Page 93 - MNU microbiology theoritical 2025

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

a- Icosahedral: 20 identical equilateral triangles, isometric or cubic; (eg. herpes

, adenovirus)

b- Helical: tubular: (eg. rabies)

c- Complex: icosahedral heads bound to helical tails. Ex: Bacteriophage

2- Viral nucleic
acidcoat)
• Only one type of nucleic acid (DNA or RNA).

• Single or double stranded.

• Linear or circular.

• DNA is always a single molecule.

• RNA can be present in a single molecule or several segments.

• It is the infectious part of the virus

3- Viral envelope

• A viral envelope is the outermost layer of many types of viruses.

• a lipid bilayer containing various proteins, surrounds the capsid coat

• similar in structure to the cell membrane of the eukaryotic cell.

• Not all viruses have envelopes

General Microbiology & Immunology (PM 401) theoretical handbook Page 82