How did scientists studying the tobacco mosaic disease know that infectious agent must be smaller than a bacterium?

Answer 1

Hello there!

Excellent question!

Here is the answer:

The scientists took sap from the plant with tobacco mosaic virus (TMV) in it and strained it through the finest of filters that left the bacteria and other stuff behind. The filtrate obtained was used to infect healthy ones and they found the same symptoms in the newly infected plants.

That is how they found that this was caused by a virus and also solid proof of its existence.

Hope this answered your question! 😃

Answer 2

Scientists knew that the tobacco mosaic disease must be smaller than a bacterium because it was a virus that lacked cell structures and organelles while bacterium have SOME structure, thus explaining the decrease in size.