on 4.2.09 with 0 comments

  • Capsid: Composed of numerous repeating subunits. Viral genome is thus conserved in that a single protein can be transcribed many times to make the capsid.

  • Capsomere: Clusters of polypeptides which, when completely assembled, form the capsid.

  • Nucleocapsid: Genome together with capsid.

  • Virion: Free viral particle, consisting of nucleocapsid, or nucleocapsid plus envelope.

  • Envelope: Lipid bilayer, usually obtained from host cell.

  • Symmetry: Three types

    • Cubic Symmetry: Icosahedral symmetry. 20 equilateral triangles.

    • Helical symmetry

    • Complex: No regular symmetry, as in poxvirus.

  • Viral Conditions:

    • Alkaline kills all viruses.

    • Ether: Enveloped viruses are susceptible to ether. Poxviruses vary in susceptibility.

    • Enveloped viruses are generally less stabile than naked viruses.

  • Host-cell Virus Interactions:

    • Productive Infection: Virus successfully completes replication cycle and produces progeny virions.

    • Abortive Infection: Virus enters the host-cell but cannot successfully complete replication.

      • Can result from a non-permissive host-cell, or because the virus is defective.

      • Abortive infections can become persistent infections.

    • Restrictive Infection: Cells are only transiently permissive, after which they become non-permissive. This results in transformation of the cell.

    • Latent Infection: Virus remains in a cell and does not replicate, as in HSV, VZV, CMV, EBV, and HIV.

  • Replication Cycle:

    • Divided according to presence of infectious virions:

      • Eclipse Phase: Virus has entered cell, but no progeny virions are created yet.

      • Maturation Phase: Viral progeny are produced and infectious virions are again present.

    • According to biosynthesis sequence

      • Early Phase: Biosynthesis of prerequisite proteins, required before replication can take place, such as replicase enzymes or enzymes that inhibit host-cell synthesis.

      • Late Phase: Synthesis of structural capsid proteins, and actual replication of the genome.

Category: Microbiology Notes



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