A LYSOGEN or LYSOGENIC BACTERIUM is a bacterial cell in which a phage exists as DNA in its dormant state (prophage ). A prophage is either integrated into the host bacteria 's chromosome or more rarely exists as a stable plasmid within the host cell. The prophage expresses gene(s) that repress the phage's lytic action, until this repression is disrupted (see lytic cycle ). Currently a variety of studies are being conducted to see whether other genes are active during lysogeny, examples of which include phage-encoded tRNA and virulence genes.
* lambda phage
* lysogenic cycle