Bacterial conjugation
Say it: bak-TEER-ee-ul kon-juh-GAY-shun
Bacterial conjugation is the direct transfer of DNA, usually a plasmid, from one bacterial cell to another through a pilus and close cell contact.
Definition
What is bacterial conjugation?
Bacterial conjugation is one of three main ways prokaryotes swap genes horizontally, alongside transformation and transduction, and the only one that needs two living cells to touch. A donor cell carrying a conjugative plasmid, or a conjugative element built into its chromosome, makes a thin protein tube called a sex pilus or conjugation pilus. The pilus catches a recipient cell and retracts to pull the two together, and a channel forms between them. Joshua Lederberg and Edward Tatum discovered the process in E. coli in 1946.
The best-studied system is the F, or fertility, plasmid of E. coli. There an enzyme called relaxase nicks one strand of the plasmid at its origin of transfer and leads it into the recipient through a type IV secretion system, while the donor rebuilds the missing strand by rolling-circle replication. The recipient copies the incoming single strand, so both cells end up with the plasmid and the former F-minus cell becomes a donor itself. When the F plasmid sits inside the chromosome, in Hfr strains, chromosomal genes can follow it across, and early geneticists mapped the E. coli chromosome by timing that transfer.
Conjugation is a major reason antibiotic resistance spreads so fast, because resistance genes on plasmids can pass between strains and even between species.
Word parts
Where does the term “bacterial conjugation” come from?
- con-
- togetherLatin con-
- jug-
- yoke, joinLatin iugum (yoke), coniugare (to join together)
Related
Terms that go with it
- PlasmidA plasmid is a small, usually circular DNA molecule that copies itself independently of the main chromosome, found mostly in bacteria.
- Antibiotic resistanceAntibiotic resistance is the ability of bacteria to survive and multiply despite an antibiotic that once killed them or stopped their growth.
- Bacterial transformationBacterial transformation is the uptake of free DNA from the surroundings by a bacterial cell, which can then gain the genes that DNA carries.
- TransductionIn microbiology, transduction is the transfer of bacterial DNA from one cell to another by a bacteriophage, a virus that infects bacteria.
- Escherichia coliEscherichia coli is a rod-shaped, gram-negative gut bacterium that is mostly harmless but includes strains that cause diarrhea and urinary infections.
- TransposonA transposon is a DNA sequence that can move from one place in a genome to another, in some cases leaving a copy behind as it goes.
Sources
Checked against
Written for biofideX in plain words, after checking these references:
- OpenStax Microbiology, 11.6 How Asexual Prokaryotes Achieve Genetic Diversity
- Virolle et al., Plasmid Transfer by Conjugation in Gram-Negative Bacteria: From the Cellular to the Community Level (Genes, 2020)
Last updated
Spotted a mistake? Tell us and we'll correct it.
Practice Microbiology
Free microbiology quizzes, with an explanation for every answer.
See the Quizzes