Which of the following can trigger a bacteriophage to enter the lytic cycle in bacteria?

• A. Increase in nutrient availability and high temperature
• B. Decrease in oxygen concentration and low pH
• C. Exposure to UV radiation and certain chemicals
• D. Addition of antibiotics and high salt concentration

Answer: (C)

Verified step by step guidance

1. Understand the two main life cycles of bacteriophages: the lysogenic cycle, where the phage DNA integrates into the host genome and remains dormant, and the lytic cycle, where the phage actively replicates and causes host cell lysis.
2. Recognize that certain environmental stresses or damaging agents can induce a prophage (a dormant phage in the lysogenic cycle) to switch to the lytic cycle.
3. Identify that exposure to UV radiation and certain chemicals causes DNA damage in the bacterial host, which acts as a signal for the prophage to exit lysogeny and enter the lytic cycle to produce new phage particles.
4. Note that other conditions like increased nutrients, temperature changes, oxygen levels, pH, antibiotics, or salt concentration do not directly trigger the lytic cycle in the same way DNA-damaging agents do.
5. Conclude that the key trigger for induction of the lytic cycle is DNA damage caused by agents such as UV radiation and specific chemicals, which activates the SOS response in bacteria and leads to prophage induction.