Lysogena

Lysogena is a term used in microbiology to describe the lysogenic state of a bacteriophage and its bacterial host. In lysogeny, temperate phages integrate their DNA into the bacterial chromosome, forming a prophage. The prophage is replicated along with the host genome and remains largely dormant, with phage genes repressed and no production of new virions. The lysogen, a bacterium carrying a prophage, may acquire properties conferred by prophage genes and often exhibits immunity to related phages, reducing superinfection.

Induction can occur when the prophage is activated by stress, such as UV light or DNA damage. This triggers excision of the prophage and entry into the lytic cycle, wherein the phage genome is replicated, new virions are produced, and the host cell typically undergoes lysis to release the progeny phages. The balance between lysogeny and lysis allows phages to persist in bacterial populations under favorable conditions and switch to rapid replication when conditions deteriorate.

Significance and consequences of lysogeny include lysogenic conversion, where prophage genes alter host phenotype and fitness. Prophages can carry virulence factors or beneficial traits, contributing to horizontal gene transfer within microbial communities. Notable examples include toxins encoded by prophages, such as the diphtheria toxin gene in Corynebacterium diphtheriae and cholera toxin genes in Vibrio cholerae carried by CTX phage; Shiga toxin–encoding phages are associated with certain pathogenic Escherichia coli strains. Overall, lysogena plays a key role in bacterial evolution, ecology, and the emergence of virulence.