Name: how viruses infect cells and multiply
Uploaded: 2019-03-11T09:21:23.000Z
Duration: 50 s
Channel: JoVE

K12 Standards

Louisiana Student Standards for Science

High School

Life Sciences

from-molecules-to-organisms-structures-and-processes

From Molecules To Organisms: Structures And Processes

HS-LS1-8

What are Viruses?

- [Narrador] Un virus es una estructura

que carga su propio material genético

en forma de ARN o ADN para invadir

y replicarse dentro de una célula húesped.

Después de que un virus
se une a los receptores

superficiales de la célula huésped,

entra y rápidamente se desensambla,

descodificando su material genético.

En el caso de virus de ADN,

el ADN viral dirige la
replicación de proteínas

de la célula huésped para
sintetizar nuevas copias

del genoma viral, que
son luego transcritas

y traducidas en proteínas virales.

Finalmente, el huésped
reensambla estos componentes

virales en progenie,
permitiéndole a una única

partícula viral producir
miles más, frecuentemente

llevando a la célula huésped a su muerte.

Yamauchi, Yohei y Ari Helenius. "Entrada de virus de un vistazo". J Cell Sci 126, no. 6 (15 de marzo de 2013): 1289–95. [<a href="https://doi.org/10.1242/jcs.119685" target="__blank">Fuente</a>]

Lin, Derek M, Britt Koskella y Henry C Lin. "Terapia con fagos: una alternativa a los antibióticos en la era de la resistencia a múltiples fármacos". Revista Mundial de Farmacología y Terapéutica Gastrointestinal 8, n.º 3 (6 de agosto de 2017): 162–73. [<a href="https://doi.org/10.4292/wjgpt.v8.i3.162" target="__blank">Fuente</a>]

"Inmunidad de los cultivos contra virus: resultados y desafíos futuros". Frontiers in Plant Science 5 (21 de noviembre de 2014). [<a href="https://doi.org/10.3389/fpls.2014.00660" target="__blank">Fuente</a>]

¿qué son los virus?

<h4>Descripción general</h4> Un virus es una partícula infecciosa microscópica que está formada por un genoma de ARN o ADN encerrado en una cubierta proteica. No es capaz de reproducirse por sí solo: solo puede producir más virus entrando en una célula y utilizando su maquinaria celular. Cuando un virus infecta una célula huésped, elimina su cubierta proteica y dirige la maquinaria del huésped para que transcriba y traduzca su material genético. La célula secuestrada ensambla los componentes replicados en miles de progenies virales, que pueden romper y matar la célula huésped. Los nuevos virus luego infectan más células huésped. <h4>¿Por qué estudiar los virus?</h4> Los virus pueden infectar diferentes tipos de células: bacterias, plantas y animales. Los virus que atacan a las bacterias, llamados bacteriófagos (o fagos), son muy abundantes. La investigación actual se centra en la terapia con fagos para tratar infecciones bacterianas multirresistentes en humanos. Los virus que infectan las plantas cultivadas también están muy estudiados, ya que las epidemias provocan enormes pérdidas económicas y de cosechas. Los virus se descubrieron por primera vez en el siglo 19th, cuando un cultivo de importancia económica, la planta del tabaco, se vio afectado por una enfermedad misteriosa ­­– más tarde identificada como virus del mosaico del tabaco. Los virus animales son de gran importancia tanto en la investigación veterinaria como en la investigación médica. Además, los virus son la base de muchas enfermedades humanas, que van desde el resfriado común, la varicela y el herpes, hasta infecciones más peligrosas como la fiebre amarilla, la hepatitis y la viruela. <h4>La estructura de un virus</h4> Los virus vienen en una variedad de formas que se especializan en atacar a su célula objetivo. Los dos componentes principales de todos los virus son el genoma viral y su cubierta proteica protectora, conocida como cápside. El genoma viral está formado por ARN o ADN, simple o bicatenario, y codifica las proteínas que forman la cápside. Juntos, el genoma viral y la cápside se conocen como nucleocápside. Una característica única de muchos virus eucariotas es la presencia de una membrana de fosfolípidos, conocida como envoltura que rodea la cápside. Esta envoltura generalmente se origina en las membranas de células huésped previamente infectadas, pero también puede incluir proteínas virales (llamadas proteínas de la envoltura) adheridas a ella. Finalmente, algunos virus animales tienen un grupo de proteínas codificadas por el virus, el tegumento viral, en el espacio entre la envoltura y la cápside. <h4>Infección viral</h4> El ciclo de vida viral se puede dividir en los siguientes cinco pasos: unión, entrada, replicación, ensamblaje y liberación. Las proteínas de la superficie del virus le ayudan a reconocer células huésped específicas. Algunos virus utilizan estas proteínas de superficie para unirse a los receptores de la célula huésped e iniciar la internalización mediante endocitosis, aunque los virus recubiertos con una envoltura pueden fusionarse directamente con la membrana de la célula huésped. Algunos bacteriófagos no entran a la célula; inyectan su genoma (y enzimas virales) en la célula huésped. Una vez dentro de la célula, el virus queda descubierto y dirige la maquinaria de la célula huésped para que transcriba y traduzca su genoma. La célula huésped empaqueta las nuevas copias del genoma viral en partículas virales para formar descendencia. Los virus de la progenie pueden almacenarse en la célula huésped antes de su liberación o extruirse continuamente de la célula brotando de la membrana celular. El ciclo de infección viral se clasifica en lítico o lisogénico. En el ciclo lítico, los nuevos virus salen de la célula huésped y la matan. En el ciclo lisogénico, el ADN viral se incorpora al genoma del huésped, donde permanece inactivo y se copia cada vez que la célula huésped se replica.

¿Qué son los virus?

Visión general

Un virus es una partícula infecciosa microscópica que consiste en un genoma de ARN o ADN encerrado en una cubierta de proteína. No es capaz de reproducirse en ...

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Biology

Biología

Genetics

Genética

Viruses

Virus

KEY TERMS AND CONCEPTS

TÉRMINOS Y CONCEPTOS CLAVE

how viruses infect cells and multiply

Viruses infect cells and make new copies by using a host cell’s own machinery. A virus is a tiny infectious particle with an RNA or DNA genome inside a protective protein coat. It cannot reproduce on its own, so it must enter a cell to make more viruses.

After infection, the virus sheds its protein coat and uses the host cell to transcribe and translate its genetic material. The cell then assembles many new viral particles. In many cases, these new viruses rupture the host cell and kill it. The released viruses can then infect other cells.

Viruses can attack bacteria, plants, and animals. Viruses that infect bacteria are called bacteriophages, or phages, and they are very abundant. Scientists also study phages as a possible therapy for multidrug-resistant bacterial infections in humans. Plant viruses matter because outbreaks can cause major crop and economic losses.

Animal viruses are important in both veterinary research and medical research. Viruses were first discovered in the 19th century during studies of tobacco plants with a mysterious disease. That disease was later identified as Tobacco mosaic virus. Viruses are also linked to many human illnesses, including the common cold, chickenpox, herpes, yellow fever, hepatitis, and smallpox.

Viruses vary in shape, but they share two main parts: the viral genome and the capsid. The genome can be single-stranded or double-stranded RNA or DNA, and it carries the instructions for making capsid proteins. The genome and capsid together form the nucleocapsid. Many eukaryotic viruses also have an envelope, which is a phospholipid membrane often taken from a host cell. Some animal viruses also contain a tegument, a layer of viral proteins between the envelope and the capsid.

A viral infection usually follows five stages: attachment, entry, replication, assembly, and release. Viral surface proteins help the virus recognize the right host cell. Some viruses bind to host receptors and enter by endocytosis, while enveloped viruses can fuse with the host cell membrane. Some bacteriophages do not enter the cell at all. They inject their genome and viral enzymes into the host cell instead.

Once inside, the virus is uncoated and directs the host cell to copy and read its genetic material. The host cell packages the new genomes into viral particles to form progeny viruses. These progeny may stay in the cell for a time or leave by budding from the cell membrane. Viral infection can be lytic or lysogenic. In the lytic cycle, new viruses burst out and kill the host cell. In the lysogenic cycle, viral DNA becomes part of the host genome, stays dormant, and is copied when the host cell divides.

How Viruses Infect Cells and Multiply

what are viruses?

Viruses infect cells and make new copies by using a host cell’s own machinery. A virus is a tiny infectious particle with an RNA or DNA genome inside a protective protein coat. It cannot reproduce on its own, so it must enter a cell to make more viruses. After infection, the virus sheds its protein coat and uses the host cell to transcribe and translate its genetic material. The cell then assembles many new viral particles. In many cases, these new viruses rupture the host cell and kill it.

viral structure

How Virus Shapes Help Infection

Viruses have specific structures that help them infect host cells and trigger immune responses. Each virus has a core that contains either a DNA-based or RNA-based genome. That core is surrounded by a protective protein coat called the capsid. The capsid is made of smaller subunits called capsomeres. The capsid and the genome-containing core together are called the nucleocapsid. Viruses are often grouped by capsid design. Most viruses have either icosahedral or helical capsids, but some have...

lytic cycle of bacteriophages

How Phages Infect and Burst Bacteria

Bacteriophages, or phages, are viruses that infect bacteria. They have a distinctive head-tail shape. In the lytic cycle, a phage first attaches to the outside of a bacterial cell. Tail proteins bind to specific receptor proteins on the bacterium’s surface. After attachment, the phage tail injects its DNA genome into the bacterial cytoplasm. The phage then uses the bacterium’s cellular machinery to make proteins needed for replication and dispersal. When phage replication is complete, some of...

lysogenic cycle of bacteriophages

Prophage Integration in Bacteria

The lysogenic cycle shows how bacteriophages can infect bacteria without killing the host right away. In this cycle, the phage genome joins the bacterial genome. The integrated phage DNA is called a prophage, and the bacterium copies it each time it replicates. Some prophages can switch back into the lytic cycle. This change can happen after DNA damage or even without an obvious outside trigger. When the prophage is induced, the phage begins making new virus particles again. Prophages can...

retrovirus life cycles

How Retroviruses Replicate in Host Cells

Retroviruses replicate by copying their RNA genome into DNA inside a host cell. After entry, the viral enzyme reverse transcriptase makes a double-stranded DNA copy from the single-stranded RNA genome. The viral DNA is then carried into the nucleus and inserted into the host genome by integrase. Once integrated, the retroviral DNA is transcribed whenever the host genome is transcribed. This produces new viral RNA that can be copied and used again. The new RNA moves into the cytoplasm, where it...

viral recombination

How Viruses Swap Genes and Spread

Viral gene swapping can happen when more than one virus infects the same cell. After the viruses break open and expose their genomes for replication, matching regions can pair up and exchange sequences. This process is called recombination. Viruses with segmented genomes can also swap whole segments, which is called reassortment. These changes can help create new diseases. Some diseases can infect more than one species. Pigs can be infected by some human and bird viruses, along with the...

viral mutations

How Virus Mutations Drive Outbreaks

Virus mutations can change how quickly a virus evolves and spreads. A mutation is a change in the sequence of bases in DNA or RNA. Some mutations happen when the genome is copied. They are caused by errors made by polymerase enzymes, which replicate DNA or RNA. RNA viruses often change faster than DNA viruses because RNA polymerase does not proofread its work. That means RNA-based genomes, such as HIV, can gather mutations more quickly. Mutation and recombination give viruses the raw material...

key terms and concepts

Learn how viruses enter host cells, use cellular machinery to replicate, and spread through lytic and lysogenic cycles in plants, animals, and bacteria.

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HS-LS1-1

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HS-LS1-2

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HS-LS1-3

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HS-LS1-4

How Viruses Infect Cells and Multiply

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