Martinus Beijerinck, the Dutch microbiologist and botanist…

Martinus Beijerinck, the Dutch microbiologist and botanist who discovers viruses, is considered one of the founders of virology.

In 1898, he publishes results on the filtration experiments demonstrating that tobacco mosaic disease is caused by an infectious agent smaller than a bacterium.

His results are in accordance with the similar observation made by Dmitri Ivanovsky in 1892.

Like Ivanovsky before him and Adolf Mayer, predecessor at Wageningen, Beijerinck cannot culture the filterable infectious agent, however he concludes that the agent can replicate and multiply in living plants.

He names the new pathogen virus to indicate its non-bacterial nature.

Beijerinck asserts that the virus is somewhat liquid in nature, calling it "contagium vivum fluidum" (contagious living fluid).

It will not be until the first crystals of the tobacco mosaic virus (TMV) obtained by Wendell Stanley in 1935, the first electron micrographs of TMV produced in 1939 and the first X-ray crystallographic analysis of TMV performed in 1941 will prove that the virus is particulate.

Beijerinck also discovers nitrogen fixation, the process by which diatomic nitrogen gas is converted to ammonium ions and becomes available to plants.

Bacteria perform nitrogen fixation, dwelling inside root nodules of certain plants (legumes).

In addition to having discovered a biochemical reaction vital to soil fertility and agriculture, Beijerinck reveals this archetypical example of symbiosis between plants and bacteria.

Beijerinck discovers the phenomenon of bacterial sulfate reduction, a form of anaerobic respiration.

He learns bacteria can use sulfate as a terminal electron acceptor, instead of oxygen.

This discovery has had an important impact on our current understanding of biogeochemical cycles.

Spirillum desulfuricans, now known as Desulfovibrio desulfuricans, the first known sulfate-reducing bacterium, is isolated and described by Beijerinck.

Beijerinck invents the enrichment culture, a fundamental method of studying microbes from the environment.