Page 98 - MNU microbiology theoritical 2025

General Microbiology & Immunology (PM 401) Second level Semester 4 2024/2025

• For enveloped viruses: endocytosis and fusion with cell membrane

• For non-enveloped virus entry directly across plasma membrane and

endocytosis

3- Uncoating

• Release of viral genome

• Cell enzymes (lysosomes) strip off the virus protein coat

• Once uncoating occurs, enter eclipse phase

• Virion can no longer be detected; known as the “eclipse period”

4- Nucleic Acid Replication and Protein Synthesis

• Protein synthesis - 2 types

✓ structural

✓ non-structural (enzymes for replication)

• Nucleic acid synthesis (new virus genome)

Most often by a virus - coded polymerase or replicase; with some DNA viruses a

cell enzyme carries this out by using a strand of parental nucleic acid as

template in nucleus or cytoplasm.

a) DNA viruses:

• Replicate their DNA in host cell nucleus mediated by viral enzymes

• synthesize capsid and other proteins in cytoplasm using host cell enzymes

General Microbiology & Immunology (PM 401) theoretical handbook Page 87