Bacteria 1

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. Bacteria 1 These bacteria give you a sore throat! These bacteria turn milk into yoghurt!

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! Bacteria 2 Pretty, but hard to draw! Draw this one – it’s simpler!

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). Bacteria 3 • 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! This picture was taken with a very powerful microscope. This bacterium lives in soil, and moves through soil water using its flagella.

4. Bacteria Extras 1Read at your own risk – this may shock you! • 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! • 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! Earth might have looked like this in the early days. Bacteria fossil, 3 million years old

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 2Read at your own risk – this may shock you! 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.) This twisty-looking bacterium eats iron for its dinner! Weird!

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 3Read at your own risk – this may shock you! • 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. 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. This is one of the types of ‘good’ bacteria that live in people’s intestines.

7. Virus Basics Viruses are the smallest type of microbe, even smaller than bacteria. Viruses are really the bad guys of the microbe world. They don’t do anything that we would call good. (Only in the last few years have scientists come up with ways of making viruses do useful things for us…) Viruses are strange things that are somehow in between being alive and not alive. If they're floating around in the air or sitting on a doorknob, they do absolutely nothing. They're about as alive as a rock. But if they come into contact with a suitable plant or animal cell, they spring into action. They infect and take over the cell like pirates hijacking a ship. As a virus cannot reproduce without using another creatures’ cells to help it, some people are not convinced that viruses are really living things. 1 This virus gives you a cold! This virus gives you flu!

8. 2 • How They Get Around • Unlike bacteria, viruses can’t move themselves around. • But once a virus has got into another creature’s cell and used it to make new copies of itself, the cell bursts, and the new virus copies get shot off into the cells next door. • What They Look Like • There are thousands of types of virus that come in many shapes. • Many have geometric shapes, like cut diamonds. Others are shaped like spiky eggs, skinny sticks or pieces of looped string. Some are more complicated and look like tiny spaceship landing pods. • Viruses don’t have a nucleus. Their DNA (genes) just floats around inside them. They aren’t really even proper cells. Draw this simple one: This is a picture taken with a microscope, showing a virus attacking a cell. Don’t draw it – it’s too complicated.

9. 3 When you have a cold and you sneeze, the cold virus is in the drops that shoot out of your nose and mouth! If it lands on someone else, it gets to work on them… • Where They’re Found • Viruses can be found almost everywhere! They’re all over the planet, in soil, water and air, just waiting around for cells to infect. • Viruses can infect every living thing. However, they tend to be picky about what type of cells they infect. Plant viruses do not infect animal cells, for example. This virus hangs around in soil, and infects wheat. …so use a tissue!

10. ExtrasRead at your own risk – this may shock you! • Viruses are Really, Really Tiny • Even compared with bacteria (and your own cells), viruses are very small. • Viruses don’t just attack cells of humans, other animals, and plants. They even attack bacteria! • If you lined up a million of them, they would only cover 1 mm in length!

11. Fungi 1 • Fungi Basics • Yeasts are single-celled fungi, so they are microbes. So is mould. • Fungi are usually bigger than bacteria. • If there is just one of them, we call it a fungus. • Fungi are more like animals than plants. For one thing, fungi cannot make their own food like plants do, but instead they eat other organisms, as animals do. • With fungi, there are good guys and there are bad guys. Some make our food go mouldy, and some cause diseases. But they also break down dead plants and animals, keeping the world tidier. • We use some fungi to do things for us, like make bread rise and brew beer. These mushrooms are fungi, but they’re big and they’ve got loads of cells, so they’re not microbes. We’ll ignore these for now. Yeast cells

12. Fungi 2 • How They Get Around • Individual fungi don’t move around. • But they can spread by making tiny spores (a bit like seeds) that are carried by wind and rain and grow into new fungus cells when they land. • Some fungi, such as moulds, make long threads of cells called hyphae. These threads are what make mould look fuzzy. Moulds can spread by growing and extending their hyphae. • What They Look Like • Fungi come in a variety of shapes and sizes and different types. They can range from single cells to enormous chains of cells that can stretch for miles. • Yeast cells look round or oval under a microscope. They're bigger than bacteria, but still too small for your eyes to see them individually. Draw and label this fungus cell

13. Fungi 3 • Where They’re Found • Fungi usually grow best in places that are slightly acidic. Fungi live in the soil and on your body, in your house and on plants and animals, in freshwater and seawater. • A single teaspoon of soil contains about 120,000 fungus cells! • If you ever get athlete’s foot (a skin complaint that gives you itchy feet), then you’ve got a fungus growing on you! (Don’t worry, it’s not serious, and you can buy an ointment that kills the fungus.) The fungus likes moisture, so drying between your toes helps to keep it away. Whoa! The mould on this bread is really out of control!

14. FungiExtrasRead at your own risk – this may shock you! The Humongous Fungus (definitely not a microbe!) • The only above-ground signs of the humongous fungus are patches of dead trees (which the fungus has killed by eating them), and the mushrooms (the ‘fruits’ of the fungus) that form at the base of infected trees. • It started out 2,400 years ago as a single spore invisible to the naked eye. It slowly grew to immense size by growing long threads of cells called hyphae, under the ground. • Fungi range in size from the microbe we call yeast to the largest known living organism on Earth — a 3.5-mile-wide fungus. • Nicknamed ‘the humongous fungus’, this honey mushroom covers 2,200 acres in the state of Oregon, in the USA. Threads called hyphae grow and spread underground