You may think that these alien species of bacteria are intruders. But in fact, they make up 90% of the living cells in our body. The human body is home to trillions of these strange and amazing bacteria.
Typical coliform bacteria of E. coli use their three tails to vigorously swim up and down inside us, and Salmonella bacteria, which are often the cause of food poisoning, live on our skin.
Until recently, the true role of bacterial populations has been largely ignored. However, a new analysis of DNA from the environment has revealed the usefulness of microbes. We simply would not exist without them. In exchange for food and nutrition, bacteria improve digestion, produce vitamins, and strengthen our immune system.