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-Bakteriophagen sind Viren, die in verschiedenen Formen vorkommen und Bakterien infizieren, indem sie ihre DNA injizieren. Sie können entweder einzelsträngige DNA, die als ssDNA bezeichnet wird, oder doppelsträngige DNA, die als dsDNA-Genome bezeichnet wird, haben. Zum Beispiel hat der ΦX174-Phagen, ein ikosaedrischer ssDNA-Phagen, ein kleines Genom mit überlappenden Genen. Auf diese Weise können mehrere Proteine über verschiedene Leserahmen kodiert werden. Dieser Phagen repliziert sich über Rolling-Circle-Replikation und bildet ein doppelsträngiges Zwischenprodukt, bevor er neue Genome erzeugt. Schließlich werden die Nachkommen über die Wirtslyse freigesetzt. Im Gegensatz dazu verlässt M13, ein filamentöser ssDNA-Phagen, die Wirtszelle durch Extrusion statt durch Lyse, was eine kontinuierliche Phagenproduktion ermöglicht, während der Wirt am Leben bleibt. Unter den dsDNA-Phagen repliziert sich der T7-Phagen bidirektional und bildet Koncatemere, die von einem Terminase-Enzym für die Genomverpackung verarbeitet werden. Auf der anderen Seite initiiert Mu die Replikation durch Transposition und fügt sich an mehrere Stellen im Wirtsgenom ein. Anschließend schneidet es sein lineares Genom aus und verpackt es in neue Virionen.

dna-bakteriophagen

Bakteriophagen, oder kurz Phagen, sind Viren, die spezifisch Bakterien infizieren und deren genetisches Material nutzen, um die zellul&#228;re Maschinerie des Wirts zur Replikation zu kapern. DNA-Bakteriophagen besitzen entweder einzelstr&#228;ngige DNA (ssDNA) oder doppelstr&#228;ngige DNA (dsDNA) als Genom. Diese Phagen weisen vielf&#228;ltige Replikationsstrategien und Wirtsinteraktionen auf, was ihre &#246;kologische Bedeutung und ihre Anwendungen in Biotechnologie und Medizin beeinflusst.
ssDNA-Bakteriophagen
ssDNA-Phagen mit ihren kleinen Genomen nutzen einzigartige Strategien zur Maximierung der genetischen Effizienz. Der &#934;X174-Phage, ein ikosaedrisches ssDNA-Virus, illustriert dies durch &#252;berlappende Gene, bei denen unterschiedliche Leseraster unterschiedliche Proteine kodieren. Diese Strategie maximiert die genetische Effizienz innerhalb des kompakten Genoms. Die Replikation beginnt mit der Synthese eines komplement&#228;ren Strangs, wodurch eine doppelstr&#228;ngige DNA-Zwischenform entsteht, die Replikationsform (RF). Diese RF dient als Vorlage f&#252;r die Rolling-Circle-Replikation, wobei neue Virusgenomen produziert und anschlie&#223;end in Virionen verpackt werden. Nach Abschluss der Replikation lysiert der Phage den bakteriellen Wirt und setzt die Nachkommen frei.
Im Gegensatz dazu verfolgt der M13-Phage, ein filament&#246;ses ssDNA-Virus, eine andere Freisetzungsstrategie. Anstatt Genome zu produzieren, die sofort in Virionen verpackt und durch Lyse freigesetzt werden, werden die M13-Virionen an der bakteriellen Membran assembliert und kontinuierlich durch einen Extrusionsprozess . Dadurch &#252;berlebt die Wirtszelle &#252;ber einen l&#228;ngeren Zeitraum und kann weiterhin Phagen produzieren. Diese anhaltende Phagenproduktion in einer Wirtszelle wird in der Molekularbiologie h&#228;ufig genutzt, beispielsweise in der Phagendisplay-Technologie oder in der Gentechnik.
dsDNA-Bakteriophagen
Im Gegensatz zu ssDNA-Phagen verf&#252;gen dsDNA-Phagen &#252;ber komplexere Replikationsmechanismen, die ihre Interaktionen mit bakteriellen Wirten erweitern. Der T7-Phage nutzt einen hocheffizienten bidirektionalen Replikationsmechanismus. Nach dem Eindringen in das bakterielle Cytoplasma beginnt T7 die Replikation an einer speziellen Ursprungsstelle und setzt diese in beide Richtungen fort. T7 verl&#228;sst sich f&#252;r die Replikation haupts&#228;chlich auf seine phagenkodierte DNA-Polymerase, die die Replikationsgeschwindigkeit erh&#246;ht. Zudem spielt die T7-RNA-Polymerase eine zentrale Rolle bei der Koordination von Genexpression und Replikationseffizienz. Die neu synthetisierten DNA-Molek&#252;le bilden Concatemere, lange kontinuierliche Str&#228;nge, die mehrere Genomeinheiten enthalten. Diese Concatemere werden anschlie&#223;end durch ein Terminase-Enzym in einzelne genomgro&#223;e Segmente geschnitten und in neue Phagenpartikel verpackt. Diese effiziente Replikationsstrategie hat T7 zu einem Modellsystem in der synthetischen Biologie und Gentechnik gemacht.
Der Mu-Phage, ein weiterer dsDNA-Bakteriophage, repliziert sich nicht durch Rolling-Circle- oder bidirektionale Mechanismen, sondern durch einen transpositionsbasierten Mechanismus. Er integriert sich an verschiedenen Stellen in das bakterielle Genom und durchl&#228;uft mehrere Zyklen der Transposition, bevor er sich zur Verpackung in neue Virionen wieder aus dem Wirtsgenom herausschneidet. Die Transposition des Mu-Phagen dupliziert die Wirts-DNA an den Insertionsstellen und unterbricht dabei h&#228;ufig Gene, was ihn zu einem n&#252;tzlichen Werkzeug f&#252;r Mutagenese und die Kartierung bakterieller Genome macht.

DNA-Bakteriophagen

Bakteriophagen, oder kurz Phagen, sind Viren, die spezifisch Bakterien infizieren und deren genetisches Material nutzen, um die zellul&#228;re Maschinerie ...

Education

Lehre

JoVE Core

Microbiology

Mikrobiologie

Unit

Einheit

Viruses

Viren

KEY TERMS AND CONCEPTS

KERNBEGRIFFE UND KONZEPTE

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

Bacterial generation time, the period required for a bacterial population to double during its exponential growth phase, serves as a critical measure of ...

Bacterial Growth Curve

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microbial-growth-measurement-direct-methods

Microbial Growth Measurement: Direct Methods

Direct methods for measuring microbial populations in a culture are essential tools in microbiology, providing quantitative data for various applications. ...

microbial-growth-measurement-indirect-methods

Microbial Growth Measurement: Indirect Methods

Estimating microbial growth is essential for understanding population dynamics and environmental adaptations. Indirect methods provide valuable insights ...

Microbial Growth Media

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Need for Obtaining Pure Cultures

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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 

Bacterial and archaeal cells exhibit remarkable diversity in shape and structure, critical in their adaptability and functionality. Among bacteria, the ...

Bacterial Cell Wall 

The bacterial cell wall is an essential structural component that encases the plasma membrane, preserving cellular integrity, determining shape, and ...

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

Microorganisms are a diverse group of microscopic entities broadly categorized into cellular and acellular types based on their structural organization. ...

environmental-applications-of-microorganisms

Environmental Applications of Microorganisms

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Community DNA Extraction from Bacterial Colonies

Source: Laboratories of Dr. Ian Pepper and Dr. Charles Gerba - The University of Arizona
Demonstrating Author: Luisa Ikner
Traditional methods of analysis ...

detecting-environmental-microorganisms-with-polymerase-chain-reaction

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 ...

rna-analysis-of-environmental-samples-using-rt-pcr

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
Demonstrating Author: Bradley Schmitz
Quantitative polymerase ...

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Water Quality Analysis via Indicator Organisms

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

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Culturing and Enumerating Bacteria from Soil Samples

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Surface ...

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
Demonstrating Author: Luisa Ikner
Bacteria are among the most ...

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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