Final answer:
A bacteriophage is a virus that infects and replicates within bacteria, undergoing either the lytic cycle, causing host cell death, or the lysogenic cycle, where it integrates into the host genome and can potentially re-enter the lytic cycle under stress conditions.
Step-by-step explanation:
What is a Bacteriophage?
A bacteriophage, commonly referred to as a phage, is a virus that infects and replicates within bacteria. During the lytic cycle, the bacteriophage hijacks the host cell's machinery to produce new virions, which leads to cell lysis and death, as seen with the T4 phage infecting Escherichia coli. Alternatively, during the lysogenic cycle, the bacteriophage integrates its DNA into the host genome as a prophage, where it can replicate along with the cell's DNA without causing immediate harm, exemplified by the λ (lambda) phage. Environmental stressors can cause a prophage to re-enter the lytic cycle. Essential to both cycles are the processes of attachment and entry, where bacteriophages bind to specific receptors on the bacterial cell surface and inject their genetic material. These traits make some bacteriophages useful in phage therapy, exploiting their ability to target and kill specific bacteria.