Introduction
 
Get used to it. You're surrounded. And covered. And filled. Unless you and everything around you just had a disinfectant shower, pretty much every square millimeter (that's a really small space; a sesame seed on top of your hamburger bun is one millimeter thick) that surrounds you has hundreds of microbes hanging out, living their best lives, having tiny conversations, arguments, buffets, you name it.
   Even though we can't see them, microbes impact our lives and our world in big, beautiful, and sometimes creepy ways. Yes, some can make us sick (hi, strep throat!), and others can be associated with lots of ick (poop, for example, is packed with 'em). But without microbes living on, in, and around us, we wouldn't be able to digest our food properly, would smell funny, and could get sick or depressed or experience lots of other terrible things.
   The little guys aren't just for us big folks. Microbes help loads of life-forms, from houseflies to houseplants, have happy lives. Well, some microbes help with the happy. Others are capable of mind control, gut liquefaction, and all sorts of weird, supercool deeds.
   Because microbes live pretty much everywhere, you're surrounded by an invisible world of joy and drama. While you're reading this, it's possible some houseflies nearby have been turned into zombies by a fungus, mice have been mind-controlled by a protist into calling cats to come play, and a microbe party in your bottom is producing a monster SBD*(* Silent But Deadly. As in, when one breaks wind. As in, a fart.). Let it fly and thank the little guys. Unless you're in class. If that's the case, sorry about that.
   In this book, you'll get a close-up view of the enchanting, thrilling microbe dramas happening right now. Like, in your yard. Or in your house. Or in you. But first, allow us to introduce you to microbes.
   A microbe is any living creature that's too small to see. For most of us, anything that's half the width of a human hair (that means less than .5 millimeters) is undetectable by our eyes. That includes most bacteria (there are a couple of bacterial whoppers you can see with the naked eye, but scientists usually include those as microbes, too, just so they won't feel left out), fungi, protozoa, archaea, algae, and some tiny animals. Some scientists say viruses don't count as microbes because they don't meet the official definition of living (viruses don't grow and they don't eat). Other scientists say, "Let viruses join the party!" In this book, we're going to let a couple of viruses join the party, only because what they do to people is so out there we want you to know about them.
   Let's break it down so you can see what makes up each kind of microbe.
  Bacteria are single-celled creatures that come in all shapes and sizes (many variations of small). They keep their DNA tangled up in something called a nucleoid instead of having a nucleus like our bodies' cells have. DNA is a chain of chemicals that holds instructions for all sorts of traits that creatures have and will pass on to future generations. These instructions include traits for how a creature will act, how it will look, and how its body will work. Some bacteria can make us sick, but plenty more make the world a pretty sweet place to live.
  Fungi. (Fungi is plural. When it's just one, it's called a fungus.) You know why everybody wants to hang out with Mr. Mushroom? Because he's such a fun-gi! Get it? Fun-gi? Fun guy? Anyway, seriously, fungi are fun. They can have one cell or many cells, but what unites them is that their cell walls are made of chitin (unlike plants, for example, which have cellulose walls). In addition to mushrooms, you know more than one fungus among us. Yeasts are a type of fungus. Lots of molds are fungi.
  Protozoa. These scooter tooters may be only one cell each, but they can move around and eat stuff.
  Archaea are a lot like bacteria, except when you look inside them, their cells don't have nuclei. They're our ancient, X-treme microbes. They hold the records for surviving in the hottest places (235°F/113°C), crazy-acidic spaces, and spots where there's no oxygen, like parts of our digestive tract.
  Algae are in lots of places, but you probably know them as that gunky junk floating around on ponds. Algae are sort of like if a bacterium and a plant cell got married and had babies. They're similar to bacteria in form, but they use chlorophyll like plants do to make energy.
  Super-tiny animals. You have mites that live on your forehead and crawl across your face at night, looking for mates. Don't freak out. That's just the way it is. Plenty of tiny critters crawl around the planet. Take little creatures called tardigrades (sounds like TAR-duh-grades), for example. Some people call them water bears because up close they look like squishy caterpillar-bear things. They have been shipped into space and can survive all sorts of wild "I didn't think of that" scenarios, like being totally dried out for thirty years. Rock on, baby bears. You're amazing.
  Viruses. Again, some say let's include them in the microbe merrymaking; others say skip 'em. Viruses are basically globs of proteins without brains (or any organs at all). They manage to make their way into cells and use the stuff of those cells to make more and more and more of themselves. Then they burst forth and move on to their next victims. Don't think about it too long. It's kind of a brain bender. And also a little scary.
   One more thing you need to know about before you read on is something called the microbiome. The microbiome is all the microbes (microscopic critters like bacteria and fungi) that live on and inside something. Each fly has its own microbiome bouquet. And so do you. And so does that weird dog that seems like it's always giving us the stink eye when we're just trying to walk down the sidewalk. And so does your grandmother's rosebush. And so does that pencil you chewed the eraser off of at school. Everything.

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Excerpted from Unseen Jungle: the Microbes That Secretly Control Our World by Eleanor Spicer Rice
All rights reserved by the original copyright owners. Excerpts are provided for display purposes only and may not be reproduced, reprinted or distributed without the written permission of the publisher.