Bacteria are everywhere, in our bodies, in the air around us, and also in the ground beneath us - in the soil. The bacteria in soil are often very important for the growth of plants, including those that humans and other animals eat. However, not much is known about soil bacteria. Now, scientists have analysed soil samples from all over the world and compared the bacterial communities living in them. They found some surprising things... Lewis Thomson spoke to Noah Fierer from the University of Colorado about this recent work.