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VIRUSES

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petra kovacikova

on 9 May 2016

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Transcript of VIRUSES

VIRUSES
OUTLINE
1. History and evolution
2. Structure and "life cycle"
3. Classification
4. World´s most unwanted
5. Statistics
6. References
The Origins of Virology
lat.
virus
= poison and other noxious substances
3700 BC - first records of a virus infections (heiroglyph,mummy)
1892, Dmitri Iwanowski - crushed leaf extracts from infected tobacco plants remain infectious after filtration
History and evolution
tobacco mosaic disease
Glossary:
paralytic poliomyelitis = paralytická poliomyelitída
Evolution of viruses
short generation times and high mutation rates
endogenous viral elements (EVEs) = retrospective evidence
4 hypotheses
A single ancestor, the LUCA
Nothing common to all viruses
Ribosome-encoding organisms (modern cells)
Capsid-encoding organisms (viruses)
"Pickpockets"
RNA world
Reduction
Coevolution
Hypotheses
derived from genomes of modern cells (mobile elements)
existence of viral genes practically denied?
protoviruses infecting non-living vesicles that became protocells
host?
evolved from small cells that parasitised larger cells
evolved independently
ancient free- living cellular lineages
"New perspective"
Structure and "life cycle"
Virion
virus particle
transmits NA of virus from one cell to another
Resources
Forterre and Prangishvili, 2009_The origin of viruses
http://www.nature.com/scitable/topicpage/the-origins-of-viruses-14398218
http://www.microbiologybytes.com/introduction/introduction.html
http://www.ucmp.berkeley.edu/alllife/virus.html
Acheson, Nicholas H. - Fundamentals of molecular virology
http://viralzone.expasy.org/
http://www.who.int/en/
Nucleic acid
Capsid
Envelope
"Naked" virions
Enveloped virions

Nucleic Acid
Capsid
Envelope
small, less complex genomes (more introns)
ss/ds
DNA/RNA virus
circular/linear genome
segmented/non segmented
protein shell
helical (TMV) or icosahedral structure
Glossary:
icosahedron - dvacetistěn
acquired - získaný
lipid bilayer membrane
acquired from an intracellular membrane of the host
Glossary:
withstand - odolávat, snést
Attachment
Entry
Replication
Self Assemly
Escape
LIFE CYCLE
viral surface protein binds to specific host surface molecule
triggers signaling pathways,
= penetration into the host cell cytoplasm
injection of genetic material (bacteriophage)
endocytosis
release of genetic material from the vesicle (uncoating)
transport of NA ( nucleus/cytoplasm)
translation of viral proteins
assembly of viral proteins and genetic materials produced in the host cell
NEW VIRIONS
lysis
budding
Classification
DNA viruses
using a DNA-dependent DNA polymerase
ssDNA
dsDNA
mRNA
dsDNA
RNA viruses
dsRNA - segmented genomes, monocistronic mRNA (1 mRNA = 1protein), replication inside capsid
ss(+)RNA - uncoats in the cytoplasm, can be translated immediately, plant viruses
ss(-)RNA - must be copied into the complementary (+)mRNA, helical nucleocapsids
ss Genomes
sequence complementary to the mRNA
PLUS
MINUS
translation
same sequence as the mRNA
(Group I. and II.)
(Group III., IV., V. )
Viruses using reverse transcriptase
Retroviruses
ss(+)RNA with DNA intermediate
RNA serves as the template for reverse transcriptase
(Group VI., VII.)
dsDNA (RT)
replicates using a single stranded RNA intermediate
hepatitis B virus
World´s most unwanted
Ebola - ss(-)RNA
Ebola hemorrhagic fever (EHF)
symptoms: intense weakness, muscle pain, headache and sore throat, internal and external bleeding, liver dysfunction
transmission: close contact with infected blood, secretions
occurrence: Africa
lethality: up to 90%
worst outbreak: 2000, Uganda 425/224/53%
Smallpox
variola virus
symptoms: fever, back pain, rash (first on the face, hands and forearms)
transmission: saliva droplets
officially eradicated in 1979
Glossary: rash - vyrážka
Polio
poliovirus
symptoms: fever, fatigue, headache, vomiting, stiffness in the neck and pain in the limbs
transmission: oral infection
occurrence: Afghanistan, Nigeria, Pakistan
Glossary: stiffness - ztuhlost, strnuost
Statistics
DNA viruses
ds
ss
DNA
nucleus/cytoplasm
unfragmented genome
largest ones
nucleus
ds intermediate
Full transcript