Related Experiment Video
Updated: Jan 19, 2026
06:10
Following Cell-fate in E. coli After Infection by Phage Lambda
Published on: October 14, 2011
24.2K
Elements in the λ immunity region regulate phage development: beyond the 'Genetic Switch'.
Lynn C Thomason1, Kathleen Morrill2, Gillian Murray2
1Basic Science Program, Frederick National Laboratory for Cancer Research, Frederick, MD, 21702, USA.
Molecular Microbiology
|September 24, 2019
Summary
Bacteriophage lambda's genetic elements, including the PLIT promoter and TIMM terminator, control its life cycle. RexA and RexB proteins are crucial for switching from lysogeny to lytic growth, impacting phage yield.
Area of Science:
- Microbiology
- Molecular Biology
- Genetics
Background:
- Bacteriophage lambda (λ) maintains lysogeny or undergoes lytic growth via a genetic switch regulated by CI and Cro repressors.
- The λ immunity region contains less-studied elements like the PLIT promoter and TIMM terminator, which influence prophage maintenance and induction.
- LexA repressor regulates PLIT, coordinating its activation with lytic promoters during the SOS response.
Purpose of the Study:
- To investigate the roles of the PLIT promoter and TIMM terminator in bacteriophage λ's life cycle.
- To understand the function of RexA and RexB proteins in the switch between lysogenic and lytic growth.
- To characterize the interaction and regulation of these genetic elements.
Main Methods:
- Bacterial two-hybrid system to study RexA and RexB protein interactions.
- Analysis of mutations in PLIT and TIMM to assess their impact on phage biology.
- Gene expression analysis to determine promoter activity and protein levels.
Main Results:
- The PLIT promoter is repressed by bacterial LexA, ensuring synchronous activation with lytic promoters during DNA damage.
- RexA and RexB proteins interact and are critical for the lysogeny-to-lytic switch; mutations in PLIT disrupt RexA/RexB balance, reducing phage yield.
- TIMM functions as a Rho-independent terminator with minimal impact on lysogenization or induction.
Conclusions:
- The PLIT promoter and RexA/RexB proteins play significant roles in regulating bacteriophage λ's lytic pathway and overall yield.
- TIMM appears to be a functional terminator but has a limited role in key λ life cycle events.
- Understanding these regulatory elements provides insight into bacteriophage-host interactions and genetic switch mechanisms.
Related Concept Videos
01:16Viral Replication: Lysogenic Cycle
1.4K
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...
1.4K
01:26DNA Bacteriophages
830
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...
830
00:43Lysogenic Cycle of Bacteriophages
67.4K
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...
67.4K
01:30Lytic Cycle of Bacteriophages
77.5K
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...
77.5K
01:16Transduction
1.3K
Among the three main modes of HGT—transformation, conjugation, and transduction—transduction is unique in that it is mediated by bacteriophages, or bacterial viruses.Transduction occurs in two ways. Generalized transduction occurs during the lytic cycle of a bacteriophage infection. In this process, bacteriophages infect bacterial cells, replicate within them, and ultimately cause cell lysis, releasing newly assembled virions. Occasionally, random fragments of the bacterial genome...
1.3K
02:53CRISPR and crRNAs
18.7K
Bacteria and archaea are susceptible to viral infections just like eukaryotes; therefore, they have developed a unique adaptive immune system to protect themselves. Clustered regularly interspaced short palindromic repeats and CRISPR-associated proteins (CRISPR-Cas) are present in more than 45% of known bacteria and 90% of known archaea.
The CRISPR-Cas system stores a copy of foreign DNA in the host genome and uses it to identify the foreign DNA upon reinfection. CRISPR-Cas has three different...
The CRISPR-Cas system stores a copy of foreign DNA in the host genome and uses it to identify the foreign DNA upon reinfection. CRISPR-Cas has three different...
18.7K