BIO 206SPRING SEMESTER 2019INSTRUCTOR: DR. RITA MOYES13 February 2019Sometimes used to grow viruses in● Flu virus is grown in embryonated eggs for vaccinesRelease● Assembled animal viruses leave host cell in one of two ways:○ Budding/Blebbing- exocytosis■ Nucleocapsid binds to membrane which pinches off and sheds theviruses gradually○ Lysis-viruses released when cell dies and ruptures● Number of viruses released during lysis is variable○ Poxvirus 3,000-4,000 released■ Very large○ Poliovirus >100,000 released■ Very smallThe process of budding in enveloped viruses.● Enveloped virus looks like the host cell membrane○ Evades immune response for a short time○ Their viral spikes give them away● Molecular mimicry○ Budding of the enveloped virus1General Structure of Viruses● Some bacteriophages (viruses that attack bacteria) have a polyhedral nucleocapsidalong with a helical tail and attachment fibersMultiplication Cycle in Bacteriophages● Bacteriophages- bacterial viruses (phages)○ Most widely studied are those that infect E. coli○ Multiplication goes through similar stages as animal viruses○ Only nucleic acid enter the cytoplasm○ Release due to cell lysis = lytic cycleVirus host range*has to be a receptor to accept viron on the surface*● Host cell infection→ due to affinity of viral surface proteins for complementaryproteins (receptors) on host cell surface means:○ Host cell must posses a receptor that interacts with viral surface■ No host receptor=no viral infectivity○ Host range is determined by the presence of complementary receptors onhost cell○ Examples of host range:■ Rabies virus→ infects dog, human, etc● broad host range■ T4 bacteriophage→ only infects certain strains of E. coli● limited host