Virology Basics and Virus Structure

Viruses

• Virology is the branch of microbiology that studies viruses
• Viruses cannot replicate independently, they need a host cell
• Viruses cannot produce their own energy
• Viruses can be seen by a light microscope (LM), but not well. An electron microscope (EM) has a much higher magnification.
• Some viruses have an envelope, some do not, envelope = made of lipids and proteins.
• Viruses can contain either DNA or RNA, but not both.
• Viruses are smaller than cells, typically 20-300 nm.
• Viruses can be detected by electron microscopy.

DNA

• Deoxyribonucleic acid
• Double-stranded
• Sugar= Deoxyribose
• Phosphate

RNA

• Ribonucleic acid
• Single-stranded
• Sugar= Ribose
• Phosphate

Virus Structure

• Capsid: protein coat
• Nucleic acid (DNA or RNA): central core
• Envelope (some viruses): protein coat surrounding the capsid
• Protective function: Capsid protects the nucleic acid
• Capsomeres: identical subunits that form the capsid
• Host Specificity- relates to the protein coat of the virus.
• Viruses may be rod-shaped, helical, cuboidal/polyhedral, filamentous, complex.
• Viral structure determines the shape.

Virus Replication

• Adsorption: virus attaches to host cell
• Penetration: virus enters host cell.
• Replication of viral parts: virus replicates its nucleic acid and proteins
• Assembly: viral components assemble into new viruses
• Release: new viruses leave the host cell
• Methods of release include lysis and budding.

Virus Classification

• Animal viruses: affect animals, contain DNA or RNA
• Plant viruses: affect plants, contain RNA
• Fungi viruses: affect fungi, contain DNA or RNA
• Bacteriophages (bacterial viruses): affect bacteria, contain DNA
• Mycophages: affect fungi, contain DNA
• Cyanophages: affect cyanobacteria, contain DNA

Cultivation of Viruses

• Animal viruses: cultured in live animals, embryonated eggs, or cell cultures
• Plant viruses: grown in plant tissue or protoplasts
• Bacteriophages: cultured in bacterial cultures

Bacteriophages

• Viruses that infect bacteria
• Lytic cycle: virus replicates and causes bacterial cell lysis
• Lysogenic cycle: virus integrates its DNA into the bacterial chromosome

Explore the fundamental concepts of virology, including the structure and function of viruses. This quiz covers the key differences between DNA and RNA, the composition of viruses, and their dependence on host cells. Test your knowledge on this intriguing branch of microbiology.