Part 5, Chapter 20 Summary and Analysis

Bacteria are the most enduring inhabitants of Earth. They survived for billions of years without us, but humans cannot survive one day without them. They pluck nitrogen from the air and form it into amino acids, a complex industrial process that generates a great deal of heat.

There are innumerable bacteria in and around each person constantly. About 100,000 live on each square centimeter of human skin. They also live in the hair, nose, stomach, eyelashes, eyes and teeth. Each human digestive system contains up to 400 types. Bacteria can create a new generation in 10 minutes or less. A single cell can produce 280,000 bacteria in just one day. They mutate quickly and share genetic code freely. This means bacteria are essentially a giant superorganism. They can eat practically anything, from wood and paint to sulfuric acid.

Bacteria are found everywhere on...