Conjugatieve

Conjugatieve is a term used to describe genetic elements that are capable of transferring DNA between bacteria through the process of conjugation. Conjugation is a form of horizontal gene transfer that requires direct cell-to-cell contact and often involves a dedicated transfer apparatus, such as a type IV secretion system and a mating bridge.

Conjugative elements include plasmids and certain chromosomal segments known as integrative conjugative elements (ICEs). These elements carry the genes necessary for initiating and sustaining transfer, including those encoding pili, transfer proteins, and regulatory circuits. Transfer typically starts at a specific origin of transfer (oriT), where a relaxase enzyme nicks one strand of the DNA. The strand is then unwound and guided through the transfer channel into the recipient cell, where complementary synthesis restores a double-stranded molecule. In many systems, the donor retains a copy of the transferred DNA, while some elements may replicate during transfer.

Different classes exist within conjugative elements. Classical examples include the F plasmid in Escherichia coli, which can mobilize itself and other DNA segments. ICEs integrate into the chromosome but can excise, form circular intermediates, and transfer to recipients as part of conjugation. Some elements are mobilizable; they require the machinery of a separate conjugative element to transfer.

Conjugatieve elements play a central role in bacterial evolution by enabling rapid spread of traits such as antibiotic resistance and metabolic capabilities. They are also tools in genetic research for studying gene transfer and horizontal gene flow among microbial populations.