Bacteria are small unicellular organisms found almost everywhere, in the deepest oceans, beneath the ground, and up to 27,000 meters in the atmosphere. There are many types of bacteria, some causing lethal diseases, while others, on the contrary, are beneficial to man.
Those that are harmful cause diseases in humans, animals and plants. They can spoil food, and even intoxicate the people who eat it.
But there is a large amount of bacteria that man and nature itself use for their benefit. For example, bacteria play an important role in making butter, sauerkraut, yogurt, cheese, and vinegar, all by a chemical change called fermentation. Bacteria attack dead plants and animals, and eventually turn them into food for the soil.
Bacteria are also used to purify water in wastewater treatment plants!
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