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Related Concept Videos

DNA Bacteriophages01:26

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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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 Replisome03:01

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DNA replication is carried out by a large complex of proteins that act in a coordinated matter to achieve high-fidelity DNA replication. Together this complex is known as the DNA replication machinery or the replisome.
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DNA Helicases00:55

DNA Helicases

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DNA unwinding helicase enzymes are a type of motor protein. Motor proteins can translocate along filaments or polymers using energy generated from ATP hydrolysis. Helicases are involved in all the important cellular processes where DNA unwinding is required, such as DNA replication, repair, recombination, and transcription. They are present in all living organisms, but vary in their structure, function, and mechanism of action. For example, in prokaryotes, DnaB helicase binds and translocates...
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Lytic Cycle of Bacteriophages01:30

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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...
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Updated: Sep 27, 2025

Kinetics of Lagging-strand DNA Synthesis In Vitro by the Bacteriophage T7 Replication Proteins
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A single bacterial enzyme i(NHI)bits phage DNA replication.

Erin Huiting1, Joseph Bondy-Denomy2

  • 1Department of Microbiology and Immunology, University of California, San Francisco, San Francisco, CA 94158, USA.

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Researchers discovered a novel bacterial defense system called nuclease-helicase immunity (Nhi). This system uses one enzyme to detect and stop phage DNA replication, offering a new strategy against viral infections.

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Area of Science:

  • Microbiology
  • Bacteriology
  • Virology

Background:

  • Bacterial infections are a growing threat due to antibiotic resistance.
  • Bacteriophages (phages) are viruses that infect bacteria and can exacerbate infections.
  • Existing anti-phage systems like CRISPR-Cas and restriction-modification (R-M) rely on sequence recognition.

Purpose of the Study:

  • To identify and characterize novel anti-phage immune mechanisms in bacteria.
  • To understand the molecular basis of phage DNA detection and replication inhibition.
  • To explore alternatives to sequence-dependent anti-phage strategies.

Main Methods:

  • Bioinformatic analysis to identify candidate genes.
  • In vitro biochemical assays to test enzyme activity.
  • Bacterial genetics to assess the function of the identified system in vivo.

Main Results:

  • Discovery of a new anti-phage system, nuclease-helicase immunity (Nhi).
  • Nhi utilizes a single enzyme with both DNA detection and nuclease activity.
  • Nhi targets phage replication intermediates, distinct from sequence-based systems.
  • The system effectively limits phage replication in bacterial hosts.

Conclusions:

  • Nhi represents a novel, enzyme-driven anti-phage defense mechanism.
  • This system offers a unique approach to combating phages by targeting replication processes.
  • Nhi provides a new avenue for developing strategies against bacterial and phage threats.