Carl Zimmer traces E. coli's pivotal role in the history of biology, from the discovery of DNA to the latest advances in biotechnology. He reveals the many surprising and alarming parallels between E. coli's life and our own. And he describes how E. coli changes in real time, revealing billions of years of history encoded within its genome. E. coli is also the most engineered species on Earth, and as scientists retool this microbe to produce life-saving drugs and clean fuel, they are discovering just how far the definition of life can be stretched.