<P> The Italian Agostino Bassi was the first person to prove that a disease was caused by a microorganism when he conducted a series of experiments between 1808 and 1813 , demonstrating that a `` vegetable parasite '' caused a disease in silkworms known as calcinaccio -- this disease was devastating the French silk industry at the time . The `` vegetable parasite '' is now known to be a fungus pathogenic to insects called Beauveria bassiana ( named after Bassi ) . </P>
who established the idea that microorganisms play a role in disease
Agostino Bassi