Lysogenic cycle of viruses
Some viruses, when they infect a host cell, do not destroy it (lytic cycle), but the viral nucleic acid is incorporated into the cellular DNA, where it is replicated and transmitted during successive generations. These viruses are called tempered or attenuated viruses or prophages, and the recipient cell, lysogen cell.
The viral DNA integrated into the bacteria is called a provirus or prophage, and it can remain latent for several generations, until a stimulus (certain inducing agents, usually physical or chemical agents that damage DNA) induces the separation of the prophage, that will start a typical lithic cycle.
Therefore, unlike the lytic cycle, in the lysogenic cycle the virus incorporates its genetic material into the genetic material or genome of the host cell where it can remain latent for an unlimited time (prophage). When it is activated it develops the phases of the lytic cycle.
When the cell contains the prophage, it is immune to other viruses of the same species, and this immunity will be transmitted to subsequent generations, since the prophage is inherited together with the cell's DNA.
Viruses are thought to play an important role in the evolution of species, since when viruses incorporate new genes when infecting a cell, the prophage entails an enrichment of the host cell genotype.