Howard Phillips 
Inside the World of Microbes [PDF ebook] 

Microbes are everywhere! They live on and under the ground. They live in all kinds of water on Earth, even around the hottest deep-sea vents. They even live on and inside your body! Since the advent of powerful microscopes, scientists have been studying our world’s smallest denizens. Many people get scared just hearing the words "bacteria, " "fungus, " and "virus" because of the diseases they cause. However, scientists have discovered many beneficial microbes that actually help support all life on Earth. Geneticists have sequenced the genomes of numerous microbes, extending our knowledge of the organisms and how they affect our lives.