Introduction to Virology – 1

  • Virus is an obligate intracellular parasite containing genetic material surrounded by proteins
  • Not living organisms, cannot produce energy or synthesize proteins independently, host cell machinery is needed
  • Viruses that infect bacteria are called bacteriophages

 

4

 

Difference between Naked Virus and Enveloped Virus

Properties

 

Enveloped Naked
Environmental stability Are destroyed by acids, detergents and drying (easily die) Stable to temperaure, acids, proteases, disinfectants and drying

 

Release from cell Budding Lysis

 

Spread to host Spreads in large droplets, secretions, transplanted organs, blood transfusions

 

Spread easily by direct contact, dust, small air droplets
Stability outside cells Must stay wet

 

Can dry out and retain infectivity

 

Effective immune respone May need antibody and cell mediated immunity for protection Antibodies are sufficient

 

Difference between bacteria and viruses

Virus

 

Bacteria
Obligate intracellular parasites Free living, can be parasitic

 

No ribosomes Has ribosomes

 

DNA or RNA, not both DNA and RNA

 

Need electronic microscopes Seen in light microscopes

 

10-100 genes 100-1000 genes

 

Tangled phylogeny

 

Natural phylogeny

 

Baltimore Classification of Viruses

2018-05-28 19 44 56

 

Replication of viruses

Image result for replication of viruses

 

 

All RNA viruses replicate in the cytoplasm except Orthomyxoviruses and Retroviruses that have replicative stages in nuclei

All DNA viruses replicate in the cytoplasm except Poxviruses that can replicate in the cytoplasm.

 

Image result for effect of animal viruses on cells

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