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Understand  –  Antibiotic resistance

Transfer of antibiotic resistance

Bacteria can share genes with each other in a process called horizontal gene transfer. This can occur both between bacteria of the same species and between different species and by several different mechanisms, given the right conditions. Gene transfer results in genetic variation in bacteria and is a large problem when it comes to the spread of antibiotic resistance genes.

Ways for bacteria to share their genes:

  • Conjugation: Two bacteria can pair up and connect through structures in the cell membranes and then transfer DNA from on bacterial cell to another.
  • Transduction: There are viruses called bacteriophages that can infect bacteria. These viruses sometimes bring along genes that they picked up during infection of another bacterium. These genes may then be incorporated into the DNA of the new bacterial host.
  • Transformation: Some bacteria can take up pieces of DNA directly from the environment around the cell.

Transfer of antibiotic resistance genes

Any gene has the potential to be transferred between bacteria in this manner, including antibiotic resistance genes. Whether or not transferred genes will be integrated into the DNA of a recipient bacterium is another question. Foreign DNA can be harmful to a bacterium, and there are machineries in place that degrades incoming DNA. However, these systems are not 100% efficient. If the incoming DNA is incorporated and provides a benefit for the bacterium it is more likely maintained. For example, if a bacterium picks up an antibiotic resistance gene and is subsequently exposed to that antibiotic, this bacterium will be better off than susceptible neighbors and can increase in number.

Selected Resources

Resource Description
Bacterial Reproduction & Exchanges of Genetic Material Narrated presentation by C. Savage about how bacteria multiply and the different processes that creates diversity in bacteria (9 min).
Horizontal gene transfer Short animation of how plasmids transfer between bacteria (conjugation).
TEDxSanAntonio: Rise of the Superbug – Antibiotic-Resistant Bacteria TEDx talk by Dr. K. Klose about conjugation, transformation and transduction in relation to antibiotic resistance and development of “superbugs” (11 min).