Transfer of antibiotic resistance

Bacteria can share genes with each other through a process called horizontal gene transfer. This can occur between bacteria of the same or different species via several mechanisms, under the right conditions. Gene transfer leads to genetic variation in bacteria and poses a significant 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 one 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 are integrated into the DNA of a recipient bacterium is another question. Foreign DNA can be harmful to a bacterium, and there are mechanisms in place that degrade incoming DNA. However, these systems are not 100% efficient. If the incoming DNA is incorporated and provides a benefit to the bacterium, it is more likely to be maintained. For example, if a bacterium picks up an antibiotic resistance gene and is subsequently exposed to that antibiotic, it will be better off than susceptible neighbors and will increase in number.

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