Study Notes from Virology Course BM 330

Course Overview

  • Virology course BM 330 teaches methods to study viruses and their metabolic activities.
  • Focus on how viruses cause diseases and the human body's defenses.
  • Understanding virus replication strategies and socio-economic impacts.

Discovery of Viruses

  • Louis Pasteur linked rabies to a ‘virus’.
  • Dimitri Iwanowski, through filtration, discovered viruses could transmit disease in plants (1892).
  • Martinus Beijerinick named the tobacco mosaic virus (TMV) in 1898.
  • First human disease linked to a virus: poliomyelitis (1909) by Karl Landsteiner and Erwin Popper.
  • Frederick Twort and Felix d’Herelle discovered bacteriophages, viruses that infect bacteria (1915-1917).

Virology in History

  • The first virus infection recorded in Egypt (~3700 BC).
  • Smallpox known in China as early as 1000 BC with variolation techniques.
  • Edward Jenner developed smallpox vaccination in 1796, leading to widespread acceptance.

Koch’s Postulates

  • Robert Koch’s four criteria for establishing disease causation:
    1. Pathogen present in all diseased individuals.
    2. Must be grown in pure culture.
    3. Should cause disease in healthy hosts.
    4. Must be re-isolated from the inflicted host.

Characteristics of Viruses

  • Viruses: nucleoproteins that reproduce only in living cells; too small for light microscopy.
  • Composed of nucleic acid (DNA or RNA) and protein; may have lipid envelopes.
  • Do not grow or divide; use host cells to multiply.
  • Viruses can cause various diseases in humans, plants, and bacteria.

Differences Between Viruses and Other Microorganisms

  • Viruses are submicroscopic and obligate intracellular parasites.
  • Unlike bacteria, viruses don’t grow or divide and lack metabolic energy generation mechanisms.
  • Viruses depend entirely on host cellular machinery for replication.

Other Pathogenic Entities

  • Viroids: small, circular RNA molecules causing plant diseases; no protein-coding capability.
  • Virusoids: dependent on viruses for replication; can cause plant diseases.
  • Prions: infectious proteins causing neurodegenerative diseases; no nucleic acid component.