Bacteria are microorganisms that come in different shapes and sizes. Some are round, oval, spiral, or rod-shaped. Some are friendly and help their host, while others are aggressive and pathogenic. Bacteria are different then viruses in that bacteria can live in soil, water, and on plants. In fact, bacteria are present in the stratosphere, earth’s crust, and deepest ocean floor. Bacteria, unlike viruses, do not require a living organism to feed off of in order to survive.