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In 1892 Dmitri Ivanowski showed that tobacco mosaic disease still spread after diseased plant juice received which treatment?
AFiltration that removed every viable bacterium
BHeating until its own proteins had set
CDilution in a large volume of pond water
DExposure to several hours of bright sunlight
Answer & Solution
Correct answer: A. Filtration that removed every viable bacterium
1. Adolph Meyer had already shown in 1886 that liquid juice from a diseased tobacco plant infects a healthy one.
2. Ivanowski repeated that transfer in 1892 but first passed the juice through a Chamberland-Pasteur filter.
3. That filter had removed all viable bacteria, and the filtered juice still transmitted the disease.
4. So the agent was smaller than any bacterium the filter could hold back.
5. Heating, dilution and sunlight were not the treatments used, so none of them is the answer.
_Source: OpenStax Biology (1st ed., CC BY 4.0), Ch 21 "Viruses", section 21.1 Viral Evolution, Morphology, and Classification_
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