What is a temperate phage?

A temperate phage is characterized by its ability to integrate its genetic material into the host bacterium's DNA. This integration can occur during the lysogenic cycle of the phage, where instead of immediately killing the host cell, the phage DNA becomes incorporated into the bacterial genome. Once integrated, the phage DNA, referred to as a prophage, can replicate along with the host DNA during bacterial cell division. Under certain conditions, the prophage can excise itself from the host genome and enter the lytic cycle, ultimately leading to the production of new phage particles and lysis of the bacterial cell.

This defining feature of temperate phages distinguishes them from other types of bacteriophages, which may only go through the lytic cycle, where the virus immediately takes over the host cell to produce new viruses before causing cell death. Thus, temperate phages represent an important mechanism in the interaction between viruses and bacteria, influencing genetic diversity and horizontal gene transfer among bacterial populations.