Temperate phage life cycle: In a lysogenized bacterial culture, the phage reproductive cycle is triggered by a process known as what?

Introduction / Context: Temperate bacteriophages can integrate into the host genome as prophage and remain quiescent under the control of a phage-encoded repressor. Under stress, the prophage can be activated to enter the lytic cycle. This activation step is called induction and is central to understanding lysogeny–lysis switches.

Given Data / Assumptions:

• Lysogeny: prophage maintained in the host chromosome.
• DNA-damaging conditions (e.g., UV) can inactivate repressors.
• Once repression is relieved, lytic genes are expressed.

Concept / Approach: In models such as phage lambda, the CI repressor maintains latency. SOS responses (RecA-mediated) cleave the repressor, resulting in induction. The prophage excises, replicates, and packages its DNA, culminating in host lysis and virion release.

Step-by-Step Solution: Define lysogeny vs. lytic growth. Identify the control protein (repressor) that prevents lytic gene expression. Recognize environmental triggers that disable repression. Name the switch event: induction.

Verification / Alternative check: Classic experiments show UV exposure of lysogens yields phage production after prophage excision, consistent with induction.

Why Other Options Are Wrong: Infection precedes lysogeny; integration is the establishment step; repression maintains dormancy; packaging is a late lytic event, not the trigger.

Common Pitfalls: Confusing “induction” with initial infection; the term specifically refers to reactivation of a prophage.

Final Answer: Induction.