I think 'bacterial, fungal, and protistan diseases' should be 'bacteria, fungi, and protists'. There's something wrong with the underlined part, with the things compared.
The discovery of viruses as a unique life form came about in 1892. Dmitri Iwanowski, a Russian scientist, accidentally revealed that viruses were responsible for a common tobacco disease. He determined this by filtering the diseased tissues in an attempt to collect the organism causing the tobacco disease. Iwanowski was amazed when he discovered that the disease organism was smaller than any known cell. Other scientists carried out similar studies on other diseases and called the disease organisms “unfilterable infectious agents.” This filtration method distinguished viruses from bacterial, fungal, and protistan diseases, which did not pass through filters. These unfilterable agents were renamed in 1915. Scientists generally used the term Twort particles for viruses causing agricultural animal disease, named after English scientist Frederick William Twort, who isolated viruses from cattle.
