1. Virus - Basics & News Taxonomy & Families
What is a virus ?
Structure
Genome
Replication

2. A virus is a virus (lat: poison)
Replication: a replicating biochemical complex without its own metabolism
requires metabolism of living host cell for replication
Structure: Submicroscopic Size, nm
(exception:orthopox)
Genome: contains genetic information, DNA or RNA

3. Virus - sizes

4. Comparison of Size: Virus/Bakterium

5. An infectious virus particle ‘Virion‘
The genome (DNA or RNA) is always packed in a protein structure the ‘Capsid‘
The combine Capsid/Genomestructure: ‘Nukleocapsid‘
The capsid structure can be spherical (Icosaeder) or helical structure (Tubulus)
Some viruses have additional structures: a lipid envelope
engulfing the capsid

6. non enveloped Virus: contains only nucleic acid and protein
Tobacco mosaic virus: helical capsid
Adenovirus: icosahedral capsid

7. ‘enveloped viruses‘ Herpes Simplex Virus Paramyxovirus
For enveloped viruses, the lipid envelope is always essential for infectivity.
The envelops can be easily destoyed by ether & detergents

8. Spherical capsids have an icosahedral structure
An Icosahedron has 20 triangular surfaces and three axes of symmetry
Picornavirus:
5-fold axes of smmetry animated X-Ray structure

9. Icosahedral capsids are built from capsomers:
Icosahedral capsids are built from capsomers: identical units of the same proteins
X-Ray structure
capsid of picornaviridae

10. The capsid surface of non enveloped viruse must carry
structures for binding to cellular receptors
These both (non related) viruses bind to CAR but the binding structures look very different
‘Canyons‘ for binding to CAR
(many enterovirus types)
Fiber (‘Spikes‘) for binding to CAR (many adenovirus types)

11. Comparison: replication of virus vs. bacterium
obligat intrazellulär
NIE auf Nährmedien, Agars usw.
lebende Zellen erforderlich:
Versuchstier
Brutei
Zellkultur
Eklipse bzw. Latenzperiode,
Adsorption, Penetration, Uncoating
Proteinsynthese & Genomreplikation
Assembly & Virusfreisetzung

12. Classical Concept of ICTV
taxonomy system: family/genus/species
family names: ...-idae
relevant for virus family:
genome type (DNA, RNA; ds-, ss-, )
capsid structure (helical, icosahedral)
enveloped/non enveloped

13. RNA viruses
RNA-Virus

15. DNA viruses
DNA-Virus

16. Baltimore System way of mRNA production (->Proteinsynthesis)
DNA Virus
RNA Virus