Name: how dna phages replicate in bacteria
Uploaded: 2025-06-12T09:30:01.000Z
Duration: 1 min 26 s
Channel: JoVE

K12 Standards

Virginia  Standards of Learning

HIgh School

Biology

BIO.4

BIO.4.a

DNA Bacteriophages

DNA bacteriophages are viruses that occur in various forms and infect bacteria by injecting their DNA.They can have either single-stranded DNA called ssDNA, or double-stranded DNA called dsDNA genomes.For example, the &#934;X174 phage, an icosahedral ssDNA phage, has a small genome with overlapping genes. This allows multiple proteins to be encoded through different reading frames.This phage replicates via rolling circle replication, forming a double-stranded intermediate before generating new genomes.Finally, the progeny are released via host lysis.In contrast, M13, a filamentous ssDNA phage, exits the host cell through extrusion rather than lysis, allowing continuous phage production while keeping the host alive.Among the dsDNA phages, the T7 phage replicates bidirectionally, forming concatemers processed by a terminase enzyme for genome packaging.On the other hand, Mu initiates replication via transposition, inserting into multiple sites across the host genome. It then excises and packages its linear genome into new virions.

dna-bacteriofagen

Bacteriofagen, ofwel fagen, zijn virussen die specifieke bacteri&#235;n infecteren en hun genetisch materiaal gebruiken om de cellulaire machinerie van de gastheer over te nemen voor replicatie. DNA-bacteriofagen gebruiken enkelstrengs DNA (ssDNA) of dubbelstrengs DNA (dsDNA) genomen. Deze fagen vertonen diverse replicatiestrategie&#235;n en interacties met hun gastheer, wat hun ecologische rollen en toepassingen in biotechnologie en geneeskunde be&#239;nvloedt.
ssDNA-bacteriofagen
ssDNA-fagen, met hun kleine genomen, hanteren unieke strategie&#235;n om genetische effici&#235;ntie te maximaliseren. De &#934;X174-fage, een icosa&#235;drisch ssDNA-virus, is hiervan een voorbeeld met overlappende genen, waarbij verschillende leesramen meerdere eiwitten coderen. Deze strategie maximaliseert genetische effici&#235;ntie binnen het compacte genoom. De replicatie begint met de synthese van een complementaire streng, waardoor een dubbelstrengs DNA-intermediair ontstaat, bekend als de replicatieve vorm (RF). Deze RF dient als matrijs voor rolling circle-replicatie, waarbij nieuwe virale genomen worden geproduceerd die vervolgens worden verpakt in virions. Na voltooiing van de replicatie lyseert de faag de bacteri&#235;le gastheer, waardoor de nakomelingen vrijkomen.
Daarentegen volgt de M13-faag, een filamentachtig ssDNA-virus, een andere afgiftestrategie. In plaats van genomen te produceren die direct in virions worden verpakt en via lysis worden vrijgegeven, worden M13-virions geassembleerd aan het bacteri&#235;le membraan en continu uitgescheiden via een extrusieproces, waardoor de gastheercel blijft leven en fagen blijft produceren. Deze eigenschap van voortdurende faagproductie wordt veelvuldig gebruikt in moleculaire biologie, zoals bij faag display en recombinante DNA-technologie&#235;n.
dsDNA-bacteriofagen
In tegenstelling tot ssDNA-fagen hanteren dsDNA-fagen meer geavanceerde replicatiemechanismen, waarmee hun interacties met bacteri&#235;le gastheren worden uitgebreid. De T7-faag maakt gebruik van een zeer effici&#235;nte bidirectionele replicatie. Eenmaal in het bacteri&#235;le cytoplasma begint T7 met replicatie vanaf een uniek oorsprongspunt, in beide richtingen. Opmerkelijk is dat T7 vertrouwt op zijn eigen faag-gecodeerde DNA-polymerase, wat de snelheid van replicatie verhoogt. Bovendien speelt het T7-RNA-polymerase een cruciale rol bij het co&#246;rdineren van genexpressie en replicatie-effici&#235;ntie. De nieuw gesynthetiseerde DNA-moleculen vormen concatemeers, lange continue strengen die meerdere genoomeenheden bevatten. Deze concatemeren worden vervolgens verwerkt door een terminase-enzym, dat ze splitst in afzonderlijke segmenten ter grootte van het genoom voor inkapseling in nieuwe fagepartikels. Deze effici&#235;nte replicatiestrategie heeft van T7 een modelsysteem gemaakt in de synthetische biologie en genetische engineering.
De Mu-faag, een andere dsDNA-bacteriofaag, repliceert via een transpositie-gebaseerd mechanisme in plaats van een conventionele rolling circle- of bidirectionele replicatie. Het integreert zich in verschillende locaties binnen het bacteri&#235;le genoom en ondergaat meerdere transpositierondes voordat het zichzelf uitsnijdt voor verpakking in nieuwe virions. De transpositie door Mu-faag dupliceert het gastheer-DNA op de insertieplaatsen, waarbij vaak genen worden onderbroken. Dit maakt het een nuttig hulpmiddel voor mutagenese en het in kaart brengen van bacteri&#235;le genomen.

DNA-bacteriofagen

Bacteriofagen, ofwel fagen, zijn virussen die specifieke bacteri&#235;n infecteren en hun genetisch materiaal gebruiken om de cellulaire machinerie van de ...

Education

JoVE Core

Microbiology

Microbiologie

Unit

Eenheid

Viruses

Virussen

KEY TERMS AND CONCEPTS

BELANGRIJKE TERMEN EN CONCEPTEN

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 overlapping genes, so different reading frames can code for different proteins. After infection, it first makes a complementary DNA strand. This creates a double-stranded replicative form, or RF, which then serves as the template for rolling circle replication.

Rolling circle replication produces new viral genomes that are packaged into virions. When replication ends, the phage lyses the bacterial host and releases the new particles. M13, another ssDNA phage, follows a different path. Its virions assemble at the bacterial membrane and are secreted continuously by extrusion, so the host cell stays alive and keeps making phages.

That steady release makes M13 useful in molecular biology. Scientists use it in phage display and in recombinant DNA work. These applications depend on the phage’s ability to keep producing particles without immediately killing the bacterium.

dsDNA bacteriophages use more elaborate replication systems. T7 begins replication at a unique origin site inside the bacterial cytoplasm and copies its DNA in both directions. It uses phage-encoded DNA polymerase, which helps replication move quickly. T7 RNA polymerase also helps coordinate gene expression and replication efficiency.

The new T7 DNA molecules form concatemers, which are long DNA strands that contain multiple genome copies. A terminase enzyme then cuts these strands into genome-sized pieces for packaging into new phage particles. This efficient system has made T7 a model for synthetic biology and genetic engineering.

Mu phage is another dsDNA bacteriophage, but it does not use a standard rolling circle or bidirectional pattern. Instead, it replicates through transposition, which means it inserts into different sites in the bacterial genome and makes multiple rounds of movement before it is excised for packaging. This process duplicates host DNA at the insertion site and can disrupt genes, which is why Mu is useful for mutagenesis and bacterial genome mapping.

How DNA Phages Replicate in Bacteria

introduction to virus

Virus Structure, Entry, and Replication

Viruses are biological entities that rely on host cells to make more copies of themselves. They do not have cells or their own metabolism, but they can show signs of life when they infect a host. Their basic structure includes a nucleic acid core, made of either DNA or RNA, surrounded by a protein coat called a capsid. Viruses are classified by the type of nucleic acid they contain and by their structure. Some viruses also have a lipid envelope that comes from the host cell membrane. Enveloped...

size and structure of viral genomes

How Viral Genomes Replicate

Viral genomes can be DNA or RNA, and their structure shapes how they replicate inside host cells. They may be linear or circular. They can also be single-stranded or double-stranded. These differences affect how a virus makes copies of itself and how it interacts with the host. RNA viruses usually have smaller genomes than DNA viruses. That smaller size is linked to high mutation rates and fast evolution. RNA virus polymerases often lack proofreading, so mistakes are more common. This helps...

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

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

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

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...

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 DNA bacteriophages copy their genomes in bacteria, from ΦX174 and M13 to T7 and Mu, with clear examples of replication and packaging.

How DNA Phages Replicate in Bacteria | 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

Alabama Course of Study Science

9-12

Unity and Diversity

9-12.B.4.13.a

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. ...

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

Viruses of Archaea

Archaeal viruses play a crucial role in the ecosystems of extremophilic archaea, particularly those belonging to the phyla Euryarchaeota and ...

Viruses with RNA Genomes

RNA viruses are categorized into positive-strand, negative-strand, or double-stranded groups based on their genomic structure and replication mechanisms. ...

The Antiviral System of Bacteria and Archaea: CRISPR

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

The CRISPR-Cas system serves as a bacterial defense mechanism against invading genetic elements such as viruses and plasmids, forming the foundation for ...

Subviral Agents

Subviral agents are infectious entities that resemble viruses but lack one or more viral components, such as a capsid or essential replication machinery. ...

The student will investigate and understand that bacteria and viruses have an effect on living systems. Key ideas include  viruses depend on a host for metabolic processes;

Binary Fission

Binary fission is the primary mode of asexual reproduction in prokaryotes, such as bacteria. It results in the production of two genetically identical ...

Generation Time

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Bacterial Growth Curve

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Microbial Growth Measurement: Direct Methods

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Microbial Growth Measurement: Indirect Methods

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Microbial Growth Media

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Factors Influencing Microbial Growth: pH

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factors-influencing-microbial-growth-temperature

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factors-influencing-microbial-growth-osmolarity

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Oxygen Requirements and Growth Patterns

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Biofilms

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The student will investigate and understand that bacteria and viruses have an effect on living systems. Key ideas include the modes of reproduction/replication can be compared

BIO.4.b

Prokaryotic vs. Eukaryotic Cells

Prokaryotic and eukaryotic cells represent two fundamental types of cellular organization, differing significantly in structure, complexity, and function. ...

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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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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Detecting Environmental Microorganisms with the Polymerase Chain Reaction and Gel Electrophoresis

Source: Laboratories of Dr. Ian Pepper and Dr. Charles Gerba - Arizona University
Demonstrating Author: Bradley Schmitz
Polymerase chain reaction (PCR) is ...

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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
Demonstrating Author: Bradley Schmitz
Reverse ...

quantifying-environmental-microorganisms-and-viruses-using-qpcr

Quantifying Environmental Microorganisms and Viruses Using qPCR

Source: Laboratories of Dr. Ian Pepper and Dr. Charles Gerba - The University of Arizona
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Water Quality Analysis via Indicator Organisms

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Demonstrating Author: Luisa Ikner
Water quality analysis monitors ...

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Isolation of Fecal Bacteria from Water Samples by Filtration

Source: Laboratories of Dr. Ian Pepper and Dr. Charles Gerba - The University of Arizona
Demonstrating Author: Luisa Ikner
The quality of water destined ...

detection-of-bacteriophages-in-environmental-samples

Detection of Bacteriophages in Environmental Samples

Source: Laboratories of Dr. Ian Pepper and Dr. Charles Gerba - The University of Arizona
Demonstrating Author: Alex Wassimi
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

Source: Laboratories of Dr. Ian Pepper and Dr. Charles Gerba - The University of Arizona
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The student will investigate and understand that bacteria and viruses have an effect on living systems. Key ideas include  bacteria and viruses have a role in other organisms and the environment; and

BIO.4.d

History of Microbiology

Microbiology, a scientific field dedicated to the study of microorganisms, has undergone profound development since its inception in the 17th century. Its ...

Infection

When a pathogen enters the body and reproduces, it can cause an infection, damage body cells, and cause illness symptoms that eventually lead to disease. ...

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 DNA Phages Replicate in Bacteria

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