Individual bacteria are too tiny to be seen without a microscope.
But recent calculations suggest that the largest amount of living matter on the planet Earth is the total mass of bacteria. This is because bacteria are found everywhere - on surfaces, throughout liquids, and even in the depths of Earth. The danger of bacterial disease Bacteria multiply very fast. Some populations double in as little as 20 minutes if they are in optimum conditions for growth. An untreated bacterial infection can quickly turn from a minor disturbance to a massive attack on the body.