The harmful effects of microorganisms are as follows:
Diseases:
∙ Microorganisms cause diseases in plants and animals.
∙ Example: Humans: Cholera caused by Vibrio cholerae
∙ Animals: Foot and mouth disease caused by virus.
∙ Plants: Citrus canker, rust of wheat caused by bacteria and fungi respectively.
Spoilage:
∙ Microorganisms spoil food by decomposing the food material.
∙ Consumption of spoilt food causes food poisoning
∙ Some microorganisms spoil leather and clothes.