Viral Replication: Lysogenic Cycle

The lysogenic cycle is a viral replication mechanism in which temperate bacteriophages like lambda integrate their DNA into a host cell without immediate lysis of the cell.

It begins when the lambda phage attaches to E. coli and injects its genetic material.

Inside the host, the linear genome circularizes and integrates into the bacterial chromosome via site-specific recombination, forming a prophage.

The prophage remains latent, with repressor proteins blocking viral gene expression.

As the bacterium divides, it copies the prophage and DNA, passing them to daughter cells.

This process results in three key outcomes for the host cell: immunity from the same phage, acquiring new bacterial traits, and horizontal gene transfer.

The prophage may be excised from the bacterial chromosome under stress, such as exposure to UV radiation, starvation, or chemicals.

This triggers a switch to the lytic cycle, where the virus replicates rapidly and ultimately causes cell lysis.