Virus

• virus= poison

• contain only one type of nucleic acid, either DNA or RNA

• genomes are smaller than prokaryotic cells

Tobacco Mosaic Virus - Iwanowski

FMD virus - Friedrich Loeffler and Paul Frosch.

Virion - fully assembled infective virus

nucleoprotein core - fundamental component of the virion, to help infect and replicate

capsid - shell of genome

capsomer or morphologic unit - protrusions on viruses

envelope - what covers the nucleocapsid

Peplomers or spikes - knob-like projections

CAPSID SYMMETRY

• Icosahedral

• helical

• complex symmetries

TAXONOMY

Criteria

• type and nature of the genome

• the mode and site of viral replication

• the structure of the virion.

International Committee on Taxonomy of Viruses (ICTV) - recognizes more than 1,500 virus species

Classification

• DNA virus

• RNA virus

REPLICATION OF VIRUS

1. Attach

2. entry to cell

3. uncoating

4. replicate

5. assemble of newly formed viruses

6. release

BIOPHYSICAL CHARACTERISTICS

1. Heat and cold

   • inactivated - 56 for 30 mins.

   • preserve - -60 or lower

   • lyophilizaton - 40

   • enveloped virus - less unstable than naked viruses

   • naked virus - -90 and 5% DMSO for stabilization

2. Vital Dyes

   • can penetrate viruses

   • inactivate viral nucleic acid upon exposure to light

3. pH

   • stable ph5 and 9

   • inactivated FMD - ph6

4. Salts-Stabilizing agent

5. Antibiotic-Rifampin readily inactivates bacterial RN