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?

Wirus to struktura, która przenosi własny materiał genomowy w postaci RNA lub DNA w celu inwazji i replikacji wewnątrz komórki gospodarza. Po tym, jak wirus zwiąże się z receptorami powierzchniowymi w komórce gospodarza, wnika i szybko się rozpada, odszyfrowując swój materiał genetyczny. W przypadku wirusów DNA, wirusowe DNA kieruje białkami replikacyjnymi komórek gospodarza w celu syntezy nowych kopii genomu wirusa, które są następnie transkrybowane i przekształcane w białka wirusowe.

Na koniec gospodarz ponownie składa te składniki wirusa w potomstwo, pozwalając pojedynczej cząstce wirusa wyprodukować 1000 więcej bakterii, co często prowadzi do śmierci komórki gospodarza.

Yamauchi, Yohei i Ari Helenius. "Wejście wirusa w skrócie." J Cell Sci 126, nr 6 (15 marca 2013): 1289–95. [<a href="https://doi.org/10.1242/jcs.119685" target="__blank">Źródło</a>]

Lin, Derek M, Britt Koskella i Henry C Lin. "Terapia fagowa: alternatywa dla antybiotyków w dobie oporności wielolekowej". World Journal of Gastrointestinal Pharmacology and Therapeutics 8, nr 3 (6 sierpnia 2017): 162–73. [<a href="https://doi.org/10.4292/wjgpt.v8.i3.162" target="__blank">Źródło</a>]

Nicaise, Valérie. "Odporność upraw na wirusy: wyniki i przyszłe wyzwania". Frontiers in Plant Science 5 (21 listopada 2014 r.). [<a href="https://doi.org/10.3389/fpls.2014.00660" target="__blank">Źródło</a>]

czym są wirusy?

<h4>Przegląd</h4>

Wirus to mikroskopijna zakaźna cząsteczka składająca się z genomu RNA lub DNA zamkniętego w białkowej otoczce. Nie jest w stanie samodzielnie się rozmnażać: może jedynie wytworzyć więcej wirusów, wchodząc do komórki i korzystając z jej maszynerii komórkowej. Kiedy wirus infekuje komórkę gospodarza, usuwa jej otoczkę białkową i kieruje maszynerią gospodarza do transkrypcji i translacji jej materiału genetycznego. Przejęta komórka składa replikowane składniki w tysiące wirusowych wirusów, które mogą rozerwać i zabić komórkę gospodarza. Nowe wirusy następnie infekują więcej komórek gospodarza.

<h4>Po co badać wirusy?</h4>

Wirusy mogą infekować różne typy komórek: bakterie, rośliny i zwierzęta. Wirusy atakujące bakterie, zwane bakteriofagami (lub fagami), są bardzo liczne. Obecne badania skupiają się na terapii fagowej w leczeniu wielolekoopornych infekcji bakteryjnych u ludzi. Wirusy infekujące rośliny uprawne są również szczegółowo badane, ponieważ epidemie prowadzą do ogromnych strat w plonach i ekonomii.

Wirusy odkryto po raz pierwszy w XIX wieku, kiedy ważną gospodarczo uprawę, tytoń, nękała tajemnicza choroba—później zidentyfikowana jako wirus mozaiki tytoniowej. Wirusy zwierzęce mają ogromne znaczenie zarówno w badaniach weterynaryjnych, jak i medycznych. Co więcej, wirusy są przyczyną wielu chorób człowieka, począwszy od przeziębienia, ospy wietrznej i opryszczki, po bardziej niebezpieczne infekcje, takie jak żółta febra, zapalenie wątroby i ospa.

<h4>Struktura wirusa</h4>

Wirusy występują w różnych postaciach i specjalizują się w atakowaniu komórki docelowej. Dwoma głównymi składnikami wszystkich wirusów są genom wirusa i jego ochronny płaszcz białkowy, znany jako kapsyd. Genom wirusa składa się z jedno- lub dwuniciowego RNA lub DNA i koduje białka tworzące kapsyd. Razem genom wirusa i kapsyd są znane jako nukleokapsyd.

Unikalną cechą wielu wirusów eukariotycznych jest obecność błony fosfolipidowej, zwanej otoczką otaczającą kapsyd. Otoczka ta zwykle pochodzi z błon wcześniej zakażonych komórek gospodarza, ale może również zawierać przyłączone do niej białka wirusowe (zwane białkami otoczki). Wreszcie, niektóre wirusy zwierzęce mają skupisko białek kodowanych przez wirusy, otoczkę wirusa, w przestrzeni pomiędzy otoczką a kapsydem.

<h4>Infekcja wirusowa</h4>

Cykl życiowy wirusa można podzielić na pięć następujących etapów: przyłączenie, wejście, replikacja, montaż i uwolnienie. Białka na powierzchni wirusa pomagają mu rozpoznać określone komórki gospodarza. Niektóre wirusy wykorzystują te białka powierzchniowe do wiązania receptorów komórki gospodarza i inicjowania internalizacji przez endocytozę, podczas gdy wirusy otoczone otoczką mogą bezpośrednio łączyć się z błoną komórkową gospodarza.

Niektóre bakteriofagi nie dostają się do komórki; wstrzykują swój genom (i enzymy wirusowe) do komórki gospodarza. Po wejściu do komórki wirus zostaje pozbawiony powłoki i kieruje maszynerią komórki gospodarza w celu transkrypcji i translacji jej genomu. Komórka gospodarza pakuje nowe kopie genomu wirusa w cząsteczki wirusa, tworząc potomstwo. Wirusy potomne mogą być przechowywane w komórce gospodarza przed uwolnieniem lub w sposób ciągły wytłaczane z komórki poprzez pączkowanie z błony komórkowej. Cykl infekcji wirusowej dzieli się na lityczny i lizogenny. W cyklu litycznym nowe wirusy wydostają się z komórki gospodarza, zabijając ją. W cyklu lizogennym wirusowy DNA jest włączany do genomu gospodarza, gdzie pozostaje uśpiony i jest kopiowany za każdym razem, gdy komórka gospodarza się replikuje.

Czym są wirusy?

Przegląd

Wirus to mikroskopijna cząsteczka zakaźna, która składa się z genomu RNA lub DNA zamkniętego w otoczce białkowej. Nie jest w stanie rozmnażać się na ...

Education

JoVE Core

Biology

Biologia

Genetics

Genetyka

Viruses

Wirusy

KEY TERMS AND CONCEPTS

Kluczowe terminy i pojęcia

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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How Viruses Infect Cells and Multiply

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