Stanley's Crystal Invaders 1935 – The Discovery of Viruses

In 1935, American biochemist Wendell Stanley astonished the scientific world when he discovered the first virus by creating crystals from tobacco mosaic virus (TMV). As scientists wondered how something living could be crystalline, TMV was described as a ghost caught between the realms of the living and the nonliving.

Today, we know the following about viruses:

• They are ultramicroscopic particles no more than 200 nm wide.
• They contain only one of the two types of nucleic acids (RNA or DNA).
• They can form pathogenic strains.
• They never display the characteristics of a living organism (they lack cellular organization).
• They are parasitic life forms that can reproduce biochemically inside host cells.

Viral shapes range from regular 20-sided objects to long helices. Rod-shaped TMV has a protein structure (coat) surrounding a single strand of RNA that carries its genetic code. 

After the virus enters a plant cell, its RNA replicates and more coat protein is produced in the plant cell. TMV causes mottled browning of tobacco leaves and commonly infects vegetables such as tomatoes. Like other viruses, TMV is too small to be seen directly with a light microscope. 

Historian of science Angela Creager writes:

"TMV was a protagonist in debates about the origin of life, a critical tool in research on biological macromolecules, and a potentially major player in the development of commercial scientific instruments. In campaigns against poliomyelitis and cancer, knowledge about TMV helped justify large-scale funding for virus research and served as a pragmatic guide to investigating human pathogens."

Description of the Article Image: Tobacco mosaic virus particles (rods), stained with heavy metal to make them visible under an electron microscope. 

Historical Figures Mentioned in This Article: Friedrich Wöhler (1800–1882), Wendell Meredith Stanley (1904–1971)

• Previous topic: Jung's Theory of Analytical Psychology 1933 – Dreams and Symbols
• Next topic: Sulfonamides 1935 – Antibacterial Drugs