R-factor

R-factors are pieces of DNA, usually plasmids, that contain resistance genes to antibiotics. Resistance genes are ones that give rise to proteins that modify the antibiotic or pump it out. Resistance genes are different from mutations that give bacteria resistance to antibiotics by preventing the antibiotic from getting in or changing the shape of the target protein. R-factors have been known to contain up to ten resistance genes. They can also spread easily as they contain genes for constructing pili, which allow them to transfer the R-factor to other bacteria. R-factors have contributed to the growing antibiotic resistance crisis because they quickly spread resistance genes amongst bacteria.^[1]

Transmission[]

Bacteria containing F-factors (said to be "F+") have the capability for horizontal gene transfer; they can construct a sex pilus, which emerges from the donor bacterium and ensnares the recipient bacterium, draws it in, and eventually triggers the formation of a mating bridge, merging the cytoplasms of two bacteria via a controlled pore. This pore allows the transfer of genetic material, such as a plasmid. Conjugation allows two bacteria, not necessarily from the same species, to transfer genetic material one way.^[2] Since many R-factors contain F-plasmids, antibiotic resistance can be easily spread among a population of bacteria. Also, R-factors can be taken up by "DNA pumps" in their membranes via transformation, or less commonly through viral mediated transduction, or via bacteriophage, although conjugation is the most common means of antibiotic resistance spread. They contain the gene called RTF (Resistance transfer factor).

References[]

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