a piece of virus DNA that becomes a part of a bacterium's genome- until activated to produce new bacteriophages
The piece of virus DNA that becomes a part of a bacterium's genome and is activated to produce new bacteriophages is called a prophage.
During the lysogenic cycle of viral infection, the virus DNA integrates into the bacterium's genome and becomes a prophage. This integration is facilitated by specific enzyme systems encoded by the viral DNA. The prophage then remains dormant within the bacterium's genome, replicating along with the bacterial DNA during cell division.
Under certain conditions, such as exposure to certain chemicals or radiation, or stress factors affecting the host cell, the prophage can be activated and initiate the lytic cycle. In the lytic cycle, the prophage DNA is excised from the bacterial genome and viral replication ensues, resulting in the production of new bacteriophages. These bacteriophages can then go on to infect other bacteria and continue the viral life cycle.