Answer to Question #55321 in Microbiology for Fāll

Question

Can a bacteriophage have only one out of the two possible life cycles ( lytic cycle and lysogenic cycle), or it can shift from one cycle to another? For example we take T2 phage, it was lytic cycle , can it also have lysogenic cycle, can it shift through cycles?

Answer 1

Yes, it can. Some of the phages cause the development of lytic cycle only. They enter the cell and reproduce immediately. Then, they leave the cell. Lysogenic phages have a combination of lysogenic stage and lytic stage because they should leave the cell in search of new hosts. However, there is a small group of phages which do not perfrom lytic cycle. It is sometimes difficult to distinguish between them and transposons. They are always present in bacterial genome and have lost the genes required for active infection. They increase the number of their copies by moving within the genome.