The world of bacteria - I am bacteria

When you think about bacteria, perhaps the first thing that comes to mind is diseases, but many bacteria are really useful, it is important for you and your health as well, but you cannot live without them! Perhaps bacteria are really very small, you can only see them under the microscope, but they are strong enough to change your life. Bacteria are present everywhere, their numbers are billions, and their shapes are varied, and each has a different function.