Lambda phage

Definition

Lambda phage is a type of bacteriophage that infects the bacterium Escherichia coli (E. coli) and is commonly used as a model organism in molecular biology studies. It can exist in two states: the lytic cycle, where it replicates and causes cell lysis, and the lysogenic cycle, where its DNA integrates into the host genome, allowing it to be replicated along with the host's DNA. This dual lifestyle makes lambda phage a significant tool for studying virus infections and host interactions.

5 Must Know Facts For Your Next Test

1. Lambda phage has a double-stranded DNA genome and is one of the simplest bacteriophages, making it an ideal model for genetic studies.
2. In the lysogenic cycle, lambda phage's genome can integrate into the E. coli chromosome at specific sites, a process that allows for genetic recombination.
3. Researchers utilize lambda phage as a vector for cloning genes and studying gene expression due to its ability to carry foreign DNA.
4. Lambda phage can switch between the lytic and lysogenic cycles based on environmental conditions, allowing it to adapt to different situations.
5. The study of lambda phage has provided insights into fundamental biological processes, such as the mechanisms of viral infections and the regulation of gene expression.

Review Questions

• How do the lytic and lysogenic cycles differ in their impact on the host E. coli cells infected by lambda phage?
  • The lytic cycle leads to the production of new lambda phage particles and ultimately results in the destruction of the E. coli host cell through lysis. In contrast, during the lysogenic cycle, lambda phage integrates its DNA into the host's genome, allowing it to replicate alongside the bacterial DNA without causing immediate harm. This means that while lytic infections are destructive and lead to cell death, lysogenic infections can persist without killing the host.
• Discuss how lambda phage serves as a valuable tool for genetic research in molecular biology.
  • Lambda phage is instrumental in genetic research because it can be engineered to carry foreign DNA, making it a useful vector for cloning genes. Scientists exploit its ability to integrate into the host genome during the lysogenic cycle to study gene expression and regulatory mechanisms. By manipulating lambda phage, researchers can investigate various genetic phenomena, such as recombination and gene regulation, contributing significantly to our understanding of molecular biology.
• Evaluate the significance of environmental triggers in determining whether lambda phage enters the lytic or lysogenic cycle during infection.
  • Environmental triggers play a crucial role in deciding whether lambda phage enters the lytic or lysogenic cycle after infecting E. coli. Factors such as nutrient availability and stress conditions influence this decision-making process. If conditions are favorable, lambda phage may opt for the lytic cycle to maximize its replication before host cell death. However, under stressful conditions where resources are scarce, it may choose the lysogenic cycle to ensure its survival by integrating into the host genome. This adaptability highlights lambda phage's evolutionary strategies and its role in understanding viral-host dynamics.

Related terms

Bacteriophage: A virus that specifically infects and replicates within bacteria.

Lytic cycle:

The phase of viral replication where the virus hijacks the host cell's machinery to produce new virions, ultimately causing cell death.

Lysogenic cycle:

The phase where the viral DNA integrates into the host's genome, remaining dormant until triggered to enter the lytic cycle.