Zoom in on microorganisms

Viruses

Influenza virusZoomZoom
© Robert Alain, SME, INRS-Institut Armand-Frappier

Viruses are at the border of the living and non-living. They depend on the cellular components and metabolites of the hosts where they multiply, which is why they are called obligatory intracellular parasites. Viruses are the smallest microorganisms (15 to 300 nanometers) and have a protein structure, the capside, containing DNA and RNA, and sometimes, an envelope.