Hunting archaeal viruses

Viruses are obligate parasites that need host cells to replicate. They can infect members of all domains of life, as became clear soon after the first viruses were discovered in the 1890s. Ivanofsky and Beijerinck independently found that tobacco mosaic disease was caused by a ‘filterable substance’, also coined virus. Their work was followed by that of d’Herelle and Twort, who discovered that bacteria could also be attacked by a filtered substance, which was named ‘bacteriophages’. Once electron microscopy became available, both filterable substances were shown to consist of viral particles.