Name: how crispr remembers viral infections
Uploaded: 2025-06-12T09:30:40.000Z
Duration: 1 min 23 s
Channel: JoVE

K12 Standards

Virginia  Standards of Learning

HIgh School

Biology

BIO.4

BIO.4.a

the-antiviral-system-of-bacteria-and-archaea-crispr

The Antiviral System of Bacteria and Archaea: CRISPR

Le brevi ripetizioni palindromiche raggruppate regolarmente intervallate - CRISPR, insieme alle proteine Cas associate a CRISPR, funzionano come sistema immunitario adattativo nei batteri e negli archei contro virus ed elementi genetici estranei. Una volta che il DNA virale è all'interno della cellula, le proteine Cas riconoscono il Protospacer Adjacent Motif o PAM, asportano il segmento del protospacer dal genoma virale e lo inseriscono nell'array CRISPR. L'array CRISPR memorizza frammenti di DNA virale come distanziatori tra le ripetizioni palindromiche, fungendo da memoria genetica per riconoscere le infezioni passate. L'array CRISPR viene trascritto in pre-crRNA, che si accoppia con il tracrRNA. La RNasi III e la Cas9 trasformano il duplex in crRNA, ciascuno dei quali porta uno spaziatore e frammenti ripetuti. Quando il virus si reinfetta, il complesso Cas-crRNA esegue la scansione alla ricerca di una corrispondenza. La proteina Cas scinde il DNA virale al momento della corrispondenza, neutralizzando l'infezione. Il PAM migliora la specificità di questa difesa assicurando che le proteine Cas colpiscano solo il DNA estraneo e non l'array CRISPR del batterio.

il sistema antivirale di batteri e archei: crispr

CRISPR, che sta per sequenze palindromiche brevi raggruppate e regolarmente intervallate, &#232; un sistema immunitario adattativo presente in batteri e archei che protegge da infezioni virali. Questo sistema consente alle cellule procariotiche di identificare, memorizzare e neutralizzare elementi genetici estranei, principalmente batteriofagi, conservando frammenti del DNA invasore come memoria genetica.
La risposta immunitaria CRISPR inizia durante un&#8217;infezione iniziale. Le proteine Cas (CRISPR-associated) svolgono un ruolo centrale in questa difesa. Al rilevamento di DNA estraneo, solitamente virale, le proteine Cas riconoscono specifiche sequenze note come motivo adiacente al protospacer (PAM). Questi motivi fungono da indicatori che distinguono il DNA invasivo dal DNA proprio. Una volta identificato, il complesso Cas ritaglia un segmento del DNA dell'invasore, chiamato protospacer, e lo integra nel genoma dell&#8217;ospite all&#8217;interno dell&#8217;array CRISPR. Questo array &#232; costituito da brevi ripetizioni palindromiche intervallate da spacer unici derivati da invasori precedenti, creando cos&#236; un archivio molecolare delle infezioni passate.
Il locus CRISPR viene successivamente trascritto in un lungo precursore di RNA chiamato pre-crRNA. Questa molecola viene processata da RNasi III e da proteine Cas accessorie in piccoli RNA CRISPR (crRNA), ciascuno costituito da un&#8217;unit&#224; spacer-ripetizione. Questi crRNA sono essenziali per guidare la risposta immunitaria durante infezioni successive.
In caso di reinfezione da parte dello stesso virus, il crRNA forma un complesso con una proteina Cas, tipicamente Cas9 in molti sistemi. Questo complesso crRNA-Cas esamina il DNA invasivo alla ricerca di una sequenza complementare allo spacer del crRNA. Se viene individuata una corrispondenza adiacente a un PAM, la proteina Cas taglia il DNA virale nel sito bersaglio, arrestando cos&#236; l&#8217;infezione. Il requisito di presenza di un PAM garantisce che il sistema CRISPR non attacchi il genoma dell&#8217;ospite, preservando l&#8217;integrit&#224; cellulare.

Il Sistema Antivirale di Batteri e Archei: CRISPR

CRISPR, che sta per sequenze palindromiche brevi raggruppate e regolarmente intervallate, &#232; un sistema immunitario adattativo presente in batteri e ...

Education

Didattica

JoVE Core

Microbiology

Microbiologia

Unit

Unità

Viruses

Virus

KEY TERMS AND CONCEPTS

TERMINI E CONCETTI CHIAVE

how crispr remembers viral infections

CRISPR is an adaptive immune system in bacteria and archaea that helps protect cells from viral infection. It works by identifying foreign genetic material, remembering it, and stopping the same invader later. In many cases, the main targets are bacteriophages, which are viruses that infect bacteria.

The first defense step begins during an initial infection. Cas proteins, which are CRISPR-associated proteins, detect foreign DNA by looking for specific sequences called Protospacer Adjacent Motifs, or PAMs. PAMs help Cas proteins tell invasive DNA apart from the cell’s own DNA. After recognition, the Cas complex removes a piece of the invader’s DNA called a protospacer and inserts it into the host genome.

That inserted DNA becomes part of the CRISPR array. The array contains short palindromic repeats with unique spacer sequences between them. Each spacer comes from a past invader, so the array acts like a genetic record of earlier infections.

The CRISPR locus is then transcribed into a long precursor RNA called pre-crRNA. RNase III and accessory Cas proteins process this RNA into shorter CRISPR RNAs, or crRNAs. Each crRNA contains one spacer-repeat unit and helps guide the immune response during future infections.

If the same virus infects the cell again, the crRNA joins with a Cas protein, often Cas9 in many systems. This complex scans the incoming DNA for a sequence that matches the crRNA spacer. When a match appears next to a PAM, the Cas protein cuts the viral DNA at that site and stops the infection. The PAM requirement also helps prevent the system from attacking the host’s own genome.

How CRISPR Remembers Viral Infections

introduction to virus

Virus Structure, Entry, and Replication

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size and structure of viral genomes

How Viral Genomes Replicate

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viral replication: lytic cycle

T4 Phage Infection of E. coli

T4 phage infection of E. coli follows a lytic cycle that lets the virus make many copies fast. Bacteriophages, or phages, are viruses that infect bacteria, and T-even phages such as T4 are known for this well-studied process. The cycle ends with the destruction of the bacterial host. The first step is attachment to the E. coli cell surface. Tail fibers on the phage bind to receptor molecules on the bacterial outer membrane, which helps the virus find the correct host. After binding, the...

viral replication: lysogenic cycle

Prophage Integration in Bacterial Cells

The lysogenic cycle shows how a bacteriophage can stay inside a bacterial cell without killing it right away. Temperate phages, such as bacteriophage lambda (λ), use this strategy to persist in Escherichia coli while the host cell remains alive. After attachment to the bacterial surface, the phage injects its genetic material into the cytoplasm. The linear phage genome then circularizes, which helps protect it from host nucleases. Next, phage-encoded integrase carries out recombination that...

dna bacteriophages

How DNA Phages Replicate in Bacteria

DNA bacteriophages are viruses that infect bacteria and use bacterial cell machinery to make more copies of themselves. They carry either single-stranded DNA (ssDNA) or double-stranded DNA (dsDNA), and each group uses a different replication strategy. Their life cycles also shape how they interact with hosts and how scientists use them in biotechnology and medicine. Some ssDNA phages keep their genomes very small and compact. The icosahedral phage ΦX174 shows this clearly because it uses...

viruses of archaea

Archaeal Virus Shapes and Extreme Survival

Archaeal viruses infect archaea that live in extreme places such as acidic hot springs and hydrothermal vents. These hosts often belong to the phyla Euryarchaeota and Crenarchaeota. The viruses help shape host evolution and gene transfer, which adds genetic diversity to microbial communities in harsh environments. Most archaeal viruses carry double-stranded DNA, or dsDNA, genomes. Some have single-stranded DNA, and some have RNA genomes. Their virions, or complete virus particles, show unusual...

viruses with rna genomes

RNA Virus Replication Strategies

RNA viruses use several replication strategies based on their genome type. They are grouped as positive-strand, negative-strand, or double-stranded RNA viruses. Some RNA viruses also use reverse transcription, which adds another layer to how they copy their genetic material. Positive-strand RNA viruses have genomes that can act like messenger RNA, or mRNA, as soon as they enter a cell. This lets the virus begin making proteins right away. Bacteriophage MS2 infects Escherichia coli by attaching...

the antiviral system of bacteria and archaea: crispr

CRISPR is an adaptive immune system in bacteria and archaea that helps protect cells from viral infection. It works by identifying foreign genetic material, remembering it, and stopping the same invader later. In many cases, the main targets are bacteriophages, which are viruses that infect bacteria. The first defense step begins during an initial infection. Cas proteins, which are CRISPR-associated proteins, detect foreign DNA by looking for specific sequences called Protospacer Adjacent...

crispr/cas9 genome editing

CRISPR-Cas9 and DNA Repair in Cells

CRISPR-Cas9 uses a bacterial defense system to change DNA in cells. The CRISPR-Cas system first evolved in prokaryotes to protect bacteria from invading genetic material such as viruses and plasmids. Scientists later adapted it into a genome-editing tool for plants, animals, and humans. The key enzyme is Cas9, a DNA-cutting protein called an endonuclease from Streptococcus pyogenes. In the lab, a synthetic single guide RNA, or sgRNA, directs Cas9 to a chosen DNA site. The sgRNA matches the...

subviral agents

Viroids, Prions, and Satellite Viruses

Viroids, prions, and satellites are subviral agents that can cause infection even though they are not complete viruses. They resemble viruses in spread and disease, but each lacks one or more key viral parts, such as a capsid or the machinery needed for replication. Viroids are the simplest of these agents. They are circular, single-stranded RNA molecules with no protein coat. Viroids infect plants only and depend on host cell machinery to copy themselves. Host RNA polymerase replicates them...

key terms and concepts

Learn how CRISPR stores viral DNA, makes crRNA guides, and uses Cas proteins to cut matching DNA during reinfection in bacteria and archaea.

How CRISPR Remembers Viral Infections | JoVE K12

JoVE Core Microbiology provides an engaging introduction to the microbial world and its influence on health, industry, and the environment. This comprehensive collection covers key concepts such as microbial structure, metabolism, genetics, and ecology. It introduces essential laboratory techniques and microscopy methods through visually engaging animations. Corresponding scientist-in-action videos bridge classroom concepts with real-world research and applications.

microbiology

Introduction to Virus

Viruses are unique biological entities that blur the boundary between living and non-living systems. Although they lack cellular structure and metabolic ...

Size and Structure of Viral Genomes

Viral genomes exhibit remarkable diversity in size, structure, and composition, influencing their replication strategies and interactions with host cells. ...

Viral Replication: Lytic Cycle

Bacteriophages, or phages, are viruses that specifically infect bacteria. Among them, T-even bacteriophages, such as T4, exhibit a well-characterized ...

Viral Replication: Lysogenic Cycle

The lysogenic cycle is a crucial viral replication strategy that allows bacteriophages to persist within host cells without immediately destroying them. ...

DNA Bacteriophages

Bacteriophages, or phages, are viruses that specifically infect bacteria, utilizing their genetic material to hijack host cellular machinery for ...

Viruses of Archaea

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Viruses with RNA Genomes

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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 ...

CRISPR/Cas9 Genome Editing

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Subviral Agents

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Binary Fission

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Generation Time

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Bacterial Growth Curve

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Microbial Growth Media

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Factors Influencing Microbial Growth: pH

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BIO.4.b

Prokaryotic vs. Eukaryotic Cells

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Microbial Morphologies 

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Bacterial Cell Wall 

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Archaeal Cell Wall

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Peptidoglycan Synthesis

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Plasma Membrane in Bacteria and Archaea

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Outer Layers of the Cell Envelope

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Flagella and Motility in Bacteria

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Fimbriae, Pili, and Axial Filaments

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Cell Inclusions

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Endospores and Sporulation

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Nucleoid

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Surface Appendages of Archaea

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The student will investigate and understand that bacteria and viruses have an effect on living systems. Key ideas include  the structures and functions can be compared

BIO.4.c

Types of Microorganisms

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Environmental Applications of Microorganisms

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Community DNA Extraction from Bacterial Colonies

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RNA Analysis of Environmental Samples Using RT-PCR

Source: Laboratories of Dr. Ian Pepper and Dr. Charles Gerba - The University of Arizona
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Reverse ...

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Quantifying Environmental Microorganisms and Viruses Using qPCR

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Water Quality Analysis via Indicator Organisms

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Isolation of Fecal Bacteria from Water Samples by Filtration

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Demonstrating Author: Luisa Ikner
The quality of water destined ...

detection-of-bacteriophages-in-environmental-samples

Detection of Bacteriophages in Environmental Samples

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Viruses are a unique group of ...

culturing-and-enumerating-bacteria-from-soil-samples

Culturing and Enumerating Bacteria from Soil Samples

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bacterial-growth-curve-analysis-and-its-environmental-applications

Bacterial Growth Curve Analysis and its Environmental Applications

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BIO.4.d

History of Microbiology

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Infection

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Defense Mechanism Against Infection

Natural flora, body system defenses, and inflammation are natural barriers of the body against infectious agents regardless of previous exposure. Normal ...

The student will investigate and understand that bacteria and viruses have an effect on living systems. Key ideas include  the germ theory of infectious disease is supported by evidence.

BIO.4.e

How CRISPR Remembers Viral Infections

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