Beijerinck, Martinus Willem  (1851-1931)

Dutch bacteriologist who in 1898 published his finding that an agent smaller than bacteria could cause diseases, an agent that he called a virus. Beijerinck was born in Amsterdam and studied chemical engineering at the Delft Polytechnic, where, after working as a bacteriologist with an industrial company, he taught and carried out research from 1895. In the 1880s and 1890s Beijerinck studied the disease that stunts the growth of tobacco plants and mottles their leaves (now called the tobacco mosaic virus disease). Trying to isolate a causative agent, he pressed out the juice of infected tobacco leaves and found that the juice alone was able to infect healthy plants, even after he had passed it through a filter that removed bacteria. Beijerinck was also certain that the causative agent was not a toxin because he could infect a healthy plant and from that plant infect another healthy plant, continuing this process indefinitely - therefore the infective agent had to be capable of reproduction. He believed that the filtered juice of the infected plants was itself alive, and he called the causative agent a filterable virus (the Latin word for poison).