Microorganisms- A living organism that is very minute to be seen by the naked eye, especially a single-celled organism, such as a bacterium is called microorganism. On the other hand, they multiply like living organisms when they are within a living body. The bacterium lactobacillus helps in the formation of curd. The microorganisms, yeast is used for the commercial production of alcohol and wine. Streptomycin, tetracycline, and erythromycin are some of the commonly used antibiotics; these are made from fungi and bacteria. Harmful microorganisms include fungi, bacteria, protozoa, etc. They cause several diseases in human beings, animals, and plants which can even lead to death. The harmful microorganisms damage not only the human body but also the food we eat.