He is considered one of the founders of virology. In 1898, he published results on the filtration experiments demonstrating that tobacco mosaic disease is caused by an infectious agent smaller than a bacterium. His results were in accordance with the similar observation made by Dmitri Ivanovsky in 1892. Like Ivanovsky before him and Adolf Mayer, predecessor at Wageningen, Beijerinck could not culture the filterable infectious agent; however, he concluded that the agent can replicate and multiply in livingplants. He named the new pathogenvirus to indicate its non-bacterial nature. Beijerinck asserted that the virus was somewhat liquid in nature, calling it "contagium vivum fluidum". It was not until the first crystals of the tobacco mosaic virus 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 proved that the virus was particulate. Beijerinck also discovered 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. In addition to having discovered a biochemical reaction vital to soil fertility and agriculture, Beijerinck revealed this archetypical example of symbiosis between plants and bacteria. Beijerinck discovered the phenomenon of bacterial sulfate reduction, a form of anaerobic respiration. He learned bacteria could 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, was isolated and described by Beijerinck. Beijerinck invented the enrichment culture, a fundamental method of studying microbes from the environment. He is often incorrectly credited with framing the microbial ecology idea that "everything is everywhere, but, the environment selects", which was stated by Lourens Baas Becking.
Personal life
Beijerinck was a socially eccentric figure. He was verbally abusive to students, never married, and had few professional collaborations. He was also known for his ascetic lifestyle and his view of science and marriage being incompatible. His low popularity with his students and their parents periodically depressed him, as he very much loved spreading his enthusiasm for biology in the classroom. After his retirement at the Delft School of Microbiology in 1921, at age 70, he moved to Gorssel where he lived for the rest of his life, together with his two sisters.
