1. Bacteria 1 Bacteria Basics Many of us know bacteria only as ‘ germs ’, invisible creatures that can invade our bodies and make us ill. They live in, on and around us all the time. Not everyone knows that bacteria also do lots of good things, like break down dead leaves and other rubbish, and make oxygen. We can even use bacteria, making them work for us! Bacteria consist of only a single cell each, whereas each one of you is made up of about 10,000,000,000,000 cells! But don’t start feeling superior – bacteria are amazing, and very important! Without them, you couldn’t even survive! If there is just one of them, we call it a bacterium. These bacteria turn milk into yoghurt! These bacteria give you a sore throat!

2. Bacteria 2 How They Get Around Bacteria have many different shapes. Some have 'tails' (called flagella) that let them swim. They rotate their flagella like tiny propellers to move themselves through liquids. Other bacteria make slime so they can ooze over surfaces like slugs. Others stay almost in the same spot. What They Look Like There are thousands of types of bacteria. Some are rod-shaped; others are shaped like little balls. Some are spirals. You could fit 1000 of them across 1 mm! Pretty, but hard to draw! Draw this one – it ’ s simpler!

3. Bacteria 3 Where They ’ re Found Bacteria can be found almost everywhere! Bacteria live on or in just about every material and place on Earth, from soil to water to air, and from your body to the North Pole to the Sahara desert. Many types can survive below freezing temperature (0°C)., and some types can survive above boiling point (100°C). This picture was taken with a very powerful microscope. This bacterium lives in soil, and moves through soil water using its flagella. Lots of them live on you, but don ’ t worry, almost all of them are good for you! Each square centimetre of your skin has about 100,000 bacteria on it. This picture shows bacteria on human skin. (They aren’t really bright pink; they’ve been coloured in pink so you can see them better.) That big tree trunk in the picture is actually a human hair. So now you can see how small bacteria are!

4. Bacteria Extras 1 Read at your own risk – this may shock you! How Long They’ve Been Around Like dinosaurs, bacteria left behind fossils. The big difference is that it takes a microscope to see them. And they are older. Bacteria were the earliest forms of life on Earth. They first appeared about 4 billion years ago, and for the next 2 billion years they were the only life on Earth! Without Bacteria, We Could Never Have Existed! Earth was a poisonous place back in the early days. There was no oxygen around, so we and most other animals and plants could not have existed. Then some types of bacteria started making oxygen using the energy from sunlight – they had invented photosynthesis! Once plenty of oxygen had built up in the atmosphere, it became possible for plants and animals to develop. So bacteria paved the way for us! Thank you, bacteria! Bacteria fossil, 3 million years old Earth might have looked like this in the early days.

5. Bacteria are Different From All Other Living Things! Like us, bacteria have DNA, or genes, inside the cell. But unlike ours, their DNA is not contained in the little package we call the nucleus. It just floats around in the cytoplasm. Different types of bacteria eat different foods. Some eat sugar and starch; others eat sulfur, or even iron! Others use sunlight to make their own food, like plants do. Bacteria Extras 2 Read at your own risk – this may shock you! This twisty-looking bacterium eats iron for its dinner! Weird! Someone has knitted this bacterium! (Real ones don’t have eyes, of course. Or ears, or noses. But they can find their way around by detecting different chemicals around them.)

6. The Bacteria in YOU! There are 100 trillion (100,000,000,000,000) bacteria – weighing 2 ½ kilos altogether - happily living in your intestines. That's ten times more bacteria than there are cells in your body, more bacteria than the number of stars in our galaxy, more bacteria than the number of humans who have ever lived (estimated, by the way, at 100 billion)... You get the picture. There are a lot. To an alien landing on our planet, we humans might just seem like a chain of bacteria hotels! Bacteria Extras 3 Read at your own risk – this may shock you! This is one of the types of ‘good’ bacteria that live in people’s intestines. The makers of this ‘probiotic’ yoghurt claim that the bacteria in it are good for your digestive system. Whether or not that’s true, they are certainly safe to eat. Babies are born with no bacteria in their intestines, but within a few weeks bacteria have got in and made their home there. Without these bacteria in our guts, we would have difficulties digesting all our food, and we would become unwell.