User:Efjager/Prophage

Prophage induction
Upon detection of host cell damage by UV light or certain chemicals, the prophage is excised from the bacterial chromosome in a process called prophage induction. After induction, viral replication begins via the lytic cycle. In the lytic cycle, the virus commandeers the cell's reproductive machinery. The cell may fill with new viruses until it lyses or bursts, or it may release the new viruses one at a time in an exocytotic process. The period from infection to lysis is termed the latent period. A virus following a lytic cycle is called a virulent virus. Prophages are important agents of horizontal gene transfer, and are considered part of the mobilome. '''Genes are transferred via transduction as the prophage genome is imperfectly excised from the host chromosome and integrated into a new host (specialized transduction) or as fragments of host DNA are packaged into the phage particles and introduced into a new host (generalized transduction). ''' All families of bacterial viruses that have circular (single-stranded or double-stranded) DNA genomes or replicate their genomes through rolling circle replication (e.g., Caudovirales) have temperate members.

Cost/benefit to the host
Lysis of host cells during prophage induction can cause the collapse of a microbial population. On the other hand, induction, transduction and superinfection exclusion mechanisms confer many beneficial functions to the host. Induction of prophages allows hosts to compete in the microbial ecology by infecting and lysing susceptible bacteria. Phages also enable the host to pick up and integrate antibiotic resistance genes from nearby cells. Additionally, phages can enable the host to acquire virulence and pathogenicity genes. Modulation of biofilm formation is also affected by infection by lysogenic phages. Superinfection exclusion, or protection against infection by multiple phages, can be conferred by prophage integration. Additionally, phage-mediated recombination mechanisms may remodel the host chromosome and provide new ways for cells to regulate metabolism and gene expression, such as those involved in sporulation and competence.