prophageencoded

Prophage-encoded refers to genes and genetic elements that are carried by a prophage—an integrated, dormant form of a temperate bacteriophage within a bacterial chromosome. When a phage infects a bacterium and enters the lysogenic cycle, its genome becomes a stable part of the host cell as a prophage. Prophage-encoded genes may be expressed by the bacterium and can influence its phenotype without immediate lysis.

These genes can play a significant role in bacterial physiology and ecology. Prophage-encoded elements include virulence factors, such as toxins or adhesion proteins, as well as immunity functions that protect the host from infection by related phages. They can also encode regulatory proteins, metabolic enzymes, or DNA-modifying functions that alter gene expression and cellular behavior. Through lysogenic conversion, bacteria acquire new traits via prophage-encoded genes, which can impact virulence, host range, and ecological interactions.

Induction of a prophage—often in response to stress or DNA damage—can trigger the lytic cycle, leading to phage production and cell lysis. Even when not induced, prophage-encoded genes may be stably maintained and expressed, shaping the fitness and evolution of bacterial populations. Several well-known examples illustrate the concept: the cholera toxin genes (ctxAB) are carried by CTX phage prophages in Vibrio cholerae; Shiga toxin genes (stx1, stx2) reside on lambdoid prophages in pathogenic Escherichia coli; and the diphtheria toxin gene is carried by corynephage in Corynebacterium diphtheriae. Prophage-encoded elements thus represent a major mechanism by which bacteriophages contribute to bacterial diversity and pathogenic potential.