Bacteria come from the Earth, just like we did. So when did and where does this bacterium originate? Like dinosaurs, bacteria left behind fossils. The big difference is that it takes a microscope to see them. And they are older. Bacteria are among the earliest forms of life that appeared on Earth, billions of years ago. Scientists think that they helped shape and change the young planet’s environment, eventually creating atmospheric oxygen that enabled other, more complex life forms to develop. Many believe that more complex cells developed as once free living bacteria took up residence in other cells, eventually becoming the organelles in modern complex cells. The mitochondrion, which makes energy for your body cells, is one example of such an organelle. Bacteria are organisms made up of just one cell but don’t let their small size and seeming simplicity fool you. They’re an amazingly complex and fascinating group of creatures. It has been found that bacteria can live in temperatures above the boiling point that would scorch you and temperatures below the freezing point that would freeze your blood. They eat everything from sugar and starch to sunlight, sulphur and iron. They are capable of multiplying by themselves, as they have the power to divide. Their shapes vary, and doctors use these characteristics to separate them into groups. Bacteria exist everywhere, inside, on and outside our bodies. Most of them are completely harmless and some of them are very useful. But some bacteria can cause diseases, either because they end up in the wrong place in the body or simply because they are designed to invade us.
