forms between them, creating a pathway for genetic material to move from the donor to the recipient.1
• Transfer: The plasmid is transferred through this bridge in a unidirectional manner. Because the donor cell retains a copy of the plasmid, the recipient acquires the new genetic information, which may include genes for antibiotic resistance.13

While plasmid transfer is the primary function of this mechanism, the bacterial chromosome can also be transferred during conjugation, though this occurs less frequently.13