In the stable state of the prophage, what role does the lambda repressor play?

The lambda repressor is crucial for maintaining the dormant state of the prophage within the bacterial host cell. When the bacteriophage lambda infects a bacterial cell, it can either enter the lytic cycle, where it replicates and causes the cell to burst, or it can enter a lysogenic cycle, integrating its DNA into the host genome. In the lysogenic state, the integrated viral DNA is called a prophage.

The lambda repressor functions by binding to specific sites on the viral DNA to inhibit the expression of genes that would lead to the lytic cycle. By doing so, it effectively silences those genes that are responsible for phage replication and the production of new phage particles. This repression is essential for sustaining the prophage in a dormant state, allowing the bacterial cell to replicate normally while carrying the viral genome without triggering a destructive lytic response.

Thus, the lambda repressor ensures a stable coexistence with the bacterial cell, and its role in maintaining this dormant state is vital for the survival of both the prophage and the bacterial host until conditions might favor a switch to the lytic cycle.