Microorganisms can be friend as well as foe. Bad microorganisms or harmful microorganisms cause illness and spoils food, leather, clothing, etc.
Cholera, Jaundice, Ring worm etc are some of the diseases caused by micro-organisms.
Microorganisms that cause illness are called pathogens. Some microbes in food can produce toxins and if such food is ingested, it can cause food poisoning and death. Example -Botulism.