Читать книгу Principles of Virology - Jane Flint, S. Jane Flint - Страница 38

Dramatic confirmation of the structural simplicity of virus particles came in 1935, when Wendell Stanley obtained crystals of tobacco mosaic virus. At that time, nothing was known of the structural organization of any biologically important macromolecules, such as proteins and DNA. Indeed, the crucial role of nucleic acids as genetic material had not even been recognized. The ability to obtain an infectious agent in crystalline form, a state that was more generally associated with inorganic material, created much wonder and speculation about whether a virus is truly a life form. In retrospect, it is obvious that the relative ease with which this particular virus could be crystallized was a direct result of its structural simplicity.

The 1930s saw the introduction of the instrument that rapidly revolutionized virology: the electron microscope. The great magnifying power of this instrument (eventually more than 100,000-fold) allowed direct visualization of virus particles for the first time. It has always been an exciting experience for investigators to obtain images of viruses, especially as they appear to be remarkably elegant (Fig. 1.9). Images of many different virus particles confirmed that these agents are very small (Fig. 1.10) and that most are far simpler in structure than any cellular organism. Many appeared as regular helical or spherical particles. The description of the morphology of virus particles made possible by electron microscopy also opened the way for the first rational classification of viruses.