There are only two portrait photos of Ivanovsky; one was used for a Russian postage stamp, and we reproduce that here second image.
Both Ivanovsky and Beijerinck died before the significance of their discovery was appreciated, so they missed out on the Nobel Prize that they assuredly deserved.
William B. Ashworth, Jr. Comments or corrections are welcome; please direct to ashworthw umkc. Scientist of the Day - Dmitri Ivanovsky November 9, Jan Feb 2. View Calendar. When German pathologist Robert Koch discovered the bacterium behind tuberculosis in , he included a short guide for linking microorganisms to the diseases they cause.
It was a windfall for germ theory, the modern understanding that pathogens can make us sick. When a blight of mosaic disease threatened European tobacco crops in the mids, plant pathologists set out to identify its root cause. For decades, only one forward-thinking botanist, Martinus Beijerinck, realized the source was neither a bacterial nor a fungal infection, but something completely different: a virus.
Today, we know that viruses can be found nearly anywhere in the air , oceans and soil. A tiny percentage of these are dangerous pathogens that cause disease, such as the current coronavirus called SARS-CoV-2 causing a worldwide pandemic.
Yet the study of viruses started not in medical science, but in botany, the study of plants. Viruses are so small—and so strange—that it would take decades for scientific consensus to agree that they exist at all. In , farmers in the Netherlands reported a disease threatening another economically vital crop: tobacco. The leaves began turning a mottled dark green, yellow, and grey, causing farmers to lose up to 80 percent of crops in affected fields.
Massive fields of tobacco that had been planted with the same crop repeatedly were especially susceptible. But Mayer ran into trouble.
When botanist Dmitri Ivanovski researched tobacco mosaic disease in Crimea beginning in , he took a different approach. He strained the sap through fine filters made of unglazed porcelain, a material with pores that were too small for bacteria to squeeze through. But when Ivanovski put the filtered sap on a healthy tobacco leaf, it turned mottled yellow with disease.
Ivanovski could barely believe his data, which he published in He concluded that the disease was caused by a toxin that fit through the filter or that some bacteria had slipped through a crack. Dutch microbiologist Beijerinck independently conducted almost the same experiments as Ivanovski, but he came to a much different conclusion.
The early pathologist added to the porcelain filter experiments with a second kind of filtration system that used a gelatin called agar to prove that no microorganisms survived the first filtration. Bacteria get stuck on top of the gelatin, but the mysterious mosaic-causing pathogen diffused through it.
Beijerinck also provided evidence that the disease agent relies on growing leaves to multiply. By re-filtering the pathogen from an infected leaf and using it to cause mosaic disease on another plant, he showed that the agent could spread without diluting its disease-causing power. When he published his findings in , Beijerinck called the infectious, filtered substance contagium vivum fluidum— a contagious, living fluid.
Although Beijerinck incorrectly thought viruses were liquid they are particles his results were close to the mark. His suggestion of a pathogen without a cell conflicted with early germ theory and was radical for the time.
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