The role of bacteria is positive and negative.

The role of bacteria in nature and human life is enormous, because there are a great many types of bacteria and it is very difficult to find a place on Earth, wherever they occur, including hot, salt springs and permafrost. In nature, bacteria are involved in the formation of humus, increasing soil fertility, and the circulation of substances in nature. Some bacteria are used by humans to obtain kefir, sour cream, table vinegar, for pickling cabbage and pickling cucumbers. It’s hard to believe, but bacteria live in you and me, their total weight in the human body is as much as 2 kg! They help us digest food, fight off disease-causing bacteria, and even produce some important vitamins. However, the negative role of bacteria is also great. Some species cause spoilage of food, diseases of animals and humans, for example, tuberculosis, dysentery, typhus, etc. Bacteria also infect plants, although this happens less often.