Related Experiment Video
Updated: Jul 15, 2026
06:10
Following Cell-fate in E. coli After Infection by Phage Lambda
Published on: October 14, 2011
Phage lambda CIII: a protease inhibitor regulating the lysis-lysogeny decision
Oren Kobiler1, Assaf Rokney, Amos B Oppenheim
1Department of Molecular Genetics and Biotechnology, The Hebrew University-Hadassah Medical School, Jerusalem, Israel. orenk@ekmd.huji.ac.il
Plos One
|April 12, 2007
Summary
Bacteriophage lambda
Area of Science:
- Molecular Biology
- Virology
- Bacteriophage Genetics
Background:
- The ATP-dependent protease FtsH (HflB) regulates bacteriophage lambda's lysis-lysogeny decision by degrading the CII protein.
- Both bacteriophage CII and CIII proteins are crucial for the lysogenic response.
- CIII acts as both an inhibitor and substrate of FtsH.
Purpose of the Study:
- To investigate the mechanism by which CIII inhibits FtsH.
- To determine the role of CIII oligomerization in its inhibitory function.
- To elucidate how CIII influences bacteriophage lambda's lysogenic response.
Main Methods:
- Biochemical characterization of CIII structure (oligomeric, alpha-helical).
- In vitro inhibition assays demonstrating competitive inhibition of FtsH by CIII.
- Site-directed mutagenesis of CIII to identify critical residues for activity.
- Analysis of CII activity in the presence and absence of FtsH, HflKC, and CIII.
- Genetic experiments to confirm FtsH inhibition by CIII.
Main Results:
- CIII functions as a competitive inhibitor of FtsH, preventing CII binding.
- CIII exists as oligomeric, amphipathic alpha-helical structures, and oligomerization is essential for its function.
- Mutations in CIII can abolish its inhibitory activity and exhibit dominant-negative effects.
- CIII enhances CII stability and promotes the lysogenic response, with its effect dependent on FtsH and HflKC.
- CIII's bacteriostatic effects are confirmed to be due to FtsH inhibition.
Conclusions:
- CIII oligomerization is critical for its function as a competitive inhibitor of FtsH.
- Early CIII expression promotes lysogeny by stabilizing CII, while later degradation reactivates FtsH for cell growth.
- This study reveals a novel regulatory mechanism for bacteriophage lambda's life cycle control involving CIII-mediated FtsH inhibition.
Related Concept Videos
01:16Viral Replication: Lysogenic Cycle
The lysogenic cycle is a crucial viral replication strategy that allows bacteriophages to persist within host cells without immediately destroying them. This process is primarily observed in temperate phages, such as bacteriophage lambda (λ), which infects Escherichia coli. The cycle allows the viral genome to persist across bacterial generations while keeping host cells viable.Integration of the Viral GenomeUpon infection, bacteriophage lambda attaches to the bacterial surface and injects its...
00:43Lysogenic Cycle of Bacteriophages
In contrast to the lytic cycle, phages infecting bacteria via the lysogenic cycle do not immediately kill their host cell. Instead, they combine their genome with the host genome, allowing the bacteria to replicate the phage DNA along with the bacterial genome. The incorporated copy of the phage genome is called the prophage. Some prophages can re-activate and enter the lytic cycle. This often occurs in response to a perturbation, such as DNA damage, but can also transpire in the absence of...
01:30Lytic Cycle of Bacteriophages
Bacteriophages, also known as phages, are specialized viruses that infect bacteria. A key characteristic of phages is their distinctive “head-tail” morphology. A phage begins the infection process (i.e., lytic cycle) by attaching to the outside of a bacterial cell. Attachment is accomplished via proteins in the phage tail that bind to specific receptor proteins on the outer surface of the bacterium. The tail injects the phage’s DNA genome into the bacterial cytoplasm. In the lytic replication...
01:26DNA Bacteriophages
Bacteriophages, or phages, are viruses that specifically infect bacteria, utilizing their genetic material to hijack host cellular machinery for replication. DNA bacteriophages employ single-stranded DNA (ssDNA) or double-stranded DNA (dsDNA) genomes. These phages exhibit diverse replication strategies and host interactions, influencing their ecological roles and applications in biotechnology and medicine.ssDNA BacteriophagesssDNA phages, with their small genomes, utilize unique strategies to...
01:20Viral Replication: Lytic Cycle
Bacteriophages, or phages, are viruses that specifically infect bacteria. Among them, T-even bacteriophages, such as T4, exhibit a well-characterized lytic replication cycle in Escherichia coli (E. coli). This process ensures the rapid proliferation of the virus while ultimately leading to the destruction of the bacterial host.Attachment and DNA InjectionThe infection process begins with the recognition and binding of the T4 phage to the E. coli cell surface. Tail fibers of the phage...
01:28Regulation of Bacterial Virulence
Pathogenic bacteria employ a range of regulatory mechanisms to modulate the expression of virulence genes in response to environmental and host-derived signals. These mechanisms ensure that virulence factors are expressed only under favorable conditions, thereby optimizing infection and survival strategies.Mechanisms of Virulence RegulationKey regulatory strategies include:Two-Component Systems: These consist of a membrane-bound sensor kinase and a cytoplasmic response regulator. Environmental...