One teaspoonful of rich soil is much more than rock particles - it is home to more than one billion busy bacteria. These microbes are nature's invisible master chemists recycling leftovers of everything else. For two billion years, bacteria lived alone and now nothing else could live without them. While one in a thousand is a pathogen or germ, the others work to breakdown or convert matter into nutrients that can be used by organisms for food. This includes the 100 trillion bacteria in our intestines that help us digest our meals. Bacteria clean up our environment by feeding on toxic wastes, petroleum, and sewage. Some bacteria make nitrogen more available to plants. Industries can culture microorganisms to produce medicines, pesticides, solvents, biodegradable plastics, and even to separate metals from ore. For thousands of years our ancestors have known that microorganisms secrete enzymes used in fermenting beer, wine, cheeses, breads, and many other foods. Aquaspirillum is a water-dwelling bacteria that seems to use magnetism to find food-rich sediment.