— The term “ lysogenic ” implies that prophages are capable of giving rise to active phages that lyse their host cells. This occurs when the viral genome exits the bacterial chromosome and initiates the lytic cycle. The triggers for this switch-over are usually environmental factors such as mutagens (e.g. radiation and presence of certain chemicals) — It depends on a few factors, such as how many phages infected the cell, whether or not the cell is in good growth conditions, and so on. — If the cell is in stress or has low amounts of nutrients, the lysogenic pathway is typically activated. — The underlying mechanism has to do with a protein cascade involving either the cro or cI protein that is encoded by the virus. — The cI protein is a repressor, and it will prevent the lytic genes from being transcribed. By default the virus will transcribe the lytic genes, so they must be repressed for lysogeny to occur. — Similarly, cro is also a transcriptional repressor....
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