Bacteriophages, first discovered around 1915, have played a unique role in viral biology. They are perhaps the best understood viruses, yet at the same time, their structure can be extraordinarily complex. The use of bacteriophages played a prominent role in elucidating that DNA in viruses can reproduce through two mechanisms: the lytic cycle and the lysogenic cycle.
Bacteriophages Image copyright Dennis Kunkel
Virulent Bacteriophages and the Lytic Cycle
Temperate viruses are those that reproduce without killing their host cell. Typically they reproduce in two ways: through the lytic cycle and the lysogenic cycle. In the lysogenic cycle, the phage's DNA recombines with the bacterial chromosome. Once it has inserted itself, it is known as a prophage. A host cell that carries a prophage has the potential to lyse, thus it is called a lysogenic cell.