Related Experiment Video
Updated: Jul 12, 2026
09:23
Understanding the Impact of Temperate Bacteriophages on Their Lysogens Through Transcriptomics
Published on: January 5, 2024
Hypervariation and phase variation in the bacteriophage 'resistome'.
Paul A Hoskisson1, Margaret C M Smith
1Strathclyde Institute of Pharmacy and Biological Science, University of Strathclyde, Royal College Building, George Street, Glasgow, United Kingdom.
Current Opinion in Microbiology
|August 28, 2007
Summary
Bacteria utilize diverse defense proteins against bacteriophages, with restriction-modification (R-M) systems rapidly evolving. Some R-M systems exhibit phase variation, potentially enhancing phage defense by switching off expression.
Area of Science:
- Microbiology
- Bacteriophage-bacteria interactions
- Molecular genetics
Background:
- Bacteria possess diverse protein mechanisms for defense against bacteriophage (phage) infection.
- Phage defense strategies are highly varied, indicating frequent independent evolution of novel processes.
- Defense genes are often plasmid or phage-encoded, with chromosomal genes frequently showing evidence of lateral transfer.
Purpose of the Study:
- To investigate the evolutionary dynamics and functional significance of bacterial phage defense mechanisms.
- To explore the role of restriction-modification (R-M) systems and contingency genes in bacterial immunity.
- To understand the counter-intuitive prevalence of phase variation in R-M systems.
Main Methods:
- Analysis of genomic data to identify phage defense determinants and their evolutionary patterns.
- Focus on restriction-modification (R-M) systems, including Type I and Type III systems.
- Examination of contingency genes and phase variation in R-M system expression.
Main Results:
- Restriction-modification (R-M) genes are among the most rapidly evolving bacterial genes.
- Contingency genes provide alternative target specificities for R-M systems, broadening phage resistance.
- Phase variation in R-M systems, though counter-intuitive, may enhance phage defense by regulating gene expression.
Conclusions:
- Bacterial phage defense is characterized by diverse, rapidly evolving mechanisms, including R-M systems.
- Adaptive strategies like contingency genes and phase variation contribute to bacterial resilience against phages.
- Switching off R-M systems via phase variation is a potential strategy for improved phage defense.
Related Concept Videos
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...
01:16Viral 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...
02:53Conservative Site-specific Recombination and Phase Variation
Because the DNA segments are cut and reorganized in a direction-specific manner, site-specific recombination has emerged as an efficient genetic engineering technique. Flippase and Cyclization recombinases or Flp and Cre, respectively, are two members of the tyrosine recombinase family derived from bacteriophages, that are used to mediate site-specific DNA insertions, deletions, and targeted expression of proteins in mammalian cell lines.
The recognition sites for Cre recombinase called LoxP...
The recognition sites for Cre recombinase called LoxP...
01:23Bacteriophages of the Human Virome
Bacteriophages are found throughout the human body. They may even outnumber eukaryotic viruses, forming an important and dynamic component of the human virome. Indeed, phages represent the most abundant viral entities, with densities in the gut reaching up to 10⁹ particles per gram of fecal matter, and many belonging to orders such as Caudovirales and Microviridae, while a substantial proportion remains unclassified as viral “dark matter.”Lysogeny and Genetic ExchangeIn the gut, bacteriophages...
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...
01:28Regulation 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...