They’re tiny organisms, invisible to the human eye, and they’re inside you right now. This isn’t a description of a sci-fi monster but it is one of bacteria — single-celled organisms that can cause illness and death but might also help us to sleep better or find the motivation to exercise.
In short, we depend on bacteria, said Timothy Paustian, a professor in the Department of Bacteriology at the University of Wisconsin-Madison.
“They’re really important for your health. You have a whole group of organisms that live inside you,” Paustian said.