BIOLOGY Volume 1 - A Guide to General Biology - 2004

2. DIVERSITY OF LIFE ON EARTH

2.4. Viruses

2.4.1. Discovery

In 1892, the Russian botanist D. I. Ivanovsky first obtained an infectious extract from tobacco plants affected by mosaic disease. When this extract was passed through a filter that retains Bacteria, the filtered liquid still retained its infectious properties. In 1898, the Dutchman Beijerinck coined the new word “virus” (from the Latin word meaning “poison”) to denote the infectious nature of certain filtered plant fluids. Although significant progress was made in obtaining highly purified virus samples and it was established that their chemical nature is nucleoprotein (complex compounds consisting of Proteins and Nucleic Acids), the particles themselves remained elusive and enigmatic because they were too small to be seen with a Light Microscope. This is precisely why Viruses were among the first biological structures to be examined under an Electron microscope immediately after its invention in the 1930s.