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?

Вирус это структура, несущая свой собственный геномный материал в виде РНК или ДНК для вторжения и репликации внутри клетки-хозяина. После того, как вирус связывается с поверхностными рецепторами клетки-хозяина, он входит и быстро распадается, расшифровывая свой генетический материал. В случае ДНК-вирусов, вирусная ДНК управляет репликацией белков клетки-хозяина, синтезируя новые копии вирусного генома, которые затем транскрибируются и транслируются в вирусные белки.Наконец, хост реорганизовывает эти вирусные компоненты в потомство, позволяя одной вирусной частице произвести тысячи себе подобных, что часто приводит к смерти клетки-хозяина.

Ямаути, Йохей и Ари Хелениус. "Проникновение вируса с первого взгляда." J Cell Sci 126, No6 (15 марта 2013 г.): 1289–95. [<a href="https://doi.org/10.1242/jcs.119685" target="__blank">Источник</a>]

Лин, Дерек М., Бритт Коскелла и Генри С. Лин. "Фаготерапия: альтернатива антибиотикам в эпоху множественной лекарственной устойчивости." Всемирный журнал гастроинтестинальной фармакологии и терапии 8, No3 (6 августа 2017 г.): 162–73. [<a href="https://doi.org/10.4292/wjgpt.v8.i3.162" target="__blank">Источник</a>]

Никез, Валери. "Иммунитет сельскохозяйственных культур против вирусов: результаты и будущие вызовы." Frontiers in Plant Science 5 (21 ноября 2014 г.). [<a href="https://doi.org/10.3389/fpls.2014.00660" target="__blank">Источник</a>]

Что такое вирусы?

<h4>Обзор</h4>

Вирус является микроскопической инфекционной частицей, которая состоит из РНК или генома ДНК, заключенного в белковую оболочку. Он не способен размножаться сам по себе: он может только сделать больше вирусов, войдя в клетку и используя его клеточного оборудования. Когда вирус заражает клетку-хозяина, он удаляет свою белковую шерсть и направляет механизм хозяина на транскрибирование и перевод его генетического материала. Угнанная клетка собирает реплицированные компоненты в тысячи вирусных потомков, которые могут разорвать и убить клетку-хозяина. Затем новые вирусы заражают больше клеток-хостов.

<h4>Зачем изучать вирусы?</h4>

Вирусы могут инфицировать различные типы клеток: бактерии, растения и животных. Вирусы, которые нацелены на бактерии, называемые бактериофагами (или фагом), очень обильны. Текущие исследования сосредоточены на фаг терапии для лечения мульти лекарственно-устойчивых бактериальных инфекций у людей. Вирусы, которые инфицируют культивируемые растения, также хорошо изучены, поскольку эпидемии приводят к огромным урожаям и экономическим потерям.

Вирусы были впервые обнаружены в19 веке, когда экономически важный урожай, табачное растение, страдает от таинственной болезни, позже идентифицированной как вирус табачной мозаики. Вирусы животных имеют большое значение как в ветеринарных исследованиях, так и в медицинских исследованиях. Кроме того, вирусы лежат в основе многих заболеваний человека, начиная от простуды, ветряной оспы и герпеса, до более опасных инфекций, таких как желтая лихорадка, гепатит и оспа.

<h4>Структура вируса</h4>

Вирусы бывают различных форм, которые специализируются на атаке их целевой клетки. Двумя основными компонентами всех вирусов являются вирусный геном и его защитная белковая шерсть, известная как капсид. Вирусный геном состоит из одной или двуединой РНК или ДНК, и он кодирует белки, которые составляют капсид. Вместе вирусный геном и капсид известны как нуклеокапсид.

Уникальной особенностью многих эукариотических вирусов является наличие фосфолипидной мембраны, известной как оболочка, которая окружает капсид. Этот конверт обычно происходит от мембран ранее инфицированных клеток-хозяй, но может также включать вирусные белки (так называемые белки конверта), прикрепленные к нему. Наконец, некоторые вирусы животных имеют скопление закодированных вирусом белков, вирусный тегумент, в пространстве между оболочкой и капсидом.

<h4>Вирусная инфекция</h4>

Вирусный жизненный цикл может быть разбит на следующие пять этапов: вложение, запись, репликация, сборка и освобождение. Белки на поверхности вируса помогают ему распознавать определенные клетки-хозяина. Некоторые вирусы используют эти поверхностные белки, чтобы связать рецепторы клеток-хозяина и инициировать интернализацию эндоцитозом, в то время как вирусы с оболочкой могут непосредственно сливаться с мембраной клетки-хозяина.

Некоторые бактериофаголы не попадают в клетку; они вводят свой геном (и вирусные ферменты) в клетку-хозяина. Оказавшись внутри клетки, вирус не помылся и направляет механизм клетки-хозяина на транскрибирование и перевод ее генома. Клетки-хозяина упаковывают новые копии вирусного генома в вирусные частицы, чтобы сделать потомство. Вирусы потомства могут храниться в клетке-хозяине перед выпуском или постоянно выдаваться из клетки, выдыхая из клеточной мембраны. Цикл вирусной инфекции классифицируется как литический или лизогенный. В литическом цикле новые вирусы вырываются из клетки-хозяина, убивая ее. В лизогенном цикле вирусная ДНК включается в геном хозяина, где она находится в спящем состоянии, и копируется каждый раз, когда клетка-хозяин размножается.

Обзор

Вирус — это микроскопическая инфекционная частица, состоящая из генома РНК или ДНК, заключенного в белковую оболочку. Он не способен размножаться на...

Education

JoVE Core

Biology

Биология

Genetics

Генетика

Viruses

Вирусы

KEY TERMS AND CONCEPTS

ОСНОВНЫЕ ТЕРМИНЫ И ПОНЯТИЯ

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.

How Viruses Infect Cells and Multiply | JoVE K12

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HS-LS1-2

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HS-LS1-4

How Viruses Infect Cells and Multiply

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