Which of the following is NOT a method of horizontal gene transfer?

Horizontal gene transfer refers to the movement of genetic material between organisms, as opposed to vertical gene transfer, which is the transmission of genetic material from parent to offspring. Conjugation, transformation, and transduction are all recognized methods of horizontal gene transfer that allow for genetic variability among bacteria.

Conjugation involves the direct transfer of DNA from one bacterium to another through a physical connection, often mediated by a pilus. This process enables the sharing of plasmids or chromosomal DNA, enhancing genetic diversity and adaptability.

Transformation is the uptake of free DNA from the environment by a bacterial cell. Bacteria can take up DNA that is released from other cells, integrate it into their own genome, and express the new traits conferred by this acquired DNA.

Transduction is the process by which bacterial DNA is transferred from one bacterium to another via a bacteriophage (a virus that infects bacteria). During the lytic cycle of the bacteriophage, bacterial DNA can be mistakenly packaged into new viral particles and transferred to another bacterium upon infection.

Mutation, however, is a process that occurs within the organism itself, involving changes to the DNA sequence that arise during replication or due to environmental factors. Unlike the other three methods, it does not involve