Bacteriophage lambda (above) lacks tail fibers, but attaches to a host cell via molecules at the base of the tail.  This is a lysogenic virus that can incorporate its dsDNA with that of its host cell, E. coli.


Though the prophage can remain dormant and even be replicated and passed to new daughter cells via fission, induction to enter the lytic cycle occurs eventually, triggered by some environmental change or physical event, such as exposure to ionizing or nonionizing radiation or to carcinogenic chemicals.

Some bacteria can undergo lysogenic conversion when infected by a prophage.  In this phenomenon, phage genes are expressed that give rise to toxins and other pathogenic compounds without the induction of the entire prophage genome.  Many bacteria such as Corynebacterium diptheriae, Yersinia pestis, Clostridium botulinum and Escherichia coli only express pathogenic characteristics as a result of lysogenic conversion.