Generalities:

Bacteriophages are viruses that attack exclusively bacteria since they have affinity with specific receptors of the cell membrane. They are wicked organisms, they can be found practically in any medium: water, intestines, etc. Once the phage infects the bacterium, it can either replicate and destroy (lysis) the lytic cycle; or, the phage genome can be incorporated into the chromosomal DNA of the bacterium and replicated along with it: lysogenic cycle. The genetic material can remain stable (plasmid) until it is necessary to replicate again, becoming a parasite of the bacteria.

They can be beneficial for the human organism in regulating bacterial populations. But they can also be pathogenic by altering the bacterial genome, unleashing processes that affect the host, such as the production of toxins or the increase in resistance.

Phages are used in molecular biology as cloning vectors.