What triggers the transition from prophage to lytic pathway?

The transition from prophage to the lytic pathway is primarily triggered by an induction event. In the context of bacteriophages, a prophage is a phage genome integrated into the bacterial chromosome, where it can remain dormant. An induction event typically occurs due to stressful conditions in the host cell, such as UV radiation, chemical exposure, or other environmental triggers that compromise the integrity of the host cell. These stresses can activate specific cellular processes which lead to the excision of the prophage from the bacterial genome and its subsequent replication and assembly into new phage particles, thus stimulating the lytic phase.

Cell replication, environmental changes, and protein synthesis play important roles in the overall lifecycle of a bacteriophage and its host but do not directly trigger the transition to the lytic pathway. Cell replication refers to the bacterial cell dividing, which can happen independently of phage activity. Environmental changes can contribute to the induction conditions but do not directly initiate the transition without specific stress signals. Protein synthesis is a continual process in the cell and is not the event that specifically causes the prophage to enter the lytic cycle.