Bacteriophage lambda

Bacteriophage lambda (also known as λ phage) is a bacteriophage that infects the bacterial species Escherichia coli (E. coli). It is a temperate phage, meaning it can either replicate via the lytic cycle or integrate its DNA into the host genome via the lysogenic cycle.

Life Cycle

Bacteriophage lambda has a complex life cycle that allows it to either reside within the host genome in a dormant state or to actively replicate and produce progeny phages. This decision between the lytic and lysogenic cycles is determined by the environmental conditions surrounding the bacteriophage.

Lytic Cycle

In the lytic cycle, bacteriophage lambda infects E. coli by binding to the outer membrane of the bacterium and injecting its DNA. The phage DNA then directs the host cell to produce new phages. Once a sufficient number of phages have been produced, the host cell is lysed, releasing the progeny phages to infect other cells.

Lysogenic Cycle

In the lysogenic cycle, the phage DNA integrates into the host genome and becomes a prophage. The prophage DNA is then replicated along with the host DNA without causing harm to the host. The prophage can remain dormant within the host genome for many generations. Under certain conditions, the prophage can be induced to excise itself from the host genome and enter the lytic cycle.

Genetic Switch

Bacteriophage lambda is well known for its genetic switch, a mechanism that determines whether the phage will enter the lytic or lysogenic cycle. This switch is controlled by two repressor proteins, cI and cro, which bind to the operator region of the phage DNA and regulate the transcription of the phage genes.

Applications

Bacteriophage lambda has been extensively used in molecular biology research. It has been a key tool in the study of gene regulation, DNA recombination, and other fundamental aspects of molecular biology. It is also used in phage display, a technique for studying protein-protein, protein-peptide, and protein-DNA interactions.

See Also

• Bacteriophage
• Lytic cycle
• Lysogenic cycle
• Molecular biology
• Phage display