Part 1

The Bacteria Book

Introduction Looking into a microscope is like peering into an alien world, one full of peculiar, pulsating creatures that act and move in strange ways. These mysterious microbes are absolutely everywhere—around you, on you, and inside you. We live in harmony with some of them, and we're at war with the rest. Some of the creatures you'll find in this book are gross and terrifying, while others are simply amazing. Get ready to discover the bacteria that makes you fart, the mite that lives in your eyelashes, and the fungus that turns ants into zombies. The world of the very small is endlessly fascinating, and I've packed these pages full of my favorite bits. Enjoy! Steve Mould

What is a microbe? A microorganism, or "microbe," is any living creature that is so small you can't see it with your eyes. The most common microbe is bacteria, which first appeared on Earth more than 3.6 billion years ago. Smaller than rice Just how small are these creatures? Zoom in three thousand times on a single grain of rice and you might start to see lots of little bacteria. Viruses, another type of microbe, are smaller still! One grain of rice is about (6 mm) 0.25 in long. There could be as many as one trillion species of microbe on Earth. ARE MICROBES REALLY ALIVE? Although they are tiny, yes! Scientists don't agree on what makes something alive, but all living things seem to share certain features, such as the ability to move and to grow. Viruses only have some of these features, however, so some people think they aren't alive. If you were a microbe... If you were shrunk down to the size of bacteria, a grain of rice would seem bigger than a mountain. That's how small microbes are. Can you imagine it?

Meet the microbes Say "hello" to the smallest critters on Earth! Here are six of the most common types of microbe. These creatures are everywhere you look— even though you usually can't see them. Bacteria Bacteria are made of just one cell each, and they are the simplest cells on the planet. There are more bacteria on Earth than any other form of life. Viruses Viruses are the smallest microbes. They are so small, they live inside the cells of other creatures. Many scientists say viruses may not even be alive since they don't eat or grow. Algae Many algae are made of one cell each, but they are usually bigger than bacteria. Like plants, algae use a green chemical called chlorophyll to turn sunlight into useful energy. Fungi Fungi, such as mold, break down dead plants and animals to use as food. A fungus can be made of one cell or of lots of cells. Protozoa Protozoa are made of only one cell. These creatures behave a bit like animals—they move around and eat other living things. Archaea Archaea look a lot like bacteria, but they behave in different ways. They can survive in extreme environments, such as very hot places or strong acids.

Seeing is believing Microbes are creatures we can't see with just our eyes, so how do we know they exist? One way is by looking through a microscope—but this isn't the only way. Microscope This tool uses curved glass lenses to make things look bigger and clearer. You can see something as small as a thousandth of a millimeter with a laboratory microscope. We dye bacteria colors like violet or red to make them easier to see under a microscope. Electron microscope Some microbes, such as viruses, are too small to be seen with a regular microscope. Scientists use a special tool called an electron microscope to fire tiny particles called electrons at the virus. The electrons help make a computer picture. Colored pictures Pictures made using an electron microscope are black-and-white. People add color to the images later to make them clearer. Growing blobs Scientists make bacteria grow on special plates called petri dishes filled with a nutrient-rich goop called agar. The nutrients in the agar help the bacteria grow. After some time, the bacteria blobs are big enough for us to see. Staphylococcus (staff-il-oh-CAWcuss) lives on most people's skin. This bacteria is usually harmless. Microbes that can make people sick are called germs.

All about cells When you think of living creatures, or organisms, you probably think of animals and plants, not microscopic blobs. But all living creatures have something in common, from the biggest mammal to the smallest bacteria: They are all made of cells. Animal cells Look at your skin under a microscope and you'll see it's made of cells. We don't think of them as being alive because they can't grow and reproduce on their own. The cells in your body work together to keep the whole organism alive. When a skin cell is separated from your body, it dies. It can no longer grow or reproduce. Skin cells work together to form a protective barrier for your body. The human body is made of about 30 trillion cells. Microbe cells These are bacteria cells. Unlike skin cells, they don't need to stick together to stay alive. If you remove one bacteria cell, it will keep growing and reproducing as long as it has enough nutrients. Bacteria and other microbe cells can live on their own. Parts of a cell Cells come in many shapes and sizes. Some have simple structures, and some are really complex. However, they all have three parts in common: DNA, cytoplasm, and a cell membrane. DNA is a big molecule that tells the cell how to grow and behave. Cytoplasm is a jelly-like substance that fills the inside of the cell. The cell membrane holds the cell together and lets chemicals in and out.