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Related Concept Videos

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DNA Bacteriophages

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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...
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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.
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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...
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Viral Replication: Lysogenic Cycle01:16

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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...
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Viral Replication: Lytic Cycle01:20

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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...
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The Antiviral System of Bacteria and Archaea: CRISPR

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CRISPR stands for Clustered Regularly Interspaced Short Palindromic Repeats is a adaptive immune system found in bacteria and archaea that protects against viral infections. This system enables prokaryotic cells to identify, remember, and neutralize foreign genetic elements, primarily bacteriophages, by storing fragments of the invader’s DNA as a genetic memory.The CRISPR immune response begins during an initial infection. Cas (CRISPR-associated) proteins play a central role in this...
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Applying an Inducible Expression System to Study Interference of Bacterial Virulence Factors with Intracellular Signaling
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Bacterial retrons encode phage-defending tripartite toxin-antitoxin systems.

Jacob Bobonis1,2, Karin Mitosch1, André Mateus1,3

  • 1Genome Biology Unit, European Molecular Biology Laboratory, Heidelberg, Germany.

Nature
|July 19, 2022
PubMed
Summary
This summary is machine-generated.

Retrons are prokaryotic genetic elements. Researchers discovered that the Retron-Sen2 system in Salmonella Typhimurium encodes a toxin (RcaT) neutralized by its own reverse transcriptase-msDNA complex, revealing a new tripartite toxin-antitoxin system for anti-phage defense.

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Area of Science:

  • Microbiology
  • Molecular Biology
  • Genetics

Background:

  • Retrons are prokaryotic retroelements that synthesize multi-copy single-stranded DNA (msDNA).
  • The precise biological functions and physiological roles of retrons have remained largely unknown despite extensive research on msDNA biosynthesis.

Purpose of the Study:

  • To elucidate the function of retron elements, specifically Retron-Sen2 from Salmonella enterica serovar Typhimurium.
  • To characterize the newly identified toxin protein RcaT and its interaction with the retron's reverse transcriptase and msDNA.
  • To investigate the role of retron systems in bacterial defense mechanisms.

Main Methods:

  • Identification and renaming of the retron-encoded accessory toxin protein as RcaT.
  • Characterization of the RcaT neutralization mechanism by the reverse transcriptase-msDNA complex.
  • Development and application of toxin activation-inhibition conjugation (TAC-TIC) for high-throughput reverse genetics.
  • Analysis of phage-derived proteins as triggers and blockers of the retron toxin-antitoxin system.

Main Results:

  • Retron-Sen2 encodes RcaT, a toxin neutralized by its reverse transcriptase-msDNA complex, forming a tripartite DNA-containing toxin-antitoxin system.
  • The reverse transcriptase binds RcaT, while msDNA provides antitoxin activity, with activation occurring upon msDNA biosynthesis disruption.
  • The TAC-TIC system identified phage proteins that activate RcaT by modifying msDNA or directly inhibit RcaT, demonstrating anti-phage activity.

Conclusions:

  • RcaT retron systems represent a novel class of tripartite DNA-regulated toxin-antitoxin systems.
  • These systems function as abortive infection anti-phage defense mechanisms.
  • The reverse transcriptase-msDNA complex acts as both an antitoxin and a sensor for phage protein activity, regulating bacterial defense.