A teaspoon of soil may have billions of microbes divided among 5,000 different types, thousands of species of fungi and protozoa, nematodes, mites and a couple of termite species. How these and other pieces all fit together is still largely a mystery. “There’s a teeming organization below ground, a factory, with soil animals and microbes, each with their own role,” said Diana H. Wall, a professor of biology at Colorado State University who has studied…