Conjugation

• DNA is transferred from a donor cell to a recipient cell due to close cell-to-cell contact between the bacteria

• there are a variety of conjugation systems that are present in bacteria, but they all encode for surface structures on the donor that can recognize a recipient cell

• the donor and recipient come together and a mating bridge forms

• a single strand of DNA from the donor cell is then transferred through the bridge into the recipient cell

• this most commonly occurs with plasmids, though there are conjugation systems for chromosomal DNA

• there are thousands of plasmids that have been isolated that encode for conjugation systems that can carry out this process of DNA transfer

• in the case of plasmids, one copy of the plasmid is preserved in the donor. the recipient then becomes a new donor

• in this way, this transfer of plasmids via conjugation can snowball through a population of bacteria

• if this plasmid confers resistance to antibiotics, then this resistance can spread rapidly through a population

• in the case of E. coli O157:H7, such a plasmid encodes for virulence genes associated with the process of converting a non-pathogenic E. coli bacterium into an enteric pathogen

Category: Microbiology Notes